Charge redistribution induced by well-dispersed cobalt oxide nanoparticles on Co3(PO4)2 surfaces enhances OER catalytic activity†

Abstract

Developing electrocatalysts for the oxygen evolution reaction (OER) with high efficiency and durability to simulate industrial application conditions is essential for addressing environmental issues and the energy crisis. Decorating or anchoring nanoparticles onto catalyst surfaces shows promise in improving catalytic performance. However, the intrinsic mechanism behind this approach is not yet fully understood. Herein, varying amounts of cobalt oxide nanoparticles (1, 2.5, 5, 10 and 20% mass ratios) were in situ synthesized on the surface of amorphous cobalt orthophosphate (Co₃(PO₄)₂) to deeply investigate the behavior of the decorated catalysts. Interestingly, the results indicate that the cobalt orthophosphate decorated with a low amount of cobalt oxide nanoparticles (Co₃(PO₄)₂@1%Co₃O₄) exhibits the highest catalytic activity (low overpotential of 313.01 mV at 20 mA cm⁻² and high stability for 100 hours) compared to samples with higher amounts of these nanoparticles. The electrochemical results reflect that the well-distributed low concentration of Co₃O₄ induced an inductive effect on the surface of Co₃(PO₄)₂ leading to the redistribution of electron configuration on the surface. These findings can be confirmed by DFT calculations, which reveal a stronger electronic coupling between neighboring cobalt oxide nanoparticles. This stronger interaction minimizes their interaction with cobalt orthophosphate resulting in a decrease in catalytic activity.