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 Cube3h with Cu vacancy (VCu–CuO Cube3h) 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 VCu 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.