Acidic oxygen evolution reaction (OER) has long been the bottleneck of proton exchange membrane water electrolysis. Ru- and Ir-based oxides are currently state-of-the-art electrocatalysts for acidic OER, but their high cost limits their widespread application. Co3O4 is a promising alternative, yet the performance requires further improvement. Crystal facet engineering can effectively regulate the kinetics of surface electrochemistry and thus enhance the OER performance. However, the facet-dependent OER activity and corrosion behavior of Co3O4 have not been thoroughly studied. In this study, we systematically investigated the OER performance and crystal facet dependency of Co3O4. The results demonstrate that Co3O4 with mixed {111} and {110} facets exhibits better OER activity and stability than Co3O4 with {111} or {100} facets. The surface Co3+ species are responsible for the high OER activity, but its transformation to CoO2 is also the root cause of the dissolution, leading to an activity-stability trade-off effect. The possible approach to addressing this issue would be to increase the Co3+ contents by nanostructure engineering. To further improve the performance, Ru is introduced to the best-performing Co3O4. The resulting Co3O4/RuO2 heterostructure exhibits an overpotential of 257 mV at 10 mA cm-2 and can stably catalyze the OER for 100 h.
© 2024 The Authors. Published by American Chemical Society.