Construction of NiS/NiS heteronanorod arrays in graphitized carbonized wood frameworks as versatile catalysts for efficient urea-assisted water splitting.

Exploring highly efficient, robust, and stable catalysts for urea electrolysis is intensively desirable for hydrogen production but remains a challenging task. In this work, novel, well-aligned, self-supported NiS/NiS heteronanorod arrays deposited on graphitized carbonized wood (GCW) are designed (denoted as NiS/NiS/GCW) and synthesized by a facile hydrothermal sulfidation strategy. Benefitting from the optimized surface hydrophilicity/aerophobicity, enhanced electrical conductivity, and 3D hierarchical directional porous architectures, the NiS/NiS/GCW show excellent activity toward the urea oxidation reaction and hydrogen evolution reaction in alkaline electrolytes. The arrays achieved a low potential of 1.33 V (vs. RHE) and 91 mV (overpotential) at 10 mA cm as well as robust stability for 100 h. Significantly, when employed as anode and cathode simultaneously, the urea electrolyzer constructed by NiS/NiS/GCW catalysts merely requires a low voltage of 1.44 V to drive 10 mA cm with superior stability for 50 h. This work not only demonstrates the application of heterogeneous sulfide for urea-assisted hydrogen production but also provides an effective guideline for using renewable wood for designing efficient catalysts in an economical way.