Redox catalysts based on amorphous porous carbons

A modular synthesis concept to prepare a library of mainly amorphous porous carbons has been developed. The carbons show – while keeping the textural properties nearly unchanged - systematically varied features such as the content of nitrogen, oxygen, iron and graphitic species, respectively. These individual features and the cross-relations between them were characterized with respect to applications of the carbons as reactants or catalysts in different test reactions, namely the temperature-programmed oxidation (TPO), the oxidation of sulphurous acid (OSA), the electrochemical oxygen reduction reaction (ORR) and the oxidative dehydrogenation of ethylbenzene (ODH), respectively. The carbon materials show striking similarities in terms of catalytic activity in TPO, OSA and ORR, respectively. The influence of individual nitrogen species and graphitic species on the catalytic behaviour was analyzed in detail. Pyrrole-like nitrogen species are obviously beneficial for the activation of molecular oxygen in different test reactions while pyridine-like species do not affect the catalytic behaviour. Graphitic species do not significantly influence the catalytic activity of otherwise amorphous carbons. For ODH, it was shown that nitrogen functionalities enhance the overall catalyst deactivation by catalysing the destruction of active sites.