Recent Advances in Ru‐Based Photothermal Catalysts: From Light Harvesting to Thermal Utilization and Reactor Design

ABSTRACT Ruthenium (Ru)‐based photothermal catalysts have attracted growing interest for solar‐driven CO 2 conversion, especially CO 2 methanation, reverse water gas shift (RWGS) reaction, and dry reforming of methane (DRM) reactions. Ru has been widely recognized as an active site which enables efficient H 2 dissociation, intermediate regulation, and the formation of tunable active structures. Based on the energy‐utilization sequence of light harvesting, heat generation, heat retention, and heat utilization, this review summarizes recent advances in Ru‐based photothermal systems from catalyst design to reactor implementation. It focuses on broadband light‐absorbing supports, plasmonic components, defective oxides, MXenes, carbon architectures, and spectrally selective structures that enhance solar absorption and light‐to‐heat conversion. The review discusses localized thermal fields, heat confinement, defect/interface regulation, Ru–support interactions, oxygen vacancies, bimetallic sites, lattice‐oxygen participation, and illumination‐driven reconstruction. Current evidence shows that Ru‐based photothermal performance depends on intrinsic Ru activity, coupled optical absorption, local heat management, interfacial charge redistribution, active‐site evolution, and reactor thermal boundaries. Finally, challenges and directions are outlined, including standardized evaluation, local‐temperature measurement, low‐Ru‐loading design, operando characterization, continuous‐flow reactors, and scalable solar‐to‐chemical conversion.