Tuning d-band center of tungsten carbide via Mo doping for efficient hydrogen evolution and Zn–H₂O cell over a wide pH range

Designing highly active transition metal carbides based electrocatalysts to substitute for the state-of-the-art noble-metal materials for hydrogen evolution reaction (HER) over a wide pH range is still a crucial challenge. Herein, we reported a novel 2D hybrid electrocatalyst containing Mo-doped WC core with particle size of ~5 nm embedded into N-doped carbon shells (Mo-WC@NCS) through a carbonization treatment of Mo-doped W/Zn bimetallic-imidazolate frameworks. Benefiting from large surface area and optimized electronic structure, the achieved Mo-WC@NCS hybrid displayed a low overpotential of 179 mV at 10 mA cm⁻² with a small Tafel slope of 81 mV dec⁻¹ for HER in base, showing almost the best performance among all previously reported WC-based hybrid HER electrocatalysts. This Mo-WC@NCS hybrid also delivered robust HER catalytic activities in both acidic and neutral media. Experimental observations and theoretical calculations demonstrated that the d-band center of W in Mo-WC@NCS hybrid was obviously downshifted after Mo dopants, which was beneficial to modulate the electronic structure of the W centers and thereby facilitated the H desorption, thus boosting hydrogen generation. Acting as a cathode in alkaline-acid Zn–H₂O fuel cell, the Mo-WC@NCS hybrid delivered a power density of up to 41.4 mW cm⁻² and maintained a long-term stability for H₂ generation.