Ni-doped amorphous iron phosphide nanoparticles on TiN nanowire arrays: An advanced alkaline hydrogen evolution electrocatalyst

Efficient and low-cost non-precious-metal-based electrocatalysts are crucial to the commercial success of the hydrogen evolution reaction (HER) under alkaline conditions. Herein, a step-by-step strategy to prepare a hierarchical structure assembled from Ni-doped amorphous FeP nanoparticles, porous TiN nanowires, and graphitic carbon fibers (Ni-FeP/TiN/CC) is described. The FeP/TiN/CC composite is plasma-implanted with Ni ions to modify the electronic structure and produce an amorphous surface. Simultaneous doping and amorphization of FeP by Ni ion implantation to enhance the HER activity is achieved for the first time. The flexible and freestanding Ni-FeP/TiN/CC catalyst produced on a carbon cloth can serve directly as an electrode in HER in an alkaline medium. The Ni-FeP/TiN/CC catalyst delivers excellent HER performance including an overpotential of 75 mV to generate a cathodic current density of 10 mA cm−2, a Tafel slope close to that of commercial Pt/C catalysts, and long lifetime indicated by a more constant cathodic current density during continuous operation for 10 h. The remarkable HER activity is attributed to the combined effects rendered by the Ni and Fe atoms in the Ni-doped FeP nanoparticles, active amorphous surface, as well as conductive nanowire scaffold, which expose a large amount of active sites, enhance the charge transfer efficiency, and prevent the catalysts from migration and aggregation.