270608 Atomically Precise, Ligand-Stabilized Au25(SR)25 Nanocatalysts for Highly Efficient Electrochemical CO2 Reduction
Atomically precise Au25(SR)18 nanoclusters are exciting catalyst candidates for reactions like CO2 reduction because they have an inherently anionic charge (q = -1), their surface structure is precisely known from single-crystal x-ray diffraction studies, and they bridge the size-gap between molecules and nanoparticles. One problem facing traditional electrocatalysts is the large overpotential typically required to convert CO2 into useful products like CO, CH4, CH3OH, etc. Remarkably, we found the Au25 nanocatalyst can promote the reduction of CO2 into CO within 90 mV of the formal electrochemical potential (thermodynamic limit). This represents a ~300 mV improvement over larger Au nanoparticles and bulk Au. Peak CO2 conversion occurred at -1V vs. the reversible hydrogen electrode with ~100% efficiency and rates ~7-700 times higher than larger Au catalysts and ~10-100 times higher than current state-of-the-art processes. Optical spectroscopy, non-aqueous electrochemistry and density functional theory (DFT) were used to study the Au25-CO2 interaction. Specifically, we found CO2 adsorption was based on an electrostatic interaction with the Au25 surface. Our studies indicate the low-voltage conversion of CO2 was promoted by unique reaction centers at the Au25 nanocatalyst surface.