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, CH 4 and CO 2 , into syngas (CO+H 2 ) 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 LaFeO 3 or LaMnO 3 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 H 2 to yield Ni 0 NPs. The prepared samples were extensively characterized by XRD, N 2 physisorption, H 2 -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 Ni 0 reoxidation, whereas a good activity and stability were ensured by Mn-perovskites, preserving the Ni 0 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/Al 2 O 3 reference catalyst demonstrated slightly higher activity than Ni/LaMnO 3 but suffered from much faster deactivation due to coking and reoxidation. • La 0.8 FeO 3 support causes Ni reoxidation during Dry Reforming: low catalytic activity. • La 0.8 MnO 3 support preserves metallic Ni: good catalytic activity and stability. • Improved photothermal activity with Ni/La 0.8 MnO 3 prepared by ADP, not by exsolution. • Light illumination reduces La 0.8 MnO 3 perovskite decomposition and coke deposition. • Ni/Al 2 O 3 is highly active but less stable because of Ni reoxidation and coking.

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