Phase transition engineering of nanoporous pyrite-phase NiSe2 foam by phosphorus doping for robust pH-universal hydrogen evolution

The present non-precious hydrogen-evolving electrocatalysts deliver high catalytic activity either in acidic or basic media but very few simultaneously exhibit superb catalytic efficiency and stability for hydrogen evolution reaction (HER) in a wide pH range, especially for pyrite-phase materials (e.g., CoS2, NiSe2), probably due to their high kinetic energy barriers of initial water dissociation process. Herein, we report a phase transition engineering of pyrite-phase porous NiSe2 into NiP1.86Se0.14 by heavy phosphorus doping, which performs excellently as a pH-universal electrocatalyst for HER. In this material, P atom replaces the sub-selenium atom in NiSe2 to modulate the electronic structures and spin states of Ni sites with lower d-band center, thus promoting sluggish hydrogen adsorption, water adsorption, and dissociation dynamics. As a result, this catalyst exhibits superior hydrogen-evolving catalytic activity in multiple media in terms of relatively low overpotentials of 56.8 and 79 mV at a current density of 10 mA cm(-2) in 0.5 M H2SO4 and 1.0 M KOH, respectively. Particularly, this porous NiP1.86Se0.14 shows good stability toward hydrogen evolution in both acidic and alkaline media, with little variation in potentials after continuous operation for approximately 80 and 70 h at 30 mA cm(-2). This work may provide a promising solution to address the poor catalytic HER activity and instability of transition metal selenides under alkaline conditions.