Carbon nanofiber-supported Cu nanoparticles for efficient nitrate reduction to ammonia

Since the d-orbitals of copper are beneficial for adsorption of nitrate and conversion to nitrite, porous carbon nanofiber-supported copper nanoparticles (Cu@CNFs) are proposed as an efficient electrocatalyst for nitrate reduction to ammonia, which achieves a large ammonia yield of 24.22 mg h^-1 mg_cat.^-1 and a high faradaic efficiency (FE) of 86.38% at -1.2 V vs. RHE. In situ electrochemical tests and density functional theory (DFT) calculations reveal that nitrate at the surface of Cu@CNFs firstly undergoes deoxygenation and then hydrogeneration to produce ammonia, and *NO-*N is the rate determining step with a barrier of only 0.79 eV.