Synthesis and characterization of quaternary PtRuIrSn/C electrocatalysts for direct ethanol fuel cells

To find a more durable anode with high performance for direct ethanol fuel cells (DEFCs), the present study investigates a series of quaternary electrocatalysts, Pt30Ru30Ir40?xSnx/C (wt.%), for the ethanol electro-oxidation reaction (EOR). The carbon-supported Pt30Ru30Ir40?xSnx/C electrocatalysts were prepared by a known impregnation-reduction (borohydride) method. The microstructure and chemical composition were determined by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). The activity of the electrocatalysts for EOR was compared to commercial Pt67Ru33/C (HISPEC5000) using linear sweep voltammetry (LSV) based on similar Pt loading. The results of this study show that electrocatalyst composition with 10 and 20% Ir (wt.%) exhibit higher electrocatalytic activity than the commercial PtRu electrocatalyst. The single fuel cell testing at 90 ?C comparing Pt30Ru30Ir40?xSnx/C to commercial Pt67Ru33/C and Pt83Sn17/C anodes showed an enhancement of Pt activity (normalized to Pt loading) in the following order: Pt30Ru30Ir10Sn30 >Pt30Ru30Sn40 ?Pt30Ru30Ir40 ?Pt83Sn17 >Pt67Ru33. After a long-term performance test, the activity changed to the following order: Pt30Ru30Ir10Sn30 >Pt30Ru30Ir40 >Pt30Ru30Sn40 > Pt83Sn17 >Pt67Ru33. Pt30Ru30Ir10Sn30/C exhibited both a higher performance with a specific power density of 29mWmgPt?1 without O2 backpressure at the cathode and an excellent long-term stability in a DEFC operating at 90 ?C.Visant à trouver une anode qui serait plus durable et qui présenterait de meilleures performances dans des piles à combustion directe d’éthanol [DEFC], la présente étude porte sur une série d’électrocatalyseurs, Pt30Ru30Ir40 12xSnx/C (% en poids), pour obtenir la réaction d’électrooxydation de l’éthanol [EOR]. Les électrocatalyseurs Pt30Ru30Ir40 12xSnx/C sur carbone ont été préparés par une méthode connue d’imprégnation-réduction (au borohydrure). La microstructure et la composition chimique ont été établies par diffraction des rayons X [XRD], par spectroscopie à dispersion d’énergie [EDX] et par microscopie électronique à transmission [TEM]. L’activité des électrocatalyseurs utilisés pour obtenir la réaction d’électrooxydation de l’éthanol a été comparée avec celle du Pt67Ru33/C (HISPEC5000) en utilisant la voltampérométrie à balayage linéaire [LSV] avec une charge de Pt semblable. Les résultats de cette étude montrent qu’une composition d’électrocatalyseurs à 10 et 20 % Ir (% en poids) présente une activité électrocatalytique supérieure au composé PtRu commercial. Les essais sur cellule à combustible unique à 90 \uf0b0C comparant le Pt30Ru30Ir40 12xSnx/C aux anodes au Pt67Ru33/C et au Pt83Sn17/C ont montré une amélioration de l’activité du Pt (normalisée en fonction de la charge en Pt) dans l’ordre suivant : Pt30Ru30Ir10Sn30 > Pt30Ru30Sn40 65 Pt30Ru30Ir40 65 Pt83Sn17 > Pt67Ru33. Après un essai de rendement à long terme, l’ordre des degrés d’activité a changé pour prendre les valeurs suivantes : Pt30Ru30Ir10Sn30 > Pt30Ru30Ir40 > Pt30Ru30Sn40 > Pt83Sn17 > Pt67Ru33. Le Pt30Ru30Ir10Sn30/C a montré un meilleur rendement, soit une densité nominale de puissance de 29 mWmgPt 121 sans contrepression d’O2 à la cathode et une excellente stabilité à long terme dans une pile DEFC fonctionnant à 90 \uf0b0C.Peer reviewed: YesNRC publication: Ye

Biocatalyzed hydrogen production in a continuous flow microbial fuel cell with a gas phase cathode

A single liquid chamber microbial fuel cell (MFC) with a gas-collection compartment was continuously operated under electrically assisted conditions for hydrogen production. Graphite feltwas used for anode construction, while the cathodewas made of Pd/Pt coated Toray carbon fiber paper with a catalyst loading of 0.5mgcm\u207b\ub2. To achieve hydrogen production, theMFCwas connected to a power supply and operated at voltages in a range of 0.5\u20131.3 V. Either acetate or glucosewas used as a source of carbon. At an acetate load of 1.67g(LA d)\u207b\ub9, the volumetric rate of hydrogen production reached 0.98 LSTP (LA d)\u207b\ub9 when a voltage of 1.16V was applied. This corresponded to a hydrogen yield of 2 mol (mol-acetate)\u207b\ub9 with a 50% conversion efficiency. Throughout the experiment, MFC efficiency was adversely affected by the metabolic activity of methanogenic microorganisms, which competed with exoelectrogenic microorganisms for the carbon source and consumed part of the hydrogen produced at the cathode.Peer reviewed: YesNRC publication: Ye

Electricity generation from carbon monoxide in a single chamber microbial fuel cell

Electricity production from carbon monoxide (CO) is demonstrated in a single chamber microbial fuel cell (MFC) with a CoTMPP-based air cathode. The MFC was inoculated with anaerobic sludge and continuously sparged with CO as a sole carbon source. Volumetric power output was maximized at a CO flow rate of 4.8 L LR\u207b\ub9 d\u207b\ub9 reaching 6.4mWLR\u207b\ub9 . Several soluble and gaseous degradation products including hydrogen, methane, and acetate were detected, resulting in a relatively low apparent Coulombic efficiency of 8.7%. Tests also demonstrated electricity production from hydrogen and acetate with the highest and fastest increase in voltage exhibited after acetate injection. It is hypothesized that electricity generation in a CO-fed MFC is accomplished by a consortium of carboxydotrophic and carbon monoxide \u2013 tolerant anodophilic microorganisms.Peer reviewed: YesNRC publication: Ye

Hydrogen production in a microbial electrolysis cell with nickel-based gas diffusion cathodes

Gas diffusion cathodes with Ni alloy and Ni catalysts manufactured by chemical deposition were tested for H2 production in a microbial electrolysis cell (MEC). In a continuous flow MEC, multi-component cathodes containing Ni, Mo, Cr, and Fe, at a total catalyst load of 1 mg cm-2 on carbon support demonstrated stable H2 production at rates of 2.8 - 3.7 L LR- 1 d- 1 with only 5% methane in the gas stream. Furthermore, a Ni-only gas diffusion cathode, with a Ni load of 0.6 mg cm-2, demonstrated a H2 production rate of 4.1 L LR- 1 d- 1. Overall, H2 production was found to be proportional to the Ni load implying that inexpensive gas diffusion cathodes prepared by chemical deposition of Ni can be successfully used for continuous production of H2 in a MEC.Peer reviewed: YesNRC publication: Ye

Microbial fuel cell operation on carbon monoxide: cathode catalyst selection

Electricity production from carbon monoxide (CO) in a microbial fuel cell (MFC) has recently been demonstrated. Efficient operation of this MFC requires a CO-tolerant and preferably inexpensive cathode. Pyrolised CoTMPP, FeTMPP, and Co/FeTMPP gas diffusion cathodes were tested in MFCs operated on acetate or CO. When the MFC was fed with acetate the best cathode performance was obtained when using a Co/FeTMPP (3:1) cathode with a Me catalyst load of 0.5 mg cm -2, although this performance was slightly lower than that obtained with a cathode containing 0.5 mg-Pt cm-2. Tests using a MFC operated on CO showed a higher power output when using the Co/FeTMPP cathode when compared both with CoTMPP and Pt cathodes.Peer reviewed: YesNRC publication: Ye

Synthesis of Pd and Nb-doped TiO 2 composite supports and their corresponding Pt-Pd alloy catalysts by a two-step procedure for the oxygen reduction reaction

Several Pd-composite Nb 0.06Ti 0.94O 2 materials are synthesized by a two-step procedure, and employed as the Pt-Pd alloy catalyst support for the PEM fuel cell oxygen reduction reaction (ORR). These supports and their supported catalysts are characterized using analytical and electrochemical methods with respect to their material morphology, chemical/electrochemical stability, electronic conductivity as well as oxygen reduction reaction (ORR) mass activity/stability. For the supported Pt-Pd catalysts, the Pt-Pd nanoparticles adhered to both the Nb 0.06Ti 0.94O 2 and composited Pd surfaces to form Pt mPd n clusters. A possible synergetic interaction between the Pt-Pd alloy catalyst and its Pd-Nb 0.06Ti 0.94O 2 composite support is believed to exist which enhances the ORR activity of these catalysts. The electronic conductivity of Nb 0.06Ti 0.94O 2 can be greatly improved after forming composites with Pd to the desired levels required for electrocatalyst applications. Three supported Pt-Pd catalysts, 20 wt% Pt 0.62Pd 0.38/Pd 10wt%-(Nb 0.06Ti 0.94O 2) 90wt%, 20 wt% Pt 0.62Pd 0.38/Pd 30wt%-(Nb 0.06Ti 0.94O 2) 70wt%, and 20 wt% Pt 0.62Pd 0.38/Pd 50wt%-(Nb 0.06Ti 0.94O 2) 50wt%, are synthesized and tested using both cyclic voltammetric and rotating disk electrode techniques with respect to their surface electrochemistry, ORR mass activity, and electrochemical stability. All three catalysts show higher Pt mass activity (>130 mA mg Pt -1 at 0.9 V vs. RHE) than that of the baseline 47 wt% Pt C -1 carbon supported catalyst (110 mA mg Pt -1). However, the durability of these catalysts needs to be further improved.Peer reviewed: YesNRC publication: Ye

Screening and further investigations on promising bi-functional catalysts for metal–air batteries with an aqueous alkaline electrolyte

A wide range catalyst screening with noble metal and oxide catalysts for a metal–air battery with an aqueous alkaline electrolyte was carried out. Suitable catalysts reduce overpotentials during the charge and discharge process, and therefore improve the round-trip efficiency of the battery. In this case, the electrodes will be used as optimized cathodes for a future lithium–air battery with an aqueous alkaline electrolyte. Oxide catalysts were synthesized via atmospheric plasma spraying. The screening showed that IrO2, RuO2, La0.6Ca0.4Co3, Mn3O4, and Co3O4 are promising bi-functional catalysts. Considering the high price for the noble metal catalysts further investigations of the oxide catalysts were carried out to analyze their electrochemical behavior at varied temperatures, molarities, and in case of La1-xCaxCoO3 a varying calcium content. Additionally all catalysts were tested in a longterm test to proof cyclability at varied molarities. Further investigations showed that Co3O4 seems to be the most promising bi-functional catalyst of the tested oxide catalysts. Furthermore, it was shown that a calcium content of x = 0.4 in LCCO has the best performance