Carbon-supported trimetallic catalysts (PdAuNi/C) for borohydride oxidation reaction

The synthesis of palladium-based trimetallic catalysts via a facile and scalable synthesis procedure was shown to yield highly promising materials for borohydride-based fuel cells, which are attractive for use in compact environments. This, thereby, provides a route to more environmentally friendly energy storage and generation systems. Carbon-supported trimetallic catalysts were herein prepared by three different routes: using a NaBH4-ethylene glycol complex (PdAuNi/CSBEG), a NaBH4-2-propanol complex (PdAuNi/CSBIPA), and a three-step route (PdAuNi/C3-step). Notably, PdAuNi/CSBIPA yielded highly dispersed trimetallic alloy particles, as determined by XRD, EDX, ICP-OES, XPS, and TEM. The activity of the catalysts for borohydride oxidation reaction was assessed by cyclic voltammetry and RDE-based procedures, with results referenced to a Pd/C catalyst. A number of exchanged electrons close to eight was obtained for PdAuNi/C3-step and PdAuNi/CSBIPA (7.4 and 7.1, respectively), while the others, PdAuNi/CSBEG and Pd/CSBIPA, presented lower values, 2.8 and 1.2, respectively. A direct borohydride-peroxide fuel cell employing PdAuNi/CSBIPA catalyst in the anode attained a power density of 47.5 mW cm−2 at room temperature, while the elevation of temperature to 75 °C led to an approximately four-fold increase in power density to 175 mW cm−2. Trimetallic catalysts prepared via this synthesis route have significant potential for future development

Ethanol Electrooxidation at Platinum-Rare Earth (RE = Ce, Sm, Ho, Dy) Binary Alloys

Proton exchange membrane fuel cells and direct alcohol fuel cells have been extensively studied over the last three decades or so. They have emerged as potential systems to power portable applications, providing clean energy, and offering good commercial viability. Ethanol is considered one of the most interesting fuels in this field. Herein, platinum-rare earth (Pt-RE) binary alloys (RE = Ce, Sm, Ho, Dy, nominal composition 50 at.% Pt) were produced and studied as anodes for ethanol oxidation reaction (EOR) in alkaline medium. A Pt-Dy alloy with nominal composition 40 at.% Pt was also tested. Their electrocatalytic performance was evaluated by voltammetric and chronoamperometric measurements in 2 M NaOH solution with different ethanol concentrations (0.2–0.8 M) in the 25–45 °C temperature range. Several EOR kinetic parameters were determined for the Pt-RE alloys, namely the charge transfer and diffusion coefficients, and the number of exchanged electrons. Charge transfer coefficients ranging from 0.60 to 0.69 and n values as high as 0.7 were obtained for the Pt0.5Sm0.5 electrode. The EOR reaction order at the Pt-RE alloys was found to vary between 0.4 and 0.9. The Pt-RE electrodes displayed superior performance for EOR than bare Pt, with Pt0.5Sm0.5 exhibiting the highest electrocatalytic activity. The improved electrocatalytic activity in all of the evaluated Pt-RE binary alloys suggests a strategy for the solution of the existing anode issues due to the structure-sensitive EOR

Vine Shoots and Grape Stalks as Carbon Sources for Hydrogen Evolution Reaction Electrocatalyst Supports

Activated bio-based carbons produced from vine shoots (VSAC) and grape stalks (GSAC), which have larger surface area and total pore volume than most of the commercially available activated carbons, are used as supports for palladium nanoparticles (Pd NPs). The prepared materials are characterised by elemental analysis, N2-sorption, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, and transmission electron microscopy analysis and are then assessed as potential cathodes for the hydrogen evolution reaction (HER) in alkaline media. The electrocatalysts’ performance for HER is evaluated from cathodic polarisation curves at different temperatures and compared to that of Vulcan XC72-supported Pd NPs. Additional chronoamperometry studies helped to assess the electrocatalysts’ activity stability. The novel VSAC-supported Pd electrocatalyst exhibits good HER activity in terms of high current density at low overpotentials, leading to the best performance

Trimetallic carbon-supported catalysts for borohydride oxidation and oxygen reduction in alkaline solutions

ECEE 2019 meeting abstract

Platinum-rare earth cathodes for direct borohydride-peroxide fuel cells

Hydrogen peroxide (H2O2) is being actively investigated as an oxidant for direct borohydride fuel cells. Herein, platinum-rare earth (RE \ubc Sm, Dy, Ho) alloys are prepared by arc melting and their activity for hydrogen peroxide reduction reaction (HPRR) is studied in alkaline media. Cyclic voltammetry and chronoamperometry measurements show that PteSm electrode displays the highest catalytic activity for HPRR with the lowest activation energy, followed by PteHo, while PteDy alloys show practically no activity. Laboratory direct borohydride-peroxide fuel cells (DBPFCs) are assembled using these alloys. The DBPFC with PteSm cathode gives the highest peak power density of 85 mW cm2, which is more than double of that obtained in a DBPFC with Pt electrodes

Electrocatalytic approach for the efficiency increase of electrolytic hydrogen production: Proof-of-concept using platinum--dysprosium alloys

Development of electrocatalytic materials for the hydrogen evolution reaction (HER) is attempted with the aim of reducing the water electrolysis overpotential and increasing its efficiency. Using linear scan voltammetry measurements of the hydrogen discharge enables evaluation of the electrocatalytic activity for the HER of platinum\u2013dysprosium (Pt\u2013Dy) intermetallic alloy electrodes of different compositions. Understanding of materials electrocatalytic performance is based on determination of several crucial kinetic parameters, including the Tafel coefficients, b, charge transfer coefficients, \u3b1, exchange current densities, j0, and activation energies, Ea. Influence of temperature on HER is investigated by performing studies at temperatures ranging from 25 \ub0C to 85 \ub0C. The effect of the Dy amount in the efficiency of the HER on the Pt\u2013Dy alloys is analysed. Results demonstrate that Dy can substantially increase the electrocatalytic activity of the Pt alloys, in comparison to the single Pt electrode. Efforts are made to correlate the microstructure of the alloys with their performance towards the HER

Investigation of nickel-rare earth electrodes for sodium borohydride electrooxidation

Nickel-dysprosium (Ni-Dy) and nickel-samarium (Ni-Sm) alloys were prepared and their morphology, composition and microstructure was analyzed using SEM/EDS and XRD. The alloys were used for fabrication of solid electrodes that were subsequently investigated for borohydride oxidation reaction in alkaline media using cyclic voltammetry, chronoamperometry and chronopotentiometry

Enhancement of hydrogen evolution in alkaline water electrolysis by using nickel-rare earth alloys

Nickel\u2013dysprosium (Ni\u2013Dy) and nickel\u2013samarium (Ni\u2013Sm) alloys with 5 and 10 at% of rare earth metal were prepared by arc melting and by induction furnace melting, respectively. The alloys microstructure, morphology and chemical composition were inspected by scanning electron microscopy and energy dispersive X-ray analysis; phases crystal structure and lattice parameters were confirmed by X-ray diffraction analysis. The alloys were used for fabrication of electrodes for hydrogen evolution reaction (HER) in alkaline media and studied using polarisation measurements. Tafel analysis suggests that HER is limited by the Volmer step at all four electrodes. Determined kinetic parameters indicate better electrocatalytic performance for HER of Ni-RE alloys with 5 at% of RE compared to those with 10 at% of RE. Activation energies were evaluated to be in the 47\u201371 kJ mol 121 range