Energy-saving hydrogen production coupling urea oxidation over a bifunctional nickel-molybdenum nanotube array

Hydrogen production via water electrolysis is promising but impeded by sluggish cathodic and anodic reactions. Consequently, highly-efficient and earth-abundant electrocatalysts are attracting considerable attention. Herein we report a bifunctional Ni-Mo alloy nanotube for efficient hydrogen production coupled with anodic urea oxidation in a hybrid water electrolysis system. Specifically, ultralow potentials of - 44 mV and 1.36 V (vs. RHE) are required to deliver 10 mA cm(-2) current density for cathodic and anodic reactions, respectively. Density functional theory (DFT) calculation results show the Mo center is the main reaction site for the chemisorption and O-H bond cleavage of H2O while Ni center is identified as the hydrogen-evolving site. Based on this bifunctional Ni-Mo electrocatalyst, a hybrid water electrolysis cell is proposed and the overall cell voltage of similar to 1.43 V is achieved for outputting 10 mA cm(-2) current density during the 10 h operation. The understandings in alternative electrode reactions coupled with highly-efficient and earth-abundant electrocatalysts for hybrid water electrolysis in this work holds encouraging potential in future energy conversion technologies and urea-related water treatments.