Enhanced Oxygen Evolution Reaction Performance of Cr-Cofe-Layered Double Hydroxide Via the Synergistic Roles of Fe Etching, Cr Doping, and Anion Intercalation

Abstract

In this study, we used nanocubic ZIF-67 as a precursor, which was initially etched with potassium ferric oxalate to create a layered CoFe-LDH structure with larger mesoporous channels. The incorporation of C2O42− anions into the LDH layers successfully enhanced mass transport for both reactants and products. The introduction of Fe species led to strong electronic interactions with the Co active sites, improving the local coordination environment and enhancing catalytic activity at the active sites. Subsequently, Cr doping facilitated hydrogen bonding between C2O42− anions and –OH groups, providing stability to the active sites and further increasing the catalyst’s OER activity. Additionally, the high-valent Fe3+ and Cr6+ ions accelerated rapid surface charge conduction. Our findings indicate that Cr-CoFe-LDH exhibits exceptional OER performance, with an overpotential of 310 mV at a current density of 10 mA cm−2, a Tafel slope of 36.48 mV dec−1, and a Faradaic efficiency of 95.77%. After normalizing to the electrochemically active surface area, the overpotential further decreased to 285 mV, reflecting its high intrinsic activity. In situ Raman spectroscopy revealed that cobalt hydroxide-oxide is the primary active species for OER within this composite material. The hierarchical Cr-CoFe-LDH composite catalyst developed in this study provides a new approach and experimental foundation for the future design of low-cost, efficient water electrolysis catalysts.

Keywords: ZIF-67, Cr-doped, CoFe-layered double hydroxide, Oxygen evolution reaction