Atomically Precise Au25 Nanoclusters for Efficient Electrochemical CO2 Conversion

Wednesday, May 14, 2014: 15:00
Bonnet Creek Ballroom VI, Lobby Level (Hilton Orlando Bonnet Creek)
D. R. Kauffman, D. Alfonso, C. Matranga (United States Department of Energy; National Energy Technology Laboratory), R. Siva (URS), H. Qian, and R. Jin (Carnegie Mellon University; Department of Chemistry)
Two problems facing traditional electrocatalysts are large overpotentials and poor product selectivity. Atomically precise, ligand-stabilized Au25 nanoclusters are exciting catalyst candidates for reactions like CO2 reduction because they have an inherent negative charge, their crystallographic surface structure is precisely known, and they bridge the size-gap between molecules and nanoparticles. Remarkably, the Au25 nanocatalysts promoted the reduction of CO2 into CO within 100 mV of the electrochemical formal potential (thermodynamic limit). This represents an approximate 200-300 mV improvement over larger Au nanoparticles and bulk Au. Peak CO2 conversion occurred at -1 V vs. the reversible hydrogen electrode with ~100% efficiency and rates 7-700 times higher than larger Au catalysts and 5-100 times higher than current state-of-the-art processes. Optical spectroscopy, non-aqueous electrochemistry and density functional theory studied the Au25-CO2 interaction. Our data suggests CO2 adsorption facilitated through and electrostatic interaction with Au25, while the highly efficient conversion of CO2 into CO was promoted by the clusters negative charge. Ongoing efforts include electrode optimization, and long term stability testing of the Au25- nanocatalysts.  The Au25- clusters show reaction turnover frequencies of approximately 70-100 molecules/Au25/s and stable operation in excess of 24 hours at -1 V. This work was published in the Journal of the American Chemical Society 2012, 134, 10237-10243; electronic DOI: 10.1021/ja303259q.