A Self-Sufficient Photocatalytic CO2 Reduction over Ionic Liquid-Modified Three-Dimensional-Printed Pt Single-Atom TiO2 Nanosheets

Abstract The photocatalytic carbon dioxide reduction reaction (CO2RR) offers a promising route to convert waste CO2 into valuable synthetic fuels and chemicals using solar energy. However, practical application is hindered by insufficient charge separation, weak CO2 activation, and poor catalyst recoverability. Herein, we systematically synthesized a self-sufficient photocatalyst comprising ionic liquid (IL)-modified Pt single atoms on TiO2 nanosheets, fabricated in both powder (IL-Pt/TiO2) and 3D-printed monolithic (3D-IL-Pt/TiO2) forms. In the photocatalytic CO2RR, the 3D-IL-Pt/TiO2 exhibits a significantly enhanced CO evolution rate of 2051.46 μmol g–1 h–1, significantly higher than that of the powder sample (1598.79 μmol g–1 h–1) and far exceeding the sum of the individual constituents without additional cocatalysts. The spectroscopic analysis reveals that while the IL alone does not perturb the TiO2 lattice, its combination with atomically dispersed Pt induces a strong interfacial electronic redistribution. This synergistic interaction of IL and Pt atoms stabilizes surface Ti3+ species and electron-rich Pt sites and modifies the surface oxygen environment without degrading the bulk structure of TiO2. Notably, the system functions most effectively without external photosensitizers, which otherwise compete for light absorption and promote charge recombination. Long-term stability tests reveal that the 3D-printed monolith retained stable performance over extended cycling, whereas the powder material gradually deactivated. These findings demonstrate that optimized interfacial electronic regulation, rather than extreme band-edge position, governs photocatalytic efficiency, offering a strategy for scalable solar-driven CO2 conversion.