James A. Poston

Decomposition of the sulfates of copper, iron (II), iron (III), nickel, and zinc: XPS, SEM, DRIFTS, XRD, and TGA study

The bulk and surface characteristics during decomposition of the transition metal sulfates of copper, iron (II), iron (III), nickel, and zinc are investigated utilizing various spectroscopic techniques. An oxidized form of sulfur was detected on the surface during decomposition of all metal sulfate samples, except zinc sulfate. Surface characteristics were not necessarily representative of the bulk characteristics. Oxy-sulfate was observed with copper sulfate only. Lower decomposition temperatures were observed in vacuum as compared to those at atmospheric pressure. Uniform sulfur distribution was observed across sample cross sections. Analysis consisted of Scanning electron microscopy/X-ray microanalysis, X-ray photoelectron spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy, thermogravimetric analysis, and X-ray diffraction.

High performance robust F-doped tin oxide based oxygen evolution electro-catalysts for PEM based water electrolysis

Identification and development of non-noble metal based electro-catalysts or electro-catalysts comprising compositions with significantly reduced amounts of expensive noble metal contents (e.g. IrO2, Pt) with comparable electrochemical performance to the standard noble metal/metal oxide for proton exchange membrane (PEM) based water electrolysis would signify a major breakthrough in hydrogen generation via water electrolysis. Development of such systems would lead to two primary outcomes: first, a reduction in the overall capital costs of PEM based water electrolyzers, and second, attainment of the targeted hydrogen production costs (<

Characterization of copper oxides, iron oxides, and zinc copper ferrite desulfurization sorbents by X-ray photoelectron spectroscopy and scanning electron microscopy

3.00/gge delivered by 2015) comparable to conventional liquid fuels. In line with these goals, by exploiting a two-pronged theoretical first principles and experimental approach herein, we demonstrate for the very first time a solid solution of SnO2:10 wt% F containing only 20 at.% IrO2 [e.g. (Sn0.80Ir0.20)O2:10F] displaying remarkably similar electrochemical activity and comparable or even much improved electrochemical durability compared to pure IrO2, the accepted gold standard in oxygen evolution electro-catalysts for PEM based water electrolysis. We present the results of these studies.

Interaction of H2S with zinc titanate in the presence of H2 and CO

Abstract Characterization of copper oxides, iron oxides, and zinc copper ferrite desulfurization sorbents was performed by X-ray photoelectron spectroscopy and scanning electron microscopy/energy-dispersive spectroscopy at temperatures of 298 to 823 K. Analysis of copper oxides indicated that the satellite structure of the Cu22p region was absent in the Cu(I) state but was present in the Cu(II) state. Reduction of CuO at room temperature was observed when the ion gauge was placed close to the sample. The satellite structure was absent in all the copper oxides at 823 K in vacuum. Differentiation of the oxidation state of copper utilizing both Cu(L 3 M 4,5 M 4,5 ) X-ray-induced Auger lines and Cu2p satellite structure, indicated that the copper in zinc copper ferrite was in the + 1 oxidation state at 823 K. This + 1 state of copper was not significantly changed after exposure to H 2 , CO, and H 2 O. There was an increase in Cu/Zn ratio and a decrease in Fe/Zn ratio on the surface of zinc copper ferrite at 823 K compared to that at room temperature. These conditions of copper offered the best sulfidation equilibrium for the zinc copper ferrite desulfurization sorbent. Analysis of iron oxides indicated that there was some reduction of both Fe 2 O 3 and FeO at 823K. The iron in zinc copper ferrite was similar to that of Fe 2 O 3 at room temperature but there was some reduction of this Fe(III) state to Fe(II) at 823 K. This reduction was more enhanced in the presence of H 2 and CO. Reduction to Fe(II) may not be desirable for the lifetime of the sorbent.

High energy density titanium doped-vanadium oxide-vertically aligned CNT composite electrodes for supercapacitor applications

Abstract The interactions of H2S and mixtures of H2S/H2 and H2S/CO with zinc titanate at temperatures of 943, 993, and 1073 K were studied using X-ray photoelectron spectroscopy. The initial sulfur products formed on the surface were sulfide and sulfate. Sulfate formation was due to the oxygen released from the sample in the presence of H2S, H2, and CO. The release of oxygen was faster in the presence of reducing gases H2 and CO than in pure H2S, although at higher exposures to H2 and CO, sulfate decomposed and was removed from the surface. Sulfide formation was not temperature dependent in the temperature range 943 to 1073 K, while sulfate formation was highly temperature dependent, with the maximum being at 993 K. The sulfide formation kinetics and the saturation coverage of sulfide on ZnO were similar to those of zinc titanate at 993 K but the saturation coverage of sulfide on TiO2 was considerably lower than that of zinc titanate. The saturation coverage of sulfide in the presence of CO on both zinc oxide at 993 K and zinc titanate at 1073 K was significantly higher as compared to that in the absence of CO. This was attributed to the formation of metallic zinc and subsequent reaction with H2S in the presence of CO. Based on the experimental results, a mechanism for the reaction of H2S with zinc titanate was proposed.

Characterization of ceramic hydrogen separation membranes with varying nickel concentrations

In this study, we provide the first report on the supercapacitance behavior of titanium doped vanadium oxide films grown on vertically aligned carbon nanotubes using a chemical vapor deposition (CVD) technique. The capacitance of CVD derived titanium doped vanadium oxide–carbon nanotube composites was measured at different scan rates to evaluate the charge storage behavior. In addition, the electrochemical characteristics of the titanium doped vanadium oxide thin films synthesized by the CVD process were compared to substantiate the propitious effect of the carbon nanotubes on the capacitance of the doped vanadium oxide. Considering the overall materials loading with good rate capability and excellent charge retention up to 400 cycles, it can be noted that attractive capacitance values as high as 310 F g−1 were reported. Ab initio theoretical studies, demonstrating the substantial improvement in the electronic conductivity of the vanadium oxide due to titanium doping and oxygen vacancies, have also been included corroborating the attractive experimental capacitance response.

Nanostructured robust cobalt metal alloy based anode electro-catalysts exhibiting remarkably high performance and durability for proton exchange membrane fuel cells

Abstract Ceramic hydrogen separation membranes in the stoichiometric form BaCe0.8Y0.2O3, doped with various concentrations of nickel, were characterized by utilizing X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and atomic-force microscopy (AFM). Characterization was performed at room temperature, 550°C and 650°C, and after exposure to hydrogen. Migration of nickel to the surface and changes in both elemental composition and oxidation states were observed at elevated temperatures. The concentration of nickel significantly affects surface morphology and roughness.

WO3 based solid solution oxide – promising proton exchange membrane fuel cell anode electro-catalyst

In recent years, the development of durable and electrochemically active electro-catalyst alloys with reduced noble metal content exhibiting similar or better electrochemical performance than pure noble metal electro-catalysts has gathered considerable momentum particularly, for proton exchange membrane fuel cell (PEMFC) application. Engineering such reduced noble metal containing electro-catalyst alloys in nano-scale dimensions with highly active electrochemical surface area (ECSA) will ultimately translate to reduced noble metal loadings to ultra-low levels which will eventually lead to an overall reduction in the capital cost of PEMFCs. Herein we report the development of nanostructured Co–Ir based solid-solution electro-catalyst alloys for the hydrogen oxidation reaction (HOR) further validated by first principles theoretical calculation of the d band center of the transition metal in the solid solution alloys. The theoretical and experimental studies reported herein demonstrate that the nanostructured alloy electro-catalysts comprising 70 at% Co (Co0.7Ir0.3) and 60 at% Co (Co0.6Ir0.4) of crystallite size ∼4 nm with a high electrochemically active surface area (ECSA) (∼56 m2 g−1) exhibit improved electrochemical activity (reduction in overpotential and improved reaction kinetics) for the HOR combined with outstanding durability in contrast to pure Ir nanoparticles (Ir-NPs) as well as state of the art commercial Pt/C system. Moreover, an optimized alloy containing 60 at% Co (Co0.6Ir0.4) showed a remarkable ∼156% and 92% higher electro-catalytic activity for the HOR than Ir-NPs and commercial 40% Pt/C, respectively, with similar loading and ECSA. The single PEMFC full cell study also shows ∼85% improved maximum power density for the Co0.6(Ir0.4) electro-catalyst compared to 40% Pt/C and excellent electrochemical stability/durability comparable to 40% Pt/C.

Diamagnetism of

There is a vital need to develop novel non-noble metals based electro-catalyst or reduced noble metal containing electro-catalyst with excellent electrochemical activity and stability fostering economic commercialization of proton exchange membrane fuel cells (PEMFCs). It is hence of paramount importance to identify and generate reduced noble metal containing electro-catalyst with high electrochemical active surface area, offering noble metal loadings in the ultra-low levels thus reducing the overall capital cost of PEMFCs. Using theoretical first principles d-band center calculations of tungsten trioxide (WO3) based electro-catalysts containing IrO2 as a solute for hydrogen oxidation reaction (HOR), we have identified, synthesized and experimentally demonstrated a highly active nanostructured (W1−xIrx)Oy (x = 0.2, 0.3; y = 2.7–2.8) electro-catalyst for HOR. Furthermore, experimental studies validate superior electrochemical activity of nanostructured (W0.7Ir0.3)Oy for HOR exhibiting improved/comparable stability/durability contrasted to pure WO3 nanoparticles (WO3-NPs), IrO2 nanoparticles (IrO2-NPs) as well as state of the art commercial 40% Pt/C system. Optimized composition of (W0.7Ir0.3)Oy was identified exhibiting ∼33% higher and almost similar electro-catalytic activity for HOR compared to IrO2-NPs and commercial 40% Pt/C catalyst, respectively. Additionally, (W0.7Ir0.3)Oy showed significant enhancement in electrochemical activity for HOR compared to pure WO3-NPs. Long-term life cycle test of (W0.7Ir0.3)Oy for 24 h also showed comparable electrochemical stability/durability compared to that of 40% Pt/C and pure WO3-NPs. The results of half and full cell electrochemical characterization bode well with the theoretical first principles studies demonstrating the promise of the WO3 based solid solution electro-catalyst.

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Results from detailed measurements of the magnetization M of a commercial β-nickel phthalocyanine (β-NiPc) powder sample characterized by X-ray diffraction are reported from 2 K to 300 K and in magnetic fields H up to 90 kOe. From the isothermal M vs. H data at several temperatures T, the diamagnetic nature of β-NiPc is established with temperature-independent susceptibility XD = -3.4 x 10-7 emu/g·Oe, consistent with the spin S = 0 state for Ni2+, in violation of violating Hunds rules. However, both the M vs. H and M vs. T data at the lower temperatures show a ferromagnetic component superposed on XD which is interpreted as resulting from a ferromagnetic impurity in the sample. X-ray photoelectron spectroscopy and X-ray microanalysis of the sample show the presence of Fe impurity with a concentration of 0.0434% (434 ppm) determined using inductively coupled plasma atomic emission spectroscopy (ICP-AES). It is argued that α-FePc is the likely source of the ferromagnetic component. The procedures described here can be used to determine ppm-level magnetic impurities in other diamagnetic semiconductor materials.