S-Doped three-dimensional graphene (S-3DG): a metal-free electrocatalyst for the electrochemical synthesis of ammonia under ambient conditions

3D-graphene provide abundant space for N₂, and the carbon–sulfur bonds provides a continuous supply of electrons for N₂ reduction. A remarkably large NH₃ yield of 38.81 μg_NH3 mg_cat⁻¹ h⁻¹ and FE of 7.72% for N₂ reduction was obtained.