Boosting hydrogen production via urea electrolysis on an amorphous nickel phosphide/graphene hybrid structure

Overall urea electrolysis has favorable thermodynamic properties and can complement traditional water splitting by simultaneously purifying urea-rich waste streams. However, the kinetics of the reaction is slow and more efficient catalysts are required. In this work, we describe a facile way to fabricate amorphous nickel phosphides on graphene nanosheets (a-Ni2P/G), which shows high efficient performance for overall urea electrolysis. The a-Ni2P/G catalyst has abundant surface area for abundant catalytic active sites and high proportion of Ni3+ active sites, realizing a superior intrinsic activity for both hydrogen evolution reaction (HER) and urea oxidation reaction (UOR). Impressively, the a-Ni2P/G catalyst requires only much lower potentials of 1.28 V and − 0.1 V for UOR and HER at 10 mA cm−2. The assembled a-Ni2P/G║a-Ni2P/G electrolyzer needs a small cell voltage of 1.39 V to deliver the current density of 10 mA cm−2. This work highlights a promising pathway to develop a cost-efficient catalyst for energy-saving H2 generation combined with waste water purification. A highly efficient amorphous catalyst of a-Ni2P/G with high surface area and abundant exposed catalytic sites is reported. The assembled a-Ni2P/G║a-Ni2P/G system shows a quite small cell voltage of 1.39 V to deliver 10 mA cm−2, which is better than most of bifunctional catalysts.