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

Abstract

CaO sorbent/catalyst bifunctional materials are promising for CO₂ capture in sorption-enhanced H₂ production such as sorption-enhanced water–gas shift. For simultaneous H₂ 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 H₂ 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 H₂ 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 H₂/CO molar ratio close to unity from CH₄ reforming of CaCO₃.