Effect of Fe and Co Incorporation on Morphology and Oxygen Evolution Reaction Performance of β-Co(OH)₂: An In Situ Electrochemical Atomic Force Microscopy Investigation

Cobalt-based hydroxides are widely used as classical electrocatalysts in the oxygen evolution reaction (OER), and their performance is usually regulated by incorporation. It is essential for improving the efficiency of catalysis to track the dynamic changes during the electrochemical process. Here, the different morphological evolution and OER performance variation of incorporation of Fe and Co into β-Co(OH) 2 nanosheets under electrochemical conditions were elucidated by in situ electrochemical atomic force microscopy. The production of numerous particles is observed on the initial flat surface of β-Co(OH) 2 nanosheets during potential cycling in a Fe 2+ -spiked electrolyte, while the formation of little flakes is the principally morphological change during potential cycling in a Co 2+ -spiked electrolyte. This type of discrepancy is due primarily to the fact that the complete irreversible oxidation of β-Co(OH) 2 is promoted by Fe incorporation instead of Co incorporation. Additionally, the OER performance of the nanosheets with Fe incorporation presents a more significant improvement compared with that of the nanosheets with Co incorporation. It is on account that the OER performance benefits from Fe incorporation as well as the resulting complete conversion of β-Co(OH) 2 into β-CoOOH and the generation of particles with a greater number of highly reactive sites for the OER. Our findings are conducive to gaining an essence of how the incorporation affects the OER properties of β-Co(OH) 2 nanosheets through modifying morphological and component evolutions, which are vital for the advancements of cobalt-based hydroxides.