Two- and three-dimensional metal chalcogenides are an emerging class of materials that display interesting mechanical, optical, and catalytic properties. Binary and ternary sulfides often display facile tunability to active site ensembles that are critical to chemical catalysis, although various reports have shown poor thermodynamic stability under certain electrochemical reaction conditions. For promising, albeit underexplored sulfide catalyst materials, using traditional methods of thermodynamic analysis in tandem with structural and electrochemical analysis will facilitate the development of transformative structure-function correlations related to energy conversion and storage. Presented herein is a collaborative investigation of a promising Chevrel-phase metal sulfide catalyst that is capable of electrochemically converting CO2 to liquid and gas fuels such as methanol and hydrogen. When promoted by copper, extended structures of Chevrel-phase Mo6S8 clusters are capable of reducing CO2 and CO to methanol in aqueous electrolyte with an overpotential of -0.4 V vs RHE. H2 gas is simultaneously evolved during this process, contributing to total current densities as high as 35 mA/cm2. Methanol and formate are the only CO2 reduction products formed from electrolysis, although utilizing CO as a feedstock has been shown to mitigate parasitic current density toward formate production. Also discussed here is the formulation of an interesting electronic structure-function correlation founded on the basis of X-ray absorption spectroscopic analyses and corroborated by results of electroanalytical evaluation as well as theoretical calculation. Lastly, via high temperature oxide melt calorimetry and zero-coverage gas adsorption isotherms, we examine the thermodynamic properties of these frameworks when promoted by various transition metals and monitor gas adsorption thermodynamics as it relates to electron donor behavior of metal promoters.

Probing ensemble effects on the selective conversion of CO2 and CO to methanol over metal-promoted Chevrel-phase sulfides

2019 Spring National Meeting

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