Surface structure regulation and evaluation of FeNi-based nanoparticles for oxygen evolution reaction

FeNi-based catalyst is very promising for oxygen evolution reaction (OER) in practical water electrolysis for hydrogen generation. Herein, we found the catalytic performance of FeNi nanoparticles, as proof of concept, for OER can be optimized via surface structure regulation by rational thermal oxidation and/or reduction approaches. Surface structure of FeNi pre-catalyst in a fully oxidized or metallic state is not active while proper synergism of these states is favorable as supported by some spectroscopic techniques and electrochemical measurements. The as-optimized FeNi catalyst requires only 230 mV overpotentials to offer 10 mA cm(-2), with faster catalytic kinetics, good stability and high active site efficiency. The efficient high valence state of Fe/Ni species synergism generated from the optimized FeNi pre-catalyst is revealed by the post and in-situ Raman spectrum analysis. The results could answer the varied performance of FeNi reported for OER and are also instructive for their performance optimization.