An Intermetallic CaFe6Ge6 Approach to Unprecedented Ca-Fe-O Electrocatalyst for Efficient Alkaline Oxygen Evolution Reaction

Based on the low-cost and relatively high catalytic activity, considerable efforts have been devoted towards developing redox-active transition metal (TM)-oxygen electrocatalysts for the alkaline oxygen evolution reaction (OER) while the role of redox-inactive alkaline earth metals has often been neglected in OER. Herein, for the first time, we developed a novel ternary intermetallic CaFe6Ge6 precatalyst, whose surface rapidly transforms into a porous ultrathin Ca-Fe-O heteroshell structure during alkaline OER through the oxidative leaching of surficial Ge. Benefiting from synergistic effects, this highly efficient OER-active material with distinct Ca-Fe-O layers has a large electrochemical surface area and more exposed active Fe sites than a Ca-free FeOx phase. Also, the presence of Ca in Ca-Fe-O is responsible for the enhanced transport and activation of hydroxyls and related OER reaction intermediate as unequivocally illustrated by a combination of quasi in-situ Raman spectroscopy and various ex-situ methods.

Automated summary

This study developed a novel ternary intermetallic CaFe6Ge6 precatalyst, which can transform into a porous ultrathin Ca-Fe-O heteroshell structure during alkaline OER. The material exhibits a large electrochemical surface area and more exposed active Fe sites, benefiting from synergistic effects. Additionally, the presence of Ca in Ca-Fe-O enhances the transport and activation of hydroxyls and related OER reaction intermediates.