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 CO 2 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–ZrO 2 dual sites. ZrO 2 is capable of stabilizing and storing more CH 3 O∗ 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 H 2 O significantly promotes the dehydrogenation of HCOO∗ intermediate by directly participating in this reaction from pulse chemisorption experiments. • A ZnZrO x oxide catalyst was developed for efficient and stable MSR reaction. • The best H 2 production rate reaches up to 2.80 mol·g cat −1 ·h −1 over ZnZr-0.5. • The high MSR activity results from synergistic effect between ZnO and ZrO 2 sites. • The MSR reaction follows a methyl formate/formate mediated pathway. • Water is verified to promote the formate dehydrogenation reaction as a direct reactant.