Transition-Metal and Nitrogen-Doped Carbon Nanotube/Graphene Composites as Cathode Catalysts for Anion-Exchange Membrane Fuel Cells

Abstract

Transition-metal and nitrogen-doped graphene-like material and carbon nanotube (M-N-Gra/CNT) composites are prepared, characterized, and used as cathode catalysts in anion-exchange membrane fuel cells (AEMFCs). Melamine as a nitrogen source and cheap iron and cobalt salts as metal precursors are used for doping via high-temperature pyrolysis. The success of doping is proven by several physicochemical analysis methods, and the catalyst materials possess rather similar textural properties. The initial assessment of the oxygen reduction reaction activity using the rotating disk electrode method shows that Fe-N-Gra/CNT, Co-N-Gra/CNT, and CoFe-N-Gra/CNT materials have very similar electrocatalytic performances in alkaline media as well as excellent short-term stability but a different yield of HO2– formation. The M-N-Gra/CNT materials as cathode catalysts together with the Aemion+ reinforced anion-exchange membrane exhibit very good AEMFC performance, especially CoFe-N-Gra/CNT, comparable to that of Pt/C, reaching a peak power density of 638 mW cm–2. Such an excellent fuel cell performance of the M-N-Gra/CNT catalyst materials is attributed to the presence of M–Nx sites, carbon-encapsulated transition-metal nanoparticles, and feasible nitrogen-containing moieties.