Kinetics of oxygen reduction reaction on supported Pt and several Pt alloy electrocatalysts (PtCo/C and PtFe/C) have been investigated in terms of the effect of alloying on the initiation and extent of surface oxide formation (water activation:  xH2O + Pt*(M) → (M)Pt−[OH] x + xH+ + xe-). For this, a systematic RRDE investigation has been conducted in trifluoromethane sulfonic acid (TFMSA) as a function of concentration (in the range 1 to 6 M) which corresponds to a change in mole ratio of water/acid from 50:1 in 1 M to 4:1 in 6 M TFMSA. This change in relative amount of water in the various concentrations can also be indirectly correlated to the relative humidity in an operating PEM fuel cell. The scope of this effort was (a) to confirm the shift and lowering of water activation on supported Pt alloy electrocatalysts relative to Pt at lower concentrations (1 M); (b) to compare the inherent activity for ORR on supported Pt and Pt alloy nanoparticles without the effect of oxide formation via activation of water, this was enabled at higher concentrations of TFMSA (6 M); (c) to relate the activation energy values at 1 M for Pt and Pt alloy electrocatalysts for further insight into the nature of the rate-determining step in the mechanism; and (d) to examine the relative formation of peroxides via a parallel pathway for Pt and Pt alloy electrocatalysts in 1 and 6 M TFMSA. Our results confirm that for fully hydrated systems akin to 1 M concentration the alloys shift the formation and extent of water activation on the Pt alloy surfaces; this has been correlated with in-situ XAS data (changes to Pt electronic states and short-range atomic order) as well as via direct EXAFS probe of the formation of oxygenated species above 0.75 V (typical potential for initiation of surface oxides on Pt). The lowering of oxide formation agrees well with the extent of enhancement of ORR activity. Activation energy determinations at 1 M concentration however revealed no difference between Pt and Pt alloys, indicating thereby that the rate-limiting step remains unchanged. At lower water activity (6 M) with negligible water activation (and hence surface oxides), the Pt surface was found to possess a higher activity for ORR as compared to the alloys. In addition, the determination of peroxide yield on the Pt surface showed that there was variation both in terms of alloy formation as well as the water activity at the interface. All these results have been discussed in the context of a PEM fuel cell operating in the low to medium temperature range (70−120 °C) and humidity variation (100 to 10%).

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This paper is a full version of an earlier short communication, where significantly higher ͑up to threefold͒ CO tolerance was reported for PtMo/C ͑atomic ratio, Pt:Mo, 3:1͒ relative to the current state-of-the-art PtRu/C ͑1:1͒ in a proton exchange membrane fuel cell ͑PEMFC͒ under standard operating conditions ͑85°C, 100% humidification, with H 2 ϩ 100 pm CO//O 2 ). We report significantly different behavior for PtMo/C in contrast to PtRu/C, wherein there is negligible variation in CO tolerance ͑100 ppm CO in H 2 ) with variations in alloying compositions ͑Pt:Mo, 1:1 to 5:1͒. Further, in contrast to Pt/C and PtRu/C, significantly lower variations in overpotential losses is observed for PtMo/C as a function of temperature ͑55-115°C͒ and CO concentrations ͑5-100 ppm, balance H 2 ). In addition, excellent long-term stability is reported for PtMo/C ͑1:1͒ under steady-state conditions ͑constant potential conditions at 0.6 V͒ for a total duration of 1500 h, with anode gas composition varied between pure H 2 and those with 100 ppm CO, with or without the presence of other reformate gases ͑primarily CO 2 and N 2 ). These are discussed in the context of detailed physicochemical characterization of the nanoparticles using a combination of X-ray diffraction, transmission electron microscopy, and in situ synchrotron X-ray absorption spectroscopy.CO tolerance in reformer-based low-and medium-temperature proton exchange membrane fuel cells ͑PEMFCs͒ is crucial for the viability of this technology for transportation and portable power applications. The choice of an appropriate anode electrocatalyst with low susceptibility to CO poisoning and a high kinetic rate for hydrogen oxidation is therefore paramount. Despite its superior activity for anodic, hydrogen oxidation, and interfacial stability under acidic pH conditions and the operating temperatures of an actual PEMFC, electrocatalysis by Pt/C suffers from the problem of high polarization losses due to CO poisoning. This is especially true for temperatures below 115°C.The large affinity for CO chemisorption at potentials lower than ϳ0.65 V on Pt/C necessitates the search for other nanophase Ptbased electrocatalysts capable of initiating CO oxidation, preferably close to the hydrogen oxidation potential. This need manifested in the ''bifunctional'' 1,2 approach, where a second, more oxidizable element, present either as an admetal or as an alloying element, initiates the CO oxidation at lower potentials. The result is enough bare surface on Pt crystallites to efficiently oxidize hydrogen at lower overpotentials.Prior literature, involving several decades of research, is replete with investigations of alloys such as PtSn, 3,4 PtRh, 5 PtRu, 6-8 and Pt with adsorbing adatoms such as Ge, Sb, and Sn, 2,9 etc. In recent years nanophase PtRu electrocatalysts have received renewed attention as promising candidates for CO oxidation in PEMFCs. 10-12 A recent report by Oetjen et al., 13 using steady-state polarization data, indicates a fourfold performance enhancement with highly dispersed ...

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A conjugated light-emitting polymer based on the binaphthyl structure was synthesized via the Wittig−Horner condensation reaction. By introducing a twisted, noncoplanar binaphthyl unit, it provides an effective approach for tailoring the spectral characteristics and solubility of the polymer. The polymer has a very high glass transition temperature (T g) of 225 °C and good solubility in common organic solvents. A single layer light-emitting diode with a configuration of (ITO/polymer/Al) showed a respectable external quantum efficiency of 0.1%.