ZnO-supported palladium catalysts via ball milling as an effective heterogeneous catalyst for methanol steam reforming

Methanol steam reforming (MSR) is considered an efficient hydrogen production approach in fuel cell applications, with the Pd-Zn catalysts being the most widely used. Prevailing Pd-Zn catalysts face the challenge of minimizing the Pd loading. To tackle this challenge, a PdZn nanoparticle (NP) catalyst and a Pd1/ZnO singleatom catalyst (SAC) were fabricated via a ball milling process. With methanol conversion maintained at 99.5 % and CO concentration below 0.71 %, 2PdZn/Al2O3 NP catalyst (Pd loading of 2 wt%) exhibited superior antioxidation ability and stability for 100 h with a WHSV of 7.2 h-1 at 350 degrees C. The TOF of 2PdZn/Al2O3 NP is 1.4 times that of 0.2PdZn SAC (Pd loading of 0.2 wt%). Intermediate species methoxy (*CH3O) and formate (*CHOO) were observed from both 2PdZn/Al2O3 NP and 0.2PdZn SAC by in situ temperature programmed DRIFTS (TPDRIFTS). Density functional theory (DFT) calculations showed that the strong adsorption of water (H2O), formaldehyde (*CH2O) and hydroxyl (*OH) on Pd1/ZnO(0 0 1) surface of the SAC model resulted in higher activation energies of water dehydrogenation and *CH2OOH formation than PdZn(1 1 1) surface of the NP model. The 2PdZn/Al2O3 NP catalyst showed immense potential for the on-board hydrogen production for fuel cell vehicles.