Highly Efficient and Stable Hydrogen Production in All pH Range by Two-Dimensional Structured Metal-Doped Tungsten Semicarbides

Transition-metal-doped tungsten semicarbide nanosheets (M-doped W₂C NSs,M=Fe, Co, and Ni) have been synthesized through carburization of the mixture of tungsten trioxide, polyvinylpyrrolidone, and metal dopant. The nanosheets grow directly on theW mesh and have the lateral dimension of several hundreds of nm to a few μm with a thickness of few tens nm. It is demonstrated that theM-dopedW2C NSs exhibit superior electrocatalytic activity for hydrogen evolution reaction (HER). Impressively, the Nidoped W₂C NSs (2 at% Ni) with the optimized HER activity show extremely low onset overpotentials of 4, 9, and 19mV and modest Tafel slopes of 39, 51, and 87mV dec^-1 in acidic (pH=0), neutral (pH=7.2), and basic (pH=14) solutions, respectively, which is close to the commercial Pt/C catalyst. Density functional theory (DFT) calculations also demonstrate that the Gibbs free energy for H adsorption of Ni-W₂C is much closer to the optimal value ΔG_H∗ = -0.073 eV as compared to -0.16 eV of W₂C. Furthermore, nearly 100% Faradaic efficiency and long-term stability are obtained in those environments. This realization of highly tolerantmetal semicarbide catalyst performing on par with commercial Pt/C in all range of pH offers a key step towards industrially electrochemical water splitting.