Microwave-powered integrated carbon capture and utilisation (ICCU) for methane production with rapid temperature response from minimal thermal inertia

•Microwave energy was developed to drive the ICCU-methanation process.•The novel technology shows rapid temperature response from minimal thermal inertia.•A possible rate-enhancing mechanism of the microwave-powered system was proposed.•The microwave-powered CO2 capture capacity over Ni-CaO-20 DFM was 3.31 mmol gDFM-1.•CO2 conversion and CH4 selectivity reached 71.01% and 98.17% with Ni-CaO-20 DFM. Integrated CO2 capture and utilisation (ICCU), emerging as an effective approach for achieving global carbon neutrality goals, demonstrates its potential through the transformation of captured CO2 into valuable methane and the concurrent hydrogen storage via methanation reaction. However, traditional ICCU strategies are heavily reliant on conventional thermal conduction heating, and the in-situ methanation process is constrained by reaction thermodynamics, posing significant challenges. In this study, we introduce for the first time a novel microwave-powered system, employing a clean and efficient energy source that offers rapid heating and on-demand operation and acts as an external field enhancement method in the ICCU-methanation procedure. The designed blend of Ni-loaded CaO and carbon nanotubes (CNTs) integrates the functions of CO2 adsorption, hydrogenation catalysis, and microwave absorbing ability. This novel approach achieved a CO2 capture capacity of 3.31 mmol gDFM-1 with CO2 conversion and CH4 selectivity reaching 71.01 % and 98.17 %, respectively, at a nickel loading of 20 wt%. We also propose a possible rate enhancement mechanism for the microwave-powered ICCU-methanation cyclic process compared to conventional methods. The microwave-powered system can substantially enhance overall efficiency by swiftly responding to temperature swings, thus reducing processing time in ICCU-methanation cycles.