Fig. 4: Investigation of the reconstructed oxyhydroxides from spinel pre-catalysts.
From: Navigating surface reconstruction of spinel oxides for electrochemical water oxidation
a The Tafel plots of the cycled spinel LixCo3−xO4. b The Tafel slope and turnover frequency (TOF) of cycled spinel LixCo3−xO4. c The calculated structural polarity of spinel Zn[Al1.5M0.5]O4 (M = FeCo, FeNi, FeMn, CoNi, CoMn, and NiMn). For each bimetallic combination, three metal-metal ratios, i.e., 1:3, 1:1, and 3:1, are calculated. d The cyclic voltammetry (CV) curves of Ni0.25Fe0.75OOH, Ni0.25Co0.75OOH, and Fe1–xCoxOOH (x = 0.25, 0.5, and 0.75). The oxyhydroxides are in situ generated from spinel pre-catalyst Zn[Al1.5Ni0.125Fe0.375]O4, Zn[Al1.5Ni0.125Co0.375]O4, Zn[Al1.5Fe0.375Co0.125]O4, Zn[Al1.5Fe0.25Co0.25]O4, and Zn[Al1.5Fe0.125Co0.375]O4. The curves are capacitance-corrected by averaging the forward and backward sweeps. e The calculated oxygen hole density (μB) of Fe1–xCoxOOH (x = 0.25, 0.5, and 0.75). The oxygen hole density of FeOOH and CoOOH is also shown for reference. f The calculated oxidation state of cobalt and iron cations in Fe1–xCoxOOH (x = 0.25, 0.5, and 0.75). The dashed lines represent the oxidation state of iron cation in FeOOH and that of cobalt cation in CoOOH.
