Electrocatalytic Activity and Stability of M-Fe Catalysts Synthesized by Polymer Complex Method for PEFC Cathode

Abstract

The polymerized complex (PC) method was used to synthesize highly dispersed iron-based catalysts for the oxygen reduction reaction (ORR). The catalysts were prepared with an addition of 1,10-phenanthroline (Phen) and transition metals (M), such as Ta, Ti, and W, in an attempt to enhance the ORR activity and durability of the catalysts. The composition and properties of the catalysts were characterized by thermogravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. The catalyst components, after extensive dissolution in a strong acid solution, were characterized by inductively coupled plasma mass spectroscopy and ultraviolet-visible spectroscopy. It was found that the Ti-Fe catalyst showed improved ORR performance, and the Ta-Fe catalyst showed enhanced stability towards ORR in acidic solution. The catalytic activity and stability for ORR was observed by adding Ti or Ta into the catalyst formulation, suggesting that the interaction between added hetero-ions (Ti and Ta) and ionic Fe active sites was beneficial for the ORR. A single-cell test with the synthesized catalyst in the cathode initially generated a high power density, but the low stability remains an issue to be solved.

Nano-nitride Cathode Catalysts of Ti, Ta, and Nb for Polymer Electrolyte Fuel Cells: Temperature-Programmed Desorption Investigation of Molecularly Adsorbed Oxygen at Low Temperature

“…As an Fe-containing reference electrode catalyst, an Fe-based Ti-containing catalyst was prepared by the PC method, as described in our previous paper . The catalysts were prepared using 1,10-phenanthroline and NH 3 gas as the nitrogen source and formed Fe-based active sites for ORR.…”

“…The first example was a catalyst consisting of transition-metal Fe or Co complexes dispersed in macrocyclic structures such as porphyrin, phenanthroline, phthalocyanine, polyacrylonitrile, polypyrrole, or polyaniline. − Later, carbon-based materials, even without transition metals, especially when doped with nitrogen, were reported to exhibit excellent ORR activity. − Nevertheless, none of these electrocatalysts has reached the catalytic activity of Pt-based electrocatalysts, and stability in an acidic environment remains an unsolved issue. Another approach for developing non-noble-metal cathodes is the use of groups IV and V transition metals, because of their abundance and high stability in acidic media. − Ota et al reported that partially oxidized TaC x N y , ZrC x N y , and NbC x N y showed onset potentials for the ORR comparable to those of Pt-based catalysts while remaining highly stable under PEFC cathode conditions. − Until recently, because the synthesis of these catalysts required high-temperature treatment, only bulky, low surface area particles were produced with diameters up to 100 nm, resulting in low current densities.…”

“…We have therefore investigated several synthetic methods to produce nano- or subnanosized ORR catalysts well dispersed on carbon black (CB) powders. − First, an arc plasma method was used to produce subnanosized Nb–oxynitride-like materials by controlling the gas atmosphere (N 2 and O 2 ) . Second, a polymer complex (PC) method in solution phase was utilized to prepare well-dispersed catalysts of Ba–Nb, Ba–Zr, and Fe–Ti on CB. − Recently, electrodeposition from a nonaqueous electrolyte bath has been established for preparation of Ta cathode catalysts with nanoscale dispersion . Alternatively, titanium nitride (TiN) nanoparticles prepared using mesoporous graphitic (mpg)-C 3 N 4 templates have been investigated as nanosized ORR catalysts .…”

Effects of transition metal precursors (Co, Fe, Cu, Mn, or Ni) on pyrolyzed carbon supported metal-aminopyrine electrocatalysts for oxygen reduction reaction

“…Unfortunately, Pt material is both expensive and low abundance, which have been identied to be the major contributors to the challenges of high-cost of PEM fuel cells. 2,4,8 Furthermore, regarding the challenge of insufficient durability, there are two major contributing factors including (1) the cathode Pt catalyst is easily to be dissolved when the electrode is performed in a highly acidic environment and polarized at a positive potential, 9 and (2) Pt catalysts can be easily poisoned by the impurities in the feed system, resulting in performance degradation. 4,10,11 To overcome these challenges, developing alternative ORR electrocatalysts such as non-precious metal catalysts (NPMCs) have been becoming the most active approach in fuel cell catalyst research and development in the recent years.…”

Effect of acid-leaching on carbon-supported copper phthalocyanine tetrasulfonic acid tetrasodium salt (CuTSPc/C) for oxygen reduction reaction in alkaline electrolyte: active site studies

“…6 To make PEM fuel cells technically feasible and practical, in the current state of technology, Pt-based catalysts must be used to catalyze the slow ORR due to their high catalytic performances for both the anode and cathode. However, as Pt-based catalysts have insufficient electrochemical durability and come at a high cost, [6][7][8] the major efforts in PEM fuel cell research and development have been put into reducing Pt loading by exploring more active catalysts, and/or replacing Pt metal with other, nonprecious, metals such as Fe, Co and Cu. 9,10 In spite of current progress, very few examples show real promise to be comparable to Pt since the requirements for both good ORR activity and stability are difficult to achieve for normal non-noble catalysts in the strongly acidic conditions of PEM fuel cell operation.…”