Controlled doping of carbon catalyst supports by atomic replacement via gasification-assisted heteroatom doping

Abstract

Due to a set of unique properties, carbon materials are applied as supports for metal-based catalysts in a wide variety of established and emerging (electro-)catalytical transformations. By introducing heteroatoms such as N, S and P into carbon supports, metal-support interactions can be tuned, enabling an optimization of catalyst performance in terms of activity, selectivity and stability. However, the exact impact of carbon heteroatom doping on catalyst performance remains often poorly understood, as the effects are inseparable from the clustered influence of other support properties such as texture and nanostructure. In this context, we present gasification-assisted heteroatom doping (GAHD) as a novel, broadly applicable post synthesis approach to exchange carbon surface atoms against heteroatoms while retaining the properties of the parental carbon. Employing GAHD, N, S and P doping of carbons with widely varying properties could be achieved, allowing, for example, incorporation of up to 13.1 wt-% S into an activated carbon at a change of specific surface area of only 4.4%. As a proof-of-concept, comparable N, S and P doped carbon nanofiber supports were used to prepare Pt-based electrocatalysts for the oxygen reduction reaction and probe the influence of the heteroatom dopants on their stability by accelerated stress tests in different potential regimes. In this context, P and S doped supports were found to exhibit a high degree of interaction with Pt, providing increased degradation resistance compared to N and non-doped support.