Ultra-small nickel phosphide nanoparticles as a high-performance electrocatalyst for the hydrogen evolution reaction

Development of efficient and robust abundant electrocatalysts for the hydrogen evolution reaction (HER) remains challenging. Previous studies have demonstrated that Ni2P nanostructures are efficient HER catalysts. In this study, we systematically investigated the synthesis of highly monodisperse, small-sized Ni2P nanoparticles with sizes ranging from 2 nm to 10 nm. Similar nanostructures were used to systematically analyze and compare catalytic activities for the HER. The resulting small-sized product possesses a high accessible surface area and a high density of exposed (001) facets. These favorable structural features render the Ni2P nanoparticles as highly active catalysts for the HER in acidic solutions. Experimental results show that 5.4 nm sample exhibits the optimal HER performance, with an HER overpotential of approximately 78 mV under an electrocatalytic current density of 10 mA cm(-2) and a Tafel slope of 41.4 mV per decade. These products also show enhanced stability after a series of 500 potential cycles and constant current density during the test.