Reaction Scheme of Low-Temperature CO2 Methanation over Rh/TiO2 Catalyst
作者单位：State Key Laboratory of Coal Combustion School of Energy and Power Engineering Huazhong University of Science and Technology
会议名称：《中国化学会·第一届全国二氧化碳资源化利用学术会议》
会议日期：2019年
学科分类：07[理学] 081705[工学-工业催化] 08[工学] 0817[工学-化学工程与技术] 070303[理学-有机化学] 0703[理学-化学]
关 键 词：CO2 methanation Rh/TiO2 catalyst Rate-limiting step Density functional theory
摘 要：Rh/TiO has been regarded as a very promising catalyst for the low-temperature CO methanation. However, the atomic-level reaction mechanism that dictates the reactivity and selectivity of CO reduction over Rh/TiO catalyst remains elusive. The reaction mechanism governed by a delicate interplay of surface reaction chemistry and thermodynamics was systematically investigated using density functional theory. Theoretical results indicate that significant charges accumulate at the perimeter of the interface between support TiO and Rh nanoparticle. Metal-support interface is identified as the most active site for CO adsorption and activation over Rh/TiO catalyst. Compared with the direct C-O bond cleavage pathway and formate pathway, reverse water-gas shift(RWGS) reaction followed by CO hydrogenation is much more thermodynamically and kinetically favorable for CO methanation over Rh/TiO catalyst. The RWGS+CO hydrogenation pathway via HCOH dissociation dominates CO methanation due to the relatively lower energy barrier. H-mediated HOCO dissociation is identified as the rate-limiting step of CO methanation over Rh/TiO catalyst. These mechanistic insights can guide the rational design of catalyst active centers to boost the activity and selectivity of CO reduction.