Efficient anodic chemical conversion to boost hydrogen evolution with low energy consumption over cobalt-doped nickel sulfide electrocatalyst

Electrocatalytic oxidation of small molecules to replace sluggish water oxidation presents a promising strategy for clean hydrogen production with low energy consumption. Herein, we reported a reliable and universal method to fabricate the leaf-like Co-doped Ni3S2 architecture anchored on Ni mesh. The optimized Co-doped Ni3S2 electrocatalyst exhibits superior electrocatalytic activity toward the alkaline hydrogen evolution reaction (HER) and chemical oxidation as well as excellent durability. Specifically, a significantly reduced cell voltage of 0.80 V is attained at 50 mA cm−2 in sulfion-containing electrolytes, which is about 0.94 and 1.20 V lower than that of urea electrolysis and water splitting, respectively. In situ Raman spectroscopy and electrochemical characterization results imply that the desired oxidation state of the NiIII formed on the surface with shortened oxidation pathway accounts for the increased urea oxidation, whereas a direct electron transfer to surface active sites is responsible for superior sulfion oxidation. In situ spectroscopic evidences further unravel that the sulfion (S2−) were stepwisely oxidized to short-chain polysulfides including S22− and S42− and then to elemental sulfur (S8). This work highlights that the integrated overall reaction holds the great promise for saving-energy H2 generation and environmentally friendly recovery of sulfur with enhanced electron utilization efficiency.