High-Performance Electrocatalysis for Hydrogen Evolution Reaction Using Se-Doped Pyrite-Phase Nickel Diphosphide Nanostructures

The study of efficient, robust, and earth-abundant electrocatalysts for the hydrogen evolution reaction (HER) is essential for hydrogen-based energy technologies. Previous works have demonstrated that pyrite-structure materials (e.g., CoS2, NiSe2) are efficient HER catalysts. Here, we first systematically investigate the nanostructure synthesis of a series of pyrite-phase nickel phosphoselenide materials-NiP2, Se-doped NiP2 (NiP1.93Se0.07), P-doped NiSe2 (NiP0.09Se1.91), and NiSe2-through a facile thermal conversion of Ni(OH)(2) nanoflakes. The similar nanostructures enable a systematic and fair comparison of their structural properties and catalytic activities for HER We found that NiP1.93Se0.07 shows the best HER performance, followed by NiP2, NiP0.09Se1.91, and NiSe2. Se-doped NiP2 grown on carbon fiber paper can achieve an electrocatalytic current density of 10 mA cm(-2) at an overpotential as low as 84 mV and a small Tafel slope of 41 mV decade(-1). This study not only estabilishes Se-doped NiP2 as a competitive HER catalyst, but also demonstrates that doping or alloying of developed catalysts (especially doping with anions from another group; e.g., selenium to phosphorus) can improve the HER catalytic activity, which provides a general strategy to improve catalytic efficiencies of existing electrocatalysts for HER.