Electrocatalytic Reduction of Nitrogen to Ammonia Using Tiara-like Phenylethanethiolated Nickel Cluster

The fixing of N-2 to NH3 is challenging due to the inertness of the N equivalent to N bond. Commercially, ammonia production depends on the energy-consuming Haber-Bosch (H-B) process, which emits CO2 while using fossil fuels as the sources of hydrogen and energy. An alternative method for NH3 production is the electrochemical nitrogen reduction reaction (NRR) process as it is powered by renewable energy sources. Here, we report a tiara-like nickel-thiolate cluster, [Ni-6(PET)(12)] (where, PET=2-phenylethanethiol)] as an efficient electro-catalyst for the electrochemical NRR at ambient conditions. Ammonia (NH3: 16.2 +/- 0.8 mu g h(-1) cm(-2)) was the only nitrogenous product over the potential of -2.3 V vs. F-c(+)/F-c with a Faradaic efficiency of 25%+/- 1.7. Based on theoretical calculations, NRR by [Ni-6(PET)(12)] proceeds through both the distal and alternating pathways with an onset potential of -1.84 V vs. RHE (i.e., -2.46 V vs. F-c(+)/F-c) which corroborates with the experimental findings.