Rational construction of high-efficiency electrocatalysts for oxygen evolution reaction

(OER) is critical for renewable-energy technologies, but it is highly challenging to rationally regulate their surface structures to improve the OER performance. Herein, we proposed a “model-etching” strategy to investigate chemical etching of Co₃O₄. The cubic Co₃O₄ nanocrystals enclosed by well-defined facets are synthesized as model crystals, whose uniform surface structures allow us to study the etching mechanism at atomic level. Etching kinetics study together with DFT calculations discloses that {111} facets, the highly active facets for OER, serve as etch-stop facets in the etching reaction and H₂SO₄ molecules play a special role in creating surface Co²⁺, the active center of OER. These results direct us to rationally optimize the surface structures of Co₃O₄ to develop highly active OER electrocatalysts. The favorable performance of overpotential (η) and the Tafel slope decrease even to 268 mV@10 mA·cm⁻² and 74 mV·dec⁻¹, respectively. In general, our study shows that chemical etching of model crystals could help us rationally construct high-efficiency electrocatalysts.