Low-Coordination Rhodium Catalysts for an Efficient Electrochemical Nitrate Reduction to Ammonia

Ammonia is an essential bulk chemical and the main component of fertilizers. In addition, the use of ammonia (NH₃) as an energy carrier and hydrogen storage material has continuously surged. Electrochemical nitrate reduction is a low-carbon, environment-friendly, and efficient method of ammonia synthesis, which has attracted extensive attention in recent years; however, the overpotential needed to produce NH₃ with most catalysts is still too large. In this work, we rationally designed rhodium nanoflowers (Rh NFs) composed of ultrathin nanosheets and explored their performance for the electrocatalytic nitrate reduction to ammonia (NITRR). With a high faradic efficiency of 95% at 0.2 V vs reversible hydrogen electrode (RHE) for ammonia production, the overpotential required for the NH₃ formation on an Rh NF catalyst is much lower than on most previously reported catalysts. X-ray absorption spectroscopy (XAS) analysis shows that there are low-coordination atoms in the Rh NF catalyst, which can promote the adsorption of NO₃^– ions and stabilize intermediates as revealed by the density functional theory (DFT) calculation, resulting in efficient NITRR performance.