Fabricating Ga doped and MgO embedded nanomaterials for sorption-enhanced steam reforming of methanol

Abstract

Sorption-enhanced steam reforming of methanol (SE-SRM) is a promising approach to creating a high-purity hydrogen supply. However, catalysts suffer from activity deactivation and low CO₂ uptake capacity. In this study, we investigate the role of Ga doping of Cu–MgO in SE-SRM by synthesizing a series of MgO embedded xGaCuMg catalytic sorbents via a sol–gel method. The TEM-EDX mapping results indicate that MgO nanoparticles can be successfully embedded in the bulk-phase of the catalytic sorbent with a stabilized microstructure. The results from in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) reveal that the Ga-doped catalytic sorbent is conducive to promoting the conversion of C-containing intermediates in SE-SRM, and absorbing CO₂ in the form of bidentate carbonate rather than monodentate carbonate. Experimental studies verify that the best uptake capacity of 18GaCuMg catalytic sorbent (36.25 mg CO₂/g MgO) achieves almost complete conversion of methanol (99.70%) with 100% H₂ selectivity at 200 °C. Specifically, no CO is formed during the kinetic-control stage of SE-SRM. Density functional theory (DFT) calculations based on the Cu(111)Ga₂O₃(202)MgO(200) model revealed that the Ga doping can enhance the adsorption energies of methanol and carbon dioxide, promoting methanol activation and increasing CO₂ uptake capacity. These findings provide valid strategies for functionalized nanomaterial design, which will substantially promote the SE-SRMR performance with desired catalytic sorbent recyclability.