NiS/MoS2 Mott-Schottky heterojunction-induced local charge redistribution for high-efficiency urea-assisted energy-saving hydrogen production

Urea-assisted water electrolysis possesses the prospective prospect for high-efficiency hydrogen production by replacing oxygen evolution reaction (OER) with thermodynamically more favorable urea oxidation reaction (UOR). Modulating the electronic structure of electrocatalysts through constructing metal-semiconductor heteminterface represents an effective strategy to promote the electrochemical performances. Herein, we construct a Mott-Schottky bifunctional electrocatalyst by in-situ growth of NiS/MoS2 hetero-nanoflowers on the conductive carbon cloth (CC) substrate (abbreviated as NiS/MoS2@CC hereafter) for both hydrogen evolution reaction (HER) and urea oxidation reaction (UOR). Thanks to the Mott-Schottky effect, the self-driven charge transfer occurs across the NiS/MoS2 heterointerfaces, which results in the built-in electric field, the accelerated charge transfer rate, and the modified chemisorption free energies for reaction intermediates, ultimately expediting the dissociation of water and urea molecules. Consequently, the as-fabricated NiS/MoS2@CC electrode only requires an overpotential of 87 mV for hydrogen evolution reaction (HER) in 1.0 M KOH and a potential of 1.36 V for UOR in 1.0 M KOH solution with 0.5 M urea to attain a current density of 10 mA cm(-2), respectively. Moreover, when served as the free-standing anode and cathode simultaneously, the NiS/MoS2@CC-assembled urea electrolyzer requires a cell voltage of 1.46 V at 10 mA cm(-2), which is 200 mV smaller than that of the pure water splitting counterpart. This study may deepen the understanding of electronic modulation via Mott-Schottky establishment.