Interface engineering of hybrid ZnCo2O4@Ni2.5Mo6S6.7 structures for flexible energy storage and alkaline water splitting

Abstract

Designing electrodes with hybrid structures is significant for improving energy storage and conversion efficiency. Overall, single-component metal oxides suffer from poor working stability and slow ionic electron mobility. In order to solve these problems, based on the easy-to-modify properties of spinel-structured ZnCo2O4, hybrid-structured ZnCo2O4@Ni2.5Mo6S6.7 was successfully grown on nickel foam through hydrothermal synthesis. The hybrid-structured ZnCo2O4@Ni2.5Mo6S6.7 exhibits high specific capacitance of 848 C g−1 at 1 A g−1, and excellent stability. The assembled supercapacitor device reaches a high energy density of 177.9 W kg−1 at 2700 Wh kg−1, excellent cycle performance, and mechanical flexibility. In alkaline water splitting, this hybrid structure presents low overpotentials, low water splitting cell voltage, and excellent stability. Density functional theory calculations confirm that the construction of Ni2.5Mo6S6.7 sulfide shell can reduce hydrogen adsorption energy, increase charge carrier density on the catalyst surface, and achieve a small Gibbs free energy difference in the fundamental rate-determining step, suggesting the improved electrocatalytic performance.