Er-Doping Enhances the Oxygen Evolution Performance of Cobalt Oxide in Acidic Medium

Exploring highly active and durable non-noble electrocatalysts for acidic oxygen evolution reaction (OER) is critical for advancing H2 production via water electrolysis using proton exchange membrane electrolyzer. However, it remains an immense challenge. Herein, we propose a strategy to synergistically enhance catalytic activity through Er doping, thereby enhancing both the intrinsic OER activity and stability of Co3O4. The cost-effective Er–Co3O4 catalyst with 4% Er demonstrates significantly improved performance with an overpotential of 321 ± 5 mV at 10 mA cm–2 and exceptional stability exceeding 250 h. Additionally, doping Er into Co3O4 induces structure defects to generate oxygen vacancies, increasing the ratio of Co3+/Co2+. In situ Raman analyses showed that during the OER process, there was an increase in Co–O active species at octahedral sites in 4% Er–Co3O4, indicating accelerated generation of the key *O intermediates for enhanced OER kinetics. Microkinetic modeling and density functional theory calculations further demonstrate an optimized GO-GHO value at Er–Co3O4, which is close to the theoretical optimal OER activity at the current density of interest. This study not only develops a cost-effective electrocatalyst for acidic OER but also provides fundamental insights into manipulating the structure of Co3O4 for water electrolysis.