Extended Data Fig. 3: Growth mechanism of PdMo bimetallene.

a–h, Typical TEM images of PdMo bimetallene products collected after reaction times of 10 min (a, b), 20 min (c, d), 1 h (e, f) and 12 h (g, h). i, Changes in the atomic composition of PdMo bimetallene, determined by TEM–EDX and ICP–AES. j, UV–visible absorption spectra of PdMo bimetallene obtained at different reaction times. k, Photograph of a cyclohexane dispersion of the as-prepared PdMo bimetallene collected at 12 h. l, Synthetic scheme for the production of PdMo bimetallene. At the early stage of synthesis (10 min), the product contained nanocrystals with dimensions of only a few nanometres, with a definite 2D morphology. From 10 min to 20 min, the size of the nanocrystals gradually increased to tens of nanometres—the ICP–AES and TEM–EDX spectra revealed negligible amounts of molybdenum in these two intermediates, indicating these initial 2D nanocrystals were composed of pure palladium. As the reaction time increased to 60 min, curved nanosheets—with dimensions of hundreds of nanometres—were formed, accompanied by an obvious increase in molybdenum content. This suggests the rapid growth of palladium nanosheets and the slow incorporation of molybdenum during this period. When the reaction time was increased to 12 h, there was no substantial change in the dimensions of the nanosheets, suggesting that most of the palladium precursors were consumed in the first 60 min. The content of molybdenum, however, rapidly increased to around 12%, indicating the incorporation and interdiffusion of molybdenum atoms into the metallene.