Non-Thermal Contribution to Ruthenium Photothermal Catalyst in Carbon Dioxide Methanation

Global economic growth has been accompanied by an increase in energy consumption and the release of CO2 into the atmosphere. Photothermal catalysis offers a promising strategy for sustainable chemical transformations by combining thermal and photonic energy to accelerate reactions under mild conditions to convert greenhouses into energy sources. However, quantifying non-thermal contributions, particularly those arising from hot electrons, remains a major challenge due to limitations in temperature measurement and mechanistic ambiguity. This dissertation addresses these challenges through the development of a non-contact near-infrared (NIR) optical thermometer capable of accurately measuring catalyst surface temperature independent of emissivity. By fitting the continuous NIR emission spectrum (950–1600 nm), this technique achieves ±1 °C accuracy above 200 °C, enabling reliable distinction between thermal and non-thermal effects. Using Ru–SiO2 as a model system for CO₂ methanation, we demonstrate over 100-fold enhancement in CH4 production in blue light compared to green light. The reaction rate scales nearly linearly with light intensity and exhibits a sharp spectral cutoff near 500 nm, disappearing at longer wavelengths. This wavelength dependence suggests a non-thermal mechanism beyond simple heating. By integrating precise temperature monitoring, studying dependence on photon energy and intensities with and without external heating, this work establishes a mechanistic framework for validating non-thermal contributions in photothermal catalysis. The approach is generalizable to other catalytic systems and offers design principles for next-generation catalysts that leverage light–matter interactions to enhance selectivity, reduce activation barriers, and enable sustainable chemical transformations.

Name thesis:degree_name

Doctor of Philosophy

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Houston

Year dc:date.issued

2025

Author dc:creator

• Chirom, Meiraba Meitei 1997-

Advisors dc:contributor.advisor

• Baldelli, Steven
• Bao, Jiming

Committee members dc:contributor.committeemember

• Brgoch, Jakoah
• Jacobson, Allan J.
• Dreyer, Daniel

• Plasmonics
• CO2 methanation
• Non contact thermometry
• Photothermal catalysis
• Non-thermal contribution
• Reaction mechanism
• Ruthenium catalyst

Language dc:language.iso

English

Handle dc:identifier.uri

https://hdl.handle.net/10657/20920

OAI identifier oai:identifier

oai:uh-ir.tdl.org:10657/20920