The Construction of g‐C 3 N 4 Coating Layer on CoN‐MoN Fiber via Thermopolymerization Nitriding Strategy for Enhanced Electrocatalytic Alkaline HER

Abstract To achieve efficient electrocatalytic alkaline hydrogen evolution (HER), novel preparation methods for dual‐transition metal nitrides, with dense g‐C 3 N 4 /transition metal nitride interface, should be proposed. Herein, a novel g‐C 3 N 4 layer‐coated CoN‐MoN fiber electrocatalyst was prepared on Co foam (CF) via thermopolymerization nitriding strategy. During the fabrication process, CoN‐MoN fiber was prepared facilely on CF, and, meanwhile, a g‐C 3 N 4 layer was successfully coated on CoN‐MoN fiber. The synthesized electrocatalyst (g‐C 3 N 4 @CoN‐MoN/CF) exhibits a low overpotential of 138 mV at 100 mA cm −2 , a small Tafel slope (89 mV dec −1 ) during alkaline HER. The high water splitting capacity could be attributed to the special g‐C 3 N 4 coating structure on the CoN‐MoN fiber. From DFT calculation, an obvious electron transfer occurred at the g‐C 3 N 4 /CoN‐MoN interface, which not only improves the hydrolytic dissociation ability but also optimizes its Gibbs free energy of hydrogen (ΔG H* ). Compared with the ΔG H* of g‐C 3 N 4 and CoN‐MoN/CF, g‐C 3 N 4 @CoN‐MoN/CF showed a suitable ΔG H* of −2.97 eV, which is relatively close to the ideal ΔG H* (0 eV). Moreover, the H─O─H bond angle of adsorbed water on g‐C 3 N 4 @CoN‐MoN/CF increased to 105.47°, and the H─O bond was extended to 1.009 Å, which facilitates the breaking of the H─O bond, thus reducing H* to H 2 .