Mechanism study on hydrogen generation from metal hydride-coupled methanol steam reforming

Abstract

Metal hydride (MH)-coupled methanol steam reforming (MSR), in which MSR is coupled with the hydrolysis of MH, is an attractive strategy for onsite hydrogen generation as it offers a high hydrogen density, high hydrogen purity and balanced thermal effect. This study provides a comprehensive mechanism study on the MH-coupled MSR over Cu/CaH₂ using online mass spectroscopy coupled with isotope labelling and in situ Fourier-transformed infrared spectroscopy. Results show that the hydrolysis of MH and MSR over Cu proceeds simultaneously via a formate-mediated pathway. The stepwise dehydrogenation of methanol primarily occurs on the Cu surface, while CaH₂ effectively activates CH₃OH at low temperatures by supplying the hydrolysis heat to the endothermic MSR. Although Ca(OCH₃)₂ and Ca(HCOO)₂ can be formed when CaH₂ is introduced, they are not active intermediates in the MH-coupled MSR due to their high thermal stability. Instead, they are converted back to CH₃OH and HCOOH via hydrolysis.