Anode Catalyst For Fuel Cells Research Articles

Ab initio calculations of the chemisorption of atomic H and O on Pt and Ir metal and on bimetallic Pt x Ir y surfaces

Abstract Understanding the chemisorption of atoms on precious metal surfaces is of substantial interest for the rational design of heterogeneous and electrochemical catalysts. In this study, we report density functional theory (DFT) investigations of the chemisorption of atomic H and O on bimetallic Pt x Ir y (111) surfaces for bifunctional anode catalyst materials in polymer electrolyte membrane (PEM) fuel cells. We found that for both adsorbates, the adsorption on the Pt(111) surface is in general less exothermic than on the Ir(111) surface. Our study has revealed that chemisorption on the bimetallic surfaces becomes more stable with increasing number of Ir surface atoms at the adsorption site. While for hydrogen atoms the ONTOP sites yield the most negative adsorption energies, the chemisorption of oxygen atoms appears to be most stable on the FCC sites for both the mono- and bimetallic surfaces. Using the ab initio thermodynamics approach, we calculated phase diagrams for the chemisorption of H and O atoms on these metal surfaces in order to transfer our findings to finite temperature and pressure conditions. Our theoretical results may provide an improved understanding of the hydrogen oxidation reaction (HOR) and oxygen evolution reaction (OER) on intermetallic Pt x Ir y (111) surfaces and may be helpful for the rational design of new bifunctional PEM fuel cell anode catalyst materials.

Highly efficient metal free aldehyde-functionalized indoles for direct glucose fuel cell anode catalyst

In this study, alternative organic catalysts to metal-containing catalysts for glucose electrooxidation were prepared by the Suzuki Miyaura coupling reaction method and characterized by nuclear magnetic resonance (NMR), fourier transform infrared spectroscopy (FT-IR), and liquid chromatography with tandem mass spectrometry (LC-MS-MS). InTA-1, InPA-1, InFA-1, InTA-2, InPA-2, InFA-2, InTA-3, InFA-3, and InPA-3 were obtained with the yield of 74%, 82%, 72%, 70%, 75%, 68%, 60%, 71%, and 85%. Among the synthesized catalysts, the InTA-3 catalyst possesses the highest electrocatalytic activity (3.17 mA cm−2) and long-term stability compared to other organic catalysts. InTA-3 catalyst has the lowest charge transfer resistance toward glucose electrooxidation. It was concluded that as a metal-free catalyst, InTA-3 is a cheap and promising electrocatalyst for direct glucose fuel cell anode.

Carbon Monoxide-Resistant Anode Catalysts for Single-Cell Direct Carbon Monoxide Fuel Cells: Binary, Ternary, And Quaternary Platinum Alloys as Anode Electrocatalysts

The objective of this paper is to present the results of experimentations on the custom-made anode electrocatalysts for direct carbon monoxide fuel cells (DCMFCs) inspired by catalysts commonly used for direct alcohol fuel cells. Seven different catalysts were fabricated and tested. The uniform and consistent manufacturing process and the test procedure allowed a meaningful comparison of the developed fuel cells. The results indicated that homemade Pt-Ru membrane-electrode assembly (MEA) could not compete with the Pt-Sn MEA. While the performance of the MEAs with Pt-Ru-Ni, Pt-Ru-Sn-Ni, and Pt-Ru-Sn-Co was not satisfactory, the Pt-Ru-Sn-Co-W MEA achieved the best performance among all MEAs with Nafion® 117 membrane. The last MEA was made of the Pt-Sn anode catalyst and Nafion® 212 membrane and outperformed all other MEAs by a wide margin. The experiments demonstrated that the performance of the best-developed MEA was three times better than the performance of the commercial Pt-Ru MEA. This means the performance of DCMFCs can be significantly improved by developing a suitable anode electrocatalyst, using a thinner membrane, and operating at optimum conditions. These results are not only applicable for DCMFCs but also are very useful for other proton exchange membrane fuel cells (PEMFCs) operating with CO-containing fuels.

Pyrolyzed POMs@ZIF-67 Exhibiting High Performance as Direct Glucose Fuel Cell Anode Catalysts

Polyoxometalates (POMs) are three-dimensional materials with unique, exceptional physical and chemical characteristics. The performance of POM-derived materials is anticipated to be enhanced by the combination of POM and metal–organic frameworks (MOFs) due to the high surface areas of MOF materials. In this study, three kinds of T-POMs@ZIF-67 (T-PMo@ZIF-67, T-SiW@ZIF-67, and T-PW@ZIF-67) were prepared by doping a cobalt-based MOF (ZIF-67) with three POMs (phosphomolybdic acid, silicotungstic acid, and phosphotungstic acid). The results show that the power density of the T-PMo@ZIF-67 catalyst anode is 3.08 times that of the blank control anode and 1.34 times that of the CoMoO4 catalyst. These findings suggest that the synthesis of MOF derivatives by doping MOFs with POM will have significant potential for use in the fuel cell industry.

Accelerated Stress Test Study on PtRu Anode Catalysts for Reformate PEM Fuel Cells

Proton-exchange membrane fuel cells (PEMFCs) are interesting candidates for heavy duty applications, e.g. in the maritime or bus and truck sector, since they convert renewable fuels into electricity efficiently [1]. Moreover, PEMFCs are flexible with respect to fuels, since they can be operated not only with hydrogen but also with reformate gas, originating from steam reforming of carbohydrates such as renewable methanol [2]. Compared to state-of-the-art carbon-supported Platinum catalysts (Pt), which are severely poisoned by CO, a side product from reforming, carbon-supported Platinum-Ruthenium catalysts (PtRu) prevail in reformate applications due to their promoting effects towards CO oxidation [3]. However, PtRu catalysts are less stable than Pt catalysts due to a higher susceptibility to dissolution [4]. Since the durability of materials in heavy duty applications is crucial to reach long operating times (> 30000 h), major efforts have to be taken to improve the stability of PtRu anode catalysts.To be able to evaluate the stability of catalysts and to investigate, identify, and understand degradation mechanisms with little time and costs, so-called accelerated stress tests (ASTs) are deployed, which induce fast electrode aging and ideally simulate electrode degradation that can be transferred to real operating conditions. For Pt cathode catalysts in PEMFC application, the U.S Department of energy proposed an AST based on square wave potential cycling between 0.6 V and 0.95 V for 30000 cycles [5]. As Ru and possibly PtRu have different dissolution potentials than Pt and are used on the anode side (therefore exposed to different potentials compared to the cathode), an AST designed for PtRu anode catalysts is required.In this work, several AST protocols based on square cycling the anode potential for 30000 cycles were developed and tested on cells with the same material composition. The carbon-supported PtRu anode electrodes were manufactured in-house with a patented technique [6], while for membranes, cathode catalysts, and GDLs commercial available products were applied. The ASTs differ by the upper potential limit, which was chosen at 0.2 VRHE, 0.65 VRHE, 0.8 VRHE, and 1.0 VRHE, respectively. The lower potential limit was set at 0.06 VRHE, (cf. Figure 1b). Before, during, and after the AST, electrochemical characterization was conducted via cyclic voltammetry, CO-stripping, and recording U-I curves (cf. Figure 1a). After the AST, post-mortem analyses were performed by means of transmission electron microscopy, X-ray diffraction, and cross-sectional scanning electron microscopy coupled with energy dispersive X-ray spectroscopy to analyze the prominent degradation mechanisms occurring for the different testing conditions.Strong differences in the degradation of the cells between the different ASTs could be observed. With increasing upper potential limit, the severity of degradation and the observed degradation phenomena increased. For example, Ru leaching occurred at ASTs with upper potentials beyond 0.65 VRHE, and increased with increasing potential, resulting in a reduced CO-tolerance. At the same time, the consequent Ru crossover to the cathode, which lowers the overall cell performance, could be only detected by EDX for ASTs beyond 0.8 VRHE, implying a correlation between Ru crossover and upper potential limit. Moreover, the data indicate that an upper potential limit of 1.0 VRHE may be too high to investigate the stability of Ru in PtRu catalysts, as an additional strong Pt degradation makes the evaluation difficult. Future work will address the correlation of these ASTs to long-term testing at constant potential.

Carbon Shell-Confined Pd-Fe Bimetallic Nanoparticles in NCNTs as Anode Catalysts for Microfluidic Direct Ethylene Glycol Fuel Cells

Carbon Shell-Confined Pd-Fe Bimetallic Nanoparticles in NCNTs as Anode Catalysts for Microfluidic Direct Ethylene Glycol Fuel Cells

Catalytically Active and Carbon-Resistive Anode Catalyst for Solid-Oxide Fuel Cells Operated at Low Temperatures (500–600 °C)

The development of active catalysts is always challenging in the field of energy devices. In this work, Li-doped, Ni–Cu-based, and Ni-free nanocomposite anode catalysts are synthesized and studied for solid-oxide fuel cells (SOFCs) operated at a low temperature using hydrogen and biogas as fuels. The catalysts with compositions Ni0.6Li0.2Cu0.2-oxide/La0.2Ce0.8O2-δ (NLC622-LDC), Ni0.2Li0.2Cu0.6-oxide/La0.2Ce0.8O2-δ (NLC226-LDC), and Ni0.0Li0.2Cu0.8-oxide/La0.2Ce0.8O2-δ (NLC028-LDC) are synthesized using the glycerol-assisted gel combustion route (GGCR). The structural analysis revealed the cubic structure of metallic oxide materials such as NiO and CuO phases while the cubic fluorite structure of CeO2 as an ionic oxide phase. The optical band gaps (Eg’s) of anode catalysts NLC622-LDC, NLC226-LDC, and NLC028-LDC are found to be 2.08, 2.29, and 2.37 eV, respectively. Furthermore, the anode catalyst with a higher nickel concentration shows better electrical conductivity and a lower activation energy of 3.47 S cm–1 and 0.67 eV at 600 °C, respectively, as compared to those of a nickel-free anode catalyst with lower nickel content. The electrochemical behavior of nanocomposites is studied at 600 °C using Nyquist plots. Electrochemical impedance analysis is carried out to see the effect of hydrocarbon fuel like biogas at the anode side. Finally, the electrochemical performance of NiLiCu-LDC catalyst-based fuel cells is tested under hydrogen and biogas fuels. Overall, the fuel cell based on the NLC622-LDC anode catalyst has higher OCV and power density with both fuels, hydrogen and biogas. Therefore, NLC622-LDC is a highly catalytically active anode catalyst which demonstrated significantly better performance for SOFCs operated at a low temperature (500–600 °C) without any carbon resistance.

Nickel-Based Anode Catalysts for Efficient and Affordable Anion-Exchange Membrane Fuel Cells.

ConspectusLow-temperature ion-exchange membrane hydrogen fuel cells, as zero-emission power sources, can largely preserve the merits of gasoline engines, including rapid fueling, extended cruising range, and low maintenance cost. To enable the widespread prevalence of fuel-cell automobiles, the U.S. Department of Energy (DOE) has set a long-term fuel-cell system cost target of US$30 kW-1. Over past decades, proton-exchange membrane fuel cell (PEMFC) technology has developed rapidly, resulting in the first commercial sales of fuel-cell-powered vehicles. Although there has been great success, the mass market penetration of PEMFCs is currently hindered by the excessive reliance on expensive platinum group metal (PGM) catalysts. Anion-exchange membrane fuel cells (AEMFCs), because of the alkaline environment that permits the use of PGM-free catalysts, have become an alternative technology with inherent long-term cost advantages. Thus far, significant progress has been made in the exploration of PGM-free catalysts for the oxygen reduction reaction at the AEMFC cathode, some of which have shown intrinsic catalytic properties comparable to PGM catalysts. However, the development of PGM-free catalysts for the anodic hydrogen oxidation reaction (HOR) has lagged behind, presumably owing to its sluggish kinetics in alkali. In alkaline media, the HOR kinetics is about 2 orders of magnitude slower than that in acid, which demands higher PGM loadings to reach similar fuel-cell performance in PEMFCs. Since Raney nickel (Ni) was explored for alkaline HOR catalysis in 1960s, research on Ni-based HOR catalysts has begun and now is flourishing, primarily thanks to their favorable adsorption energies of key HOR intermediates (e.g., Ni-Had and Ni-OHad). At present, a number of strategies have been developed to improve HOR performances of Ni-based materials, such as alloying, Ni nitridation, and alloy amorphization, which yield cost-effective HOR catalysts that rival or even exceed the activity and stability of PGM counterparts.In this Account, we describe our recent research endeavors toward the development of efficient Ni-based HOR catalysts for practical AEMFC anodes. First, we briefly highlight the important merits of AEMFC technology and why Ni-based materials are appealing for alkaline HOR catalysis. Critical innovations in the design of Ni-based nanostructured and bulky catalysts were then discussed, showing their great promise to catalyze alkaline HOR that traditionally relied on PGMs. To demonstrate utility, performances of the elaborately designed Ni-based catalysts under realistic fuel-cell conditions were examined, along with an initial effort to develop a CO-tolerant AEMFC anode. We conclude by outlining future research directions that allow access to next-generation PGM-free HOR catalysts for advanced AEMFCs.

Application of Low-Cost Plant-Derived Carbon Dots as a Sustainable Anode Catalyst in Microbial Fuel Cells for Improved Wastewater Treatment and Power Output

Microbial fuel cells (MFC) can generate electric energy from wastewater which can be enhanced further by anode catalysts. The recovery of electrons produced by oxidation of organics catalyzed by bacteria in the anode was enhanced when carbon dots(CDs) were added into the MFC. In this present study, a novel strategy for designing anode material and the fabrication of a high-efficient and environmentally friendly anode for energy generation from wastewater was reported. The CDs were synthesized by the pyrolysis of a peanut shell at the temperature of 250 °C for 2 h with a heating rate of 10 °C min−1. Thus synthesized CDs were characterized by transmission electron microscopy (TEM), UV/Vis spectroscopy, and fluorescence spectroscopy. The TEM analysis showed morphology with an average size of 1.62 nm. The UV/Vis absorbance of the CDs shows a wide absorption band without a characteristic peak. The excitation spectrum of CDs recorded at the emission wavelength of 440 nm exhibits a peak around 320 nm. CDs were investigated as an anode material in a MFC utilizing acetate as the organic substrate. The average chemical oxygen demand (COD) removal in closed circuit operation mode was 89%. The maximum power density production (7.2 W/m3) was observed in MFC containing 1 mg/cm2 CD-impregnated anode (CDsIA). The CDsIA provides the ability to promote efficient biofilm formation. These results emphasize the application of CD-based electrodes in MFCs for the simultaneous treatment of wastewater and electricity generation while also providing additional benefits.

Anode Catalysts for Solid Oxide Fuel Cells That Run Directly on Hydrocarbon Fuels

Solid oxide fuel cells (SOFCs) can efficiently generate electricity from a wide variety of fuels, offering unique advantages over the conventional power generation systems based on combustion. In particular, SOFCs can directly use low-cost and readily available hydrocarbon fuels as the energy source. To be commercially competitive, however, breakthroughs in materials development is required. For instance, a durable and electro-catalytically active anode material or catalyst is needed that can facilitate hydrocarbon reforming and avoiding carbon deposition (coking) for SOFCs to operate stably on hydrocarbon fuels, including natural gas, ethanol, and iso-octane.Hydrocarbon fuels, especially liquid ones, have several advantages over hydrogen fuel: low-cost, high volumetric energy density, and ease for transportation and storage. Currently, direct-hydrocarbon SOFCs suffer from severe performance degradation due to carbon deposition. In this presentation, we report a promising anode catalyst for SOFCs operated on various hydrocarbon fuels, from methane to ethanol and iso-octane. The catalyst has been successfully applied to both small button cells and tubular cells with an effective area of about 38 cm2. For both cases, our cells demonstrate stable performance for continuous operation of >1,000 hours.

Pd electrodeposition on a novel substrate of reduced graphene oxide/ poly(melem-formaldehyde) nanocomposite as an active and stable catalyst for ethanol electrooxidation in alkaline media

Palladium nanoparticles (Pd NPs) were successfully electrodeposited on a reduced graphene oxide/poly(melem-formaldehyde) nanocomposite (rGO/PMF) NC as a catalyst for ethanol electrooxidation in alkaline media; melem was used as a nitrogen-rich source in the substrate structure for the first time. The specific surface area and average pore diameter of (rGO/PMF) NC were 481.61 m2 gr−1 and 10.23 nm, respectively. High nitrogen doping and structural defects improved the dispersion and anchoring of Pd NPs on (rGO/PMF) NC. The onset potential (Eonset) of Pd/(rGO/PMF) NC was shifted negatively to 110 mV, in comparison to Pd/rGO. Also, the current density and electrochemical active surface area (EASA) of Pd/(rGO/PMF) NC were enhanced to 44 mA cm−2 and 67.58 m2 gr−1, respectively, as compared to Pd/rGO. Furthermore, the stability of Pd/(rGO/PMF)NC was indicated against ethanol oxidation intermediates during 7000 s. This work also produced a superior graphene-based material for direct ethanol fuel cell anode catalysts applications.

Direct Formic Acid Fuel Cell Anode Catalyst Layer: Enhanced Mass Transport with Increased Porosity

Batteries are the predominant portable power source, but are inefficient due to their limited charge capacity, lengthy recharging times, and exponential degradation. Direct formic acid fuel cells present a sustainable replacement to batteries with their instantaneous refueling times and high efficiency. However, small pore size (~20 nm) between the agglomerates in the anode catalyst layer and two-phase flow hinders the mass transport and reduces the cell performance. Therefore, enhancing the cell performance also requires the two-phase flow optimization of the liquid reactant (formic acid, HCOOH) and gaseous product (carbon dioxide, CO2). To accomplish this, pore-forming agent (magnesium oxide, MgO) was incorporated during the anode catalyst layer fabrication and subsequent removal leaving behind lager pores to improve the two-phase flow through the anode catalyst layer.In 2012, the addition and subsequent removal of pore-former (lithium carbonate, LiCO3), formed ~10 μm pores within the anode catalyst layer.[1] The optimal performance was found for pores formed from with 17.5 wt% LiCO3; however, the formic acid electrooxidation charge transfer activity was reduced, due to the size of the pore-former increased the separation of the agglomerates and reduced the connected electrochemical surface area.To avoid damaging the integrity of the anode catalyst layer, previous work to integrate a smaller pore-former MgO (~50 nm), into the anode catalyst layer was investigated. [2] Compared to an anode catalyst layer without pore-former, 25 wt% pore-former increased the electrochemical surface area and cell performance by 293% and 86%, respectfully. The present study aims to further explore varying wt% of pore-former with additional sonication of the catalyst/ionomer ink prior to fabrication. The uniformity and effect of agglomerate size vs. MgO addition will be explored by quantifying the viscosity of the catalyst ink. [3] Bauskar, A.S. and Rice, C.A., Impact of Anode Catalyst Layer Porosity on the Performance of a Direct Formic Acid Fuel cell. 2012, 62, 36-41.Lam, S., Bixby, M.M., and Rice, C.A., Optimization of Mass Transport within Direct Formic Acid Fuel Cell Catalyst Layer via Pore Formers.Khandavalli, S., Park, H.J., Kariuki, N.N., Myers, J.D., Stickel, J.J., Hurst, K., Neyerlin, C.K., Ulsh, M., and Mauger, A.S., Rheological Investigation on the Microstucture of Fuel Cell Catalyst Inks. 2018, 10, 50.

The preparation, characterization, and electrooxidation of colloidal palladium modified poly(methacrylic acid) hydrogel as formic acid fuel cell anode catalyst

AbstractAt present, poly(methacrylic acid) (MA), poly(MA) hydrogel, and Pd‐doped poly(MA) hydrogel modified electrodes are constructed on graphite pencil (G). The Pd precursor is coated on the poly(MA)/G electrodes surface using the electrodeposition method. These electrodes are characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy, and scanning electron microscopy‐energy dispersive X‐ray. Poly(MA) hydrogel and Pd‐doped poly(MA) hydrogel are successfully prepared by the polymerization and further electrodeposition. Formic acid electro‐oxidation (FAEO) activities are examined with cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). Poly(MA)/G and Pd doped poly(MA) electrodes exhibit promising electro‐catalytic activity with 60 mA current density, greater than literature values. Pd‐doped poly(MA) hydrogel electrodes are promising electrodes for FAEO.

Highly active carbon nanotube supported iridium, copper, ruthenium catalysts for glucose electrooxidation

AbstractHerein, carbon nanotube (CNT) supported ruthenium (Ru), iridium (Ir), and copper (Cu) catalysts at 0.1 to 20 wt% metal loading are prepared by the NaBH4 reduction method for glucose electrooxidation reaction (GER). These catalysts are successfully characterized by X‐ray diffraction, scanning electron microscope, and N2 adsorption‐desorption measurements. Voltammetric measurements of these catalysts are taken using cyclic voltammetry and chronoamperometry techniques. The crystallite sizes of these catalysts are calculated as 2.53 nm for Ru/CNT, 2.94 nm for Ir/CNT, and 13.06 nm for Cu/CNT by using Scherrer equation. For GER, 10% Ru/CNT, 0.1% Ir/CNT, and 0.5% Cu/CNT catalysts have high current densities as 1.86 mA cm−2 (160.6 mA mg−1 Ru), 3.03 mA cm−2 (23 857.2 mA mg−1 Ir), and 1.12 mA cm−2 (1768.8 mA mg−1 Cu), respectively. These catalysts have also good stability. Results reveal that 10% Ru/CNT, 0.1% Ir/CNT, and 0.5% Cu/CNT catalysts are promising catalysts as direct glucose fuel cell anode catalysts.

Crusty-Structured Cu@NiCo Nanoparticles as Anode Catalysts in Alkaline Fuel Cells

Crusty-Structured Cu@NiCo Nanoparticles as Anode Catalysts in Alkaline Fuel Cells

In-situ exsolution of Ni nanoparticles to achieve an active and stable solid oxide fuel cell anode catalyst on A-site deficient La0.4Sr0.4Ti0.94Ni0.06O3-δ

(La,Sr)TiO3 has been investigated as a promising anode material for solid oxide fuel cells (SOFCs) owing to its high electronic conductivity and superior phase stability. However, the low catalytic activity of (La,Sr)TiO3 materials is a major obstacle to the application of SOFCs. Exsolution has emerged as an effective strategy to overcome the low catalytic activity of (La,Sr)TiO3 materials. In this work, Ni-doped A-site-deficient La0.4Sr0.4TiO3-δ (LST) (i.e., La0.4Sr0.4Ti0.94Ni0.06O3-δ; LSTN) with in-situ exsolved Ni nanoparticles (NPs) was developed and the effects of exsolved Ni NPs on H2 oxidation was investigated. The doped Ni was exsolved and formed NPs on the LSTN surface under reducing conditions. Owing to the high catalytic activity of the exsolved Ni NPs, the SOFC with LSTN-Ce0.9Gd0.1O2-δ (GDC) yielded a maximum power density of 0.46 W cm−2 at 850°C, 91% higher than that of the cell with LST-GDC, as well as high long-term and redox stability. Furthermore, density functional theory calculations revealed that the adsorption and dissociation of H2 were more favorable for exsolved Ni NPs than for pure Ni owing to the more positively charged surface of the exsolved Ni NPs in the LSTN. These results demonstrated that exsolution is an effective method for improving the electrocatalytic activity of perovskite (La,Sr)TiO3 materials.

Graphene and Spherical CeO2-ZrO2 Support Pt Nanoparticles as Anode Catalysts for Direct Methanol Fuel Cells

Spherical CeO2 and CeO2-ZrO2 solid solutions are prepared using a hydrothermal method, Pt/CeO2-ZrO2/GO and Pt-CeO2/GO catalysts are prepared using graphene as a carrier, and the effects of the addition of a CeO2-ZrO2 solid solution on the electrocatalytic activity, stability and anti-CO poisoning performance of methanol fuel cell anodes are investigated. The catalyst samples are characterized via X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the electrochemical properties of the catalysts are investigated using an electrochemical workstation (IVIUM). The results show that Pt/CeO2-ZrO2/GO has a higher electrocatalytic activity and stability against CO oxidation than Pt-CeO2/GO, Pt/GO and commercial Pt/C catalysts, which is attributed to ZrO2. When Zr4+ is added into the CeO2 lattice, the activity of oxygen in the CeO2 lattice, the oxygen mobility and the oxygen vacancies are increased, the oxygen storage capacity is improved, and the intermediate product of CO is more easily oxidized. This finding indicates that Pt/CeO2-ZrO2/GO is a methanol oxidation anode catalyst with a good catalytic activity, stability and resistance to CO poisoning.

直接甲醇燃料电池阳极催化剂研究现状及展望

直接甲醇燃料电池阳极催化剂研究现状及展望

Investigation of hydrazine electrooxidation performance of carbon nanotube supported Pd monometallic direct hydrazine fuel cell anode catalysts

In this study, carbon nanotube (CNT) supported Pd catalysts at varying Pd molar ratios are prepared via NaBH4 reduction method. Catalysts prepared for hydrazine electrooxidation are characterized via N2 adsorption-desorption measurements (BET), X-ray photoelectron spectroscopy (XPS), and transmission electron microscope (TEM). Electrochemical measurements are performed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques by CHI660E potentiostat in a three-electrode system. According to the characterization results, Pd/CNT catalysts are successfully synthesized. For 5% Pd/CNT catalyst, the average particle size and the surface area determined as 5.17 nm and 773.10 m2 g-1 via TEM and BET, respectively. Between the Pd containing (0.1-20 wt %) CNT supported catalysts prepared, 5% Pd / CNT catalyst shows the best current density as 6.81 mA cm-2 (1122.63 mA mg-1 Pd). Furthermore, 5% Pd/CNT catalyst shows littlest charge transfer resistance (Rct) compared to Pd/CNT catalysts.

PtSn Nanoalloy Thin Films as Anode Catalysts in Methanol Fuel Cells

Reactions of SnX2 (X = Cl, Br) with [PtMe2(bipy)], 1, (bipy = 2,2'-bipyridine), followed by NaBH4 reduction at the toluene/water interface in the presence or absence of graphene oxide support rendered PtSn nanoalloy thin films. They were characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The electrocatalytical activity of the PtSn thin films was investigated in the methanol oxidation reaction. Our studies showed that the PtSn/reduced-graphene oxide (RGO) thin film gave better catalytic results for MOR in comparison to bare PtSn or Pt thin films. A maximum jf/jb ratio (jf and jb are the maximum current densities in the forward and backward scans, respectively) of 6.77 was obtained for the PtSn/RGO thin film deriving from the 1 + SnBr2 + NaBH4 sequence.