Experimental study of microwave-driven two-step thermochemical cycling for the preparation of carbon monoxide

Atmospheric CO2 reduction into chemicals is crucial for carbon cycling. However, when using traditional solar-driven thermochemical cycles for carbon dioxide conversion, the required temperature exceeds 1300 °C, leading to excessive energy demands and significant obstacles in technological scaling. This study introduces a two-step thermochemical cycling system utilizing microwave-excited non-equilibrium gadolinium-doped CeO2 (CGO). We analyzed the power threshold of the system, as well as the effects of different material doping concentrations and gas components introduced during the oxidation process on the reaction. The system achieves faster carbon dioxide conversion than conventional methods, reducing the reaction temperature by 77 % (from 1300 °C to 380 °C) and reducing the reaction time by 94 %.Under optimal conditions, the yield of O2 and CO in a single cycle is 0.77 mL/g and 1.11 mL/g, respectively. The kinetic analysis revealed that the apparent activation energy of the microwave-driven CGO is 69.48 kJ/mol, which is 52 % lower than that of traditional thermal activation methods. Furthermore, the microwave-to-chemical energy conversion efficiency reaches 11 %–20 %, surpassing the performance of traditional solar thermochemical approaches. This study further explores the microwave-driven CO2 conversion process and optimizes the reaction conditions, and also shows a good industrial application prospect.