Effect of the Nature of the Metal Co-Catalyst on CO 2 Photoreduction Using Fast-Grown Periodically Modulated Titanium Di
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Effect of the Nature of the Metal Co-Catalyst on CO2 Photoreduction Using Fast-Grown Periodically Modulated Titanium Dioxide Nanotube Arrays (PMTiNTs) Babak Amirsolaimani1, Xiaojiang Zhang1,2, Fei Han,2 Samira Farsinezhad1, Arash Mohammadpour1, Greg Dechaine2 and Karthik Shankar1,3 1
Department of Electrical & Computer Engineering, University of Alberta, 9107 - 116 St, Edmonton, AB T6G 2V4. 2
Department of Chemical & Materials Engineering, University of Alberta, 9107 - 116 St, Edmonton, AB T6G 2V4. 3
National Institute for Nanotechnology, National Research Council, 11421 Saskatchewan Drive, Edmonton, AB, T6G 2M9, Canada. ABSTRACT Anodically formed TiO2 nanotube arrays composed of the anatase phase with periodically modulated diameters (PMTiNTs) are excellent photocatalysts for the sunlight-driven transformation of carbon dioxide into hydrocarbons. Exploiting the full potential of this nanoarchitecture for CO2 photoreduction requires integration with metal nanoparticles that function as catalytic promoters for multistep electron transfer reactions. We studied the effect of different metallic and bimetallic nanoparticles on the rate of generation of light hydrocarbons by the photoreduction of CO2. All the metal nanoparticles were loaded on to the TiO2nanotubes using the technique of photodeposition, which standardized the coating process and enabled examination purely of the effect of different metals. Photodeposition was used not only due to its simplicity but also because it enabled us to engineer very fine coatings possessing excellent uniformity and depth penetration into the nanotubes. The best performing co-catalysts were found to be CuPt (atomic ratio of 0.33:0.67), Pt and NiPt (1:2), which when loaded onto the PMTiNTs yielded total hydrocarbon generation rates of 3.5, 0.85 and 0.8 mL g-1 hr-1 respectively. The time required to form PMTiNTs was reduced by a factor of 160 by using a recently reported recipe based on fluoride ion bearing electrolyte containing lactic acid. PMTiNTs formed using the ultrafast growth lactic acid-based electrolytes exhibited similar photocatalytic properties to samples obtained more slowly using conventional ethylene glycolbased electrolytes. 1.0 INTRODUCTION The photochemical conversion of CO2 into hydrocarbon fuels is an approach that offers multiple advantages for sustainable economic growth. TiO2-based nanomaterial photocatalysts are typically less energy intensive to produce and amenable to solution-based processing for large areas. Photocatalysis makes use of abundant sunlight, a renewable energy resource and is potentially capable of the direct and selective reduction of CO2 in air. The collection and storage of hydrocarbon fuels, which are the products of the CO2 photoreduction reaction is simpler than the storage of transient electrical energy generated by photovoltaic panels. By considering CO2 as a feedstock (to generate useful chemicals) instead of a waste product, a transformative change in the management of emissions of CO2 (the primary greenhouse gas), is envisaged.
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