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Insights into Rh size-dependent reactivity of CO2 methanation over Rh-Al2O3 catalysts
Jinshi Dong1, Hongli Yang1, Shengtong Li1
1Laboratory of New Energy and Environmental Catalysis, School of Biological and Chemical Engineering, Guangxi University of Science and Technology Liuzhou 545006 Guangxi China jinshidong@gxust.edu.cn.
Abstract:
The hydrogenation of CO2 to methane at atmospheric pressure is a significant chemical approach to achieve carbon neutrality and gain renewable energy. However, developing catalysts with high selectivity and high methane yield remains challenging. In this study, a series of Rh-Al2O3 catalysts with varying Rh particle sizes were prepared by modulating the Rh loading amounts. Rh nanoparticles (Rh NPs) were found to exhibit superior performance compared to Rh single atoms (Rh SAs) under identical reaction conditions. The sharp decrease in CH4 selectivity at high temperature is dominantly attributed to the side reaction of dry reforming of methane instead of the limitation of reaction thermodynamics. It was found that there was the coexistence of formate and CO pathways in CO2 methanation on Rh-Al2O3 catalysts regardless of Rh loadings and formate pathway is dominate for CO2 methanation when the temperature high than 400 °C. Turnover frequency (TOF) calculations indicated that the theoretical CH4 generation frequency of Rh NP was three times higher than that of Rh SA. Kinetic experiments and DFT calculations revealed that the dissociation and activation of H2 is the key factor affecting the performance of Rh-Al2O3 catalyst. This study facilitates our understanding of Rh size-dependent chemistry for CO2 methanation reaction.
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