Photo-assisted methane dry reforming over Ni–Co–CeO2–Al2O3 catalysts with enhanced activity: synergistic effect of Ni and Co

Abstract

Photo-thermo-chemical dry reforming of methane (PTC-DRM) presents advantages over thermocatalytic DRM by storing solar and thermal energy as chemical energy, yet maintaining high efficiency and stability remains a challenge. Herein, we report an efficient PTC-DRM process on Ni–Co–Ce–Al catalysts and investigate the synergistic effect of Ni and Co on reaction performance. Characterization results revealed that the introduction of Co increases the concentration of acidic sites on the Ni-based catalyst surface. An appropriate number of acidic sites facilitates the DRM reaction. Co-incorporated catalysts demonstrate excellent light responsiveness, and generate more energetic hot charge carriers under light irradiation. Density functional theory (DFT) calculations confirm that the interfacial electronic structure of the Ni–Co–Ce–Al catalyst facilitates spontaneous electron transfer from CeO₂ to NiCo bimetallic quantum dots (QDs), which is mediated by the built-in electric field at the metal–semiconductor interface—attributed to the inherent work function difference between CeO₂ (5.45 eV) and NiCo alloys (4.93 eV). The incorporation of an optimal amount of Co significantly improves the catalytic performance, with the Ni_0.9–Co_0.1–Ce–Al catalyst exhibiting the highest thermal and photocatalytic activity. At 650 °C, the conversions of CH₄ and CO₂ increased from 55.8% and 60.1% under dark conditions to 65.1% and 67.9% under light irradiation, respectively. Accordingly, the yields of H₂ and CO increased from 21.4 and 26.5 μmol min⁻¹ g⁻¹ to 23.6 and 27.7 μmol min⁻¹ g⁻¹. This study demonstrates that the synergy between bimetallic components coupled with photothermal integration can effectively enhance DRM efficiency and coke resistance, providing a valuable catalyst design strategy for solar-driven conversion of carbon resources.