Structural Evolution and Stabilization of TiO ₂ -Supported P-Doped Rh Catalysts Dominated by Metal–Support Interactions during CO ₂ Hydrogenation

Revealing the multiple interactions in heterogeneous catalysts and the potential structural evolution under the reaction conditions is crucial for the rational design of catalysts. Herein, we elucidate the complex interactions within P-doped Rh catalysts supported on rutile TiO2 (r-TiO2) and anatase TiO2 (a-TiO2) as well as their structural evolution behavior during CO2 hydrogenation. Before P-doping, Rh/r-TiO2 with Rh ensemble sites primarily catalyzes CO2 methanation, while Rh/a-TiO2 with TiOx-encapsulated Rh sites originating from strong metal–support interaction (SMSI) shows high CO selectivity. P-doping into Rh/r-TiO2 transforms Rh ensemble sites into separated Rh sites, switching the catalytic selectivity from CH4 to CO at low reaction temperatures. Interestingly, the selectivity reverses from 100% CO to 95% CH4 with increasing temperature, demonstrating a dynamic structural evolution. The metastable P-doped Rh species is reconstructed into Rh ensemble and phosphate species due to electronic metal–support interaction and O* intermediate oxidation in a weakly oxidative reaction atmosphere, while it can be regenerated in a H2 atmosphere. For the a-TiO2-supported P-doped Rh catalyst, moderate TiOx encapsulation originating from SMSI contributes to stabilizing the P-doped Rh species during CO2 hydrogenation. Our study reveals that regulating metal–support interaction within TiO2-supported P-doped Rh catalysts can modulate their structural evolution behavior during the reaction, guiding the rational design of P-doped metal catalysts on reducible supports.