The current study explores the potential utilization of tungsten monocarbide (WC) and Pd-modified WC as anode electrocatalysts in direct methanol fuel cells (DMFC). Density functional theory (DFT) calculations and ultrahigh vacuum (UHV) studies were performed to determine how the presence of Pd affected the bonding and reaction pathways of methanol on the WC surface. These studies showed that the WC surface was very active toward the O–H bond cleavage to produce a methoxy intermediate, although WC was less active for the C–H bond scission. Adding Pd on WC enhanced the scission of the C–H bonds of methoxy, suggesting a synergistic effect of using Pd-modified WC as electrocatalysts for methanol decomposition. The prediction from UHV studies was verified in electrochemical experiments using cyclic voltammetry (CV) and chronoamperometry (CA) measurements of electro-oxidation of methanol in an alkaline environment.

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[a] Supercapacitors have attracted much attention in recent years [1] due to their ability to store energy comparable to batteries such as PbO 2 /Pb or Ni/MH, and to deliver the stored energy much more rapidly than batteries.[2] Supercapacitors not only store charges between the electrode and electrolyte interfaces as electrochemical double layer capacitor (EDLC), [3,4] but they also store extra charges with a fast and reversible redox reaction between electrode and the electroactive species in the electrolyte as pseudocapacitors.[5-10] Such a redox reaction often takes place in oxides where metal ions have multiple valence states. [11][12][13] Most studies have focused on increasing the surface area of electrodes in order to increase the capacitance. [14][15][16] Although this is a viable approach, [17][18][19][20] it is also critical to determine whether there is significant contribution from the bulk of the materials, and if so, how one can take advantage of the bulk contribution by understanding its characteristics. The existence of the bulk contribution is evident from the fact that the capacitance is much larger in amorphous materials than their crystalline counterparts. [21,22] However, there is no quantitative understanding concerning the capacitance in electrodes of different structures. With these questions in mind, it is worthwhile to point out that the purpose of the current work is not to demonstrate another supercapacitor with enhanced performance. More importantly, our goal is to establish the quantitative understanding of surface and bulk contributions between amorphous and crystalline electrodes and their electrochemical characteristics, which will benefit future electrode design. We have chosen NiO films as a model system. Our experimental results indicate the surface contribution to supercapacitance is the same for amorphous and crystalline materials where the bulk contribution is three times greater in amorphous materials. The results are believed to also be applicable to other electrode materials.Both crystalline and amorphous NiO films were made by radio requency (RF) magnetron sputtering in a mixture of O 2 and Ar gases at a fixed pressure (1.33 Pa). The relative flow rates were varied to control the stoichiometry and crystallinity. At 5 % (flow rate) O 2 , crystalline NiO phase was achieved as shown in Figure 1 , within the potential window of 0 V-0.85 V in reference to the normal hydrogen electrode (NHE). Similar CV curves, but with much smaller current density, were observed in the crystalline NiO films. Peak 1 and peak 2 are a pair of redox processes with insertion/extraction of OH À according to:Peak 3 was attributed to the evolution of oxygen gas from the decomposition of aqueous solution. NiO-based electrochemical capacitor showed an ideal capacitance behavior in the potential window between 0 to 0.5 V (Figure 1 b), that is, the current density was weakly dependent on the applied potential. The ideal specific capacitance (SC) was estimated to be 258 F g À1 at a scanning rate of ...

Selectively converting biomass-derived oxygenates to H 2 or syngas (H 2 and CO) is critical in the utilization of biomass to replace fossil fuels. In previous studies, monolayer (ML) Ni on a Pt substrate showed enhanced conversion and selectivity for oxygenate conversion. In the current work, tungsten monocarbide (WC) is used to support monolayer Ni, with the aim of replacing ML Ni−Pt with ML Ni−WC. C2 oxygenates with different functional groups, ethylene glycol, acetaldehyde, and acetic acid, are studied on clean WC and Ni-modified WC surfaces. For each C2 oxygenate, density functional theory (DFT) calculations reveal different binding energies on WC and Ni−WC surfaces. Parallel experimental measurements using temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS) confirm the different reaction pathways on the two types of surfaces, with the dominant decomposition pathway being C−O bond scission on clean WC and C−C bond cleavage on Ni-modified WC surfaces. Furthermore, using ethylene glycol decomposition as a probe reaction, the ML Ni−WC surface exhibits a similar net reaction pathway as that of ML Ni−Pt(111).

Synthesis of high yield single helical carbon microsprings by catalytic chemical vapor deposition and an experimental investigation of their growth mechanism Investigation of the nanostructure and wear properties of physical vapor deposited CrCuN nanocomposite coatings J. Vac. Sci. Technol. A 23, 423 (2005); 10.1116/1.1875212Growth of cubic SiC thin films on Si(001) by high vacuum chemical vapor deposition using 1,3-disilabutane and an investigation of the effect of deposition pressureThe synthesis of tungsten monocarbide ͑WC͒ thin films has been performed by physical vapor deposition on various substrates including glassy carbon, carbon fiber sheet, carbon foam, and carbon cloth. The WC and W 2 C phase contents of these films have been evaluated with bulk and surface analysis techniques such as x-ray diffraction, x-ray photoelectron spectroscopy, and scanning electron microscopy. These characterization techniques were also used to determine the effects of synthesis by nonreactive and reactive sputtering. The synthesis of WC particles supported on the carbon fiber substrate has also been accomplished using the temperature programmed reaction method. Overall, the results demonstrate that the phase purity of tungsten carbides can be controlled by the deposition environment and annealing temperatures.