Photothermal Dry Reforming of Methane on Yolk‐Shell Co–Ni Alloy@SiO₂ Catalyst

Abstract Photothermal dry reforming of methane (PT‐DRM) is an appealing pathway to convert carbon dioxide and methane into synthesis gas, a mixture of carbon monoxide and hydrogen, via photothermal heating induced by concentrated sunlight. However, coke formation and sintering of active metal nanoparticles are key issues for catalyst stability. In the present study, we demonstrated Co–Ni alloy nanoparticles encapsulated with a porous SiO 2 shell exhibited improved catalytic activity and stability for PT‐DRM using visible/near‐IR light irradiation without any other external heating. The addition of a tiny amount of Co (1–5 mol% relative to total metal) and SiO 2 encapsulation enhanced the stability by simultaneously suppressing coke formation and sintering of the metal nanoparticles. Furthermore, we revealed that the position of the light irradiation spot has a crucial role in the conversions of methane and carbon dioxide and product selectivity, presumably due to the large temperature gradient under the light irradiation. These findings would contribute to designing effective PT‐DRM catalysts with improved activity and enhanced resistance for both coke formation and sintering and emphasize the significant contribution of the temperature gradients to the performance of PT‐DRM.