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Studying the ORR activity of platinum-based electrocatalysts is an urgent task in the development of materials for proton-exchange membrane fuel cells. The catalytic ink composition and the formation technique of a thin layer at the RDE play a significant role in studying ORR activity. The use of a polymer ionomer in the catalytic ink provides viscosity as well as proton conductivity. Nafion is widely used as an ionomer for research both at the RDE and in the MEA. The search for ionomers is a priority task in the development of the MEA components to replace Nafion. The study also considers the possibility of using the LF4-SK polymer as an alternative ionomer. The comparative results on the composition and techniques of applying the catalytic layer using LF4-SK and Nafion ionomers are presented, and the influence of the catalytic ink composition on the electrochemical characteristics of commercial platinum–carbon catalysts and a highly efficient platinum catalyst based on an N-doped carbon support is assessed. [ABSTRACT FROM AUTHOR]

We report the development of a novel electrocatalyst composed of nanoarchitectured spinel cobalt manganese oxide and graphene for the oxygen reduction reaction (ORR). A combination of co-precipitation and hydrothermal methods achieved the unique nanoarchitecture of the electrocatalyst. The formation of CoMn2O4 electrocatalyst was confirmed by X-ray diffraction, transmission electron microscopy, and other spectroscopic and microscopic techniques. In addition to synthesizing CoxOy and MnxOy as control electrocatalysts, we created a physical mixture of CoMn2O4 and graphene to investigate the impact of their interface on electrocatalytic activity. Our findings indicate that CoMn2O4/graphene exhibits improved ORR activity, stability, and methanol tolerance in an alkaline medium. This enhancement can be attributed to the synergistic effect and strong interface interaction between CoMn2O4 and graphene. This study demonstrates the potential of the proposed electrocatalyst as a cost-effective and eco-friendly alternative for oxygen reduction in fuel cells applications. [ABSTRACT FROM AUTHOR]

As a kind of nitrogen-containing material, polyamide acid (PAA) was doped by Fe using ferric trichloride (FeCl 3 ), thus obtaining a carbon material (Fe-PAA) containing iron and nitrogen. The preparation efficiency of this material as electrocatalyst was improved and the cost was reduced. In this study, Fe-PAA was used as cathode electrocatalyst in microbial fuel cells (MFCs), and the effect of holding time (HT) on the oxygen reduction was investigated. The oxygen reduction reaction (ORR) electron transfer number of the Fe-PAA was about 3.55 when the HT was 90 min. This result demonstrates that Fe-PAA could be a promising highly efficient and low-cost cathode catalyst which could be further applied in MFC expansion. [ABSTRACT FROM AUTHOR]

A planar iron-polyphthalocyanine (PPcFe) oxygen reduction reaction (ORR) catalyst for magnesium air fuel cells (MAFC) is prepared by dispersing PPcFe on carbon black (C) and heating under argon. Thermogravimetric analysis shows PPcFe is stable below 600 °C. The X-ray diffraction and X-ray photoelectron spectroscopy results show the active site of PPcFe/C is the FeN4 in the phthalocyanine ring. The rotating disk electrode measurements in 0.5 M L−1 H2SO4 solution show the initial potential for ORR is 0.82 V vs. RHE at 20 °C and that it mainly occurs via a four-electron process. Almost no performance degradation is observed over continuous cyclic voltammetry at 10,000 cycles, linear sweep voltammetry at 200 cycles, and 60 h of the chronoamperometry test. The infrared spectrum of PPcFe, after all the durability tests, shows no changes from the initial characteristics. The polarization curves of the air electrodes with PPcFe/C, iron-phthalocyanine/C and Pt/C catalysts exhibit excellent polarization performances. The discharge performance of a MAFC single cell with PPcFe/C cathode catalyst shows an open circuit potential of 1.74 V, with a peak power density of 50.5 mW cm−2 at 20 °C. The cell voltage decreases less than 0.01 V during continuing discharge @ 20 mA cm−2 for more than 11 h. [ABSTRACT FROM AUTHOR]

A new platinum group metal (PGM)-free proton exchange membrane fuel cell (PEMFC) cathode catalyst materials, synthesized using the VariPore™ method by Pajarito Powder, LLC, are characterized for their structure and activity. The physico-chemical analysis of the iron-nitrogen-carbon (Fe-N-C) electrocatalysts show mesoporous carbon material effectively doped with iron and nitrogen. The materials have an average pore size of 7–8 nm and high specific surface area. The Fe-N-C catalysts exhibit good oxygen reduction reaction (ORR) activity in 0.5 M H 2 SO 4 electrolyte with high half-wave potential and sustainable electrochemical stability over 10,000 repeated potential cycles with insignificant losses in their activities. As cathode catalysts in a PEMFC, the Fe-N-C materials deliver remarkably good fuel cell performance at low overpotential approaching that of the commercial Pt catalyst. The high ORR electrocatalytic activity of these Fe-N-C catalysts is credited to the synergy between nitrogen-moieties, specifically pyrrolic-N, pyridinic-N, and graphitic-N, and iron in addition to the high mesoporosity that facilitate an effective reaction path in boosting the electrocatalytic activity and stability. [Display omitted] • State-of-the-art commercial PGM-free catalysts for ORR were characterized and evaluated. • Was shown that active centres are atomically dispersed. • Performance of electrocatalysts was evaluated in industrially manufactured MEA form-factor. • The fuel cell performance is close to the state-of-the-art R&D PGM-free catalysts. [ABSTRACT FROM AUTHOR]

Abstract: Fuel cells, especially low temperature fuel cells are clean energy devices that are expected to help address the energy and environmental problems that have become prevalent in our society. Platinum-based electrocatalysts are usually used as the electrocatalysts for both the anode (hydrogen oxidation) and cathode (oxygen reduction) reactions. The high cost and limited resources of this precious metal hinder the commercialization of fuel cells. Recent efforts have focused on the discovery of palladium-based electrocatalysts with little or no platinum for hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR). This paper overviews the recent progress of electrocatalysis of palladium-based materials including both extended surfaces and nanostructured ones for HOR and ORR. The properties of CO and methanol tolerances of palladium-based electrocatalysts are also summarized. [Copyright &y& Elsevier]

The oxygen reduction reaction (ORR) is still the most research-intensive aspect of a fuel cell. The sluggish kinetics of the electrocatalysts toward the ORR requires large amounts of platinum to be used as cathode material, which calls for alternatives to replace or minimize the amount of the noble metals used. This study describes the synthesis and complete characterization of a copper metallopolymer (Cu MP) based on a conducting polymer (CP) and single-site catalytic centers for the electrocatalytic ORR. The copper (II) catalyst, embedded in a redox-active and conducting polymeric environment, was pursued as a potential candidate to replace noble metals in fuel cell applications. Performance studies at a rotating disk electrode (RDE) showed that the metallopolymer exhibited a direct four-electron reduction at potentials between −150 and −350 mV vs. the reversible hydrogen electrode (RHE) and high kinetic current densities of over 22.62 mA/cm2. The kinetic current densities obtained at the Cu MP electrode outperformed most of the reported state-of-the art electrocatalysts toward the ORR. Further analysis of the Cu/CP hybrid revealed the copper being largely reduced to the oxidation state +I. [ABSTRACT FROM AUTHOR]