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.