Photothermal activation of methane dry reforming on perovskite-supported Ni-catalysts: Impact of support composition and Ni loading method

Abstract

The Dry Reforming of Methane (DRM) is an intriguing process to convert two greenhouse gases, CH₄ and CO₂, into syngas (CO+H₂) and to upgrade biogas into biosyngas. However, the challenges of high operating temperatures and catalyst deactivation have hindered its large-scale implementation so far. Recently, photothermal catalysis has emerged as a sustainable alternative to conventional thermocatalysis, enabling a reduction of the required temperature and improvement of catalyst stability. This approach necessitates the development of a suitable photocatalyst. Herein, we proposed the use of active Ni nanoparticles (NPs) with plasmonic features, supported over semiconductive perovskites LaFeO₃ or LaMnO₃ with La-deficiency. The incorporation of Ni was achieved through either B-site substitution within the perovskite lattice or surface loading via Ammonia Deposition Precipitation (ADP), followed by a reductive treatment under H₂ to yield Ni⁰ NPs. The prepared samples were extensively characterized by XRD, N₂ physisorption, H₂-TPR, SEM-EDX, HAADF STEM-EDX, XPS, UV-Vis DRS. The pre-reduced catalysts were then tested for thermal and photothermal DRM under visible light illumination (3 suns) at 600 °C. The Fe-based samples were poorly active because of Ni⁰ reoxidation, whereas a good activity and stability were ensured by Mn-perovskites, preserving the Ni⁰ active species. Among the Ni loading procedures, only ADP ensured improved activity in photothermal conditions thanks to high Ni NPs concentration, while the B-site doped catalyst showed better thermal than photo-activity because of low surface Ni concentration. Interestingly, light illumination was found to reduce perovskite decomposition and coke deposition. A Ni/Al₂O₃ reference catalyst demonstrated slightly higher activity than Ni/LaMnO₃ but suffered from much faster deactivation due to coking and reoxidation.