Uncovering the Origin of Light-Promoted Synergetic Effect and Y Doping in Enhancing Photothermocatalytic Dry Reforming of Methane on Ni/Ni-Y2-Al2O3

Abstract

Photothermocatalytic dry reforming of methane (DRM) can convert CH₄ and CO₂ into syngas, offering an effective approach to reducing greenhouse gas emissions. However, photothermocatalytic DRM reaction generally needs a high light intensity surpassing 192 kW m⁻² to attain high light-fuel conversion. Also, catalysts applied to photothermocatalytic DRM are liable to inactivation due to carbon deposition. Herein, a nanocomposite of Ni nanoparticles supported on Ni- and Y-doped Al₂O₃ (Ni/Ni-Y₂-Al₂O₃) is prepared. It achieves high H₂ and CO production rates with a light-to-fuel efficiency (29.2%) at a lower intensity (80.1 kW m⁻²). Meanwhile, it sustains excellent photothermocatalytic durability and accomplishes a 37-fold reduction in carbon deposition rate compared to Ni/Al₂O₃. The substantially enhanced catalytic activity and carbon resistance of Ni/Ni-Y₂-Al₂O₃ are correlated with accelerating carbon species (C*) oxidation (the rate-determining steps of DRM). This acceleration derives from the synergetic effect and carbonate species resulting from Y doping, which participate in C* oxidation via two separate reaction pathways. When in light, the synergetic effect further facilitates C* oxidation. Simultaneously, light immensely reduces activation energy, activates the NiO bonds at the interface region, and expedites the reaction between carbonate species and C* in the interface, enhancing catalytic activity and carbon resistance.