Hollow Submicrospherical Ni/Co-Promoted CaO/Ca12Al14O33 for H2 Production from Sorption-Enhanced Water-Gas Shift with In Situ CO2 Conversion via CH4 Reforming of CaCO3

CaO sorbent/catalyst bifunctional materials are promising for CO2 capture in sorption-enhanced H-2 production such as sorption-enhanced water-gas shift. For simultaneous H-2 production with CO2 in situ capture and utilization, the integrated process of sorption-enhanced water-gas shift and in situ CO2 conversion by CH4 reforming of CaCO3 was proposed. This work focused on the tailored design of a CaO sorbent/catalyst bifunctional material for both efficient H-2 production and in situ CO2 conversion in this integrated process. The template-assisted strategy of hydrothermal carbonization followed by self-reduction and template removal via steam gasification was first proposed to obtain the hollow submicrospherical Ni/Co-promoted CaO/Ca12Al14O33. The as-synthesized material exhibits high and stable H-2 production, CO2 capture, and in situ CO2 conversion performance in the integrated process due to the unique hollow submicrospherical structure and enhanced catalytic activity. Ni-Co interaction boosts oxygen vacancy and Ni-Co alloy, which are the active catalytic sites for the water-gas shift and CH4-CaCO3 reactions. Moreover, the oxygen vacancy-mediated mechanism on CH4 reforming of CaCO3 over the hollow submicrospherical Ni/Co-promoted CaO/Ca12Al14O33 is confirmed. After 20 cycles, CO conversion from sorption-enhanced water-gas shift using the as-synthesized material retains 97.0%, accompanied by high CH4 conversion of 95.1% and the H-2/CO molar ratio close to unity from CH4 reforming of CaCO3.