Teijin Limited is developing a non-platinum carbon alloy catalyst (CAC) for the cathode oxygen reduction reaction (ORR) in polymer electrolyte fuel cells. CAC is made from polyacrylonitrile (PAN) and steel via carbonization. Less expensive and more readily available than platinum, PAN enables the catalyst to be produced at reduced cost and in higher volumes.
Teijin has been developing and refining its CAC technologies in collaboration with researchers at the Tokyo Institute of Technology. The effort is part of a project targeting the development of automotive fuel cells using CAC, led by the New Energy and Industrial Technology Development Organization (NEDO). (NEDO launched work on CAC as part of a larger fuel cell effort in FY 2008.) Teijin says it will continue to advance the properties and durability of its CAC, targeting commercial use by 2025.
In a 2014 paper in the Journal of the American Chemical Society, researchers from the Tokyo institue of Technology noted that:
The efficiency of PEMFC [proton exchange membrane fuel cells] is determined by oxygen reduction reaction (ORR) at the cathode, and up to now the most effective cathode catalysts for the ORR are platinum-based catalysts. However, its large scale commercial applications are hindered by high cost of Pt, and the Pt-based electrode also suffers from low selectivity, poor durability, and CO deactivation.
Currently, the carbon alloy catalysts (CACs) are the most promising catalysts alternative to Pt-based catalysts because of their good performance for ORR, low cost, rich resource, and free from CO “poisoning”, although the ORR activity is not yet so high as that of Pt-based catalysts, particularly in acidic conditions. The N-doped CACs are much more intensively studied than the related CACs doped with P, S, and B. Generally, the N-containing CACs are synthesized by carbonization of transition-metal macrocyclic compounds together with some carbon sources or N-containing precursors with transition-metal salts. The basic structural components of CACs are multilayered nanographene (nano- graphite) including carbon nanotubes (CNTs).
Although intensive investigations have been performed on CACs, the active sites and reaction mechanisms are poorly understood and controversial. Whether the ORR activity of N-doped CACs is attributed to pyridinic nitrogen (denoted as p-N), graphitic nitrogen (denoted as g-N), or transition metal elements (such as FeNx centers) has been a topic of intense debate for a long time.—Chai et al.
Teijin says that CAC demonstrates excellent performance using catalytic particles miniaturized by proprietary polymer chemistry and carbonization processes. It enables fuel cells to achieve electrical generation on levels equal to those of other high-quality fuel cells using a non-platinum catalyst.
Conventional catalysts in fuel cells contain large amounts of expensive platinum; the development of less costly and more easily obtainable substitutes has been seen as an enabler of the expansion of fuel cell use.
Jisung Park, Yuta Nabae, Teruaki Hayakawa, and Masa-aki Kakimoto (2014) “Highly Selective Two-Electron Oxygen Reduction Catalyzed by Mesoporous Nitrogen-Doped Carbon,” ACS Catalysis 4 (10), 3749-3754 doi: 10.1021/cs5008206
Guo-Liang Chai, Zhufeng Hou, Da-Jun Shu, Takashi Ikeda, and Kiyoyuki Terakura (2014) “Active Sites and Mechanisms for Oxygen Reduction Reaction on Nitrogen-Doped Carbon Alloy Catalysts: Stone–Wales Defect and Curvature Effect,” Journal of the American Chemical Society 136 (39), 13629-13640 doi: 10.1021/ja502646c
Masayuki Chokai, Masataka Taniguchi, Shogo Moriya, Katsuyuki Matsubayashi, Tsuyoshi Shinoda, Yuta Nabae, Shigeki Kuroki, Teruaki Hayakawa, Masa-aki Kakimoto, Jun-ichi Ozaki, Seizo Miyata (2010) “Preparation of carbon alloy catalysts for polymer electrolyte fuel cells from nitrogen-containing rigid-rod polymers,” Journal of Power Sources, Volume 195, Issue 18, Pages 5947-5951 doi: 10.1016/j.jpowsour.2010.01.012