The critical role of Ga doped Cu/Al2O3 aerogels in carbon monoxide suppression during steam reforming of methanol

Abstract

Steam reforming of methanol is an effective method for providing high-purity hydrogen to polymer electrolyte membrane fuel cells, however, this technology still faces the challenge of high CO selectivity. Herein, a series of Ga2O3/Cu/Al2O3 aerogels with different Ga doping (0–50 wt%) were synthesized through freeze-drying assisted sol-gel method. Experimental studies verify that 20GaCuAl exhibits the best performance, which achieves 100% methanol conversion with no CO production. It is demonstrated that Ga doping facilitates the formation of smaller Cu crystalline size, which improves the affinity of catalyst to CO, thus inhibiting CO formation. Results also indicate that the aerogel materials have larger specific surface area and porosity, which is conducive to the homogeneous distribution of the active sites, the intensified diffusion of reactant molecules, and the suppression of their sintering and agglomeration. The methanol reforming performance, especially for CO suppression capability and long-term durability, can be comprehensively promoted, attributing to the synergy of Ga doping and aerogel material fabrication. In situ DRIFTS results illustrate that SRM on Ga2O3/Cu/Al2O3 aerogel undergoes the following process: CH3OH → CH3O* → HCHO→ monodentate HCOOH→ H2 and CO2. The strong absorbed monodentate formate is to the benefit of water-gas shift reaction, thus hindering the generation of CO.