Reduction of Aqueous CO2 to 1-Propanol at MoS2 Electrodes

Reduction of carbon dioxide in aqueous electrolytes at single-crystal MoS2 or thin-film MoS2 electrodes yields 1-propanol as the major CO2 reduction product, along with hydrogen from water reduction as the predominant reduction process. Lower levels of formate, ethylene glycol, and t-butanol were also produced. At an applied potential of -0.59 V versus a reversible hydrogen electrode, the Faradaic efficiencies for reduction of CO2 to 1-propanol were, similar to 3.5% for MoS2 single crystals and similar to 1% for thin films with low edge-site densities. Reduction of CO2 to 1-propanol is a kinetically challenging reaction that requires the overall transfer of 18 e(-) and 18 H+ in a process that involves the formation of 2 C-C bonds. NMR analyses using (CO2)-C-13 showed the production of C-13-labeled 1-propanol. In all cases, the vast majority of the Faradaic current resulted in hydrogen evolution via water reduction. H2S was detected qualitatively when single-crystal MoS2 electrodes were used, indicating that some desulfidization of single crystals occurred under these conditions.