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 β-Mo 2 C in full pH range. In this report, a CH 4 (10%)/H 2 inducing universal method for the formation of heteroatom-doped (F, N, S, or B) β-Mo 2 C nanoparticles (NPs) with nanosized and clean surface supported on reduced graphene oxide (rGO) (Mo 2 E x C 1– x /rGO, E = F, N, S, or B) is proposed. Doping with different heteroatoms introduced different promoting effects on Mo 2 C toward HER in the full pH range. The Mo 2 F x C 1– 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 HClO 4 . More noteworthy is the fact that the Mo 2 F x C 1– 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 Mo 2 F x C 1– 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 Mo 2 F x C 1– x /rGO. However, the promoting effect of HER by tuning the electronic structures through doping of B and S into Mo 2 C is very limited. Moreover, doped Mo 2 C-based electrocatalysts in this work show superior stabilities for HER in the full pH range.