Hollow NiCoP Nanoprisms Derived from Prussian Blue Analogues as Bifunctional Electrocatalysts for Urea-Assisted Hydrogen Production in Alkaline Media

Integrating the hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) is an energy-saving approach for electrolytic H-2 production. Here, hollow NiCoP nanoprisms are derived from Prussian blue analogues by a combined self-template coordination reaction and gas-phase phosphorization strategy. Benefiting from the strong electron interaction, unique hollow nanostructure, and enhanced mass/charge transfer, NiCoP nanoprisms display outstanding alkaline HER and UOR performance. Specifically, low potentials of -0.052, -0.115, and -0.159 V for HER and ultralow potentials of 1.30, 1.36, and 1.42 V for UOR at current densities of 10, 50, and 100 mA cm(-2) are obtained. Moreover, in a urea-assisted water electrolysis system, NiCoP nanoprisms only require cell voltages of 1.36, 1.49, and 1.57 V to offer current densities of 10, 50, and 100 mA cm(-2), about 170, 180, and 200 mV less than the traditional water electrolysis. Theoretical calculations indicate the Co substitution in Ni2P promotes the adsorption and dissociation of water molecules, optimizes the desorption energy of active hydrogen atoms, and enhances the adsorption of urea molecules, thus accelerating the kinetics of HER and UOR. This work facilitates the application of hollow bimetallic phosphides in electrochemical preparation of clean energy and provides a successful paradigm for urea-rich wastewater electrolysis.

Automated summary

Hollow NiCoP nanoprisms show excellent performance in alkaline HER and UOR, requiring low cell voltages for high current densities. The Co substitution in Ni2P is found to enhance the adsorption and dissociation of water molecules, optimizing the energy for active hydrogen atoms and improving urea molecule adsorption, thus accelerating kinetics.