Plasma-assisted nitrogen doping in Ni-Co-P hollow nanocubes for efficient hydrogen evolution electrocatalysis.

To surmount the issues of a limited specific surface area and slow electrolyte diffusion in composite electrocatalysts, three-dimensional (3D) porous hollow nanocubes are fabricated, in which bimetal Ni-Co phosphide composites are covered with nanoparticles. The abundant hollow space provides more active sites for the catalyst, and simultaneously ensures efficient mass transfer and electron transport during the hydrogen evolution reaction (HER). A plasma-assisted approach is employed for smart N-doping in the Ni-Co phosphide hollow nanocubes (N-Ni-Co-P HNCs). The N-Ni-Co-P HNC catalyst exhibits a remarkable HER performance in 1 M KOH, evidenced by the low overpotentials of 47.9 mV and 150.5 mV at the current density of 10 mA cm-2 and 50 mA cm-2, respectively, as well as the excellent long-time stability. Essentially, the N doping tailors the electronic states and optimizes the free energy of hydrogen adsorption (ΔGH*) greatly, and the 3D porous hollow structure with porous nanoparticles stacked enlarges the specific active area substantially. Their synergistic effects result in the remarkably enhanced catalytic activity for the HER.