Selectively Se-doped Co3O4@CeO2 nanoparticle-dotted nanoneedle arrays for high-efficiency overall water splitting

Abstract

Transition metal oxides are well-known for their excellent activity and stability during oxygen evolution reaction process, while their hydrogen evolution reaction performance still is unsatisfactory. Herein, we firstly introduced the selectively Se-doped Co3O4@CeO2 nanoparticle-dotted nanoneedle arrays through three continuous operations of mild hydrothermal, air calcination and selective selenation. The remarkable HER and OER performance of SCCN-1 resulted from abundant oxygen vacancy as well the heterostructure and was testified by the overpotentials at a certain current density: 48 mV@10 mA cm−2 and 175 mV@50 mA cm−2 for HER; 188 mV@20 mA cm−2 and 293 mV@50 mA cm−2 for OER. In addition, the SCCN-1//SCCN-1 electrode couple only required a small cell voltage of 1.49 V to deliver a current density of 10 mA cm−2, which outperformed most recently reported bifunctional catalyst and exhibited outstanding stability in 1.0 M KOH over 12 h for overall water splitting process. Density functional theory calculations show that Se-doped Co3O4 exhibits stronger water adsorption energy compared to CeO2, which proves that Se-doped Co3O4 is a true reactive center. It's worth noting that this selective Se doping strategy is versatile to improve the HER activity of transition metal oxides and further use for catalyzing water splitting process.