Effect of Temperature for Platinum/Carbon Electrocatalyst Preparation on Hydrogen Evolution Reaction

This research was carried out to study the effect of preparation temperature of the Pt/C electrocatalyst on the hydrogen evolution reaction (HER). Pt/C electrocatalyst was synthesized using the polyol method in ethylene glycol with 1 M ascorbic acid as a mild reducing agent. The investigated parameter was the temperature, which will vary from room temperature to 120˚C. From the cyclic voltammetry (CV), the results showed that the Pt/C electrocatalyst synthesized by the polyol method at room temperature and 60˚C cannot promote hydrogen desorption peak compared to other catalysts. The Pt/C catalyst synthesized at 100˚C gave the highest electrochemical surface area (ESA) at around 32.59 m2/gPt. From the linear sweep voltammetry (LSV) tested in an acid solution, the Pt/C catalyst synthesized at 100˚C exhibited the highest HER activity. The exchange current density, Tafel slope and overpotential at 10 mA/cm2 were around 5.208 mA/cm2, -59.3 mV/dec and -0.277 VSCE, respectively. From the value of Tafel slope: -59.3 mV/dec, it indicated that the mechanism of the 20%Pt/C electrocatalyst synthesized at 100˚C catalyst occurs through Heyrovsky mechanism

Stability of TiO2 Promoted PtCo/C Catalyst for Oxygen Reduction Reaction

International audienceThis work was carried out to explore the effect of TiO2 on activity and stability of a PtCo/C catalyst for an oxygen reduction reaction (ORR). Two types of TiO2, including commercial TiO2 (TCOM) and a home-prepared TiO2 by chemical vapor deposition (TCVD), were incorporated on the PtCo/C catalyst layer. The activity of all prepared-catalysts was tested in a single proton exchange membrane (PEM) fuel cell under an H2/O2 environment at ambient pressure, while their stability was tested by the linear sweep voltammetry (LSV) in 0.5 M H2SO4. The preliminary results demonstrated that the TCVD promoted PtCo/C catalyst (TCVD-PtCo/C) exhibited the highest activity in a PEM fuel cell for both activation polarization and ohmic polarization regions, which can produce the current density of 434 mA/cm2 (277 mW/cm2 or 1,847 W/gPtcm2) at 0.6 V. It also exhibited the highest stability in 0.5 M H2SO4 with performance loss of around 40% after 6,000 LSV-cycles

Effect of the TiO2 phase and loading on oxygen reduction reaction activity of PtCo/C catalysts in proton exchange membrane fuel cells

We investigated the effect of the TiO2 phase, as either pure rutile (TiO2(R)) or a 4 : 1 (w/w) anatase: rutile ratio (TiO2(AR)), and the loading on the activity of PtCo/C catalyst in the oxygen reduction reaction (ORR) in a proton exchange membrane (PEM) fuel cell. The incorporation of the different phases and loading of TiO2 on the PtCo/C catalyst did not affect the alloy properties or the crystalline size of the PtCo/C catalyst, but affected importantly the electrochemical surface area (ESA), conductivity of catalyst layer and the water management ability. The presence of TiO2(AR) at appropriate quantity can decrease the mass transport limitation as well as the ohmic resistance of catalyst layer. As a result, the optimum loading of TiO2(AR) used to incorporated in the layer of PtCo/C catalyst was 0.06mg/cm2. At this content, the TiO2(AR)-PtCo/C catalyst provided the highest current density of 438 mA/cm2 at 0.6V at atmospheric pressure in PEM fuel cell and provided the kinetic current in acid solution of 20.53 mA/cm2. In addition, the presence of TiO2(AR) did not alter the ORR electron pathway of PtCo/C catalyst. The electron pathway of ORR of TiO2(AR)-PtCo/C was still the four-electron pathway

Effect of MO2 (M = Ce, Mo, Ti) layer on activity and stability of PtCo/C catalysts during an oxygen reduction reaction

The performance of PtCo/C catalysts in the presence of a metal oxides layer for an oxygen reduction reaction (ORR) was investigated. Different types of metal oxides (CeO2, MoO2 and TiO2) and metal loadings (0.03–0.45 mg/cm2) were incorporated on the PtCo/C catalyst layer. Their activity was analyzed in acid solution and proton exchange membrane (PEM) fuel cell under a H2/O2 environment at 60 °C and ambient pressure, while the stability was tested in an N2-saturated H2SO4 solution using repetitive potential cycling. It was found that the addition of metal oxides on a catalyst layer had no influence for PtCo/C morphology. However, they significantly affected the electrochemical surface area (ESA), internal contact resistance (ICR) and hydrophilic/hydrophobic properties of the catalysts layer. Furthermore, they significantly affected the ORR activity and stability in acid solution and PEM fuel cell operation. Among all studied metal oxides, the TiO2 exhibited the best property for use as the catalyst interlayer in PEM fuel cell for both activity and stability enhancement

Stability of TiO2 Promoted PtCo/C Catalyst for Oxygen Reduction Reaction

This work was carried out to explore the effect of TiO2 on activity and stability of a PtCo/C catalyst for an oxygen reduction reaction (ORR). Two types of TiO2, including commercial TiO2 (TCOM) and a home-prepared TiO2 by chemical vapor deposition (TCVD), were incorporated on the PtCo/C catalyst layer. The activity of all prepared-catalysts was tested in a single proton exchange membrane (PEM) fuel cell under an H2/O2 environment at ambient pressure, while their stability was tested by the linear sweep voltammetry (LSV) in 0.5 M H2SO4. The preliminary results demonstrated that the TCVD promoted PtCo/C catalyst (TCVD-PtCo/C) exhibited the highest activity in a PEM fuel cell for both activation polarization and ohmic polarization regions, which can produce the current density of 434 mA/cm2 (277 mW/cm2 or 1,847 W/gPtcm2) at 0.6 V. It also exhibited the highest stability in 0.5 M H2SO4 with performance loss of around 40% after 6,000 LSV-cycles

Deposition of tin oxide, iridium and iridium oxide films by metal-organic chemical vapor deposition for electrochemical wastewater treatment

In this research, the specific electrodes were prepared by metal-organic chemical vapor deposition (MOCVD) in a hot-wall CVD reactor with the presence of O2 under reduced pressure. The Ir protective layer was deposited by using (Methylcyclopentadienyl) (1,5-cyclooctadiene) iridium (I), (MeCp)Ir(COD), as precursor. Tetraethyltin (TET) was used as precursor for the deposition of SnO2 active layer. The optimum condition for Ir film deposition was at 300 °C, 125 of O2/(MeCp)Ir(COD) molar ratio and 12 Torr of total pressure. While that of SnO2 active layer was at 380 °C, 1200 of O2/TET molar ratio and 15 Torr of total pressure. The prepared SnO2/Ir/Ti electrodes were tested for anodic oxidation of organic pollutant in a simple three-electrode electrochemical reactor using oxalic acid as model solution. The electrochemical experiments indicate that more than 80% of organic pollutant was removed after 2.1 Ah/L of charge has been applied. The kinetic investigation gives a two-step process for organic pollutant degradation, the kinetic was zero-order and first-order with respect to TOC of model solution for high and low TOC concentrations, respectively

Preparation of a high performance Pt-Co/C electrocatalyst for oxygen reduction in PEM fuel cell via a combined process of impregnation and seeding

The preparation of a Pt-Co/C electrocatalyst for the oxygen reduction reaction in PEM fuel cells was achieved via a combined process of impregnation and seeding. The effects of initial pH of the precursor solution and Pt loading were all found to have a significant effect on both the electrocatalyst morphology and the cell performance when tested in a single PEM fuel cell. The optimum condition found for preparing the Pt-Co/C electrocatalyst was from an initial precursor solution pH of 2 at the metal loading of 23.6-30.3% (w/w). The Pt-Co/C electrocatalysts, formed under these optimal conditions, tested in a single PEM fuel cell with the carbon sub-layer, gave a cell performance of 772 mA/cm2 or 460 mW/cm2 at 0.6 V in a H2/O2 system. An electron pathway of oxygen reduction on the prepared Pt-Co/C electrocatalyst was also determined using a rotating disk electrode.Pt-Co/C electrocatalyst PEM fuel cell 4-electron pathway Cell performance

Recovery of copper, chromium and nickel, from electroplating effluent by electrochemical technique

Ce travail concerne la récupération des matériaux lourds (cuivre, chrome et nickel) d'effluents d'industries galvanoplastiques pour des raisons économiques et environnementales. Ce travail comporte 3 parties. La première concerne l'élimination du cuivre de solutions synthétiques au moyen de deux types de réacteurs, le premier est un réacteur classique sans membrane alors que le second correspond à un réacteur dédié à la récupération des métaux lourds, l'électrode poreuse percolée pulsée (E3P). La seconde partie de ce travail rapporte les travaux relatifs à la récupération du chrome et du nickel à l'aide d'un réacteur comprenant une membrane anionique. La dernière partie s'intéresse à l'élimination des trois métaux présents sous forme de mélanges dans des solutions synthétiques et des effluents industriels. Les résultats montrent que les conditions optimales de récupération sont différentes pour chaque métal. Le principal résultat est que le cuivre, le nickel et le chrome peuvent être éliminés de la solution. Il est également montré que le chrome sous sa forme hexavalente (Cr6+) affecte la récupération du cuivre alors que sous sa forme trivalent, ce dernier n'a aucun effet.TOULOUSE-ENSIACET (315552325) / SudocSudocFranceThailandFRT

Highly efficient ZnO/WO3 nanocomposites towards photocatalytic gold recovery from industrial cyanide-based gold plating wastewater

Abstract Discharging the gold-contained wastewater is an economic loss. In this work, a set of ZnO/WO3 was facile synthesized by hydrothermal method in order to recover gold from the industrial cyanide-based gold plating wastewater by photocatalytic process. Effect of ZnO contents coupled with WO3 was first explored. Then, effects of operating condition including initial pH of wastewater, type of hole scavenger, concentration of the best hole scavenger and photocatalyst dose were explored. A series of experimental results demonstrated that the ZnO/WO3 nanocomposite with 5 wt% ZnO (Z5.0/WO3) depicted the highest photocatalytic activity for gold recovery due to the synergetic effect of oxygen vacancies, a well-constructed ZnO/WO3 heterostructure and an appropriate band position alignment with respect to the redox potentials of [Au(CN)2]− and hole scavengers. Via this ZnO/WO3 nanocomposite, approximately 99.5% of gold ions was recovered within 5 h using light intensity of 3.57 mW/cm2, catalyst dose of 2.0 g/L, ethanol concentration of 20 vol% and initial pH of wastewater of 11.2. In addition, high stability and reusability were observed with the best nanocomposite even at the 5th reuse. This work provides the guidance and pave the way for designing the ZnO/WO3 nanocomposite for precious metal recovery from a real industrial wastewater