Boosted charge and proton transfer over ternary Co/Co3O4/CoB for electrochemical nitric oxide reduction to ammonia

Fan, Xiaoxuan; Teng, Zhenyuan; Han, Lupeng; Shen, Yongjie; Wang, Xiyang; Qu, Wenqiang; Song, Jialing; Wang, Zhenlin; Duan, Haiyan; Wu, Yimin A.; Liu, Bin; Zhang, Dengsong

doi:10.1038/s41467-025-60043-6

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Published: 26 May 2025

Boosted charge and proton transfer over ternary Co/Co₃O₄/CoB for electrochemical nitric oxide reduction to ammonia

Nature Communications volume 16, Article number: 4874 (2025) Cite this article

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Abstract

The electrochemical nitric oxide reduction reaction (NORR) holds a great potential for removing environmental pollutant NO and meanwhile generating high value-added ammonia (NH₃). Herein, we tactfully design and synthesize a ternary Co/Co₃O₄/CoB heterostructure that displays a high NH₃ Faradaic efficiency of 98.8% in NORR with an NH₃ yield rate of 462.18 µmol cm⁻² h⁻¹ (2.31 mol h⁻¹ g_cat⁻¹) at −0.5 V versus reversible hydrogen electrode, outperforming most of the reported NORR electrocatalysts to date. The superior NORR performance is attributed to the enhanced charge and proton transfer over the ternary Co/Co₃O₄/CoB heterostructure. The charge transfer between CoB and Co/Co₃O₄ yields electron-deficient Co and electron-rich Co₃O₄. The electron-deficient Co sites boost H₂O dissociation to generate *H while the electron-rich low-coordination Co₃O₄ sites promote NO adsorption. The *H formed on electron-deficient Co sites is more favorable to transfer to electron-rich Co₃O₄ sites adsorbed with NO, facilitating the selective hydrogenation of NO. This study paves the way for designing and developing highly efficient electrocatalysts for electrochemical reduction of NO to NH₃.

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Introduction

Ammonia (NH₃) is an indispensable chemical for agriculture, chemical industry, refrigerant, hydrogen carrier, and healthcare^1,2,3,4,5. Unfortunately, NH₃ production by traditional Haber-Bosch method requires harsh conditions of high temperature and high pressure, emitting a large quantity of greenhouse gases^6,7. One of the alternatives to the Haber-Bosch method for NH₃ synthesis is the electrocatalytic reduction of nitrogen-containing species, including nitrogen gas (N₂), nitric oxide (NO), nitrite (NO₂⁻), and nitrate (NO₃⁻)^8,9,10,11. The nitrogen reduction reaction (NRR) suffers from low NH₃ Faradaic efficiency (FE_NH3) and NH₃ yield rate because of the high dissociation energy (941 kJ mol⁻¹) of N ≡ N and the competitive hydrogen evolution reaction (HER) (the reduction potential of N₂ (0.093 V vs. RHE) and H₂O (0 V vs. RHE) are close to each other)^12,13,14. The electroreduction of NO₂⁻ and NO₃⁻ to NH₃ (NO₂⁻RR and NO₃⁻RR) have more complicated reaction pathways, and generate more types of N-containing by-products^15,16. Compared with NRR, the electrochemical NO reduction reaction (NORR) is kinetically and thermodynamically more favorable because NO possesses a lower dissociation energy (204 kJ mol⁻¹) and a more positive reduction potential (0.71 V vs. RHE)^17,18,19. The approach to couple NO oxidation with NO₃⁻ reduction is also considered as an alternative to NORR. But NORR to produce NH₃ generally requires lower energy consumption^20,21. In recent years, NORR is becoming increasingly attractive because NORR not only can remove environmental pollutant NO from industrial exhaust gas, but also produces value-added chemicals.

The electrochemical reduction of NO involves chemical activation of NO followed by NO hydrogenation^22,23,24. Currently, the FE_NH3 and NH₃ yield rate in electrochemical NORR are still impeded by the weak adsorption of NO and the sluggish proton supply. To improve the NORR performance, researchers have made endeavors to enhance the adsorption of NO by transition metal oxide modification or vacancy engineering^25,26. The proton supply could be enhanced by using metal-based electrocatalysts that would facilitate H₂O dissociation^24,27. Constructing single atoms in amorphous metal oxides with oxygen vacancies to form metal-O moieties could accelerate hydrogenation of NO to produce NH₃^28,29,30. However, till now, it is still intractable to acquire both high FE_NH3 and NH₃ yield rate simultaneously because of the complex balance of the NO adsorption and H₂O dissociation. Early studies have shown fairly high NO adsorption capacity over Co₃O₄ surface^31,32,33,34. However, the poor activation and dissociation of H₂O on Co₃O₄ greatly restricts the hydrogenation reaction in NORR³⁵. Metallic Co on Co₃O₄ heterostructure is designed to promote H₂O dissociation to increase available *H³⁶. But this concurrently accelerates HER, leading to a low NORR FE_NH3 and NH₃ yield rate^{27,30,37,38,39}. Tuning charge distribution on catalyst’s surface is able to directionally drive *H transfer to enhance NO hydrogenation during NORR^40,41. Boron (B) possesses a 2s²p¹ electronic structure, which exhibits flexible valence states during catalytic reactions. Introducing B into the Co/Co₃O₄ heterostructure is anticipated to optimize NO adsorption and H₂O dissociation, and in the meantime induce *H transfer to promote NO hydrogenation and suppress HER during NORR, thus greatly enhancing NORR activity and selectivity.

In this study, we tactfully designed and synthesized a ternary Co/Co₃O₄/CoB heterostructure by reducing Co₃O₄ with NaBH₄. The ternary Co/Co₃O₄/CoB catalyst exhibited an excellent electrochemical NORR performance, achieving an NH₃ yield rate of 462.18 µmol cm⁻² h⁻¹ (2.31 mol h⁻¹ g_cat⁻¹) and an FE_NH3 of 98.80% at −0.5 V vs. RHE, outperforming most of the reported NORR electrocatalysts to date. To demonstrate the application potential, a Zn-NO battery was assembled using the Co/Co₃O₄/CoB as the cathode, which delivered a high power density of 10.06 mW cm⁻². A series of experiments and density functional theory (DFT) calculations revealed that the enhanced charge and proton transfer over the ternary Co/Co₃O₄/CoB effectively boosted the electrochemical NORR. In detail, the charge transfer between CoB and Co/Co₃O₄ yielded electron-deficient Co and electron-rich Co₃O₄. The electron-deficient Co sites boosted H₂O dissociation to generate *H, while the electron-rich low-coordination Co₃O₄ sites promoted NO adsorption and *H transfer. Thanks to the enhanced charge and proton transfer, the energy barrier of the NORR potential-determining step from *NO to *HNO over the ternary Co/Co₃O₄/CoB was greatly reduced. Furthermore, the Co/Co₃O₄/CoB could also facilitate adsorption of *NH and *NH₂, beneficial for NO reduction to produce NH₃.

Results

Catalyst synthesis and structure characterization

The ternary Co/Co₃O₄/CoB heterostructured electrocatalyst was synthesized by reducing Co₃O₄ using NaBH₄ in an Ar atmosphere at 500 °C for 4 h (Fig. 1a). By applying the same method, Co/Co₃O₄ could also be obtained by decreasing the quality ratio of NaBH₄/Co₃O₄. The as-prepared Co/Co₃O₄/CoB shows the morphology of nanoparticles supported on nanosheets based on the transmission electron microscope (TEM, Supplementary Fig. 1) measurement. The average thickness of the nanosheets is ∼3.3 nm determined by atomic force microscopy (AFM, Fig. 1b). The nanoparticles on the nanosheets are composed of large nanoparticles surrounded by many small nanoparticles (HRTEM, Supplementary Fig. 2). Co/Co₃O₄/CoB shows Co₃O₄ (311) and CoB (021) crystalline phases from the HRTEM image (Fig. 1c). To precisely determine the structure of Co/Co₃O₄/CoB, aberration-corrected HAADF-STEM measurement was further performed. As shown in Fig. 1d, abundant interfaces among Co, Co₃O₄, and CoB phases can be clearly observed, suggesting the formation of a ternary Co/Co₃O₄/CoB heterostructure. The electron energy loss spectroscopy (EELS) mapping (Fig. 1e) combined with the HRTEM image (Supplementary Fig. 2) clarifies that the Co/Co₃O₄/CoB heterostructure is composed of a CoB nanosheet supported with large Co and small Co₃O₄ nanoparticles. For comparison, Co/Co₃O₄ shows a heterostructure of Co nanoparticles supported on Co₃O₄ nanosheets (Supplementary Figs. 3 and 4).

**Fig. 1: Synthesis and morphology of Co/Co₃O₄/CoB.**

The structure and valence state of Co/Co₃O₄/CoB were analyzed by X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). As shown in Fig. 2a, the XRD patterns show clear diffraction peaks of Co₃O₄ (PDF #42-1467), Co (PDF #15-0806) and CoB (PDF #03-0959) for Co/Co₃O₄/CoB, and Co₃O₄ (PDF #42-1467) and Co (PDF #15-0806) for Co/Co₃O₄. The B 1s XPS spectrum of Co/Co₃O₄/CoB also evidences the formation of CoB (Supplementary Fig. 5). In Fig. 2b, the Co 2p_3/2 XPS spectrum of Co/Co₃O₄ exhibits three peaks at binding energies of 779.7, 781.0 and 783.1 eV, which can be attributed to Co⁰, Co³⁺ and Co²⁺, respectively^42,43,44. For Co/Co₃O₄/CoB, the Co⁰ peak slightly shifts to a higher binding energy (780.1 eV), while the Co³⁺ (780.7 eV) and Co²⁺ (782.2 eV) peaks shift toward lower binding energies as compared to those of Co/Co₃O₄. Because Co⁰ and Co³⁺/Co²⁺ mainly exist in Co and Co₃O₄, respectively, it can be inferred that the introduction of CoB leads to more electron loss in Co and more electron gain in Co₃O₄. To clarify the electron transfer among different interfaces in Co/Co₃O₄/CoB and Co/Co₃O₄, DFT calculations were conducted. Herein, by balancing the computation power and calculation accuracy, the Co/Co₃O₄/CoB was modeled by Co (111) and Co₃O₄ (311) clusters supported on CoB (021), while Co/Co₃O₄ was modeled by Co (111) clusters supported on Co₃O₄ (311) (for details see DFT calculations in Method section). Firstly, the Bader charge was analyzed over Co/Co₃O₄ and Co/Co₃O₄/CoB models. For the Co/Co₃O₄ model, 3.64 |e| is transferred from Co to Co₃O₄ (Supplementary Fig. 6, Supplementary Table 1, and Supplementary Data 1). In Co/Co₃O₄/CoB, Co₃O₄ gets 2.23 |e| and 2.36 |e| from Co and CoB, respectively (Supplementary Fig. 7, Supplementary Table 1, and Supplementary Data 1). The charge density difference analysis of Co/Co₃O₄/CoB indicates a significant charge redistribution at the interface between CoB and Co/Co₃O₄ (Fig. 2c), with electron transfer from Co to CoB and from CoB to Co₃O₄. Furthermore, the average numbers of electron transfer per Co atom in Co/Co₃O₄/CoB and Co/Co₃O₄ were analyzed. As compared in Supplementary Table 1, Co loses more electrons (−0.22 e vs. −0.13 e) and Co₃O₄ gains more electrons (+0.51 e vs. +0.08 e) in Co/Co₃O₄/CoB as compared to Co/Co₃O₄, evidencing that CoB introduction can modulate the electronic structure of Co and Co₃O₄ in Co/Co₃O₄/CoB. X-ray absorption spectroscopy (XAS), including X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), was performed to examine the electronic structure and coordination environment of Co in Co/Co₃O₄/CoB and Co/Co₃O₄. In the Co K-edge XANES spectra (Fig. 2d), the position of the absorption edge for Co/Co₃O₄/CoB and Co/Co₃O₄ are located between that for Co foil and Co₃O₄ references, indicating that the average valence state of Co atom in Co/Co₃O₄/CoB and Co/Co₃O₄ are within 0 and +2/+3, owing to co-existence of both metallic Co and Co₃O₄. To understand the local structure around Co atom in these samples, the EXAFS spectra are transformed into R-space. The R-space EXAFS spectra (Fig. 2e) display dominant peaks of Co-B (1.60 Å)⁴⁵, Co-Co (2.17 Å)⁴⁶, and Co-O (1.44 Å)⁴⁷ coordination bonds in CoB, Co foil and Co₃O₄, respectively. The FT-EXAFS spectra of Co/Co₃O₄/CoB and Co/Co₃O₄ can be well-fitted using backscattering paths of Co-Co, Co-B and Co-O (Fig. 2f, Supplementary Tables 2 and 3). Notably, the Co-O coordination number (2.2) in Co/Co₃O₄/CoB is significantly lower than that (5.7) in Co/Co₃O₄. The low-coordinated Co-O structure in Co/Co₃O₄/CoB is beneficial for NO adsorption⁴⁸. The wavelet transform (WT) contour plot of Co/Co₃O₄/CoB (Fig. 2g) displays three intensity maximums at around 7.2, 5.9, and 5.4 Å⁻¹, corresponding to the Co-Co, Co-B, and Co-O coordination, respectively^47,49. For comparison, Co/Co₃O₄ only shows Co-Co and Co-O coordinations (Supplementary Fig. 8).

**Fig. 2: Structural features of Co/Co₃O₄/CoB.**

Electrochemical NORR performance

The electrochemical NO reduction performance over Co/Co₃O₄/CoB was assessed in an H-type electrolytic cell filled with 0.1 M phosphate buffer saline (PBS) aqueous solution. As shown in Fig. 3a and Supplementary Fig. 9, the linear sweep voltammetry (LSV) curves (iR-corrected or not) reveal that both Co/Co₃O₄/CoB and Co/Co₃O₄ exhibit a significantly increased current density in 10 vol.% NO/Ar atmosphere as compared to pure Ar atmosphere, suggesting preferred NORR on Co/Co₃O₄/CoB and Co/Co₃O₄ surface. Chronoamperometric (1 h electrolysis) and ultraviolet-visible (UV-vis) colorimetric measurements were used to quantitatively determine the NH₃ Faradaic efficiency (FE) and yield rate (Supplementary Figs. 10 and 11). At −0.5 V vs. RHE, the Co/Co₃O₄/CoB displays the optimum FE_NH3 of 98.80% and NH₃ yield rate of 462.18 µmol h⁻¹ cm⁻² (2.31 mol h⁻¹ g_cat⁻¹), much higher than Co/Co₃O₄ (FE_NH3 of 91.28% and NH₃ yield rate of 252.34 µmol h⁻¹ cm⁻², Fig. 3b, c). ¹H nuclear magnetic resonance (NMR) measurements give comparable results (Supplementary Figs. 12–14). The possible by-products produced over Co/Co₃O₄/CoB during NORR were checked by differential electrochemical mass spectroscopy (DEMS), UV-vis absorption spectroscopy, and gas chromatography (Supplementary Figs. 15–18). The hydroxylamine (NH₂OH), N₂ and N₂O by-products were not detected. Moreover, we conducted the NORR experiment over Co/Co₃O₄/CoB in 0.1 M KOH aqueous electrolyte. The NORR performance was poorer as compared with the experiment conducted in 0.1 M PBS (Supplementary Fig. 19). The better NORR performance of Co/Co₃O₄/CoB as compared to that of Co/Co₃O₄ can be further reflected by the smaller semicircle radius in the electrochemical impedance spectroscopy (EIS) spectrum (Supplementary Fig. 20), indicating a smaller charge transfer resistance (R_ct) over Co/Co₃O₄/CoB surface. A series of control experiments indicate that the nitrogen in the NH₃ product originates solely from NO (Fig. 3d). Carbon paper itself shows negligible NORR activity, disclosing that NH₃ is mainly produced on Co/Co₃O₄/CoB (Fig. 3d). Using isotopic ¹⁵NO as the reactant, the characteristic double peaks (inset in Fig. 3d) appear with a separation of 72 Hz, corresponding to ¹⁵NH₄⁺, indicating that ¹⁵NO is the sole nitrogen source of NH₃ production. Besides excellent catalytic activity, Co/Co₃O₄/CoB also displays good catalytic stability. During five consecutive electrolysis cycles at −0.5 V vs. RHE, the FE_NH3 and NH₃ yield rate remain nearly unchanged (Fig. 3e). Moreover, this catalyst exhibits good current stability for ~100 h at −0.5 V vs. RHE (Supplementary Fig. 21). Co/Co₃O₄/CoB shows a good structural stability during the NORR based on the XRD, HRTEM and XPS characterizations (Supplementary Figs. 22–24). The ternary Co/Co₃O₄/CoB achieves a high FE_NH3 of 98.80% and NH₃ yield rate of 462.18 µmol h⁻¹ cm⁻² as well as long-time stability at a low cathodic potential of −0.5 V vs. RHE, superior to most of the reported NORR electrocatalysts (Fig. 3f and Supplementary Tables 4 and 5). To demonstrate the practical application potential of the Co/Co₃O₄/CoB catalyst, a Zn-NO battery with Co/Co₃O₄/CoB cathode and Zn plate anode was assembled (Supplementary Fig. 25), which could deliver an open circuit voltage (OCV) of 2.04 V (Supplementary Fig. 26) and a maximum power density of 10.06 mW cm⁻², outperforming all reported results in the literature (Supplementary Figs. 27 and 28, Supplementary Table 6). The output discharge current density increases continuously from 0.5 to 8 mA cm⁻² and each step exhibits a stable discharging plateau, indicating that our cell has an excellent discharge capability (Supplementary Fig. 29). Moreover, the NH₃ yield rate exhibits a maximum of 1627.67 µg h⁻¹ mg_cat⁻¹ at 8 mA cm⁻² (Supplementary Fig. 30). Significantly, the Zn-NO battery can remove NO pollutant, produce NH₃ and generate electricity at the same time.

Reaction mechanism

To understand the excellent NORR performance of Co/Co₃O₄/CoB, Brunauer-Emmett-Teller (BET) surface area and electrochemically active surface area (ECSA) of the as-prepared catalysts were first measured. Compared to Co/Co₃O₄, Co/Co₃O₄/CoB displays a higher BET surface area (Supplementary Fig. 31) and ECSA (Supplementary Fig. 32), which shall offer more active sites to catalyze electrochemical NORR. To clarify the reactive sites for NO adsorption/activation and H₂O dissociation as well as the protonation process of adsorbed intermediates on Co/Co₃O₄/CoB, a series of DFT calculations, NO breakthrough and electron paramagnetic resonance (EPR) measurements were conducted. The NO adsorption energies with N-end/O-end on the Co sites of Co (111), Co₃O₄ (311), and CoB (021) and the B sites of CoB (021) were computed by DFT (Fig. 4a and Supplementary Figs. 33–35). The results indicate that NO prefers to adsorb on Co sites of Co₃O₄ (311) in the form of N-end adsorption, having the most negative adsorption energy of −3.64 eV. Compared to Co/Co₃O₄, Co/Co₃O₄/CoB binds to NO more strongly (Fig. 4b and Supplementary Data 1). The low-coordinated Co-O structure in Co/Co₃O₄/CoB (Fig. 2f and Supplementary Table 2) contributes to NO adsorption as demonstrated by NO breakthrough analysis (Fig. 4c)⁴⁷. A crystal orbital Hamilton population (COHP) was further employed to investigate the NO adsorption strength on Co/Co₃O₄/CoB and Co/Co₃O₄ (Fig. 4d)^50,51,52. Compared to Co/Co₃O₄, Co/Co₃O₄/CoB displays a more negative integrated COHP (ICOHP) value of the Co-N bond, indicating a stronger NO adsorption on the Co/Co₃O₄/CoB surface⁵³. DFT calculation was further performed to explore the water dissociation process. The energy barrier for water transformation from the adsorbed state (H₂O*) to the transition state (TS) on Co/Co₃O₄/CoB and Co/Co₃O₄ are 0.50 eV and 0.66 eV, respectively (Fig. 4e, Supplementary Figs. 36 and 37, Supplementary Table 6). This result indicates that the dissociation of H₂O is more kinetically favorable on Co/Co₃O₄/CoB. In order to further investigate the H₂O dissociation ability of Co/Co₃O₄/CoB and Co/Co₃O₄, in-situ Raman spectroscopy measurements were conducted at different applied cathodic potentials. Three types of O-H stretching modes belonging to 4-HB·H₂O, 2-HB·H₂O, and M·H₂O (M = Na⁺/K⁺), respectively⁵⁴, are observed. The relative proportion of M·H₂O displays a little increasing trend along with increasing the applied cathodic potential, suggesting that M·H₂O is closer to the catalyst’s surface and could be more affected by the electric field. The M·H₂O proportion over Co/Co₃O₄/CoB is always higher than that over Co/Co₃O₄ at all studied cathodic potentials, suggesting better water dissociation ability over Co/Co₃O₄/CoB (Supplementary Figs. 38 and 39)^55,56. Consequently, Co/Co₃O₄/CoB could generate more *H as reflected in the liquid EPR measurement using 5,5-dimethyl-1-pyrroline-N-oxude (DMPO) as the *H trapping regent (Fig. 4f)⁵⁷. The DMPO-H signal completely disappeared when NO was introduced into the reaction system (Supplementary Fig. 40), indicating that the generated *H could be rapidly consumed by NO on the Co/Co₃O₄/CoB surface. This further verifies that *H is more favorable for bonding with NO to form NH_x intermediates rather than generating H₂⁵⁸. The *H generated on the metallic Co sites in Co/Co₃O₄/CoB can be quickly transferred to the neighboring Co₃O₄ surface to trigger the *NO hydrogenation reaction (Fig. 4g), thanks to the relatively electron-richer Co₃O₄ in Co/Co₃O₄/CoB than that in Co/Co₃O₄. As a result, the enhanced charge and *H transfer over Co/Co₃O₄/CoB promote electrochemical NO reduction to produce NH₃. The COHP analysis was performed to investigate the adsorption capacity of nitrogen-containing intermediates on Co/Co₃O₄/CoB and Co/Co₃O₄. The ICOHP value of the Co-NH/Co-NH₂ bond is −3.83/3.20 and −2.65/1.70 on Co/Co₃O₄/CoB and Co/Co₃O₄, respectively (Fig. 4h, i, Supplementary Figs. 41 and 42), indicating a higher bonding state energy of *NH/*NH₂ on Co/Co₃O₄/CoB than Co/Co₃O₄. The projected density of states (PDOS) of Co/Co₃O₄/CoB and Co/Co₃O₄ upon adsorption of *NH and *NH₂ were analyzed (Supplementary Figs. 43 and 44). The E_p (the highest peak below the Fermi level) position of Co/Co₃O₄/CoB is higher than that of Co/Co₃O₄ upon adsorption of *NH and *NH₂, indicating that the antibonding states of NORR intermediates are located at higher energies with lower occupancies on Co/Co₃O₄/CoB surface, which results in stronger bindings of intermediates on Co/Co₃O₄/CoB during NORR⁵⁹. Both the COHP and PDOS results indicate enhanced adsorption of *NH and *NH₂ intermediates over Co/Co₃O₄/CoB, which is conducive to NORR for producing NH₃.

To reveal the reaction pathway of electrochemical NORR, in-situ attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) measurements were conducted to probe the reaction intermediates in the potential range from OCP to −0.7 V (vs. RHE). Over the Co/Co₃O₄/CoB surface (Fig. 5a), the bands at 1103 and 3224 cm⁻¹ belong to *HNO species while the bands at 1167, 1245, and 1504 cm⁻¹ are related to N-H stretching, -NH₂ wagging, and -H-N-H bending, respectively^60,61. The gradually increased bands at 1456 and 1635 cm⁻¹ can be attributed to NH₄⁺ and -OH species accumulation on the Co/Co₃O₄/CoB surface⁶². Additionally, a wide overlapped absorption at around 3000 ~ 3800 cm⁻¹ is observed, in which the bands at 3380 and 3731 cm⁻¹ are assigned to the stretching of -OH and -NH, respectively⁶³. The in-situ ATR-SEIRAS spectra as a function of time also display the same reaction intermediates over Co/Co₃O₄/CoB surface (Supplementary Fig. 45). Compared to Co/Co₃O₄ (Fig. 5b), a large number of important reactive intermediates including *NH and *NH₂ can be observed over Co/Co₃O₄/CoB surface at less negative cathodic potentials, suggesting much enhanced NORR reaction kinetics on Co/Co₃O₄/CoB. On the other hand, a larger amount of *NH and *NH₂ intermediates were observed accumulating on Co₃O₄ surface compared with Co/Co₃O₄ and Co/Co₃O₄/CoB, implying the weaker ability of supplying *H on Co₃O₄ (Supplementary Fig. 46). To further confirm the key reaction intermediates, the DEMS measurement was performed over Co/Co₃O₄/CoB at −0.5 V vs. RHE. As displayed in Fig. 5c and Supplementary Fig. 47, it can be observed that NO decreases with a decrease of NOH and HNOH intermediates, and meanwhile NH, NH₂, and NH₃ increase. These intermediates observed in DEMS align well with the results obtained from in-situ ATR-SEIRAS measurements. Therefore, the NORR pathway taking place on the Co/Co₃O₄/CoB surface is speculated to follow *NO → *HNO→ *NHOH → *NH → *NH₂ → *NH₃ → NH₃. Additionally, the signal of NH₃ in the DEMS measurement is much stronger than that of H₂, N₂, NH₂OH, and N₂O, explaining the high FE_NH3 in NORR over Co/Co₃O₄/CoB. Figure 5d compares the reaction energy diagram of NORR over Co/Co₃O₄/CoB and Co/Co₃O₄ surface (the structural models of intermediates are shown in Supplementary Figs. 48 and 49). Compared with *NOH, the first protonation of NO is more energetically favorable to form *HNO (Supplementary Figs. 50 and 51), which is the potential-determining step (PDS) of NORR on Co/Co₃O₄/CoB and Co/Co₃O₄. Clearly, Co/Co₃O₄/CoB shows a lower reaction energy barrier (0.81 eV) in PDS than that (1.11 eV) of Co/Co₃O₄, owing to the accelerated protonation process of NO over Co/Co₃O₄/CoB. The second proton preferentially reacts with *HNO to generate *HNOH with a ΔG of −1.88 eV, rather than *N with a ΔG of −0.82 eV. Finally, three successive protonation processes occur until NH₃ is formed. Besides, the reaction energy of NORR was also calculated over Co₃O₄, Co, and CoB (Supplementary Figs. 52–55 and Table 7). The reaction energy of the potential-determining step (*NO to *HNO) is 1.25, 2.81 and 1.6 eV over Co₃O₄, Co, and CoB, respectively, much higher than that over Co/Co₃O₄/CoB. This result evidences that the first step of NO hydrogenation can be notably boosted over the ternary Co/Co₃O₄/CoB heterostructure.

Discussion

In summary, we have designed and prepared a ternary Co/Co₃O₄/CoB heterostructure through a thermal solid-state reduction reaction of Co₃O₄ by NaBH₄. The prepared Co/Co₃O₄/CoB displayed a high FE_NH3 of 98.80% with NH₃ yield rate of 462.18 µmol cm⁻² h⁻¹ (2.31 mol h⁻¹ g_cat⁻¹) and long-time stability at a low cathodic potential of −0.5 V vs. RHE, outperforming most of the reported NORR electrocatalysts in the literature. The extraordinary NORR performance of Co/Co₃O₄/CoB was resulted from the unique charge and mass transfer within the Co/Co₃O₄/CoB heterostructure (Fig. 5e). The enhanced electron transfer in Co/Co₃O₄/CoB yielded electron-deficient Co and electron-rich Co₃O₄. The electron-deficient Co sites could effectively boost H₂O dissociation to generate *H while the electron-rich low coordination Co₃O₄ sites promoted NO adsorption. The *H formed on electron-deficient Co site was more favorable to transfer to electron-rich Co₃O₄ site adsorbed with NO, facilitating the selective hydrogenation of NO. Thanks to the enhanced charge and proton transfer, the energy barrier of the potential-determining step from *NO to *HNO in NORR over Co/Co₃O₄/CoB was significantly reduced. Moreover, the introduction of CoB in Co/Co₃O₄/CoB could also facilitate the adsorption of *NH and *NH₂ intermediates. All of which greatly promoted electrochemical NORR. This study paves the way for designing and developing highly efficient electrocatalysts for reducing NO to NH₃.

Methods

Reagents and materials

Carbon paper (99.99%) and Ketjen carbon were purchased from Suzhou Sinero Technology Co., Ltd. Cobalt(II) acetate tetrahydrate (Co(CH₃COO)₂^.4H₂O, ≥99%), polyvinyl pyrrolidone (PVP, ≥99%), sodium borohydride (NaBH₄, ≥98.0%), chloride (NH₄Cl, 99.99%), ethanol (C₂H₅OH, ≥99.5%), were purchased from Shanghai Titan Scientific Co., Ltd. Hydroxylammonium chlorideammonium (NH₂OH·HCl, ≥99%), dimethyl Sulfoxide-D6 (C₂D₆OS, 99.8%), sodium hydroxide (NaOH, ≥98%), trisodium citrate (C₆H₅Na₃O₇, 98%), sodium nitroprusside dihydrate (C₅H₄FeN₆Na₂O₃·H₂O, ≥99.98%), sulfuric acid (H₂SO₄, >95%), hydrogen peroxide (H₂O₂, 30%), and phosphate buffer solution (PBS, 10X, pH = 7.3 ± 0.1) were purchased from Shanghai Adamas Reagents Co., Ltd. Sodium hypochlorite solution (NaClO, available chlorine 4.0%), salicylic acid (C₇H₆O₃, 99%) were purchased from Macklin Biochemical Technology Co., Ltd. Deionized water (18.25 MΩ cm resistivity) was obtained via an ultrapure water equipment in laboratory. All the reagents are analytical-grade and directly used without further purification.

Synthesis of Co₃O₄ nanosheets

The Co₃O₄ nanosheets were prepared by a hydrothermal method as follows: Co(CH₃COO)₂.4H₂O (0.75 g) and PVP (2.4 g) were dissolved in 70 mL methanol under stirring for 30 min. The mixture was transferred into a 100 mL Teflon-lined stainless-steel autoclave that was sealed and heated to 190 °C for 12 h. After cooling to 25 °C, the products were harvested by centrifugation, washed three times with ethanol, dried at 60 °C, and calcined at 350 °C for 5 h in air⁶⁴.

Synthesis of Co/Co₃O₄/CoB and Co/Co₃O₄

In a typical synthesis of Co/Co₃O₄/CoB, Co₃O₄ and NaBH₄ were uniformly mixed in a mortar at a mass ratio of 1:1.5. The mixture was then placed in a horizontal quartz tube and heated to 500 °C at a ramp rate of 2 °C min⁻¹ under an Ar atmosphere, which was maintained at 500 °C for 4 h. The resulting products were washed extensively by an ethanol/deionized water mixture and collected by filtration. Finally, the washed Co/Co₃O₄/CoB was dried at 80 °C for 12 h in a vacuum oven. For preparing Co/Co₃O₄, the mass ratio of Co₃O₄ and NaBH₄ was adjusted to 1.5:1, while other preparation parameters were kept unchanged.

Electrochemical measurements

Electrochemical measurements were performed on a CHI660E electrochemical workstation in an H-type electrochemical cell (Supplementary Fig. 56) separated by a Nafion 117 membrane (10*10 cm, thickness was 183 µm, Dupont) in a three-electrode configuration at 25 °C. We chose 0.1 M PBS buffer solution (pH = 7.3 ± 0.1) to maintain the pH of the electrolyte during NORR. The membrane was sequentially treated in a H₂O₂ (5 wt.%) aqueous solution at 80 °C for 1 h, then in a 0.5 M H₂SO₄ solution at 80 °C for 2 h and finally in deionized water at 25 °C for 6 h. The catalyst coated on carbon paper (CP,1 cm²) was used as the working electrode, a platinum plate (1 cm²) was used as the counter electrode, and an Ag/AgCl (saturated 3.5 M KCl aqueous solution) electrode was used as the reference electrode. The Ag/AgCl reference electrode was calibrated in H₂-saturated 0.1 M PBS using a symmetric Pt electrode system.

To prepare the working electrode, 2.5 mg of electrocatalyst and 2.5 mg of Ketjen carbon were ultrasonically dispersed in 300 μL ethanol, 150 μL ultrapure water, and 25 μL Nafion solution (5 wt.%, Du Pont) to form a homogeneous catalyst ink followed by dropping 38 µL of the catalyst ink onto a piece of CP (1 cm²) that was dried at 25 °C, the catalyst mass loading was 0.2 mg cm⁻². Before all electrochemical tests, 30 min of high-purity Ar gas (99.999%) and 30 min of NO/Ar gas (10 vol.%) saturated the electrolyte to exclude air in the reaction system.

Linear sweep voltammetry (LSV) was performed at a scanning rate of 5 mV/s prior to 50 cycles of cyclic voltammetry at a scan rate of 50 mV/s to obtain a stable curve with 90% iR-correction. The non-iR corrected data for all catalysts are provided in the Supplementary Information. The electrochemical impedance spectroscopy (EIS) was obtained without iR-correction in the frequency range from 0.01 Hz to 100 kHz upon an AC voltage amplitude of 5 mV at an open-circuit potential under 25 °C. The chronoamperometry was operated to evaluate the stability under continuous stirring (1600 rpm) at different current densities. All potentials in this study were converted to the reversible hydrogen electrode (RHE) scale according to the following equation:

$${{{\rm{E}}}}({{{\rm{V}}}}\,{{{\rm{vs}}}}.{{{\rm{RHE}}}})={{{\rm{E}}}}({{{\rm{V}}}}\, {{{\rm{vs}}}}.{{{\rm{Ag}}}}/{{{\rm{Ag}}}}{{{\rm{Cl}}}})+0.198\, {{{\rm{V}}}}+0.059\times {{{\rm{pH}}}}$$

(1)

Calculation of Faradaic efficiency (FE) and yield rate (Y)

$${{{{\rm{FE}}}}}_{i}\left( \% \right)=\frac{{{{{\rm{Q}}}}}_{i}}{{{{{\rm{Q}}}}}_{{{{\rm{total}}}}}}\times 100 \%=\frac{{{{{\rm{c}}}}}_{i}\times {{{\rm{V}}}}\times {{{\rm{n}}}}\times {{{\rm{F}}}}}{{M}_{i}\times {{{{\rm{Q}}}}}_{{{{\rm{total}}}}}}\times 100 \% $$

(2)

$${{{{\rm{Y}}}}}_{i}({{{\rm{\mu mol}}}}\, {h}^{-1}\, {{cm}}^{-2})=\frac{{{{\rm{V}}}}{\times {{{\rm{c}}}}}_{i}}{{M}_{i}\times {{{\rm{t}}}}\times {{{\rm{s}}}}}$$

(3)

Where Q_i is the charge of product i, Q_total is the total charge, c_i is the concentration of products (µg mL⁻¹), V is the volume of electrolyte in the cathode compartment (25 mL), n: the number of electron transfer in products; F: Faraday constant (96485 C mol⁻¹); M_i: the molar mass of products (g mol⁻¹); s: the area of the electrode (1 cm²); t: the reaction time (1 h).

ECSA analysis

Electrochemical active surface area (ECSA) was evaluated through cyclic voltammetry (CV) measurements conducted within the non-Faradaic potential region in 0.1 M PBS electrolyte, where iR drop is negligible. The electrochemical double-layer capacitance (C_dl) was determined from the linear slope of capacitive current (Δj = 0.5 × |j_charge − j_discharge|) plotted against scan rate (20–120 mV s⁻¹). The ECSA of the catalyst was determined by normalizing the double-layer capacitance (C_dl) against the standard specific capacitance (C_s) for smooth metal surfaces in 1.0 M netural electrolyte, following the relation: ECSA = C_dl/C_s.

Quantification of NH₃

The yield rate of NH₃ in NORR was quantitatively determined by the indophenol blue method and NMR. For the indophenol blue method, the concentration-absorbance curves were calibrated using a standard NH₃ solution with a series of concentrations. The fitting curve (y = 0.4149x – 0.0264, R² = 0.9999) shows a good linear relationship between absorbance and NH₃ concentration. For NMR measurement, after NORR, the electrolyte was taken out, whose pH was adjusted to 3 using a 0.5 M HCl aqueous solution, and then sent for quantification by ¹H NMR (600 MHz) with internal standard of maleic acid (3.5 M). The number of scans was 128 for all NMR measurements. The fitting curve (y = 2.7375x – 1.9166, R² = 0.9993) shows a good linear relationship.

¹⁵N isotope labeling experiment

The ¹⁵N isotope labeling experiment proceeded on the ¹H NMR spectroscopy (600 MHz) to identify the nitrogen source for NORR. Replace ¹⁴NO with ¹⁵NO to conduct the NORR experiment at −0.5 V vs. RHE. After the experiment, take 2 mL of the catholyte were acidized by H₂SO₄ (2 mL, 1 M). 60 μL of the above solutions were respectively added to a NMR tube and mixed with maleic acid aqueous solution (20 μL, 3.6 mM), H₂SO₄ aqueous solution (20 μL, 4 M) and DMSO-d₆ (500 μL), and then analyzed by ¹H NMR measurements.

Quantification of hydroxylamine (NH₂OH)

To quantify NH₂OH, the following literature procedures were executed: 1.0 mL of the catholyte (or 0.1 mM~0.5 mM standard NH₂OH solution) was added 1.0 mL PBS buffer (pH = 7.3 ± 0.1) and 1.0 mL 1% 8-hydroxylquinoline. Under vigorous shaking, 1.0 mL 0.1 M Na₂CO₃ was added and the mixture was heated at 100 °C for 1 min. In the presence of NH₂OH, the solution would turn from light yellow to blue-green, showing an absorption peak at ~705 nm. Plotting the peak absorbance with NH₂OH concentration yielded a calibration curve.

Zn-NO battery

A Co/Co₃O₄/CoB coated on carbon paper was employed as the cathode to perform the NORR in a cathodic electrolyte (0.1 M PBS). A polished Zn plate was applied as the anode in an anodic electrolyte (1 M KOH), and a Nafion 117 membrane was used to separate the cathode from the anode. The Zn-NO battery was assessed on a CHI660E electrochemical workstation under an ambient atmosphere at 25 °C.

Characterizations

The morphological information was characterized by atomic force microscopy (AFM, Park NX10), field emission scanning electron microscopy (SEM, Zeiss-sigma-300), and transmission electron microscopy (TEM, JEOL JEM-1400). High-resolution transmission electron microscopy (HRTEM) and aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) were conducted on a JEOL JEM 2100 F and JEM-ARM 300 F Grand ARM. X-ray diffraction (XRD) patterns were recorded on a Bruker D8 Advance Diffractometer (Cu-Kα radiation: λ = 0.15406 nm). The surface valence states were studied by X-ray photoelectron spectroscopy (XPS, PHI-5300) with Mg Kα radiation (hν = 1486.6 eV). The X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra at the Co K-edge were collected at the HXMA beamline of the Canadian Light Source (CLS) using Fluorescence mode and Si (111) monochromator. The samples were pressed into wafers for collecting the data at 25 °C. The EXAFS raw data were background subtracted, normalized and Fourier transformed by standard procedures using the ATHENA program. The acquired EXAFS data were processed according to the standard procedures using the ATHENA module implemented in the IFEFFIT software packages. The k³-weighted EXAFS spectra were obtained by subtracting the post-edge background from the overall absorption and then normalizing for the edge-jump step. The ultraviolet-visible (UV‒vis) absorbance spectra were measured on an Agilent S3 Cary 5000. A Bruker 600 M NMR instrument with water suppression was used to record the ¹H NMR spectra. The Brunauer-Emmett-Teller (BET) surface area was measured on a U.S. Quantachrome ASAP 2020 M at 77 K.

NO adsorption breakthrough measurements

The NO adsorption breakthrough measurements were carried out on a dynamic sorption analyzer (mixSorb S) equipped with a thermal conductivity detector (TCD) combined with a mass spectrometer (OMNISTARTM). Firstly, 40 mg of catalyst was pre-treated in a high purity He atmosphere at a flow rate of 30 mL/min for 1 h. Afterwards, the sample was exposed to NO gas (0.02 vol.% NO balanced by He) at a total gas flow rate of 20 mL/min at 25 °C accompanied by recording the TCD signal and the MS signal of NO at m/z = 30 until the outlet mass signal of NO achieved saturation.

In-situ attenuated total reflection-surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) measurements

In-situ ATR-SEIRAS spectra were recorded on an INVENIO-R FTIR spectrometer (Bruker) equipped with a liquid nitrogen-cooled mercury cadmium telluride (MCT) detector (Supplementary Fig. 57). The catalyst ink was prepared by mixing 5 mg of catalyst, 300 μL ethanol, 150 μL ultrapure water, and 25 μL Nafion solution under sonication for 30 min. Next, 40 μL catalyst ink was slowly dropped onto a face-angled Si crystal to prepare the working electrode of the custom-made spectroelectrochemical cell fixed on the ATR accessory. Ag/AgCl electrode was employed as the reference electrode and a Pt wire was used as the counter electrode. Electrolyte was added in advance with continuous Ar flow at a flow rate of 50 mL/min for 30 minutes to remove interference of H₂O and O₂ prior to ATR-SEIRAS measurement. The background was measured at open circuit potential. Subsequently, 10% NO/Ar gas was injected and the absorption spectra were recorded at different applied potentials from OCP to −0.7 V vs. RHE. Afterwards, spectrum was collected at −0.5 V vs. RHE every 5 min for 60 min.

Online differential electrochemical mass spectroscopy (DEMS) measurements

In-situ DEMS measurement was conducted on Linglu (Supplementary Fig. 58). A Teflon layer was applied to separate the electrolyte from the vacuum system. The vacuum system, comprising of two dry pumps and one turbo pump, kept the vacuum degree below 10⁻⁷Pa. The catalyst ink was prepared by mixing 3 mg of catalyst, 460 μL ethanol, 500 μL ultrapure water, and 40 μL Nafion solution under sonication for 30 min. Next, 40 μL catalyst ink was slowly dropped onto gold film to prepare the working electrode. Ag/AgCl electrode was employed as the reference electrode and a Pt wire was used as the counter electrode. Before the DEMS measurement, NO/Ar was bubbled into the electrolyte until saturation. I-t test for 100 s was used to conduct DEMS investigations.

In-situ Raman spectroscopy

The in-situ Raman measurements were carried out jointly by an RXN1 Raman instrument (KAISER OPTICAL SYSTEM) and a CHI660E electrochemical workstation. A custom-made spectroelectrochemical cell was used as a reactor to enable the in-situ measurements. The obtained Co/Co₃O₄/CoB catalyst, Ag/AgCl, and platinum wire served as the working electrode, reference electrode, and counter electrode, respectively. The working electrode was immersed in the electrolyte and positioned such that the electrode plane was perpendicular to the laser. In-situ Raman spectra were obtained while the electrodes were under potentiostatic control. The experiment was conducted for 200 s under each fixed potential.

EPR measurements

5,5-dimethyl-1-pyrroline N-oxide (DMPO) was used to capture the unstable hydrogen radical to form the DMPO-H adduct to generate EPR spectrum. Briefly, 5 mL of electrolyte was mixed with 100 μL of DMPO and the mixture was deoxygenated by bubbling Ar. The constant current electrolysis was carried out for 10 min in the H-type cell under the protection of Ar. EPR measurement was performed on a JES X320, JEOL Co. spectrometer operated at a frequency near 9.5 GHz, sweep width of 200 G, and power of 20 mW. Co/Co₃O₄/CoB fitting parameters: g = 2.0045, AN = 15.5 G, AH = 21.0 G, lwpp = 0.3. Co/Co₃O₄ fitting parameters: g = 2.0043, AN = 15.6 G, AH = 20.8 G, lwpp = 0.3.

Density functional theory (DFT) calculations

Considering the limitations of computational power, we opted for a simplified mode, namely CoB supported neighboring Co and Co₃O₄ clusters, combininng with the morphology and three interfaces of Co/Co₃O₄/CoB heterostructure. The choice of using crystal facets of Co (111), Co₃O₄ (311), and CoB (021) to model Co/Co₃O₄/CoB heterostructure is primarily based on the XRD characterizations. These crystal facets exhibit the strongest diffraction in the XRD patterns and are also the thermodynamically stable facets. It is noted that the Co (111) and Co₃O₄ (311) clusters are taken from (111) facet of Co single crystal and (311) facet of Co₃O₄ single crystal, respectively.

All calculations were performed in the framework of the density functional theory with the projector augmented plane-wave method, as implemented in the Vienna ab initio simulation package (VASP)⁶⁵. The generalized gradient approximation proposed by Perdew, Burke, and Ernzerhof was selected for the exchange-correlation potential⁶⁶. The Grimme D3 correction used a coordination number dependent dispersion correction⁶⁷. The cut-off energy for the plane wave was set to 450 eV. The energy criterion was set to 10⁻⁵ eV in the iterative solution of the Kohn-Sham equation. A vacuum layer of 15 Å was added perpendicular to the sheet to avoid artificial interaction between periodic images. The Brillouin zone integration was performed using a 2 × 2 × 1 k-mesh⁶⁸. All the structures were relaxed until the residual forces on the atoms had declined to less than 0.05 eV/Å. The maximum atomic force in Co/Co₃O₄/CoB is 0.047, which meets the convergence requirement. In addition, we also evaluated the structural stability by using ab initio molecular dynamics (AIMD). The Brillouin zone was sampled using 1 × 1 × 1 k-point grid. Self-consistent calculations were conducted with an energy convergence threshold of 10⁻⁵eV. The AIMD was performed within the canonical (NVT) ensemble by Nosé-Hoover thermostats with a time step of 1.0 fs at a finite temperature of 300 K⁶⁹. In the AIMD simulation up to 10 ps, the heterostructure of Co/Co₃O₄/CoB was not destroyed, and the basic crystal structure was stable, proving the rationality of the structure (Supplementary Figs. 59–61 and Supplementary Data 2). Spin polarization was included in the calculations and the default setting of magnetic moment (MAGMOM= number of atoms of Co*1.0) was chosen for all calculations. The Gibbs free energy (ΔG) of reaction intermediates was calculated by the following:

$$\Delta {{{\rm{G}}}}=\Delta {{{\rm{E}}}}+{\Delta {{{\rm{E}}}}}_{{{{\rm{ZPE}}}}}-{{{\rm{T}}}}\Delta {{{\rm{S}}}}$$

(4)

where ΔE is the adsorption energy. ΔE_ZPE and ΔS are the difference for the zero-point energy and entropy, respectively. The zero-point energy and entropy were calculated at the standard conditions corresponding to the pressure of 101325 Pa ( ~ 1 bar) of H₂ at the temperature of 298.15 K. The climbing image nudged elastic band (cNEB) method was used to search the reaction path and transition state, and the vibration frequency calculation was used to confirm it further⁷⁰.

Data availability

Source data for all the figures and tables generated in this study are provided as a Source Data file. Source data are provided with this paper.

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Acknowledgements

The authors gratefully acknowledge financial support from the National Natural Science Foundation of China (22125604 and 22436003 to D.S.Z.), Shanghai Rising-Star Program (22QA1403700 to L.P.H.) and Science and Technology Commission of Shanghai Municipality (23230713700 to D.S.Z.), the City University of Hong Kong startup fund (9020003 to B.L.), ITF–RTH - Global STEM Professorship (9446006 to B.L.), and JC STEM lab of Advanced CO₂ Upcycling (9228005 to B.L.). X.Y.W. acknowledges the receipt of support from the CLSI Student Travel Support Program. XAFS spectra were tested at the HXMA beamline of the Canadian Light Source (CLS), a national research facility of the University of Saskatchewan, which is supported by the Canada Foundation for Innovation (CFI), the Natural Sciences and Engineering Research Council (NSERC), the National Research Council (NRC), and the Government of Saskatchewan. The authors thank Shenzhen HUASUAN Technology Co., Ltd for assistance on DFT calculations (https://huasuankeji.com).

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Authors and Affiliations

Innovation Institute of Carbon Neutrality, International Joint Laboratory of Catalytic Chemistry, State Key Laboratory of Advanced Special Steel, Department of Chemistry, College of Sciences, Shanghai University, Shanghai, China
Xiaoxuan Fan, Lupeng Han, Wenqiang Qu, Jialing Song, Zhenlin Wang, Haiyan Duan & Dengsong Zhang
Department of Materials Science and Engineering, City University of Hong Kong, Hong Kong SAR, China
Zhenyuan Teng & Bin Liu
Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Sapporo, Japan
Yongjie Shen
Department of Mechanical and Mechatronics Engineering, Waterloo Institute for Nanotechnology, University of Waterloo, ON, Waterloo, Canada
Xiyang Wang & Yimin A. Wu
Department of Chemistry, Hong Kong Institute of Clean Energy (HKICE) & Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, Hong Kong SAR, China
Bin Liu

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Xiaoxuan Fan
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Zhenyuan Teng
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Lupeng Han
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Yongjie Shen
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Xiyang Wang
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Zhenlin Wang
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Yimin A. Wu
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Bin Liu
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Contributions

X.X.F. performed the experiments, analyzed the data, and wrote the first draft of the manuscript. Z.Y.T., Y.J.S., W.Q.Q., J.L.S., Z.L.W. and H.Y.D. helped with the measurements and analysis, discussed and revised the manuscript. X.Y.W. and Y.A.W. performed the XAFS measurements and analysis. L.P.H., B.L. and D.S.Z. supervised the project, manuscript preparation and discussion.

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Correspondence to Lupeng Han, Bin Liu or Dengsong Zhang.

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Fan, X., Teng, Z., Han, L. et al. Boosted charge and proton transfer over ternary Co/Co₃O₄/CoB for electrochemical nitric oxide reduction to ammonia. Nat Commun 16, 4874 (2025). https://doi.org/10.1038/s41467-025-60043-6

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Received: 13 October 2024
Accepted: 24 April 2025
Published: 26 May 2025
DOI: https://doi.org/10.1038/s41467-025-60043-6