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 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

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

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

Extraction of Lead Ions and Partitioning Behaviour in Aqueous Biphasic Systems Based on Polyethylene Glycol and Different Salts

Lead ions are environmental pollutants often present in very low concentrations, which makes them difficult to detect and, thus, present problems for environmental monitoring. In this study, we examined the performance of aqueous biphasic systems based on polyethylene glycol (PEG, molecular mass of 4000 g mol–1) with ammonium sulfate (NH4)2SO4, magnesium sulfate (MgSO4), sodium sulfate (Na2SO4), and trisodium citrate (Na3C6H5O7) for the separation of lead(II) ions from aqueous solutions. We investigated the effects of salt types and the ratio of PEG4000 to salt on the extraction efficiency of lead(II) removal at constant temperatures of 303 K and 0.1 MPa. Additionally, we determined the cloud points (solubility equilibrium curve) and tie-lines for four ternary systems comprising PEG4000, water, and salt (either (NH4)2SO4, MgSO4, Na2SO4, or Na3C6H5O7) under the same conditions. A maximum lead(II) extraction efficiency of 74.4% was achieved using the PEG4000/(NH4)2SO4 system with a mass fraction ratio of PEG4000 to (NH4)2SO4 of 0.2:0.12. This outcome highlights the significant potential of utilizing aqueous biphasic systems based on PEG4000 to separate lead(II) from aqueous solutions efficiently

Comparative Study of the ORR Activity and Stability of Pt and PtM (M = Ni, Co, Cr, Pd) Supported on Polyaniline/Carbon Nanotubes in a PEM Fuel Cell

The oxygen reduction reaction (ORR) activity and stability of platinum (Pt) and PtM (M = Ni, Co, Cr, Pd) supported on polyaniline/carbon nanotube (PtM/PANI-CNT) were explored and compared with the commercial Pt/C catalyst (ETEK). The Pt/PANI-CNT catalyst exhibited higher ORR activity and stability than the commercial Pt/C catalyst even though it had larger crystallite/particle sizes, lower catalyst dispersion and lower electrochemical surface area (ESA), probably because of its high electrical conductivity. The addition of second metal (M) enhanced the ORR activity and stability of the Pt/PANI-CNT catalyst, because the added M induced the formation of a PtM alloy and shifted the d-band center to downfield, leading to a weak chemical interaction between oxygenated species and the catalyst surface and, therefore, affected positively the catalytic activity. Among all the tested M, the addition of Cr was optimal. Although it improved the ORR activity of the Pt/PANI-CNT catalyst slightly less than that of Pd (around 4.98%) in low temperature (60 °C)/pressure (1 atm abs), it reduced the ESA loss by around 14.8% after 1000 cycles of repetitive cyclic voltammetry (CV). In addition, it is cheaper than Pd metal. Thus, Cr was recommended as the second metal to alloy with Pt on the PANI-CNT support

Photoinduced Glycerol Oxidation over Plasmonic Au and AuM (M = Pt, Pd and Bi) Nanoparticle-Decorated TiO2 Photocatalysts

In this study, sol-immobilization was used to prepare gold nanoparticle (Au NP)-decorated titanium dioxide (TiO2) photocatalysts at different Au weight % (wt. %) loading (Aux/TiO2, where x is the Au wt. %) and Au–M NP-decorated TiO2 photocatalysts (Au3M3/TiO2), where M is bismuth (Bi), platinum (Pt) or palladium (Pd) at 3 wt. %. The Aux/TiO2 photocatalysts exhibited a stronger visible light absorption than the parent TiO2 due to the localized surface plasmon resonance effect. Increasing the Au content from 1 wt. % to 7 wt. % led to increased visible light absorption due to the increasing presence of defective structures that were capable of enhancing the photocatalytic activity of the as-prepared catalyst. The addition of Pt and Pd coupled with the Au3/TiO2 to form Au3M3/TiO2 improved the photocatalytic activity of the Au3/TiO2 photocatalyst by maximizing their light-absorption property. The Au3/TiO2, Au3Pt3/TiO2 and Au3Pd3/TiO2 photocatalysts promoted the formation of glyceraldehyde from glycerol as the principle product, while Au3Bi3/TiO2 facilitated glycolaldehyde formation as the major product. Among all the prepared photocatalysts, Au3Pd3/TiO2 exhibited the highest photocatalytic activity with a 98.75% glycerol conversion at 24 h of reaction time

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

Optimal Hydrogen Production Coupled with Pollutant Removal from Biodiesel Wastewater Using a Thermally Treated TiO2 Photocatalyst (P25): Influence of the Operating Conditions

This work aimed to produce hydrogen (H2) simultaneously with pollutant removal from biodiesel wastewater by photocatalytic oxidation using a thermally-treated commercial titanium dioxide (TiO2) photocatalyst at room temperature (~30 °C) and ambient pressure. The effects of the operating conditions, including the catalyst loading level (1–6 g/L), UV light intensity (3.52–6.64 mW/cm2), initial pH of the wastewater (2.3–8.0) and reaction time (1–4 h), on the quantity of H2 production together with the reduction in the chemical oxygen demand (COD), biological oxygen demand (BOD) and oil and grease levels were explored. It was found that all the investigated parameters affected the level of H2 production and pollutant removal. The optimum operating condition for simultaneous H2 production and pollutant removal was found at an initial wastewater pH of 6.0, a catalyst dosage of 4.0 g/L, a UV light intensity of 4.79 mW/cm2 and a reaction time of 2 h. These conditions led to the production of 228 μmol H2 with a light conversion efficiency of 6.78% and reduced the COD, BOD and oil and grease levels by 13.2%, 89.6% and 67.7%, respectively. The rate of pollutant removal followed a pseudo-first order chemical reaction with a rate constant of 0.008, 0.085 and 0.044 min−1 for the COD, BOD and oil and grease removal, respectively