Electrocatalysts For Ethanol Electro-oxidation Research Articles

Electrochemical and fuel cell evaluation of PtAu/C electrocatalysts for ethanol electro-oxidation in alkaline media

PtAu/C electrocatalysts in different atomic ratios and supported on Vulcan XC 72 carbon were tested for ethanol electro-oxidation in alkaline media. The electrocatalysts were prepared using borohydride as reducing agent. PtAu/C X-ray diffraction (XRD) patterns showed peaks characteristic of Pt face-centered cubic (fcc) structure and carbon. PtAu/C (70:30) and (50:50) XRD patterns showed a shift to lower values of 2θ when compared to Pt/C, this way suggesting the formation of PtAu alloy. Transmission electron micrographs showed the nanoparticles with particle size between 4 and 6.5 nm for all PtAu/C electrocatalysts. Electrochemical characterization of the PtAu/C materials suggested the PtAu/C (50:50) as the most promising material for ethanol electro-oxidation while experiments in single fuel cell suggested PtAu/C (70:30). The discrepancy in the results obtained can be explained by the electrode construction since PtAu/C (50:50) yields a much thicker electrode than PtAu/C (70:30), due to the Pt load is the same. The best results obtained with PtAu/C electrocatalysts could be explained by the presence of Pt and Au in close contact (alloy) associated to the extend in the platinum lattice parameters since these properties could contribute to the C–C breaking bond.

Acid-treated PtSn/C and PtSnCu/C electrocatalysts for ethanol electro-oxidation

PtSn/C with Pt:Sn atomic ratio of 50:50 and PtSnCu/C electrocatalysts with different Pt:Sn:Cu atomic ratios were prepared using NaBH4 as reducing agent and carbon black Vulcan XC72 as support. In a second step, the electrocatalysts were treated with nitric acid to remove the less noble metals (chemical dealloying). The obtained materials were characterized by X-ray diffraction, EDX analysis, TEM images with EDX scan-line and cyclic voltammetry. The electro-oxidation of ethanol was studied by chronoamperometry and on single direct ethanol fuel cell (DEFC). The X-ray diffractograms of the as-synthesized electrocatalysts showed the typical face-centered cubic (FCC) structure of Pt alloys. After acid treatment the FCC structure was maintained and Sn and Cu atoms were removed from the nanoparticles surface. Chronoamperometry measurements showed a strong increase of performance of PtSn/C and PtSnCu/C electrocatalysts after acid treatment; however, under DEFC conditions at 100 °C, only acid-treated PtSn/C electrocatalyst showed superior performance compared to commercial PtSn/C from BASF.

Ni nanowire supported 3D flower-like Pd nanostructures as an efficient electrocatalyst for electrooxidation of ethanol in alkaline media

A Ni nanowire array (NiNWA) supported three-dimensional flower-like Pd nano-electrocatalyst with high electrocatalytic performance for the electrooxidation of ethanol in alkaline media has been fabricated by borohydride hydrothermal reduction method. This novel hybrid NiNWA/PdNF (nanoflowers) electrocatalyst exhibits large electrochemically active surface area (EASA, 45m2g−1(Pd)), excellent electrocatalytic activity (765mAmg−1(Pd)), and high level of the poisoning tolerance (If/Ib=1.2) to the carbonaceous oxidative intermediates for the electrooxidation reaction in alkaline media. In addition, the electrochemical stability of NiNWA/PdNF is significantly higher than that of NiNWA/PdNP (nanoparticles) electrocatalyst, as evidenced by chronoamperometry experiments in which the electrooxidation current of nanoflowers is controlled by the diffusion transport of ethanol species rather than the carbonaceous poisoning. This high electrocatalytic activity can be attributed to the more open structure with higher electrochemically active sites and shape of Pd nanoflowers. This is further enhanced by the core support NiNWA with a very large surface area and the open interspaces that ensure easy alcohol access even to remote active sites for fast ion adsorption/desorption.

Effect of decreasing platinum amount in Pt–Sn–Ni alloys supported on carbon as electrocatalysts for ethanol electrooxidation

Literature describes the influence of morphological and structural electrocatalysts characteristics, on the catalytic activity toward ethanol electrooxidation. Thus, in this work Pt and ternary Pt–Sn–Ni alloys nanoparticles, supported on Vulcan carbon, were obtained by impregnation/reduction method. The aim of this work was to evaluate the influence of the decrease of platinum and increase of nickel content of the electrocatalysts obtained. The electrocatalysts were characterized by Rutherford backscattering spectroscopy, X-ray diffraction, transmission electronic microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The results obtained showed that it was possible to obtain Pt–Sn–Ni nanoparticles with a uniform size distribution in a narrow particle size range with a composition control. Moreover, the simultaneous addition of Sn and Ni to Pt did not affect reticular lattice a value, but the crystallite size decreases significantly. Besides, electrochemical results suggest that the substitution of platinum by nickel, in the electrocalatyst alloys studied, does not compromise the catalytic activity toward ethanol eletrooxidation.

PdBi/C electrocatalysts for ethanol electro-oxidation in alkaline medium

PdBi/C electrocatalysts (Pd:Bi atomic ratios of 95:05, 90:10, 80:20 and 70:30) were prepared by borohydride reduction using Pd(NO 3) 2.2H 2O and Bi(NO 3) 3.5H 2O as metal sources and Vulcan XC72 as support. The electrocatalysts were characterized by energy-dispersive X-ray analysis, X-ray diffraction, transmission electron microscopy and cyclic voltammetry. The activity for the ethanol electro-oxidation in alkaline medium was investigated at room temperature by chronoamperometry and the results were compared with Pt/C and PtBi/C electrocatalysts. PdBi/C (95:05) electrocatalyst showed a significant increase of performance for ethanol electro-oxidation compared to Pd/C and others PdBi/C electrocatalysts. The final current value after holding the cell at −0.4 V versus Ag/AgCl electrode for 30 min in alkaline medium for PdBi/C (95:05) electrocatalyst was about eleven times higher than the current value of the Pt/C electrocatalyst and 1.5 times higher than PtBi/C (50:50).

The high activity of PtBi/C electrocatalysts for ethanol electro-oxidation in alkaline medium

Pt/C, Bi/C and PtBi/C (Pt:Bi atomic ratios of 90:10, 70:30 and 50:50) electrocatalysts were prepared by borohydride reduction using H2PtCl6·6H2O and Bi(NO3)3·5H2O as metal sources and Vulcan XC72 as carbon support. The obtained electrocatalysts were characterized by energy-dispersive X-ray analysis, X-ray diffraction, transmission electron microscopy and cyclic voltammetry. The activity of the electrocatalysts for ethanol electro-oxidation was studied by chronoamperometry. PtBi/C electrocatalysts showed a significant increase of performance compared to Pt/C, while Bi/C showed no activity. Also, the performances of the PtBi/C electrocatalysts for ethanol electro-oxidation in alkaline medium were very superior to the ones obtained in acid medium.

High activity of Pd–In2O3/CNTs electrocatalyst for electro-oxidation of ethanol

National Natural Science Foundation of China [20476001]; Natural Science Foundation of Anhui province [070414160]

Ethanol oxidation on a nichrome-supported spherical platinum microparticle electrocatalyst prepared by electrodeposition

A novel electrode was rapidly prepared by depositing microparticle platinum onto a nichrome substrate in dilute chloroplatinic acid solution by cyclic voltammetry. The SEM results revealed that the deposits were composed of spherical Pt microparticles. Cyclic voltammetry and chronoamperometry were used for the characterization of the electrodes. Results of the electrochemical measurements showed that the spherical Pt microparticle electrodes retained the properties of metal platinum, increased the catalytic activity and promoted the electrocatalytic oxidation of ethanol. Moreover, the deposited Pt microparticles improved the electrochemical properties of the support material and reduced the dosage of noble metal platinum remarkably. The cost could be reduced dramatically by decreasing the contents of platinum. The spherical Pt microparticles deposited on the nichrome supports are likely a potential electrocatalyst for ethanol electrooxidation.

Comparison of different promotion effect of PtRu/C and PtSn/C electrocatalysts for ethanol electro-oxidation

Abstract Well dispersed PtSn/C, PtRu/C and Pt/C electrocatalysts were synthesized by a modified polyol process and characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and inductively coupled plasma-atomic emission spectrometry techniques. XRD patterns show that Ru induces the contraction of Pt lattice parameter while Sn makes the Pt crystal lattice extended. Ethanol oxidation activities on the catalysts were studied via cyclic voltammetry (CV) and chronoamperometry (CA) methods at room temperature. It is found that the electrode potential plays an important role in the electrochemical behavior of ethanol oxidation on PtRu/C and PtSn/C catalysts. In the lower potential region, PtSn/C possesses higher performance for ethanol oxidation, while in the higher potential region PtRu/C is more active. The different promotion effects of PtSn/C and PtRu/C to ethanol oxidation can be explained by the structural effect and modified bi-functional mechanism in different potential region. Single cell test of a direct ethanol fuel cell (DEFC) was also carried out to elucidate the promotion effect of PtRu/C and PtSn/C catalysts on the ethanol oxidation at 90 °C.

Pd nanowire arrays as electrocatalysts for ethanol electrooxidation

Highly ordered Pd nanowire arrays were prepared by template-electrodeposition method using anodic aluminum oxide template. The Pd nanowire arrays, in this paper, have high electrochemical active surface and show excellent catalytic properties for ethanol electrooxidation in alkaline media. The activity of Pd nanowire arrays for ethanol oxidation is not only higher that of Pd film, but also higher than that of commercial E-TEK PtRu(2:1 by weight)/C. The micrometer sized pores and channels in nanowire arrays act as structure units. They make liquid fuel diffuse into and products diffuse out of the catalysts layer much easier, therefore, the utilization efficiency of catalysts gets higher. Pd nanowire arrays are stable catalysts for ethanol oxidation. The nanowire arrays may be a great potential in direct ethanol fuel cells and ethanol sensors.

Effects of Treatment in Different Atmosphere on Pt3Sn/C Electrocatalysts for Ethanol Electro-oxidation

Pt3Sn/C catalyst was prepared by a modified polyol process and treated in air, H2/Ar, and Ar atmosphere, respectively. XRD analyses indicate that all of these catalysts have face-centered cubic (fcc) crystal structure. Temperature-programmed reduction (TPR) experiments show that more Sn exists in zero-valence in the Ar-treated PtSn catalyst than in the others. Cyclic voltammetry (CV), chronoamperometry (CA) experiments, and the performance tests of direct ethanol fuel cell (DEFC) indicate that the catalytic activity of PtSn/C for ethanol oxidation was affected significantly by the chemical state of Sn in catalyst particles. The as-prepared PtSn/C gives the higher power density, while Ar-treated PtSn/C shows the lower cell performance. It seems that the multivalence Sn rather than the zero-valence Sn in the PtSn catalyst is the favorable form for ethanol oxidation. Energy dispersion X-ray analysis (EDX) of the PtSn/C-as prepared and PtSn/C (after stability test) shows the active species (platinum, tin, and...