Thermally Regulated Photocarrier Dynamics Govern the Evolution of Key Intermediates in Photothermal Dry Reforming of Methane

Abstract Photothermal catalysis offers a promising pathway for the conversion of CH4 and CO2 into value-added chemicals at relatively lower temperatures than conventional thermocatalysis, and understanding the synergy between photogenerated charge carriers and thermal energy is essential for the precise manipulation and rational design of this reaction. Ni/ZnO serves as a model catalyst for investigating the photothermal synergistic mechanism in dry reforming of methane (DRM). Femtosecond transient absorption spectroscopy (TAS) reveals that Ni loading introduces interfacial defect states that accelerate the trapping of photogenerated holes and electrons from the ZnO band-edge states, thereby redistributing the carrier-relaxation pathways. Temperature-dependent TAS further shows that thermal fields promote the transfer of photogenerated electrons to Ni nanoparticles by enabling the thermal detrapping of defect-trapped electrons and accelerating interfacial electron injection at elevated temperatures. In situ TAS under reactive atmospheres shows that CH4 and CO2 introduce additional photocarrier-depletion channels during DRM, with an apparent carrier-consumption efficiency of approximately 61%. Corroborated by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), these results suggest that enhanced photocarrier utilization promotes the formation and transformation of key intermediates (CHxO* and HCOO*) under photothermal conditions. This more efficient utilization of photogenerated carriers is associated with markedly reduced apparent activation barriers for DRM, lowering the activation energies for CO and H2 formation by 29.4 and 27.1%, respectively. This study reveals how thermal fields modulate photogenerated charge dynamics, provides essential insights into photothermal synergistic effects, and guides the design and optimization of more efficient photothermal catalytic systems.