Carbon dioxide (CO2) from the atmosphere is a potentially sustainable source of carbon for the production of renewable fuels. The photocatalytic conversion of CO2 and water to hydrocarbons is a particularly attractive route, as it uses solar energy as the source of reducing electrons to drive this conversion process. However, the photocatalytic reduction of CO2 is an extremely challenging task due to the stable thermodynamic properties of CO2. The low yield of CO2 conversion calls for more efficient photocatalysts, but the development of efficient photocatalysts requires understanding of CO2?catalyst interactions and electron transfer pathways deduced from computational studies at the molecular level. The overall objective of the proposed research is to use solar radiation to photocatalytically reduce CO2 to fuels (CO, methane, methanol, and other hydrocarbons) at high conversion efficiency through manipulation of catalyst composition and nanostructure. Toward this end, the proposed research has three objectives. The first objective is to fabricate nanostructured photocatalysts, specifically brookite-containing mixed-phase TiO2 nanoparticles with controlled phase contents such as lattice-doped iodine and surface Cu clusters, to achieve visible light responsiveness and facilitate charge separation. The second objective is to develop a fundamental understanding of the catalyst properties and charge separation mechanism at the mixed-phase (e.g., anatase-brookite) nanocrystalline interfaces through closely coupled experiments and computational chemistry (density functional theory) modeling. The third objective is to optimize catalyst composition and nanostructure (e.g., TiO2 phase composition, crystal size, surface structures, dopant concentration, etc.) to synergistically improve CO2 photoreduction efficiency. In this regard, the proposed research will integrate experimental and computational approaches to evaluate brookite-based catalyst activity toward CO2 photoreduction, and will advance fundamental understanding in the multidisciplinary areas of material science, surface chemistry, photocatalysis, and nanotechnology.
Broader Impacts
Processes for photoreduction of CO2 and water to hydrocarbon fuels tackle the simultaneous challenges of greenhouse gas management and renewable fuels production. The educational and outreach activities will be in the context of the proposed research. Topics related to CO2 reduction and solar fuels will be incorporated into solar engineering, chemical reactor design, and air quality engineering courses at Arizona State University (ASU) and the University of Wisconsin-Milwaukee (UWM). Outreach activities at ASU sponsored though the Ira A. Fulton Schools of Engineering (IAFSE) will provide hands-on experiences in solar fuels to students from underrepresented groups as well as local teachers. An animated educational module on CO2 conversion by sunlight will also be created to engage students and the general public. This module will be posted on the websites of the principal investigators as well as on the ASU IAFSE outreach website. Complimentary outreach activities at UWM will be coordinated through the Urban Ecology Center (UEC) in Milwaukee, Wisconsin, who has partnerships with forty-four inner-city elementary and high schools and provides ?outdoor classrooms? in science education for urban youth.
