Integration of bimetallic spinel sulfides CoNi2S4 nanosheets with the hierarchically porous wood framework as efficient bifunctional catalysts for urea-assisted hydrogen generation

Abstract

Replacing anodic oxygen evolution reaction (OER) by urea oxidation reaction (UOR) provides a feasible approach to achieve high-efficiency hydrogen (H2) generation. However, the design of a robust catalyst for urea-assisted H2 generation remains a difficult problem. In this study, an innovative strategy to integrate bimetallic spinel sulfides CoNi2S4 nanosheet arrays with graphitized carbonized wood (denoted as CoNi2S4/GCW) for synergistically optimizing the electroconductivity and the hierarchical porous structure of the CoNi2S4/GCW catalyst is proposed. Benefitting from the optimized three-dimensional (3D) porous structure and the CoNi2S4 nanosheet arrays, the CoNi2S4/GCW catalyst exhibit brightly electrocatalytic performance toward both for UOR and hydrogen evolution reaction (HER). The synthesized CoNi2S4/GCW needs an ultralow potential (1.29 V vs. RHE) for UOR and a comparative small overpotential (119 mV) for HER at a current density of 20 mA cm−2, respectively, enabling a two-electrode configuration at a cell voltage of 1.42 V to output 20 mA cm−2 for urea-assisted electrocatalytic H2 generation. The enhanced urea-assisted performance of CoNi2S4/GCW is supposed to arise from a synergistic effect between the CoNi2S4 nanosheets and the 3D hierarchical porous wood framework, which offers sufficient active sites and expedite the mass transfer process between them. This work exhibits the application of bimetallic spinel sulfides CoNi2S4 in urea-assisted H2 generation and provides a promising strategy for utilizing sustainable wood for developing versatile electrocatalyst.