Design and construction of 2D/2D sheet-on-sheet transition metal sulfide/phosphide heterostructure for efficient oxygen evolution reaction

Highlights: • Proposed a controllable strategy to construct 2D/2D TMS/TMP heterostructure. • Studied the relationship between deposition time, surface morphology, and performance. • Studied the roles of vertical vdW interface of 2D/2D TMS/TMP heterostructure during OER. • Co_xP@Ni-Co-S/NF only requires 271/289 mV to achieve 50/100 mA cm⁻², respectively. The design and construction of a transition metal-based electrocatalyst is essential for the application of hydrogen energy. Oxygen evolution reaction (OER), a semi-reaction of water splitting, is generally the rate-determining step because of its sluggish kinetics and high overpotential. In this study, a 2D/2D sheet-on-sheet heterostructure of transition metal sulfide and phosphide was successful synthesized via facile hydrothermal treatments followed by a controllable electrodeposition process. Owing to the sheet-on-sheet morphology formed in the electrodeposition process, a highly developed porous structure was formed, which was favorable for the electrode reaction. Additionally, the refined electronic structure resulting from the close interaction of the transition metal sulfide and phosphide was considered in the heterostructure design. At an optimal deposition time, the Co_xP@Ni-Co-S grown on nickel foam (NF) exhibited OER activity with low overpotentials of 271 and 289 mV to afford current densities of 50 and 100 mA cm⁻², respectively. Benefitting from the highly stable porous structure, Co_xP@Ni-Co-S/NF showed a high catalytic stability during the 30-h harsh oxygen evolution process. This 2D/2D sheet-on-sheet transition metal sulfide/phosphide heterostructure provides a new route for the development of practical transition metal oxygen evolution catalysts.