Lattice Oxygen-Mediated CO2 Photothermal Reduction with Tunable CO/H2 Ratio on K-Doped Nb2O5 Nanoribbons

Abstract

Thermocatalytic or photocatalytic CO₂ reduction to CO─without H₂ or sacrificial hole scavengers─remains challenging due to prohibitively high energy barriers or the lack of coupled oxidation half-reactions. Photothermal catalysis enables autonomous CO₂ dissociation via synergistic photon-thermal activation under mild conditions. However, it remains a grand challenge to design high-performance catalysts that achieve rapid lattice oxygen dynamic equilibrium by harmonizing photogenerated carriers with thermal lattice vibrations. Here, we report K-doped Nb₂O₅ nanoribbons (K–Nb₂O₅ NRs) that synergistically integrate photothermal energy and lattice oxygen redox cycling to effect direct CO₂ decomposition under mild photothermal conditions (50–250 °C). The K–Nb₂O₅ NRs achieve CO production rates of 4.1–405 μmol·g^–1·h^–1 with 100% selectivity, outperforming undoped Nb₂O₅ by 6.3-fold at 250 °C. Mechanistic studies reveal that K doping optimizes the electronic structure of Nb₂O₅, accelerating oxygen vacancy regeneration and enhancing CO₂ adsorption. At the same time, the photothermal effect decouples lattice oxygen oxidation (photogenerated holes) and CO₂ reduction (photogenerated electrons), thereby suppressing electron–hole recombination. By introducing H₂O as a dynamic oxygen chemical potential modulator, the H₂/CO ratio is continuously tuned from 1.4 to 0.3 through competitive adsorption at oxygen vacancy sites. Remarkably, the catalyst maintains syngas production for 50 h in a flow reactor. This study provides new ideas for the design of catalysts for photothermal CO₂ conversion.