Reduction of Aqueous CO₂ to 1-Propanol at MoS₂ Electrodes

Reduction of carbon dioxide in aqueous electrolytes at single-crystal MoS 2 or thin-film MoS 2 electrodes yields 1-propanol as the major CO 2 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 CO 2 to 1-propanol were ∼3.5% for MoS 2 single crystals and ∼1% for thin films with low edge-site densities. Reduction of CO 2 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 13 CO 2 showed the production of 13 C-labeled 1-propanol. In all cases, the vast majority of the Faradaic current resulted in hydrogen evolution via water reduction. H 2 S was detected qualitatively when single-crystal MoS 2 electrodes were used, indicating that some desulfidization of single crystals occurred under these conditions.