Speciation of Ru sites in single atom alloy-based plasmonic photocatalysts for the CO2 reduction to ethanol

The utilization of captured CO2 as a feedstock for the production of chemicals and fuels is regarded as one key strategy to effectively tackle the global climate change. Ethanol is considered as a particularly attractive target because it serves as a building block for the manufacture of a multitude of chemicals and could be applied as an energy carrier in the future. Inspired by the natural photosynthetic process, photocatalytic CO2 reduction (CO2RR) constitutes a sustainable approach for ethanol production because it operates at ambient temperature and pressure using solely water and renewable solar energy as feedstocks. To this aim, we have developed single atom alloy (SAA)-based plasmonic photocatalysts consisting of single Ru-, Cu-, or Ni-atom sites, that are catalytically active, and a plasmonic Au component that provides strong light absorption and thus efficient generation of hot carriers under illumination, and used SiO2 as carrier. Experimental results demonstrate that RuAu SAA outperforms the CuAu-based material in terms of activity whilst keeping almost 100% selectivity to ethanol whereas lower performance is observed for the NiAu catalyst. XAS experiments are expected to help us elucidate the local environment and electronic structure of the Ru sites that would explain the different catalytic behaviour. In particular, we intend to establish if Ru is present as single sites or as low-nuclearity clusters, i.e., dimers, trimers, on the Au substrate.