Pyridine Functionalized Pt/C: Ligand-Mediated Bifunctional Catalyst for the Enhanced Oxygen Reduction and Methanol Oxidation Tolerance in Fuel Cells

Abstract

Ligand is usually deemed to be unfavorable towards catalytic reactions. Herein, we found that a certain amount of pyridine modified Pt/C catalyst showed enhanced oxygen reduction reaction (ORR) activity compared to surface cleaned Pt/C. The surface coverage of pyridine is a key factor to regulate the ORR activity. Pt/C catalyst with a pyridine surface coverage of 60% shows 50% enhancement towards ORR mass activity. The specific activity is increased with the surface coverage of pyridine (6 times enhanced specific activity was achieved at a surface coverage of 80%). The enhancement of the activity is due to the competition between the steric effect and electronic effect induced by pyridine, which was elucidated by in-situ FTIR, CO stripping and DFT calculation. On the other hand, the MOR activity was decreased linearly with the coverage of pyridine, indicating the MOR activity was dominated by the steric effect of ligand. Consequently, the pyridine-saturated Pt/C catalyst showed 10 times enhanced methanol-tolerant ability accompanied by maintaining the ORR activity when used as a cathode catalyst in fuel cells. More ligands (such as oleylamine, butylamine, triphenylphosphine) were further compared and discussed in this presentation. Figure 1