Tailoring the Durability of Carbon-Coated Pd Catalysts Towards Hydrogen Oxidation Reaction (HOR) in Alkaline Media

Abstract

For the hydrogen oxidation reaction (HOR), platinum group metal (PGM) catalysts are still the norm, and their large initial catalytic activity is counterbalanced by their uncertain durability in alkaline environments: harsh degradations proceed, like detachment and agglomeration of metallic nanoparticles from the carbon support, as witnessed from dedicated accelerated stress tests (AST). Herein, a strategy to increase such catalysts’ durability is provided, using carbon layers surrounding the Pd-based carbon-supported nanoparticles. The robustness of such catalysts, baring 0.5- or 0.7-nm-thick carbon cap over the Pd nanoparticles, is evaluated from AST combined with several pre/post-test characterization techniques: identical location transmission electron microscopy (IL-TEM), ex situ X-ray photoelectron spectroscopy (XPS) and ex situ inductively coupled plasma mass spectrometry (ICP-MS). The carbon layer protection limits the Pd-based nanoparticles’ agglomeration, detachment, and metal leaching, improving long-term catalyst durability in HOR-like operation. Thicker carbon layers surrounding the Pd nanoparticles lead to higher materials durability and lower degradation rate (larger performance stability) upon AST, compared to thinner carbon layers. In addition, the carbon-capped catalysts enable to maintain better the required Pd/PdO state of the surface that is essential for fast HOR, resulting in superior intrinsic HOR activity versus unprotected Pd/C. Overall, this work demonstrates that the activity-durability relationship can be tuned for carbon-capped catalysts.

Graphical Abstract