Enhancing Nitrogen Electroreduction to Ammonia by Doping Chlorine on Reduced Graphene Oxide

As one of the possible alternatives to the Haber–Bosch process, electrochemical ammonia synthesis has been attracting considerable interest in recent years. However, most electrocatalysts are confronted with the predicament of a low yield rate for ammonia production. In this study, we report the chlorine-doped reduced graphene oxide that can efficiently electroreduce nitrogen to ammonia. At an applied potential of −0.3 V (vs RHE), the chlorine-doped reduced graphene oxide attains a high NH3 yield of 70.9 μg h–1 mgcat–1 (2.84 μg h–1 cm–2) with a Faraday efficiency (FE) of 5.97%, which shows a considerable ammonia yield in terms of the metal-free carbonaceous material electrocatalysts. Experimental results indicate that the chlorine doping can be propitious to remarkably strengthen the nitrogen adsorption in the defect structure. Density functional theory calculations verify this result and further reveal that the adsorbed nitrogen is reduced through the associative distal pathway. These results come down to the appropriate electronegativity of chlorine, which can induce the electron redistribution of the adjacent carbon atoms, favoring the electroreduction of N2. Our work expands a new member for the application of nonmetallic carbonaceous materials in nitrogen electroreduction.