Integrated CO 2 capture and reverse water–gas shift reaction over CeO 2 -CaO dual functional materials

Achieving carbon neutrality is one of the most important tasks to meet the environmental challenges due to excessive CO 2 emissions. Integrated CO 2 capture and utilization (ICCU) represents an effective process for direct utilization of CO 2 -contained exhaust gas (e.g. flue gas), in which converting the captured CO 2 into CO via reverse water–gas shift (RWGS) reaction is a promising route. The dual functional materials (DFMs), containing CO 2 adsorbents and catalysts, are widely applied to achieve ICCU. The conventional active metals (Ni, Fe, etc.)-based DFMs and non-transition metal DFMs (e.g. CaO) are restricted by low CO selectivity, catalytic efficiency or CO generation in the CO 2 capture step. To address the above obstructs in the application of DFMs, the metal oxides-based DFMs, MO x -CaO (M = Al, Ce, Ti or Zr), are synthesized and evaluated. The CeO 2 -CaO outperformed the other metal oxides-based DFMs and possessed significantly improved catalytic performance. It is found that 33% CeO 2 -CaO DFM displayed approximately 49% CO 2 conversion and approximately 100% CO selectivity in integrated CO 2 capture and reverse water–gas shift reaction (ICCU-RWGS) at 650°C, while CaO-alone only achieved approximately 20% CO 2 conversion at the same condition. The surface basicity of CeO 2 is revealed to contribute to the improved catalytic performance by enhancing CO 2 chemisorption and activation in the hydrogenation step. Furthermore, CeO 2 -CaO material possessed excellent cycle stability in 20 cycles ICCU-RWGS, achieving a sustainable and high-efficient performance in CO 2 conversion and CO selectivity.