TiO₂-Phase-Mediated Size Effect of Rh Nanoparticles on Photothermal Catalytic CO₂ Hydrogenation

Photothermal catalytic CO₂ hydrogenation on TiO₂-based catalysts has drawn extensive attention. However, few reports have focused on the impact of particle size of the active sites by altering TiO₂ crystal phase on the CO₂ hydrogenation activity. Herein, we successfully regulated Rh nanoparticle size by adjusting the crystal phases of TiO₂ at different calcination temperatures and obtained impressive photothermal catalytic CO₂ hydrogenation performance. Notably, the anatase-phase TiO₂ loaded with Rh nanoparticles achieved a CH₄ production rate of 2.7 mmol h^-1 with nearly 100 % selectivity and a single-pass CO₂ conversion rate of 69.4 %. Given the anatase-phase TiO₂ is more favorable for the presence of surface hydroxyl groups and oxygen vacancies, which can facilitate the distribution of Rh cations, Rh nanoparticles on the anatase-phase TiO₂ exhibited the smallest sizes. Small Rh particle size further enhanced CO₂ adsorption and activation, leading to high photothermal CO₂ hydrogenation performance. Furthermore, the optimized Rh nanoparticle-loaded anatase-phase TiO₂ catalyst exhibited high structural stability and resistance to coke accumulation, maintaining stability during long-term performance tests. This work investigated the particle size effect of active sites adjusted by crystal phase of light-harvesting materials on the photothermal catalytic performance, providing guidance for the preparation of effective catalysts for CO₂ hydrogenation to CH₄.