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A method involving HNO3/NH3 treatments of a carbon support (Vulcan XC-72R), addition of Fe from inorganic precursors, and a thermal treatment at 900 °C under an inert atmosphere for the preparation of Fe-based oxygen reduction electrocatalysts for use in polymer electrolyte fuel cells has been investigated. The prepared materials were evaluated in acidic medium by the rotating disk electrode technique using the potential at the oxygen reduction peak, E p, as a measure of the electrocatalytic activity. Two sets of experiments were performed: (i) varying the conditions of the HNO3/NH3 treatments of Vulcan XC-72R, and (ii) varying Fe loadings added to the HNO3/NH3 pretreated C samples. In the first set of experiments, no Fe was adsorbed on the C support. It was shown that a combined HNO3 and NH3 treatment of the carbon support gave higher activity for oxygen reduction than either HNO3 or NH3 treatment alone. In the second set of experiments, it was shown that the activity of the HNO3/NH3-modified C support increases steadily as the iron content is increased from 10 to about 1000 ppm. Above that Fe content, the activity of the materials first levels off and then decreases for even larger Fe concentrations. The value of E p at saturation increases with the total N surface content of HNO3/NH3-pretreated C support. X-ray photoelectron spectroscopy reveals that at maximal electrochemical activity, there is only 1 Fe atom per 100 N atoms at the surface of the carbon support. For larger Fe contents another mechanism, i.e., the aggregation of small iron-containing particles, probably accounts for all additional Fe ions adsorbed on the modified carbon black during the preparation procedure.

The capacitive behavior of TiC-derived carbon powders in two different electrolytes, NEt 4 BF 4 in acetonitrile ͑AN͒ and NEt 4 BF 4 in propylene carbonate ͑PC͒, was studied using the cavity microelectrode ͑CME͒ technique. Comparisons of the cyclic voltammograms recorded at 10-1000 mV/s enabled correlation between adsorbed ion sizes and pore sizes, which is important for understanding the electrochemical capacitive behavior of carbon electrodes for electrical double-layer capacitor applications. The CME technique also allows a fast selection of carbon electrodes with matching pore sizes ͑different sizes are needed for the negative and positive electrodes͒ for the respective electrolyte system. Comparison of electrochemical capacitive behavior of the same salt, NEt 4 BF 4 , in different solvents, PC and AN, has shown that different pore sizes are required for different solvents, because only partial desolvation of ions occurs during the double-layer charging. Squeezing partially solvated ions into subnanometer pores, which are close to the desolvated ion size, may lead to distortion of the shape of cyclic voltammograms. Global warming, as well as the increasing price and decreasing availability of fossil fuels, all highlight the need to move toward a sustainable development where renewable energy and electric/ hybrid vehicle engines are widely used. Renewable energy sources such as sunlight, wind, or hydro ͑rivers, waves, etc.͒ generate electrical energy which must be stored for use in autonomous systems such as transportation or electronics. Therefore, the development of high-performance electrical-energy storage devices is required.There are two major types of electrical-energy storage devices, batteries and electrical double-layer capacitors ͑EDLCs͒. Batteries are electrochemical-energy storage devices that can be fully discharged in a few minutes or hours efficiently. Li-ion batteries, for example, exhibit high specific energy ͑ϳ150 Wh/kg͒ but are today limited in high-power delivery/uptake as well as in low-temperature operation ͑failure below −20°C͒ and cycle life.1 EDLCs, also known as supercapacitors or ultracapacitors, can be reversibly charged/discharged at higher rates as compared to batteries, thus enabling energy recovery ͑harvesting͒ at much higher rates as well.2,3 Their cycle life ͑Ͼ500,000 cycles͒ as well as lowtemperature operation ͑down to −40°C͒ positively compare to batteries. However, the specific energy of supercapacitors is about 20 times less than that of Li-ion batteries. EDLCs thus have to be used complementary with batteries in many of the applications where high-power delivery/uptake is needed, such as in hybrid electric vehicles, photo and video cameras, cell phones, etc. 3Recent publications suggested that a real breakthrough in improving the specific energy of EDLCs could be obtained using tailored microporous carbons 4 such as carbide-derived carbons ͑CDCs͒.5 CDCs are obtained by the extraction of a metal from its carbide at high temperatures.6-8 Using TiC as the precursor and chlo...

Large areal capacitance electrodes made of ruthenium oxide on highly porous gold current collectors are realized by an attractive approach. The hybrid structure exhibits a capacitance in excess of 3 F cm(-2) and an areal energy density for all-solid-state microsupercapacitors that is comparable to those of microbatteries.

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To enhance the catalytic activity of gold nanoparticles (AuNPs) for the hydrogenation of nitro-aromatic chemicals, Pt was introduced into AuNPs to form "bare" PtAu alloy NPs using a physical approach, pulsed laser ablation in liquid (PLAL), on single metal-mixture targets. These PLAL-NPs are deemed to favor catalysis due to the absence of any surfactant molecules on their unique "bare and clean" surface. The PLAL-NPs were facilely assembled onto CeO2 nanotubes (NTs) by simply mixing them without conducting any surface functionalization, representing another advantage of these NPs. Their catalytic activity was assessed in 4-nitrophenol (4-NP) hydrogenation. The reaction catalyzed by alloy-NP/CeO2-NT catalysts demonstrates a remarkably higher reaction rate in comparison with that catalyzed by pure Au and Pt NPs, and other similar Au and Pt containing catalysts reported recently. A "volcano-like" catalytic activity dependence of the alloy NPs on their chemical composition suggests a strong synergistic effect between Au and Pt in the 4-NP reduction, far beyond the simple sum of their individual contributions. It leads to the significantly enhanced catalytic activity of Pt30Au70 and Pt50Au50 alloy NPs, outperforming not only each single constituent, but also their physical mixtures and most recently reported AuNP based nanocatalysts. The favorable d-band center shift of Pt after alloying, and co-operative actions between Pt clusters and nearby Au (or mixed PtAu) sites were proposed as possible mechanisms to explain such a strong synergistic effect on catalysis.