Co(OH)2 confined in MIL-100 nanosheets with enriched oxygen vacancies for efficient electrocatalytic water splitting

Abstract

Exploring cost-effective and advanced bifunctional electrocatalysts is crucial for overall water splitting. Confinement engineering integrates electronic structure and interface transfer for synergistic cooperation between active sites and carriers, thus realizing enhanced electrocatalytic performance. Herein, Co(OH)2 confined MIL-100 nanosheets are grown on nickel foam (Co(OH)2/MIL-100) by cobalt acetate colloid. The confinement effect guarantees the highly dispersed Co(OH)2 in MIL-100. The two-dimensional nanosheet arrays of Co(OH)2/MIL-100 provide sufficient active sites and rich channels for facilitated ion/electron transportation. The characterizations and theoretical calculation prove that the strong coupling between Co(OH)2 and MIL-100 induces oxygen vacancies and highly active Fe3+ species to promote charge transfer and regulate the d-band center. As a result, the intermediate adsorption strength is optimized, which is beneficial to boost the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) process. The Co(OH)2/MIL-100 exhibits competitive OER and HER overpotentials of 260 mV and 160 mV at 50 mA cm−2 in alkaline electrolyte, respectively. Furthermore, the two-electrode electrolyzer equipped with Co(OH)2/MIL-100(+) || Co(OH)2/MIL-100(-) displays a low operation potential of 1.62 V (50 mA cm−2) and maintains high stability for 20 h. Thus, this work offers a novel colloid-assisted confinement strategy to simultaneously tailor the electronic structure and active sites for highly efficient electrocatalysts.