Cathode Catalysts Based on Cobalt- and Nitrogen-Doped Nanocarbon Composites for Anion Exchange Membrane Fuel Cells

Abstract

Cobalt- and nitrogen-doped carbide-derived carbon/carbon nanotube (CDC/CNT) composites are prepared and used as oxygen reduction reaction (ORR) electrocatalysts for an anion exchange membrane fuel cell (AEMFC) cathode. For the doping, high-temperature pyrolysis is applied using a cobalt salt and a nitrogen precursor (either dicyandiamide, urea, or melamine). During the doping, (i) new mesopores are formed as confirmed by the N2 physisorption results, (ii) atomically dispersed cobalt is present on the catalysts as detected by scanning transmission electron microscopy, and (iii) N-pyridinic and Co–N4 are the dominant N-containing species as shown by X-ray photoelectron spectroscopy. This indicates that using the composite of CDC and CNTs as well as the cobalt salt and nitrogen precursor is advantageous for the preparation of electrocatalysts. All three catalyst materials demonstrate similarly good electrocatalytic activity toward O2 electroreduction in alkaline medium and excellent stability after 10000 repetitive potential cycles. The Co-N-CDC/CNT catalyst as the cathode material together with a hexamethyl-p-terphenyl poly(benzimidazolium) (HMT-PMBI) membrane exhibits excellent AEMFC performance by reaching maximum power density of 577 mW cm–2.