Hierarchical core-shell structure of ZIF-8 derived porous carbon supported PdZn nanoalloys within mesoporous silica shells as efficient methanol oxidation electrocatalysts

The anodic precious metal catalyst of direct methanol fuel cell (DMFC) is poisoned due to CO adsorption, which makes the methanol oxidation reaction (MOR) kinetics tardily. In this study, a series of hierarchical core-shell structure catalysts PdZn/ZDC@SiO2 were synthesized by loading PdZn nanoparticles (NPs) on ZIF-8 derived porous carbon (ZDC) and protecting by the mesoporous silica (SiO2) are reported. A hierarchical core-shell structure informed in PdZn/ZDC@SiO2(20) caused by mesoporous silica shell leads to well-dispersed and uniform of PdZn NPs (10 nm). Compared with commercial palladium carbon (Pd/C), the optimized catalyst PdZn/ ZDC@SiO2(20) has higher current density (765.2 mA/mg) and stronger CO toxicity tolerance (If/Ib = 3.30). And the onset potential and the peak potential of PdZn/ZDC@SiO2(20) (-0.294 V,-0.203 V) are more negative in CO stripping experiment. Silica is an inorganic oxide that can provide oxygen-containing species to the adjoining precious metal sites and promote CO oxidation. In addition, PdZn NPs can accelerated electron transport and then improve methanol oxidation performance due to the changing electronic structure of Pd and the modifying the surface adsorption of the catalyst. PdZn/ZDC@SiO2(20) is a potential substitute material for noble metal catalyst that can be used for direct methanol fuel cells.