Ultrasmall tungsten phosphide nanoparticles embedded in nitrogen-doped carbon as a highly active and stable hydrogen-evolution electrocatalyst

Rational design and synthesis of highly efficient and stable non-noble metal electrocatalysts are critical for the hydrogen evolution reaction (HER) associated with some renewable energy conversion systems. Herein, we report a one-step facile synthesis of ultrasmall tungsten phosphide nanoparticles (WP NPs) embedded within a nitrogen-doped carbon (NC) matrix (WP NPs@NC). The optimized catalyst, consisting of WP NPs of less than 5 nm diameter encapsulated by ultrathin carbon shells, shows excellent HER activity in strongly acidic media with a low onset overpotential (40 mV), high current density (j = 10 mA cm^-2 at η = 102 mV), small Tafel slope (58 mV dec^-1), and superior durability (4 days). The as-prepared WP NPs@NC catalyst also offers excellent HER activity in both neutral and alkaline conditions, as well as remarkable durability. This synthesis strategy opens up a new avenue for obtaining transition metal phosphide nanoparticles as a new class of non-noble-metal electrocatalysts for water splitting and hydrogen generation.