2025 AIChE Annual Meeting

(195f) Computational Insights into Non-Thermal Effects in Photothermal CO2 Methanation on Ru Catalyst

Authors

Fahmida Akter - Presenter, University of Houston
Jiming Bao, University of Houston
Lars Grabow, University of Houston
Gas-phase photothermal reactions utilizing metallic catalysts have recently emerged as a promising strategy due to their potential for reducing activation energies and enhancing reaction selectivity, leveraging the synergistic effects of both photonic and thermal energy. The dual-energy approach of photons and heat can drive catalytic reactions; however, the interactions involved are complex, particularly in validating non-thermal contributions with precise temperature measurements, optimizing strategies to enhance non-thermal effects, and developing a comprehensive microscopic understanding.

CO2 methanation on Ru-decorated Ti nanostructures exhibits significant enhancements in CH4 production rates under 1 sun illumination, with over a 100-fold increase in reaction rate when white light serves as both the thermal and photonic source under identical operating conditions, underscoring substantial non-thermal contributions. These contributions are further corroborated by the observed wavelength-dependent reaction rate enhancements.

In this study, we employ density functional theory (DFT) to investigate the electronic characteristics driving the CO2 methanation reaction on Ru catalysts. Density of states (DOS) analysis reveals strong CO2 chemisorption on Ru surfaces, evidenced by the hybridization of metal d-states and adsorbate molecular orbitals. This strong chemisorption and the resultant metal-induced perturbation of the free CO2 molecular electronic states lead to a marked reduction in the HOMO-LUMO gap from 8.67 eV in free, gas-phase CO2. Photolysis of the C-O bond becomes feasible as incoming photons facilitate electronic excitation pathways across the Fermi level, populating anti-bonding states.

Our study elucidates the role of non-thermal effects in photon-assisted catalysis and provides mechanistic insights into how metal–adsorbate electronic interactions can be tuned to enhance photothermal processes. Our computational framework opens new avenues for designing photoactive catalysts with tailored optical and electronic properties for photothermal CO2 methanation.