Enhanced mass transfer and optimized electronic structure on Pd-Ag nanoparticles embedded in mesoporous carbon for superior electro-oxidation

The development of economically viable anode catalysts for the alcohol oxidation reaction (AOR) has been a long-standing challenge in direct alcohol fuel cells (DAFCs). A series of Pd-Ag nanoparticles embedded in mesoporous carbon were fabricated in this study using a green approach that did not require the use of a surfactant, which exhibited better catalytic properties for AOR. Experiments and DFT calculations reveal that the d-band center of Pd is influenced by both strain and ligand effects, with the ligand effect predominating. The electrochemical studies demonstrated that the composite-optimized Pd-Ag alloy at a Pd/Ag molar ratio of 1:1 was the highest in terms of ethanol oxidation (EOR) and ethylene glycol oxidation (EGOR) catalytic activity. The mass activities of Pd1Ag1/MC for EOR and EGOR were 7921 mA mg(-1) and 11,520 mA mg(-1), respectively, which were 3.77 and 5.3 fold greater than Pd/C. The impressive performance of Pd1Ag1/MC catalyst could be attributed to the vital roles of the unique mesoporous structure of carbon sphere with abundant self-doping defect and the boosting effect of Ag (benefit from optimized d-band electronic structure and bi-functional mechanism). The present simple method of synthesizing low-cost, easy-to-use, and high-performance catalysts contributes to the exploration of the large-scale practical applications of direct alkaline alcohol fuel cells.