Cu vacancy engineering on facet dependent CuO to enhance water oxidation efficiency

The performance of the electrocatalyst is strongly depended on its electronic structure. Herein, the cuprous oxide (Cu₂O) with three different morphology (facet) is successfully synthesized to reveal the correlated relationship between oxygen evolution reaction (OER) activity and electronic structure, where the Cu₂O cube enclosed by high electronic density facet (100) exhibits enhanced OER performance. Then, CuO samples with different surface oxidation degree are obtained for further investigating the structure-function relationship. Finally, the CuO Cube_3h with Cu vacancy (V_Cu–CuO Cube_3h) contains more electroactive species and shows high catalytic performance with an onset overpotential of 252 mV and a Tafel slope of 63.4 mV dec^?1, respectively. It only needs 330 mV overpotential to drive 10 mA cm^?2 current density and maintains its catalytic property for at least 48 h. The density functional theory (DFT) calculation reveals that the exist of V_Cu has a positive effect on neighboring atoms to generate new electronic states near the Fermi level at the intermediate-absorbed structure, which also optimizes the absorption energy of oxygen intermediates, leading to faster charge transport to participate in the OER. This work provides a guidance for improving the OER performance by accurately regulating the surface charge distribution of the catalyst.