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High-Rate Solar-light Photoconversion of CO2 to Fuel: Controllable Transformation from C1 to C2 Products

Abstract

The production of solar fuels offers a viable pathway for reducing atmospheric CO2 concentrations and the storage and transport of solar energy. While photoconversion of CO2 into C1 hydrocarbon products, notably methane CH4, is known, the ability to directly achieve significant quantities of higher-order hydrocarbons represents an important step towards practical implementation of solar fuel technologies. We describe an efficient, stable, and readily synthesized CO2-reduction photocatalyst, Pt-sensitized graphene-wrapped defect-induced blue-colored titania, that produces a record high combined photocatalytic yield of ethane C2H6, and methane CH4. For the first time, a systematic ultraviolet photoelectron spectroscopy study on the mechanism underlying ethane formation indicates the process dependent upon upward band bending at the reduced blue-titania/graphene interface. Furthermore, transient absorption spectroscopy indicates photogenerated holes move into the graphene while electrons accumulate on the Ti3+ sites, a phenomenon contradicting prior assumptions that graphene acts as an electron extractor. We find that both mechanisms serve to enhance multielectron transfer processes that generate CH3. Utilizing a continuous flow-through (CO2, H2O) photoreactor, over the course of multiple 7 h runs an approximate total of 77 μmolg-1 C2H6 and 259 μmolg-1 CH4 are obtained under one sun AM 1.5G illumination. The photocatalyst exhibits an apparent quantum yield of 7.9%; 5.2% CH4 and 2.7% C2H6, and stable photocatalytic performance over the test duration of 42 h. The carbon source for both the products is verified using 13CO2 isotopic experiments.

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Publication details

The article was received on 04 Apr 2018, accepted on 04 Jul 2018 and first published on 09 Jul 2018


Article type: Paper
DOI: 10.1039/C8EE00983J
Citation: Energy Environ. Sci., 2018, Accepted Manuscript
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    High-Rate Solar-light Photoconversion of CO2 to Fuel: Controllable Transformation from C1 to C2 Products

    S. Sorcar, J. Thompson, Y. J. Hwang, Y. H. Park, T. Majima, C. Grimes, J. Durrant and S. In, Energy Environ. Sci., 2018, Accepted Manuscript , DOI: 10.1039/C8EE00983J

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