Carbon supported dual functional materials for integrated carbon dioxide capture and methanation: Performance of different support materials and carbon footprint assessment

Integrated CO₂ capture and utilization (ICCU) serves an effective strategy to achieve carbon neutrality, while the dual function materials (DFMs) are the key for high-efficient ICCU process. A series of CaONi based DFMs with different support materials, including Al₂O₃, CeO₂, graphene (GPE) and commercial multi-walled carbon nanotubes (MWCNTs), were synthesized and compared for integrated CO₂ capture and methanation (ICCM). The effect of operational temperatures on carbon conversion and CH₄ production was also explored. Results show that metal oxides supported DFMs exhibit relatively high CH₄ yield, while the carbon materials possessed comparable activity but very good durability in a continuous ICCM test for 10 cycles. The improved stability was contributed by the resistance in metal phase aggregation which restrained the increase of Ni particle size during cycle test. A favorable performance with CO₂ capture capacity of 0.24 mmol/g_DFMs and CO₂ conversion of 80 % were achieved in the presence of DFMs supported by commercial MWCNTs at 450 °C. Furthermore, cost-effective plastic waste derived MWCNTs were used to replace the commercial samples for the above ICCM process from a green and sustainable perspective. It is found that Co modified CaONi DFMs supported by plastic derived MWCNTs displayed excellent performance with approximately 0.15 mmol/g_DFMs of CH₄ yield and even 100 % of CH₄ selectivity in ICCM. This may be contributed by the enhanced CO₂ adsorption/activation and H₂ chemisorption with Co addition. Carbon footprint assessment show that the plastic waste assisted ICCM process achieved around 92 % and 20 % reduction in global warming potential compared to two prevalent industrial carbon conversion and methanation scenarios. These findings highlight the promising potential of the proposed ICCM for enhancing industrial sustainability and combating climate change.