The continuously growing concentration of atmospheric carbon dioxide (CO2) is a major driving force of R&D activities, aiming towards efficient mitigation strategies. Among several different possibilities, solar fuel generation is an attractive remediation avenue, as it may reduce the quantity of CO2, in conjunction with the production of useful fuels or other chemicals. For the direct photoelectrochemical (PEC) reduction of CO2, p-type semiconductor photoelectrodes (cathodes) are required. Oxide semiconductors are promising candidates in this manner, because of their low preparation cost and relatively high stability compared to their elemental and chalcogenide counterparts. At the same time, novel synthesis methods are required allowing for the rational design of new materials, in terms of optoelectronic and morphological properties. Solution combustion synthesis (SCS) is considered a green and sustainable alternative to the widely employed energy- and/or time-consuming synthesis methods, and I will show two examples how it can be utilized to obtain nanostructured photoelectrodes. Copper-based delafossites (CuMO2, where M: Cr, Al, Fe, Rh, etc.) are attractive photocathode materials, because their conduction band position lies at a sufficiently negative potential, with respect to the thermodynamic potential of both carbon dioxide reduction. In the first part of my talk, I will present the synthesis of phase pure CuCrO2 by SCS, via optimizing the reaction conditions. For the first time, PEC CO2 reduction was studied on CuCrO2 photocathodes and the formation of CO, CH4, and H2 was confirmed. Structure-property relationships were studied and an impressive PEC performance was found when CuCrO2 had an interconnected nanostructure. In the second part of my talk I will demonstrate that careful modification of the SCS protocol (by adding foreign ions of Fe(III) and Mn(II) into the precursor solution) can result in bandgap narrowing of Bi2Ti2O7. Further, the phase composition of these materials and the amount of the foreign metal ions incorporated in the parent structure, could be effectively controlled. Finally, insights on the photoelectrochemical performance of these new materials are presented, taking into account all the governing parameters (e.g., surface area, light absorption, crystallinity, etc.).

Ternary oxide semiconductor nanostructures for photoelectrochemistry and photocatalysis

254th National Meeting (2017)

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