Heteroatom Doping of Molybdenum Carbide Boosts pH-Universal Hydrogen Evolution Reaction

Tuning electronic structures through heteroatom doping to weaken the Mo-H binding strength and constructing larger specific surface areas are considered an effective strategy to improve the hydrogen evolution reaction (HER) activity on beta-Mo2C in full pH range. In this report, a CH4 (10%)/H-2 inducing universal method for the formation of heteroatom-doped (F, N, S, or B) beta-Mo2C nanoparticles (NPs) with nanosized and clean surface supported on reduced graphene oxide (rGO) (Mo2ExC1-x/rGO, E = F, N, S, or B) is proposed. Doping with different heteroatoms introduced different promoting effects on Mo2C toward HER in the full pH range. The Mo2ExC1-x/rGO electrocatalysts show the best activity for HER in acidic, alkaline, and neutral media, with the onset overpotentials of 37, 45, and 105 mV, respectively, which achieve 10 mA cm(-2) at overpotentials of only 95 mV in 1 M HClO4. More noteworthy is the fact that the Mo2ExC1-x/rGO electrocatalysts only require 232 and 397 mV of overpotentials to reach 400 mA cm -2 in acidic and alkaline solutions, respectively. Besides, the Mo2ExC1-x/rGO electrocatalysts only need 480 mV of overpotential to reach 200 mA cm(-2 )in neutral conditions. Meanwhile, larger specific surface areas with nanosized and clean surfaces also contribute to improving the performance of HER, especially Mo2ExC1-x/rGO. However, the promoting effect of HER by tuning the electronic structures through doping of B and S into Mo2C is very limited. Moreover, doped Mo2C-based electrocatalysts in this work show superior stabilities for HER in the full pH range.