N + -Implantation on Nb Coating as Protective Layer for Metal Bipolar Plate in PEMFCs and Their Electrochemical Characteristics

Nitrogen ions were implanted into the coated Nb layer by plasma immersion ion implantation to improve resistance to corrosion of a metal bipolar plate. Due to nitrogen implantation, the corrosion behavior of the Nb layer was enhanced. The electron microscope observation reveals that the microstructu...

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Bibliographic Details
Published in:	Materials 2022-12, Vol.15 (23), p.8612
Main Authors:	Kim, Yu-Sung, Choi, Jin-Young, Kim, Cheong-Ha, Lee, In-Sik, Jun, Shinhee, Kim, Daeil, Cha, Byung-Chul, Kim, Dae-Wook
Format:	Article
Language:	eng
Subjects:	Air pollution bipolar plate Climate change Coatings Corrosion and anti-corrosives Corrosion resistance Electric vehicles Electrodes Electrolytes Energy minerals Fossil fuels Fuel cell industry Fuel cells Galvanic corrosion Global warming Graphite Ion implantation Mass spectrometry Mechanical properties Monte Carlo simulation niobium Nitrogen Nitrogen ions Plasma etching plasma immersion ion implantation Protective coatings Scientific imaging Stainless steel Transplants & implants
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Summary:	Nitrogen ions were implanted into the coated Nb layer by plasma immersion ion implantation to improve resistance to corrosion of a metal bipolar plate. Due to nitrogen implantation, the corrosion behavior of the Nb layer was enhanced. The electron microscope observation reveals that the microstructure of the Nb layer became denser and had fewer defects with increasing implantation energy. As a result, the densified structure effectively prevented direct contact with the corrosive electrolyte. In addition, at a higher implantation rate (6.40 × 10 N /cm ), a thin amorphous layer was formed on the surface, and the implanted nitrogen ions reacted at neighboring Nb sites, resulting in the localized formation of nitrides. Such phase and structural changes contributed to further improve corrosion resistance. In particular, the implanted Nb layer at bias voltage of 10 kV exhibited a current density more than one order of magnitude smaller with a two times faster stabilization than the as-deposited Nb layer under the PEMFC operating conditions.
ISSN:	1996-1944 1996-1944