Effect of Chromium Doping on Electrochemical Water Oxidation Activity by Co3-xCrxO4 Spinel Catalysts

We have synthesized a series of Co3-xCrxO4 (0 < x < 2) catalysts via thermal decomposition and explored their activity for the oxygen evolution reaction (OER). By changing the Cr content, we were able to modify the overall OER activity. Among the compositions investigated, Co2.25Cr0.75O4 is the most active, which achieves 10 mA cm(-2) current density per geometric area and a mass activity of 10.5 A/g at 0.35 V overpotential. We hypothesize that this enhanced OER activity is due to the increase of the adsorption energy of the intermediates (*O, *OH, and *OOH) resulting from the increased electrophilicity of Co2+ sites in the material after the introduction of the electron-deficient Cr. This systematic doping strategy enables the investigation of the correlation between the doping and OER activity and allows for the rational design of future catalysts with higher activity and efficiency.