Mechanistic insights into methanol steam reforming over a ZnZr oxide catalyst with improved activity

Methanol steam reforming (MSR) holds great potential for mobile hydrogen production, but it still requires an active and stable catalyst. In this work, we report a high-performance ZnZr-0.5 composite oxide catalyst for this reaction, with a hydrogen production rate of 2.80 mol·g_cat⁻¹·h⁻¹ and CO₂ selectivity of 99.6% at a methanol space velocity of 22,762 mL·g_cat⁻¹·h⁻¹. It also exhibits superior long-term durability in the TOS test for more than 100 h. Such good activity results from a synergistic effect of ZnO–ZrO₂ dual sites. ZrO₂ is capable of stabilizing and storing more CH₃O∗ and HCOO∗ intermediates while ZnO is in charge of the dehydrogenation of these key intermediates. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and chemisorption results reveal that the MSR reaction experiences successively the hydrolysis of methyl formate and dehydrogenation of formate. More importantly, it is found that H₂O significantly promotes the dehydrogenation of HCOO∗ intermediate by directly participating in this reaction from pulse chemisorption experiments.