Synthesis of Molybdenum–Tungsten Bimetallic Carbide Hollow Spheres as pH‐Universal Electrocatalysts for Efficient Hydrogen Evolution Reaction

Abstract Development of highly efficient non‐noble metal electrocatalysts to replace platinum for hydrogen evolution reaction (HER) has attracted tremendous attention in recent years. In this work, a kind of novel Mo x W 2− x C@C hollow spheres with tunable stoichiometry is successfully synthesized. The synergetic effect of appropriate W‐introducing and hollow structure enables the composites to have superior performance for electrocatalytic HER and long‐term stability in a wide pH range. The Mo x W 2− x C@C with an optimized Mo/W ratio of 1.26/0.74 exhibits an overpotential (η 10 ) of 106, 127, and 152 mV at 10 mA cm −2 in 1 m KOH, 0.5 m H 2 SO 4 , and 1 m phosphate buffer saline (PBS), respectively, and its overpotential in high current density region (η 300 ) is only 237 and 250 mV in alkaline and acidic electrolytes, which are significantly better than most of the previously reported electrocatalysts.