Recent advances, challenges, and future prospects in the selective thermal reduction of carbon dioxide to methane

Abstract

Carbon dioxide methanation technology exhibits dual significance, namely, in the mitigation of climate crisis and construction of a circular carbon economy, as it converts greenhouse gases into high-value chemicals. As a core reaction for realizing carbon cycling and energy storage in thermal catalysis, the innovation of its catalytic systems focuses on multiscale catalyst structure design and reaction-pathway regulation to address intrinsic thermodynamic and kinetic constraints. This review provides an innovative summary of knowledge-driven catalyst designs for CO₂ methanation based on a comparative analysis of its two dominant reaction mechanisms. Furthermore, it examines the structural features, applicable scenarios, and core advantages and disadvantages of several typical reactors. A coherent logical framework that integrates mechanism comparison, tailored catalyst design, reactor compatibility analysis, and techno-economic and life cycle assessments is established. Following this framework, the review first analyzes the technical bottlenecks and thermodynamic limitations of CO₂ hydrogenation to methane, clarifying the correlation between CO₂ activation energy barriers and product selectivity. Second, by systematically summarizing the widely accepted and experimentally verified reaction mechanisms, such as the CO pathway and formate pathway, coupled with theoretical calculations and experimental characterizations, this work profoundly dissects the evolution rules of key intermediates and the underlying pathway selection mechanisms. Subsequently, efficient catalyst systems are rationalized based on the aforementioned reaction mechanisms, encompassing the effects of the properties of catalyst supports on catalytic performance, modification strategies to mitigate deactivation, and the role of active metal loading in modulating reaction pathways. The currently employed mainstream reactor configurations are also summarized. Finally, techno-economic and life cycle assessments and the existing challenges in CO₂ methanation are comprehensively discussed. Overall, this review intends to offer robust theoretical support for the rational design of novel catalysts and process development of CO₂ methanation.