Iron based nitrogen doped carbon (FeNC) catalysts are synthesized by high-pressure pyrolysis of carbon and melamine with varying amounts of iron acetate in a closed, constant-volume reactor. The optimum nominal amount of Fe (1.2 wt%) in FeNC catalysts is established through oxygen reduction reaction (ORR) polarization. Since the quantity of iron used in FeNCs is very small, the amount of Fe retained in FeNC catalysts after leaching is determined by UV-VIS spectroscopy. As nitrogen is considered to be a component of active sites, the amount of bulk and surface nitrogen retention in FeNC catalysts are measured using elemental analysis and X-ray photoelectron spectroscopy, respectively. It is found that increasing nominal Fe content in FeNC catalysts leads to a decreased level of nitrogen retention. Thermogravimetric analysis demonstrates that increasing nominal Fe content leads to increased weight loss during pyrolysis, particularly at high temperatures. Catalysts are also prepared in the absence of iron source, and with iron removed by washing with hot aqua regia post-pyrolysis. FeNC catalysts prepared with no Fe show high retained nitrogen content but poor ORR activity, and aqua regia washed catalysts demonstrate similar activity to Fe-free catalysts, indicating that Fe is an active site component.

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A role of the gas diffusion layer (GDL) in cationic contamination and mitigation has been studied with isopropanol (IPA) as a wetting agent of the GDL. For this test, the catalyst coated membrane is not in direct contact with the contaminating solution, being separated by both the GDL and the gasket. The hydrophobic layer of the GDL acts as a barrier to the transport of foreign cations into a membrane. The effect on performance of the added 15% IPA as a wetting agent in the cationic solution was verified by an ex-situ soak method and by an in-situ injection method for both mitigation and recovery processes. Wetting forces and contact angles were measured to quantify the GDL wettability changes attributed to the added IPA solution. The cationic mitigation solution and the acid cleaning solution can transport across the GDL into the CCM, but the overall cell performance was not fully recovered.

The effect of Ca2+ ion contamination on a low-Pt loaded PEFC cathode (0.1 mg/cm2) was investigated systematically. Calcium sulfate dissolved in water was injected at the cathode of a single cell in aerosol form under a constant current (1 A/cm2). For comparison, a baseline test was also performed at the same conditions with deionized water. The performance decay rate for the baseline cell was 175 µV/h, whereas the CaSO4 injected cell declined much faster with a decay rate of 804 µV/h. Electrochemical, physical and spectroscopical studies confirm that injecting CaSO4 at the cathode affects the catalyst layer resulting in thinning, alters the GDL as salt deposits in the pores and no effect was seen in the polymer electrolyte membrane.

Cationic contamination in polymer electrolyte fuel cells (PEFC) is investigated by contaminating a catalyst coated membrane (CCM) in Ca2+ solution prior to a long term durability test. The cathode catalyst layer of the contaminated CCM becomes significantly thinner over the entire active area of the CCM as compared to an as-received, uncontaminated CCM. It is found that there is no change in the total Pt content in cathode catalyst layer, and the only possible element loss that may cause significant catalyst layer thickness change is carbon. Since the cation tends to accumulate in the cathode catalyst layer during the fuel cell test, it is hypothesized that the cation accumulation in the catalyst layer can render the Pt inactive, and either directly or indirectly increases the carbon oxidation reaction rate resulting in catalyst layer thinning.

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Electrodeposition of Zn-Mn alloys were carried out in an acidic chloride bath. The influence of electrolytic bath composition and deposition parameters on the alloys’ composition, cathodic current efficiency and corrosion properties were examined. It was found that the composition of plating baths and deposition potential have significant effect on manganese content and Zn-Mn deposit morphology, as well as on the corrosion properties of the alloy. Linear and Tafel polarization studies showed that the incorporation of Mn in the Zn enhances the corrosion resistance when compared to bare Zn. Anodic passivation studies indicated two orders of magnitude lower passivation current for the Zn-Mn alloy (17% Mn) when compared to that of Zn.

Owing to the sluggish kinetics of oxygen reduction reaction (ORR), conventionally, high surface carbon-supported Pt serves as an electrocatalyst. However, carbon corrosion occurs at high potentials and conditions result in agglomeration/sintering of Pt catalyst particles and subsequent decrease in electrochemical surface area (ECSA) and ORR activity. As a result, more stable and non-carbon based catalyst supports are increasingly getting attention. Among the alternative support materials, the transition metal oxides are considered to be emerging candidates for catalyst-support.1 In these, TiO2, being cost-effective and acid stable, is particularly attractive.2  Brewer and Wenger3 reported that the hypo d-electron character of titanium oxide facilitates its interaction with noble metals, like Pt, changing the catalytic activity of the noble metal. Suitability of TiO2 as a catalyst support material has been studied extensively.1,2 Although TiO2shows higher durability in relation to conventional carbon supports, its electronic conductivity is relatively lower, resulting in increased ohmic resistance. In the present work, TiO2 nanorods with specific length and width are synthesized through physical vapor deposition (PVD) technique using the glancing angle deposition (GLAD). Subsequently, the interconnected Pt nanoparticles are deposited on surface of the TiO2 nanorods for efficient catalytic activity and fine electron connectivity towards the electrode substrate. In addition, the controlled porous catalyst matrix would aid the efficient reactant and product transport. Figure 1 shows the scanning electron microscopy images of TiO2 and Pt-TiO2 on silica wafer substrates. These images show the nanorods of TiO2 are encapsulated by ‘bud’ shaped inter connected Pt particles. As the surface energy of Pt is higher than TiO2 surface,4 Pt does not cover the TiO2surface homogeneously resulted structured morphologies. Generally, the electrochemical reactions are surface reactions, the Pt rich edges are possibly involve the ORR reactions and tiny bottom layers are contribute to the electron connectivity. To study the electrochemical behavior of the synthesized Pt-TiO2, cyclic voltammetry measurements are performed in aq. perchloric acid (0.1 M) on glassy carbon substrates and by using Pt and Ag/AgCl/Cl- as the counter and reference electrodes, respectively.  The characteristics peaks of H2 adsorption and desorption (Figure 2) indicate the metallic nature of Pt. The preliminary results that obtained from ORR reveal the enhanced activity and the ultra-high stability of Pt-TiO2catalyst. Acknowledg e ments The authors gratefully acknowledge financial support from the National Science Foundation (CBET-0748063).  References Y. Wang, D. P. Wilkinson and J. Zhang, Chem. Rev., 111, 12 (2011). S. Huang, P. Ganesan, S. Park and B. N. Popov, J. Am. Chem. Soc., 131, 39 (2009). L. Brewer and P. R. Wengert, Metall. Trans., 4, 83 (1973). C. T. Campbell, Surf. Sci. Rep. 27, 1 (1997). Figure 1