One of the main challenges in the commercialization of low temperature fuel cells is the slow oxygen reduction reaction (ORR) kinetics and the high cost and scarcity of platinum (Pt)-based catalysts. As a result, alternative non-noble electrocatalysts to Pt materials for ORR is needed to realize the practical application of fuel cells. In this study, nitrogen-doped carbon nanotubes (NCNTs) were synthesized as a non-noble electrocatalyst for the ORR using ethylenediamine (EDA-NCNT) and pyridine (Py-NCNT) as different nitrogen precursors by a single-step chemical vapor deposition (CVD) process. The resulting EDA-NCNT has shown similar ORR performance compared to platinum on carbon support in terms of onset and half-wave potentials. Moreover, EDA-NCNT showed superior ORR performance in terms of limiting current density, number of electrons transferred, and H 2 O selectivity. The effects of nitrogen content on ORR performance of NCNT were investigated by comparing EDA-NCNT with Py-NCNT. The ORR performance of Py-NCNT was inferior compared to EDA-NCNT in terms of onset and half-wave potentials, limiting current density, number of electrons transferred, and H 2 O selectivity. Further material characterizations by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy illustrated a higher nitrogen content and more defects in EDA-NCNT compared to that of Py-NCNT which indicates the important role of the nitrogen precursor on nitrogen content and structure of NCNT. By combining the results of ORR activity and material characterization, it is concluded that higher nitrogen content and more defects of NCNT lead to high ORR performance.

As an alternative for platinum to reduce the cost, nonprecious catalysts for the oxygen reduction reaction (ORR) were synthesized by deposition of an Fe/Co−N x composite onto nanoporous carbon black with ethylenediamine (EDA) as a nitrogen precursor. Two different nanoporous carbon supports, Ketjen Black EC300J (KJ300) and EC600JD (KJ600), were used as catalyst supports for the nonprecious catalysts. Rotating ring disk electrode measurements were carried out to investigate the ORR activity and selectivity of these catalysts. The results obtained from the optimized FeCo/EDA-carbon catalyst, using KJ600 as the support, showed improved onset and half-wave potentials and superior selectivity than that of the KJ300. Similarly, the catalyst showed good performance in the hydrogen−oxygen PEM fuel cell. At a cell voltage of 0.6 V, the fuel cell managed to produce 0.37 A/cm2 with a maximum power density of 0.44 W/cm2. A fuel cell life test at a constant voltage of 0.40 V demonstrated promising stability up to 100 h. The catalysts were characterized by X-ray diffraction, energy-dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy. The characterizations indicated that pyridinic-type nitrogen of the nonprecious metal catalysts is critical for ORR catalytic activity and selectivity. These results suggest that a higher pore volume and surface area of the carbon support could lead to a higher nitrogen content, providing more active sites for ORR, and this type of catalyst has great potential used as a nonprecious PEM fuel cell catalyst.

Novel tin-oxide (SnO(2))-coated single-walled carbon nanotube (SWNT) bundles supporting platinum (Pt) electrocatalysts for ethanol oxidation were developed for direct ethanol fuel cells. SnO(2)-coated SWNT (SnO(2)-SWNT) bundles were synthesized by a simple chemical-solution route. SnO(2)-SWNT bundles supporting Pt (Pt/SnO(2)-SWNTs) electrocatalysts and SWNT-supported Pt (Pt/SWNT) electrocatalysts were prepared by an ethylene glycol reduction method. The catalysts were physically characterized using TGA, XRD and TEM and electrochemically evaluated through cyclic voltammetry experiments. The Pt/SnO(2)-SWNTs showed greatly enhanced electrocatalytic activity for ethanol oxidation in acid medium, compared to the Pt/SWNT. The optimal SnO(2) loading of Pt/SnO(2)-SWNT catalysts with respect to specific catalytic activity for ethanol oxidation was also investigated.

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