We have prepared a novel mixed transition metal oxide catalyst for photo-electrochemical CO2 reduction. Electrochemical studies show that this catalyst displays selective photocurrent meaning that it is photoactive in CO2-saturated aqueous electrolyte but produces no photocurrent in argon-purged electrolyte, indicating that charge transfer from the catalyst surface to CO2 is strongly preferred over proton reduction. Reaction studies show that this photo-electrocatalyst is also highly efficient for C–C bond coupling, producing acetate from CO2 with greater than 60% Faradaic efficiency. XPS and SEM/EDAX spectroscopy provide important insights into the mechanism of selectivity and efficiency in this catalyst system. To better understand the photo-physics of this material leading to highly selective charge transfer to CO2 and subsequent C–C bond coupling, we are investigating this system using ultrafast soft x-ray transient absorption spectroscopy at the metal M edges of this mixed metal oxide system. This experiment, which utilizes a tabletop high harmonic generation soft x-ray light source with femtosecond time resolution, promises to reveal the element-specific electron dynamics leading to efficient charge separation and injection during the photo-electrocatalytic reduction of CO2 to acetate.

Understanding electron dynamics in mixed metal oxide catalysts showing high selectivity for photo-electrochemical CO2 reduction to acetate

252nd National Meeting (2016)

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