Au is known to be catalytically active for CO2 reduction. The catalytic activity of Au is highly size-dependent as confirmed by numerous previous studies. In particular, ultrasmall Au nanocatalysts (&lt; 2 nm), referred to Au nanoclusters with a few to hundreds of atoms, have received substantial attention recently, since they hold a high surface-to-volume ratio and a large proportion of surface (edge and corner particularly) atoms. However, all current synthetic approaches of ultrasmall Au nanocatalysts require excess surface ligands to prevent the overgrowth and stabilize the nanoclusters, due to the high surface energy. We show a robust and universal “soft” nitriding method to in situ grow ligand-free ultrasmall Au nanocatalysts onto carbon supports. Through a low-temperature urea-annealing pretreatment (300 oC), “soft” nitriding that enriches the nitrogen-containing species on the surface of carbon supports, can enhance the affinity of Au precursors and/or its nanocatalysts to carbon supports. Sub 2 nm, ligand-free Au can grow in situ on 7 different types of nitrided carbons in the absence of any organic capping agents via chemical reduction or thermolysis. Ligand-free Au supported on nitrided carbon is found to be electrocatalytically very active for CO2 reduction, compared to their counterparts with surface capping agents and/or larger nanocrystals. We demonstrate, the activity and selectivity of supported Au nanocatalysts are highly dependent on the surface N sites that act as Lewis base to tune the binding affinity of CO2 to Au.

Ultrasmall Au nanocatalysts supported on nitrided carbon supports for CO2 electrochemical reduction

254th National Meeting (2017)

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