Non-platinum nanocatalyst on porous nitrogen-doped carbon fabricated by cathodic vacuum arc plasma technique

Abstract

© 2015 Elsevier B.V. All rights reserved. Polymer electrolyte membrane fuel cells (PEMFCs) convert chemical energy directly into electrical energy where catalysts composing of non-noble transition metals, nitrogen, and carbon compounds are the most promising materials to replace the expensive platinum catalysts for oxygen reduction reaction (ORR). In this research, cathodic vacuum arc plasma (CVAP) technique was used to fabricate porous nitrogen doped carbon (NC) and non-platinum catalyst on porous NC (Fe-NC) directly on ion exchange membrane for being used as an ORR catalyst at the cathode. The porous NC layer was fabricated on silicon wafer at 0.05 mTorr, 0.1 mTorr, 0.5 mTorr, 1 mTorr, and 5 mTorr of nitrogen gas inlet. The AFM, and SEM images are observed to be regularly big with quite high hillocks and thin NC layers; these results indicate that the optimum process pressure of nitrogen gas inlet is 5 mTorr for porous NC fabrication. The SEM-EDS detects Fe, N, and C elements in the prepared catalysts, and the XRD pattern reviews the iron nitride and the carbon nitride phases. The SEM images in the backscattered electron mode (BSE) reveal good dispersion of very small metal particles (bright spots) on the highly porous coral-like carbon film. The TEM images clearly show the spherical Fe nanoparticles (64 nm) dispersed on the porous carbon film. However, the XANES (X-ray absorption near edge structure) analysis specifies that the prepared Fe is in the form of iron(III). As a result of no FeN standard for confirmation, both the XRD and the XANES results are used to confirm the Fe(III) compound. In preparing the catalyst as FeN, all these results specify that the CVAP technique can be used to produce the catalyst on the membrane.