Journal of the American Chemical Society | 26 Oct 2013
W Zhu, R Michalsky, O Metin, H Lv, S Guo, CJ Wright, X Sun, AA Peterson and S Sun
We report selective electrocatalytic reduction of carbon dioxide (CO2) to carbon monoxide (CO) on gold (Au) nanoparticles (NPs) in 0.5 M KHCO3 at 25℃. Among monodisperse 4-, 6-, 8-, and 10-nm NPs tested, the 8 nm Au NPs show the maximum Faradaic efficiency (FE) (up to 90% at -0.67 V vs. reversible hydrogen electrode, RHE). Density functional theory (DFT) calculations suggest that the presence of dominant edge sites over corner sites (active for the competitive H2 evolution reaction) on the Au NP surface facilitates the stabilization of the reduction intermediates, such as COOH*, and the formation of CO. This mechanism is further supported by the fact that Au NPs embedded in a matrix of butyl-3-methylimidazolium hexafluorophosphate for more efficient COOH* stabilization exhibit even higher reaction activity (3 A/g mass activity) and selectivity (97% FE) at -0.52 V (vs. RHE). The work demonstrates the great potentials of using monodisperse Au NPs to optimize the available reaction intermediate binding sites for efficient and selective electrocatalytic reduction of CO2 to CO.
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