High-Performance Ammonium Cobalt Phosphate Nanosheet Electrocatalyst for Alkaline Saline Water Oxidation

The development of highly efficient electrocatalysts toward the oxygen evolution reaction is imperative for advancing water splitting technology to generate clean hydrogen energy. Herein, a two dimensional (2D) nanosheet ammonium cobalt phosphate hydrate (NH4CoPO4 center dot H2O) catalyst based on the earth-abundant non-noble metal is reported. When used for the challenging alkaline saline water electrolysis, the NH4CoPO4 center dot H2O catalyst with the optimal thickness of 30 nm achieves current densities of 10 and 100 mA cm(-2) at the record low overpotentials of 252 and 268 mV, respectively, while maintaining remarkable stability during the alkaline saline water oxidation at room temperature. X-ray absorption fine spectra reveal that the activation of Co (II) ions (in NH4CoPO4 center dot H2O) to Co (III) species constructs the electrocatalytic active sites. The 2D nanosheet morphology of NH4CoPO4 center dot H2O provides a larger active surface area and more surface-exposed active sites, which enable the nanosheet catalyst to facilitate the alkaline freshwater and simulated seawater oxidation with excellent activity. The facile and environmentally-benign H2O-mediated synthesis route under mild condition makes NH4CoPO4 center dot H2O catalyst highly feasible for practical manufacturing. In comparison with noble metals, this novel electrocatalyst offers a cost-effective alternative for economic saline water oxidation to advance water electrolysis technology.

Automated summary

A novel 2D nanosheet ammonium cobalt phosphate hydrate catalyst has been developed for efficient oxygen evolution in alkaline saline water electrolysis, achieving high current densities at record-low overpotentials. The activation of Co (II) ions to Co (III) species constructs electrocatalytic active sites, providing larger active surface area and more surface-exposed active sites for facilitating oxidation reactions. The environmentally-benign synthesis route and cost-effective alternative to noble metals make this catalyst highly feasible for practical manufacturing.