Mechanistic Study of the Hydrogen Oxidation/Evolution Reaction over Bimetallic PtRu Catalysts

In this work, the activity of bimetallic PtRu/C with varying amounts of Ru for the hydrogen oxidation/evolution reactions (HOR/HER) was determined. The results demonstrate that surface Ru is not necessary for high activity, which shows that the improved activity of the bimetallic PtRu comes from the electronic interaction of Ru with Pt and the tuning of the hydrogen binding energy (HBE). Using the charge transfer coeffiecient from Butler-Volmer fitting and kinetic modeling, it was determined that Ru affects the HOR/HER mechanism in two ways: changing the pathway from Tafel-Volmer to Heyrovsky-Volmer, and lowering of the activation barrier of the Volmer step. Utilizing catalysts with Heyrovsky-Volmer(RDS) mechanism as well as focusing on tuning the HBE might help improve the activity of non-precious metal catalysts; allowing PGM-free fuel cells to become economically viable.