NiCo Alloy Catalysts for Low-Temperature Solar-Driven Methane Dry Reforming: Insights into CH4 Activation and Carbon Accumulation

Solar-driven dry reforming of methane (DRM) offers a milder, more cost-effective, and promising environmentally friendly pathway compared to traditional thermal catalytic DRM. Numerous studies have extensively investigated inexpensive Ni-based catalysts for application in solar-driven DRM. However, these catalysts often suffer from activity loss due to carbon accumulation. In this study, we enhanced the Ni-based catalyst by introducing a secondary cobalt active component. The Al₂O₃ supporting NiCo alloy catalyst (NiCo/Al₂O₃), synthesized from layered double hydroxides (LDH), exhibits superior light-absorbing properties. This catalyst demonstrates enhanced resistance to carbon accumulation and greater stability compared to Ni monometallic catalysts in solar-driven DRM. Under the extremely demanding conditions of low light irradiation intensity (1.34 W·cm^-2), the yields of H₂ and CO from the Ni₂Co₁/Al₂O₃ catalysts in DRM were 596.6 and 499.1 μmol·g^-1·h^-1, respectively. In addition, in the light-assisted thermal-driven catalytic DRM test, the H₂ and CO yields of Ni₂Co₁/Al₂O₃ catalysts increased by 44.5% and 29.2%, respectively, with the application of only 0.28 W·cm^-2 of light irradiation during heating at 350 °C. In situ infrared spectroscopy revealed that the reaction pathways of solar-driven DRM closely resemble those of thermally catalytic DRM, suggesting that the NiCo/Al₂O₃ absorbed light and converted it into heat and drived the DRM reaction. Furthermore, the in situ infrared spectroscopy tests showed that light irradiation could suppress the reverse water-gas shift reaction. The photothermal catalysts developed in this work provide a green industrial route to the production of DRM.