Insights into Photothermocatalytic Dry Reforming of Methane on Ru/La‐Al ₂ O ₃ using Carbonate Species and Reactive Oxygen Species to Enhance the Fuel Production Rates and Completely Prevent Coking

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Photothermocatalytic dry reforming of methane (DRM) offers a promising strategy for converting solar energy into fuel. However, the high light intensity required for high fuel production rates and thermodynamically more favorable coking side reactions limit this strategy. Herein, a nanocomposite of La‐doped Al 2 O 3 supporting Ru nanoparticles (NPs) (Ru/La‐Al 2 O 3 ) is synthesized. At relatively low light intensity (80.2 kW m −2 ), Ru/La‐Al 2 O 3 obtains high production rates of CO and H 2 per gram of Ru ( r Ru, CO and r Ru, H2 , 8410.19 and 7181.94 mmol g Ru −1 min −1 ) with light‐to‐fuel efficiency ( η , 26.6%), and completely prohibits coking. In striking contrast, the reference catalyst without La doping (Ru/Al 2 O 3 ) exhibits lower r Ru, CO , r Ru, H2 , η and produces large amounts of coke. The improved photothermocatalytic performance stems from the fact that reactive oxygen species and carbonate species are involved in the oxidation of carbon species (rate‐determining steps of DRM) through two different reaction pathways, which significantly increases catalytic activity and prevents the carbon species from polymerizing into coke. Additionally, light not only enhances the DRM on Ru NPs and the oxidation reaction between carbonate species and carbon species but also promotes the dissociation of CH 4 and desorption of H 2 , which improves the catalytic activity and product selectivity of Ru/La‐Al 2 O 3 .