Investigation of the Photocatalytic Activity of Copper-Modified Commercial Titania (P25) in the Process of Carbon Dioxide Photoreduction

The photocatalytic reduction of CO2 to useful products is an area of active research because it shows a potential to be an efficient tool for mitigating climate change. This work investigated the modification of titania with copper(II) nitrate and its impact on improving the CO2 reduction efficiency in a gas-phase batch photoreactor under UV–Vis irradiation. The investigated photocatalysts were prepared by treating P25-copper(II) nitrate suspensions (with various Cu2+ concentrations), alkalized with ammonia water, in a microwave-assisted solvothermal reactor. The titania-based photocatalysts were characterized by SEM, EDS, ICP-OES, XRD and UV-Vis/DR methods. Textural properties were measured by the low-temperature nitrogen adsorption/desorption studies at 77 K. P25 photocatalysts modified with copper(II) nitrate used in the process of carbon dioxide reduction allowed for a higher efficiency both for the photocatalytic reduction of CO2 to CH4 and for the photocatalytic water decomposition to hydrogen as compared to a reference. Similarly, modified samples showed significantly higher selectivity towards methane in the CO2 conversion process than the unmodified sample (a change from 30% for a reference sample to 82% for the P25-R-Cu-0.1 sample after the 6 h process). It was found that smaller loadings of Cu are more beneficial for increasing the photocatalytic activity of a sample.