Metal-Sulfur Linkages Achieved by Organic Tethering of Ruthenium Nanocrystals for Enhanced Electrochemical Nitrogen Reduction.

Inspired by the metal-sulfur (M-S) linkages in the nitrogenase enzyme, here we show a surface modification strategy to modulate the electronic structure and improve the N2 availability on a catalytic surface, which suppresses the hydrogen evolution reaction (HER) and improves the rate of NH3 production. Ruthenium nanocrystals anchored on reduced graphene oxide (Ru/rGO) are modified with different aliphatic thiols to achieve M-S linkages. A high faradaic efficiency (11 %) with an improved NH3 yield (50 μg h-1  mg-1 ) is achieved at -0.1 V vs. RHE in acidic conditions by using dodecanethiol. DFT calculations reveal intermediate N2 adsorption and desorption of the product is achieved by electronic structure modification along with the suppression of the HER by surface modification. The modified catalyst shows excellent stability and recyclability for NH3 production, as confirmed by rigorous control experiments including 15 N isotope labeling experiments.