Ligand-mediated bifunctional catalysis for enhanced oxygen reduction and methanol oxidation tolerance in fuel cells

Abstract

Though it is widely accepted that both electronic and steric effects are important in ligand-regulated heterogeneous catalysis, no experimental method has visually distinguished these two effects. Herein, by controllably tuning the surface coverage of pyridine on Pt nanoparticles, we successfully achieve bifunctional catalysis in direct methanol fuel cells with simultaneously improved oxygen reduction and methanol oxidation tolerance. More importantly, by combining the experimental results and density functional theory calculations, we reveal that the variation of the activity with the surface coverage of pyridine in these two reactions is due to the competition or cooperation between the electronic and steric effects. Other ligand experiments further confirmed the above conjecture. The stability of the pyridine ligand on Pt was also systematically studied in this paper.