Nickel-selenide templated binary metal–organic frameworks for efficient water oxidation

Abstract

The development of highly active and stable non-precious metal electrocatalysts is of great significance for energy conversion with the oxygen evolution reaction (OER) being a rate-determining step. Herein, we report a hybrid material bearing a three-dimensional (3D) core–shell hierarchical structure, in which binary metal–organic framework nanosheets (NiFe-MOF NSs) are rationally decorated on NiSe_x nanosheet (NS) arrays supported on Ni foam (NF). With this approach, the highly conductive NiSe_x NSs ensure rapid charge transfer, the NiFe-MOF NSs provide a large number of exposed active sites, and the 3D hierarchical structure benefits gas release and electrolyte diffusion. As a result the NiFe-MOF/NiSe_x/NF electrode delivers current densities of 10 and 100 mA cm⁻² at overpotentials of 198 and 230 mV and reveals a low Tafel slope of 30.6 mV dec⁻¹ toward the OER. When NiFe-MOF/NiSe_x/NF was used as both the anode and cathode for overall water splitting, the potential to deliver a current density of 10 mA cm⁻² was 1.59 V, lower than that for the benchmark IrO₂/NF(+)‖Pt/C/NF(−) system (1.66 V at 10 mA cm⁻²).