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.