Harry Rivera - Academia.edu (original) (raw)
Papers by Harry Rivera
Physical Chemistry Chemical Physics, 2008
Sonochemically prepared PtRu (3 : 1) and Johnson Matthey PtRu (1 : 1) were analyzed by X-ray abso... more Sonochemically prepared PtRu (3 : 1) and Johnson Matthey PtRu (1 : 1) were analyzed by X-ray absorption spectroscopy in operating liquid feed direct methanol fuel cells. The total metal loadings were 4 mg cm À2 unsupported catalysts at the anode and cathode of the membrane electrode assembly. Ex situ XRD lattice parameter analysis indicates partial segregation of the Ru from the PtRu fcc alloy in both catalysts. A comparison of the in situ DMFC EXAFS to that of the as-received catalyst shows that catalyst restructuring during DMFC operation increases the total metal coordination numbers. A combined analysis of XRD determined grain sizes and lattice parameters, ex situ and in situ EXAFS analysis, and XRF of the as-received catalysts enables determination of the catalyst shell composition. The multi-spectrum analysis shows that the core size increases during DMFC operation by reduction of Pt oxides and incorporation of Pt into the core. This increases the mole fraction of Ru in the catalyst shell structure.
Journal of Power Sources, 2008
Lifetime testing of a single cell direct methanol fuel cell (DMFC) was carried out at 100 mA cm −... more Lifetime testing of a single cell direct methanol fuel cell (DMFC) was carried out at 100 mA cm −2 , ambient pressure and 60 • C. X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS) were used to characterize the anode and cathode catalysts before and after lifetime testing. The XRD results showed that the particle sizes and lattice parameters of anode catalyst increased from 2.8 to 3.2 nm and from 3.8761 to 3.8871Å; the cathode catalyst increased from 7.3 to 8.9 nm and from 3.9188 to 3.9204Å before and after the lifetime test, respectively. The XPS results indicated that during the lifetime period, the extent of oxidation of the anode Pt and Ru components increased, and Ru appears in the XPS of the cathode. Polarization curves, power density curves, and in situ cyclic voltammetry were employed to test the performance of fuel cell and electrochemically active specific surface areas (S EAS) of the anode and cathode catalysts before and after the lifetime test. The overall findings are that the cathode suffers the greatest degradation over the test period and that subtle changes at the anode can have substantial adverse effects on the cathode.
Meeting abstracts, 2008
not Available.
Analytical Chemistry, Sep 10, 2020
Operando high-throughput evaluation of heterogeneous catalysts by laser-activated membrane introd... more Operando high-throughput evaluation of heterogeneous catalysts by laser-activated membrane introduction mass spectrometry (LAMIMS) elucidates the Pt loading dependence of methylcyclohexane dehydrogenation on platinized γ-alumina beads. A CO 2 marking laser rapidly and sequentially heats catalyst beads positioned on a heat-dissipating carbon paper support that overlays a silicone membrane, separating the bead library reaction zone from a quadrupole mass analyzer. The toluene m/z peak varies logarithmically with Pt loading, suggesting that reactivity includes factors that are negatively correlated to Pt loading. These factors may include the Pt/γ-Al 2 O 3 surface interfacial region as one component of a heterogeneous catalytically active surface area/ mass. This work demonstrates LAMIMS as a broadly applicable high-throughput operando screening method for heterogeneous catalysts.
Meeting abstracts, Aug 29, 2008
not Available.
International Journal of Hydrogen Energy, Jul 1, 2012
Effects of different carbon sources and carbonized carbon contents during carbon riveting process... more Effects of different carbon sources and carbonized carbon contents during carbon riveting process (CRP) on the stability of Pt/C catalysts have been systematically studied. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammograms (CV), and accelerated potential cycling tests (APCT) have been carried out to characterize the catalysts. Experimental results show that the carbon riveted Pt/C catalysts treated by different carbon sources have different stability due to different properties of Pt and carbon after the CRP. The best carbon source for the carbon riveted Pt/C catalysts is glucose and is ascribed to the most content of Pt (0) and sp 3-C after the CRP. APCT results indicate that the stability of Pt/C catalysts carbon-riveted by glucose exhibits the increasing trend with the increase of carbonized carbon contents because of increasing anchor effect to Pt nanoparticles. However, a larger carbon content from the carbonization of glucose can also reduce the electrochemically active specific surface areas (ESA) of the carbon riveted Pt/C catalyst by covering the active sites of Pt nanoparticles. Taking into account both activity and stability of the carbon riveted Pt/C catalysts, 6% carbon from the carbonization of glucose is the optimized content.
ECS Meeting Abstracts, 2012
View the article online for updates and enhancements.
ECS Meeting Abstracts, 2011
ECS Meeting Abstracts, 2008
not Available.
ECS Meeting Abstracts, 2008
MRS Communications, 2016
We analyze the effect of functionalization in the surface of zinc oxide crystal structure by 3-me... more We analyze the effect of functionalization in the surface of zinc oxide crystal structure by 3-mercaptopropionic acid. X-ray powder diffraction data and extended x-ray absorption fine structure studies confirms a wurtzite structure. However, the morphology of the surface seems to be reduced and shows a film-like surface as demonstrated by x-ray absorption near edge structure and scanning electron microscopy. As a result of surface functionalization, the energy levels of the semiconductor were shifted toward reductive potentials (by 50 mV) as determined by diffuse reflectance and cyclic voltammetry.
Materials Research Express, 2014
ABSTRACT Semiconductor materials offer several potential benefits as active elements in the devel... more ABSTRACT Semiconductor materials offer several potential benefits as active elements in the development of harvesting-energy conversion technologies. In particular, lead selenide (PbSe) semiconductors have been used and proposed to design solar energy harvesting devices, IR sensors, FET devices, etc. Lead salts have drawn particular attention from the applied and fundamental research communities due to their exceptionally strong quantum confinement effects. Several syntheses of PbSe have been proposed using long chain surfactants to allow the formation of particles and nanoparticles. Here we present a synthesis using benzoic acid as the capping ligand in ambient atmosphere. Although the particles are not in nanometric size, we compare the crystal structure (using x-ray powder diffraction data), the near infrared and mid-infrared absorption properties of PbSe using oleic acid as the capping ligand with PbSe using benzoic acid as the capping ligand. The new synthetized particles were shown to have similar crystal structure and absorb light in the near infrared region at 1410 nm. We also performed cyclic voltammetry of these particles drop-casted in the surface of a glassy carbon electrode. The particles showed electrochemical behavior with an oxidation peak near (−402 ± 5 mV) versus Ag/AgCl reference electrode. The particles seem to form a polymeric film at the surface of a glassy carbon electrode.
The Journal of Physical Chemistry B, 2008
The CO2 in the cathode exhaust of a liquid feed direct methanol fuel cell (DMFC) has two sources:... more The CO2 in the cathode exhaust of a liquid feed direct methanol fuel cell (DMFC) has two sources: methanol diffuses through the membrane electrode assembly (MEA) to the cathode where it is catalytically oxidized to CO2; additionally, a portion of the CO2 produced at the anode diffuses through the MEA to the cathode. The potential-dependent CO2 exhaust from the cathode was monitored by online electrochemical mass spectrometry (ECMS) with air and with H2 at the cathode. The precise determination of the crossover rates of methanol and CO2, enabled by the subtractive normalization of the methanol/air to the methanol/H2 ECMS data, shows that methanol decreases the membrane viscosity and thus increases the diffusion coefficients of sorbed membrane components. The crossover of CO2 initially increases linearly with the Faradaic oxidation of methanol, reaches a temperature-dependent maximum, and then decreases. The membrane viscosity progressively increases as methanol is electrochemically depleted from the anode/electrolyte interface. The crossover maximum occurs when the current dependence of the diffusion coefficients and membrane CO2 solubility dominate over the Faradaic production of CO2. The plasticizing effect of methanol is corroborated by measurements of the rotational diffusion of TEMPONE (2,2,6,6-tetramethyl-4-piperidone N-oxide) spin probe by electron spin resonance spectroscopy. A linear inverse relationship between the methanol crossover rate and current density confirms the absence of methanol electro-osmotic drag at concentrations relevant to operating DMFCs. The purely diffusive transport of methanol is explained in terms of current proton solvation and methanol-water incomplete mixing theories.
Nanoscale, 2012
Pt catalyst supported on nanocapsule MWCNTs-Al(2)O(3) (multi-walled carbon nanotubes, MWCNTs) cat... more Pt catalyst supported on nanocapsule MWCNTs-Al(2)O(3) (multi-walled carbon nanotubes, MWCNTs) catalyst has been prepared by microwave-assisted polyol process (MAPP). The results of electrochemical measurements show that the nanocapsule Pt/MWCNTs-Al(2)O(3) catalyst has higher activity due to more uniform dispersion and smaller size of Pt nanoparticles, and higher stability ascribed to the stronger metal-support interaction (SMSI) between Pt nanoparticles and nanocapsule support than in Pt/MWCNTs. Furthermore, the carbon-riveted nanocapsule Pt/MWCNTs-Al(2)O(3) catalyst has been designed and synthesized on the basis of in situ carbonization of glucose. The physical characteristics such as X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDAX), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) have indicated that α-Al(2)O(3) indeed entered into the inside of the MWCNTs and formed a nanocapsule support of MWCNTs with α-Al(2)O(3) as stuffing. The accelerated potential cycling tests (APCT) show that carbon-riveted nanocapsule Pt/MWCNTs-Al(2)O(3) possesses 10 times the stability of Pt/C and has 4.5 times the life-span of carbon-riveted Pt/TiO(2)-C reported in our previous work. The significantly enhanced stability for carbon-riveted nanocapsule Pt/MWCNTs-Al(2)O(3) catalyst is attributed to the reasons as follows: the inherently excellent mechanical resistance and stability of α-Al(2)O(3) and MWCNTs in acidic and oxidative environments; SMSI between Pt nanoparticles and the nanocapsule support; the anchoring effect of the carbon layers formed during the carbon-riveting process (CRP); the increase of Pt(0) composition during CRP.
Journal of The Electrochemical Society, 2010
... Rotating Disk-Slurry Electrode Technique. [Journal of The Electrochemical Society 157, F189 (... more ... Rotating Disk-Slurry Electrode Technique. [Journal of The Electrochemical Society 157, F189 (2010)]. Diana Santiago, Gabriel G. Rodríguez-Calero, Harry Rivera, Donald A. Tryk, M. Aulice Scibioh, Carlos R. Cabrera. Abstract. ...
International Journal of Hydrogen Energy, 2012
Effects of different carbon sources and carbonized carbon contents during carbon riveting process... more Effects of different carbon sources and carbonized carbon contents during carbon riveting process (CRP) on the stability of Pt/C catalysts have been systematically studied. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammograms (CV), and accelerated potential cycling tests (APCT) have been carried out to characterize the catalysts. Experimental results show that the carbon riveted Pt/C catalysts treated by different carbon sources have different stability due to different properties of Pt and carbon after the CRP. The best carbon source for the carbon riveted Pt/C catalysts is glucose and is ascribed to the most content of Pt (0) and sp 3-C after the CRP. APCT results indicate that the stability of Pt/C catalysts carbon-riveted by glucose exhibits the increasing trend with the increase of carbonized carbon contents because of increasing anchor effect to Pt nanoparticles. However, a larger carbon content from the carbonization of glucose can also reduce the electrochemically active specific surface areas (ESA) of the carbon riveted Pt/C catalyst by covering the active sites of Pt nanoparticles. Taking into account both activity and stability of the carbon riveted Pt/C catalysts, 6% carbon from the carbonization of glucose is the optimized content.
Electrochimica Acta, 2012
Metal hydride foils can serve as support structures for electronically insulating proton conducto... more Metal hydride foils can serve as support structures for electronically insulating proton conductors to afford metal hydride-barrier composite electrolytes operating at temperatures in between molten carbonate fuel cells and phosphoric acid fuel cells. In addition, such barrier electrolytes entirely decouple anode and cathode reactant streams and water management, enabling general analytical methods that separate electrode kinetic from reactant crossover effects. This strategy was exemplified with a direct methanol fuel cell catalyzed with PtRu. No fuel-stream reactant or product crossover other than protons was detected.
Inorganic Chemistry, 2012
The direct intercalation of a pyrazolate-bridged platinum(II) bipyridyl dimer ([{Pt(dmbpy)(μ-pz)}... more The direct intercalation of a pyrazolate-bridged platinum(II) bipyridyl dimer ([{Pt(dmbpy)(μ-pz)} 2 ] 2+ ; dmbpy = 4,4′-dimethyl-2,2′-bipyridine, pz − = pyrazolate) within a zirconium phosphate (ZrP) framework has been accomplished. The physical and spectroscopic properties of [{Pt(dmbpy)(μ-pz)} 2 ] 2+ intercalated in ZrP were investigated by X-ray powder diffraction and X-ray photoelectron, infrared, absorption, and luminescence spectroscopies. Zirconium phosphate layers have a special microenvironment that is capable of supporting a variety of platinum oxidation states. Diffuse reflectance spectra from powders of the blue-gray intercalated materials show the formation of a low-energy band at 600 nm that is not present in the platinum dimer salt. The nonintercalated complex is nonemissive in room-temperature fluid solution, but gives rise to intense blue-green emission in a 4:1 ethanol/methanol 77 K frozen glassy solution. Powders and colloidal suspensions of [{Pt(dmbpy)(μ-pz)} 2 ] 2+-exchanged ZrP materials exhibit intense emissions at room-temperature.
Physical Chemistry Chemical Physics, 2008
Sonochemically prepared PtRu (3 : 1) and Johnson Matthey PtRu (1 : 1) were analyzed by X-ray abso... more Sonochemically prepared PtRu (3 : 1) and Johnson Matthey PtRu (1 : 1) were analyzed by X-ray absorption spectroscopy in operating liquid feed direct methanol fuel cells. The total metal loadings were 4 mg cm À2 unsupported catalysts at the anode and cathode of the membrane electrode assembly. Ex situ XRD lattice parameter analysis indicates partial segregation of the Ru from the PtRu fcc alloy in both catalysts. A comparison of the in situ DMFC EXAFS to that of the as-received catalyst shows that catalyst restructuring during DMFC operation increases the total metal coordination numbers. A combined analysis of XRD determined grain sizes and lattice parameters, ex situ and in situ EXAFS analysis, and XRF of the as-received catalysts enables determination of the catalyst shell composition. The multi-spectrum analysis shows that the core size increases during DMFC operation by reduction of Pt oxides and incorporation of Pt into the core. This increases the mole fraction of Ru in the catalyst shell structure.
Journal of Power Sources, 2008
Lifetime testing of a single cell direct methanol fuel cell (DMFC) was carried out at 100 mA cm −... more Lifetime testing of a single cell direct methanol fuel cell (DMFC) was carried out at 100 mA cm −2 , ambient pressure and 60 • C. X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS) were used to characterize the anode and cathode catalysts before and after lifetime testing. The XRD results showed that the particle sizes and lattice parameters of anode catalyst increased from 2.8 to 3.2 nm and from 3.8761 to 3.8871Å; the cathode catalyst increased from 7.3 to 8.9 nm and from 3.9188 to 3.9204Å before and after the lifetime test, respectively. The XPS results indicated that during the lifetime period, the extent of oxidation of the anode Pt and Ru components increased, and Ru appears in the XPS of the cathode. Polarization curves, power density curves, and in situ cyclic voltammetry were employed to test the performance of fuel cell and electrochemically active specific surface areas (S EAS) of the anode and cathode catalysts before and after the lifetime test. The overall findings are that the cathode suffers the greatest degradation over the test period and that subtle changes at the anode can have substantial adverse effects on the cathode.
Meeting abstracts, 2008
not Available.
Analytical Chemistry, Sep 10, 2020
Operando high-throughput evaluation of heterogeneous catalysts by laser-activated membrane introd... more Operando high-throughput evaluation of heterogeneous catalysts by laser-activated membrane introduction mass spectrometry (LAMIMS) elucidates the Pt loading dependence of methylcyclohexane dehydrogenation on platinized γ-alumina beads. A CO 2 marking laser rapidly and sequentially heats catalyst beads positioned on a heat-dissipating carbon paper support that overlays a silicone membrane, separating the bead library reaction zone from a quadrupole mass analyzer. The toluene m/z peak varies logarithmically with Pt loading, suggesting that reactivity includes factors that are negatively correlated to Pt loading. These factors may include the Pt/γ-Al 2 O 3 surface interfacial region as one component of a heterogeneous catalytically active surface area/ mass. This work demonstrates LAMIMS as a broadly applicable high-throughput operando screening method for heterogeneous catalysts.
Meeting abstracts, Aug 29, 2008
not Available.
International Journal of Hydrogen Energy, Jul 1, 2012
Effects of different carbon sources and carbonized carbon contents during carbon riveting process... more Effects of different carbon sources and carbonized carbon contents during carbon riveting process (CRP) on the stability of Pt/C catalysts have been systematically studied. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammograms (CV), and accelerated potential cycling tests (APCT) have been carried out to characterize the catalysts. Experimental results show that the carbon riveted Pt/C catalysts treated by different carbon sources have different stability due to different properties of Pt and carbon after the CRP. The best carbon source for the carbon riveted Pt/C catalysts is glucose and is ascribed to the most content of Pt (0) and sp 3-C after the CRP. APCT results indicate that the stability of Pt/C catalysts carbon-riveted by glucose exhibits the increasing trend with the increase of carbonized carbon contents because of increasing anchor effect to Pt nanoparticles. However, a larger carbon content from the carbonization of glucose can also reduce the electrochemically active specific surface areas (ESA) of the carbon riveted Pt/C catalyst by covering the active sites of Pt nanoparticles. Taking into account both activity and stability of the carbon riveted Pt/C catalysts, 6% carbon from the carbonization of glucose is the optimized content.
ECS Meeting Abstracts, 2012
View the article online for updates and enhancements.
ECS Meeting Abstracts, 2011
ECS Meeting Abstracts, 2008
not Available.
ECS Meeting Abstracts, 2008
MRS Communications, 2016
We analyze the effect of functionalization in the surface of zinc oxide crystal structure by 3-me... more We analyze the effect of functionalization in the surface of zinc oxide crystal structure by 3-mercaptopropionic acid. X-ray powder diffraction data and extended x-ray absorption fine structure studies confirms a wurtzite structure. However, the morphology of the surface seems to be reduced and shows a film-like surface as demonstrated by x-ray absorption near edge structure and scanning electron microscopy. As a result of surface functionalization, the energy levels of the semiconductor were shifted toward reductive potentials (by 50 mV) as determined by diffuse reflectance and cyclic voltammetry.
Materials Research Express, 2014
ABSTRACT Semiconductor materials offer several potential benefits as active elements in the devel... more ABSTRACT Semiconductor materials offer several potential benefits as active elements in the development of harvesting-energy conversion technologies. In particular, lead selenide (PbSe) semiconductors have been used and proposed to design solar energy harvesting devices, IR sensors, FET devices, etc. Lead salts have drawn particular attention from the applied and fundamental research communities due to their exceptionally strong quantum confinement effects. Several syntheses of PbSe have been proposed using long chain surfactants to allow the formation of particles and nanoparticles. Here we present a synthesis using benzoic acid as the capping ligand in ambient atmosphere. Although the particles are not in nanometric size, we compare the crystal structure (using x-ray powder diffraction data), the near infrared and mid-infrared absorption properties of PbSe using oleic acid as the capping ligand with PbSe using benzoic acid as the capping ligand. The new synthetized particles were shown to have similar crystal structure and absorb light in the near infrared region at 1410 nm. We also performed cyclic voltammetry of these particles drop-casted in the surface of a glassy carbon electrode. The particles showed electrochemical behavior with an oxidation peak near (−402 ± 5 mV) versus Ag/AgCl reference electrode. The particles seem to form a polymeric film at the surface of a glassy carbon electrode.
The Journal of Physical Chemistry B, 2008
The CO2 in the cathode exhaust of a liquid feed direct methanol fuel cell (DMFC) has two sources:... more The CO2 in the cathode exhaust of a liquid feed direct methanol fuel cell (DMFC) has two sources: methanol diffuses through the membrane electrode assembly (MEA) to the cathode where it is catalytically oxidized to CO2; additionally, a portion of the CO2 produced at the anode diffuses through the MEA to the cathode. The potential-dependent CO2 exhaust from the cathode was monitored by online electrochemical mass spectrometry (ECMS) with air and with H2 at the cathode. The precise determination of the crossover rates of methanol and CO2, enabled by the subtractive normalization of the methanol/air to the methanol/H2 ECMS data, shows that methanol decreases the membrane viscosity and thus increases the diffusion coefficients of sorbed membrane components. The crossover of CO2 initially increases linearly with the Faradaic oxidation of methanol, reaches a temperature-dependent maximum, and then decreases. The membrane viscosity progressively increases as methanol is electrochemically depleted from the anode/electrolyte interface. The crossover maximum occurs when the current dependence of the diffusion coefficients and membrane CO2 solubility dominate over the Faradaic production of CO2. The plasticizing effect of methanol is corroborated by measurements of the rotational diffusion of TEMPONE (2,2,6,6-tetramethyl-4-piperidone N-oxide) spin probe by electron spin resonance spectroscopy. A linear inverse relationship between the methanol crossover rate and current density confirms the absence of methanol electro-osmotic drag at concentrations relevant to operating DMFCs. The purely diffusive transport of methanol is explained in terms of current proton solvation and methanol-water incomplete mixing theories.
Nanoscale, 2012
Pt catalyst supported on nanocapsule MWCNTs-Al(2)O(3) (multi-walled carbon nanotubes, MWCNTs) cat... more Pt catalyst supported on nanocapsule MWCNTs-Al(2)O(3) (multi-walled carbon nanotubes, MWCNTs) catalyst has been prepared by microwave-assisted polyol process (MAPP). The results of electrochemical measurements show that the nanocapsule Pt/MWCNTs-Al(2)O(3) catalyst has higher activity due to more uniform dispersion and smaller size of Pt nanoparticles, and higher stability ascribed to the stronger metal-support interaction (SMSI) between Pt nanoparticles and nanocapsule support than in Pt/MWCNTs. Furthermore, the carbon-riveted nanocapsule Pt/MWCNTs-Al(2)O(3) catalyst has been designed and synthesized on the basis of in situ carbonization of glucose. The physical characteristics such as X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDAX), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) have indicated that α-Al(2)O(3) indeed entered into the inside of the MWCNTs and formed a nanocapsule support of MWCNTs with α-Al(2)O(3) as stuffing. The accelerated potential cycling tests (APCT) show that carbon-riveted nanocapsule Pt/MWCNTs-Al(2)O(3) possesses 10 times the stability of Pt/C and has 4.5 times the life-span of carbon-riveted Pt/TiO(2)-C reported in our previous work. The significantly enhanced stability for carbon-riveted nanocapsule Pt/MWCNTs-Al(2)O(3) catalyst is attributed to the reasons as follows: the inherently excellent mechanical resistance and stability of α-Al(2)O(3) and MWCNTs in acidic and oxidative environments; SMSI between Pt nanoparticles and the nanocapsule support; the anchoring effect of the carbon layers formed during the carbon-riveting process (CRP); the increase of Pt(0) composition during CRP.
Journal of The Electrochemical Society, 2010
... Rotating Disk-Slurry Electrode Technique. [Journal of The Electrochemical Society 157, F189 (... more ... Rotating Disk-Slurry Electrode Technique. [Journal of The Electrochemical Society 157, F189 (2010)]. Diana Santiago, Gabriel G. Rodríguez-Calero, Harry Rivera, Donald A. Tryk, M. Aulice Scibioh, Carlos R. Cabrera. Abstract. ...
International Journal of Hydrogen Energy, 2012
Effects of different carbon sources and carbonized carbon contents during carbon riveting process... more Effects of different carbon sources and carbonized carbon contents during carbon riveting process (CRP) on the stability of Pt/C catalysts have been systematically studied. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammograms (CV), and accelerated potential cycling tests (APCT) have been carried out to characterize the catalysts. Experimental results show that the carbon riveted Pt/C catalysts treated by different carbon sources have different stability due to different properties of Pt and carbon after the CRP. The best carbon source for the carbon riveted Pt/C catalysts is glucose and is ascribed to the most content of Pt (0) and sp 3-C after the CRP. APCT results indicate that the stability of Pt/C catalysts carbon-riveted by glucose exhibits the increasing trend with the increase of carbonized carbon contents because of increasing anchor effect to Pt nanoparticles. However, a larger carbon content from the carbonization of glucose can also reduce the electrochemically active specific surface areas (ESA) of the carbon riveted Pt/C catalyst by covering the active sites of Pt nanoparticles. Taking into account both activity and stability of the carbon riveted Pt/C catalysts, 6% carbon from the carbonization of glucose is the optimized content.
Electrochimica Acta, 2012
Metal hydride foils can serve as support structures for electronically insulating proton conducto... more Metal hydride foils can serve as support structures for electronically insulating proton conductors to afford metal hydride-barrier composite electrolytes operating at temperatures in between molten carbonate fuel cells and phosphoric acid fuel cells. In addition, such barrier electrolytes entirely decouple anode and cathode reactant streams and water management, enabling general analytical methods that separate electrode kinetic from reactant crossover effects. This strategy was exemplified with a direct methanol fuel cell catalyzed with PtRu. No fuel-stream reactant or product crossover other than protons was detected.
Inorganic Chemistry, 2012
The direct intercalation of a pyrazolate-bridged platinum(II) bipyridyl dimer ([{Pt(dmbpy)(μ-pz)}... more The direct intercalation of a pyrazolate-bridged platinum(II) bipyridyl dimer ([{Pt(dmbpy)(μ-pz)} 2 ] 2+ ; dmbpy = 4,4′-dimethyl-2,2′-bipyridine, pz − = pyrazolate) within a zirconium phosphate (ZrP) framework has been accomplished. The physical and spectroscopic properties of [{Pt(dmbpy)(μ-pz)} 2 ] 2+ intercalated in ZrP were investigated by X-ray powder diffraction and X-ray photoelectron, infrared, absorption, and luminescence spectroscopies. Zirconium phosphate layers have a special microenvironment that is capable of supporting a variety of platinum oxidation states. Diffuse reflectance spectra from powders of the blue-gray intercalated materials show the formation of a low-energy band at 600 nm that is not present in the platinum dimer salt. The nonintercalated complex is nonemissive in room-temperature fluid solution, but gives rise to intense blue-green emission in a 4:1 ethanol/methanol 77 K frozen glassy solution. Powders and colloidal suspensions of [{Pt(dmbpy)(μ-pz)} 2 ] 2+-exchanged ZrP materials exhibit intense emissions at room-temperature.