Boosted Photoelectrochemical N₂ Reduction over Mo₂C In Situ Coated with Graphitized Carbon

Photoelectrochemical N₂ reduction reaction (PEC NRR) is a promising method to solve the problems of environmental protection and energy sustainability. However, the strong chemical stability of the N≡N bond and competitive hydrogen evolution reaction (HER) cause the nonideal efficiency of N₂ → NH₃ conversion in actual operation. For the first time, a Mo₂C/C heterostructure was fabricated as a PEC cathode for N₂ reduction under environmental conditions. The Mo₂C/C heterostructure could effectively decrease the coverage of hydrogen spillover and inhibit the competitive HER, resulting in a desirable selectivity for N₂ activation. Meanwhile, the decoration of the C shell further promoted the stability and conductivity of Mo₂C. Mo sites of Mo₂C were considered as activation centers, which played a dominant role in the final PEC performance. An optimal NH₃ yield rate of up to 6.6 μg h^-1 mg^-1 was achieved with the Mo₂C/C heterostructure, which was almost 3 times that with pristine C. The faradic efficiency (FE) of the Mo₂C/C heterostructure was 37.2% at 0.2 V (vs Ag/AgCl). This work not only provides an insight into the interplay between the Mo₂C/C heterostructure and N₂ activation, but also reveals its great potential in NH₃ synthesis by a green route.