Photothermal CO₂ hydrogenation for C₁ fuels: fundamentals, reaction pathways and reactor design

Photothermal CO₂ hydrogenation has emerged as a promising strategy for converting CO₂ into value-added C₁ fuels and chemicals by coupling solar-energy harvesting with catalytic hydrogenation. Compared with conventional thermocatalysis and photocatalysis, photothermal catalysis relies on the synergistic effects of photon-to-heat conversion and photoinduced electronic processes. Localized heating accelerates CO₂ activation, H₂ dissociation, and surface hydrogenation kinetics, while photoexcited charge carriers and interfacial electronic redistribution regulate reactant activation and the evolution of reaction intermediates, thereby directing reaction pathways and product selectivity. Recent advances have demonstrated that rational catalyst design-including the engineering of active sites, oxygen vacancies, metal-support interfaces, hydrogen-transfer pathways, and Lewis acid-base pairs-can selectively steer CO₂ hydrogenation toward CO, CH₄, or CH₃OH through distinct reaction pathways. In parallel, reactor-engineering strategies, such as continuous-flow operation, solar concentration, thermal confinement, structured porous architectures, and 3D-printed reactors, further enhance photon utilization, heat management, and mass transfer, enabling efficient solar-driven catalysis. This review provides an integrated perspective on the fundamental mechanisms of photothermal CO₂ hydrogenation, highlighting photothermal synergistic effects, reaction pathways, catalyst-design principles governing selective C₁ product formation, and emerging reactor-design strategies for practical solar-fuel production. Finally, the remaining challenges and future opportunities for catalyst-reactor co-design and the scalable implementation of photothermal CO₂ hydrogenation are discussed.