Light-accelerated Catalytic CO₂ Reduction
CO2 reduction (CO2 + H2 ↔ CO +H2O) is central to CCU technologies because it converts CO2 into CO, an important building block of syngas for producing fuels and chemicals. The main challenge is the high energy demand required to reach temperatures at which the reaction proceeds at a sufficiently high rate. In our study, we focused on the effect of visible light on accelerating Co2 reduction using a photoactive 3Cu/Ti-CeO2-x catalyst.
We prepared Ti-modified cerium oxide nanorods and deposited different copper loadings on the support. The most active catalyst contained 3 wt.% Cu, where copper is present as nanoparticles and the catalyst, under operating (partially reduced) conditions, features a high concentration of oxygen vacancies and Cu-Ov-Ce3+ interfacial sites that act as the active centers during the reaction. Upon illumination with blue light, the photon efficiency is highest and enables simultaneous photoactivation of the Cu nanoparticles and the Ti-doped semiconducting support, leading to a dramatic decrease in the apparent activation energy for CO formation from 92 to 26 kJ/mol. This is a consequence of a change in the reaction mechanism. Under white-light illumination, we achieved nearly 60-fold increase in the CO formation rate compared with the reaction in the dark, while maintaining 100% selectivity to CO. The enhanced photocatalytic activity is attributed to the destabilization and accelerated hydrogenation of the surface-adsorbed carbonates and formates, as well as faster Co desorption from the catalyst surface.
The study is supported by in-house developed in-situ and operando spectroscopic techniques and provides mechanistic insight into the photocatalytic reduction of CO2 to CO under visible-light illumination.
More information: https://onlinelibrary.wiley.com/doi/10.1002/cey2.70102
Contact: petar.djinovic(at)ki.si