Electrochemical ethanol oxidation reaction (EOR) is one of the promising reactions to replace oxygen evolution reaction (OER) in overall water splitting due to its lower ther-modynamic equilibrium potential and non-poisonous reactant. However, the reaction mechanism and the electrocatalyst evolution of EOR remain unclear, especially for non -precious metal based electrocatalysts. In this work, the femtosecond laser assisted elec-trodeposition method is used for the preparation of electrocatalysts with different phase compositions of NiFeOOH. Detailed electrochemical studies and in situ Raman spectra indicate that EOR and OER possess different reaction pathways. Neither p-NiOOH or y-NiOOH shows structural evolution before EOR, indicating the initial phase is the active phase for EOR. Between them, the y-NiOOH shows more benign intrinsic activity towards EOR. However, for OER, both of p-NiOOH and y-NiOOH would undergo a structural evolu-tion before OER, that is the pre-catalysis process. The OER catalytic performance is determined by the final phase component and the density of active sites after the pre -catalysis process. This work takes full advantage of electrochemical methods and in situ Raman spectroscopy, and finds out mechanism differences between EOR and OER to guide further catalyst design.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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