Remarkable CO2 photoreduction activity using TiO2 nanotube arrays under favorable photothermal conditions driven by concentrated solar light

The photoreduction of carbon dioxide (CO2) to solar fuels is meaningful in many fields relevant to CO2 emission control, solar energy conversion and storage, carbon-neutral fuel production, CO2 conversion, and carbon cycle closure. The CO2 photoreduction on TiO2 nanotube arrays using concentrated sunlight under favorable photothermal conditions is considered in this work. TiO2 is a typical catalyst for the process while the reaction rate is still kept at rather poor level, partly because of the mild reaction conditions employed. In this study, the TiO2 photocatalyst was shaped as nanotube arrays and the current process limitations were tackled by raising the incident light intensity and reaction temperature by using concentrating solar light (concentration ratio between 200 and 800), while jointly increasing the achievable H2O and CO2 partial pressure. The results showed that the rate of CO2 photoreduction on the TiO2 nanotube array was increased by hundred times. The use of concentrated solar light heightens the hydrocarbons production rate to thousand μmol g−1 h−1 and enriches hydrocarbons products to CH4, C2H4, and C2H6. The favorable effects on enhancing the catalyst performance were ascribed to the intensification of reaction conditions. This noticeable breakthrough may represent an important step forward in the deployment of CO2 photoreduction technologies.