Direct Methanol Fuel Cell Tests Research Articles

Facile Synthesis of PtP2 Nanocrystals as Highly Active Electrocatalysts for Methanol Oxidation.

Although significant efforts have been made in the past few decades, the development of affordable, durable, and effective electrocatalysts for direct methanol fuel cells (DMFCs) remains a formidable challenge. Herein, we present a facile and efficient phosphorization approach for synthesizing PtP2 intermetallic nanocrystals and utilize them as electrocatalysts in the methanol oxidation reaction (MOR). Impressively, the synthesized PtP2 nanocatalysts exhibit a mass activity of 2.14 mA μg-1 and a specific activity of 6.28 mA cm-2, which are 5.1 and 9.5 times higher than those achieved by the current state-of-the-art commercial Pt/C catalyst, respectively. Moreover, the PtP2 nanocatalysts demonstrate improved stability toward acidic MOR by retaining 92.1% of its initial mass activity after undergoing 5000 potential cycles, far surpassing that of the commercial Pt/C (38%). Further DMFC tests present a 2.7 times higher power density than that of the commercial Pt/C, underscoring their potential for application in methanol fuel cells. Density functional theory calculations suggest that the accelerated MOR kinetics and improved CO tolerance on PtP2 can be attributed to the attenuated binding strength of CO intermediates and the enhanced stability due to strong Pt-P interaction. To our knowledge, this is the first report identifying the MOR performance on PtP2 intermetallic nanocrystals, highlighting their potential as highly active and stable nanocatalysts for DMFCs.

Relay Catalysis of Multi‐Sites Promotes Oxygen Reduction Reaction

AbstractThe two‐electron pathway to form hydrogen peroxide (H2O2) is undesirable for the oxygen reduction reaction (ORR) in iron and nitrogen doped carbon (Fe–N–C) material as it not only lowers the catalytic efficiency but also impairs the catalyst durability. In this study, a relay catalysis pathway is designed to minimize the two‐electron selectivity of Fe–N–C catalyst. Such a design is achieved by introducing two other sites, that is, MnN4 site and α‐Fe(110) face. A combination of transmission electron microscopy image and X‐ray absorption spectra verify the three site formation. Electrochemical test coupled with post‐treatment confirm the improvement of MnN4 site and α‐Fe(110) face on catalyst performance. Theoretical calculation proposes a relay catalysis pathway of three sites, that is, H2O2 released from the FeN4 site migrates to the MnN4 site or α‐Fe(110) face, on which the captive H2O2 is further reduced to H2O. The relay catalysis pathway positioned the as‐prepared catalyst among the best ORR catalysts in both aqueous electrode and alkaline direct methanol fuel cell test. This study examples an interesting relay catalysis pathway of multi‐sites for the ORR, which offers insights into the design of efficient electrocatalysts for fuel cells or beyond.

The development of sulfonated polyether ether ketone (sPEEK) and titanium silicon oxide (TiSiO4) composite membranes for DMFC applications

This work aims to develop composite membranes based sPEEK polymer matrix with TiSiO4 for direct methanol fuel cell (DMFC) applications. The sPEEK having 53% of degree of sulfonation (DS) was preferred to avoid dissolution and high-swelling problems of the polymer matrix at the operating conditions. The various content of TiSiO4, prepared by the calcination reaction of TiO2 and SiO2 nano-powders, was placed into the sPEEK matrix using the solution-casting method. The thermal and physicochemical properties of the composite membranes were characterized. AC impedance spectroscopy and methanol diffusivity measurements were conducted to determine the fuel cell characteristics of the membranes. The composite sPEEK membrane with 2.5 wt% TiSiO4 performed the highest single-cell DMFC test performance compared with sPEEK and Nafion™ 117 membranes. It can be concluded that the composite sPEEK membranes with TiSiO4 can be promising and low-cost alternative membranes for DMFC applications.

Alternative Aqueous Phase Synthesis of a PtRu/C Electrocatalyst for Direct Methanol Fuel Cells

Carbon-supported PtRu nanoalloy (PtRu/C) is widely used as the anode catalyst for direct methanol fuel cells (DMFC), and an aqueous phase synthesis of PtRu/C is in high demand due to for energy-saving and environmentally-benign considerations, however, it is very challenging to attain stoichiometric reduction, good dispersion and a high alloying degree. Herein, we report a facile aqueous phase approach with dimethylamine borane (DMAB) as the reducing agent to synthesize a PtRu/C(DMAB). TEM, XRD, XPS and ICP-AES characterizations indicate that the structural parameters in the PtRu/C(DMAB) are improved significantly as compared to those obtained in a PtRu/C(NaBH4) and a commercial PtRu/C, contributing to an enhanced electrocatalytic performance. It turns out that the PtRu/C(DMAB) exhibits the highest methanol electro-oxidation (MOR) performance among all of the tested samples, with the peak current up to 1.8 times as much as that of the state-of-the-art commercial PtRu/C, corroborating the highest output power density in comparative DMFC tests. In-situ attenuated total reflection infrared (ATR-IR) spectroscopy correlates the higher methanol electro-oxidation performance of the PtRu/C(DMAB) with its enhanced CO resistance and CO2 generation. This simple aqueous synthetic approach may provide an alternative route for developing efficient anode electrocatalysts of DMFCs.

Sulfonated polyethersulfone/polyetheretherketone blend as high performing and cost-effective electrolyte membrane for direct methanol fuel cells

Abstract Blended electrolyte membranes based on sulfonated Polyethersulfone (sPES) and sulfonated Poly(ether ether ketone) (sPEEK) were prepared in two different ratios (i.e. 50/50 and 25/75) via a simple, scalable and inexpensive solution casting process to investigate their suitability for direct methanol fuel cell (DMFC) applications. Thermo-mechanical analysis revealed higher flexibility and thermal resistance with the blending of these two macromolecules, without any evidence of phase-segregation, and with good chemical stability. Furthermore, the proton transport was facilitated while the methanol permeability was dramatically reduced. The DMFC tests confirmed outstanding performance by using the membrane with the blend ratio 25/75, reaching a power density of about 130 mW cm−2 at 80 °C in 4 M methanol solution. These features and the cost-effectiveness of sPES-SPEEK membranes make them interesting candidates for use in next-generation DMFCs.

High‐Performance Direct Methanol Fuel Cells with PGM‐Free Cathode

Direct methanol fuel cells (DMFCs) hold great promise for applications ranging from portable power for electronics to transportation. However, apart from the high costs, current Pt‐based cathodes in DMFCs suffer significantly from performance loss due to severe methanol crossover from anode to cathode. The migrated methanol in cathodes tends to contaminate Pt active sites through yielding a mixed potential region resulting from oxygen reduction reaction and methanol oxidation reaction. Therefore, highly methanol‐tolerant cathodes must be developed before DMFC technologies become viable. The newly developed MOF‐based Fe‐N‐C cathode exhibits high methanol tolerance and exceeds the performance of current Pt cathodes, as evidenced by both rotating disk electrode and DMFC tests. In addition to the highly oxygen-reduction active atomically dispersed FeN4 sites, the unique morphology of MOF-derived carbon in Fe‐N‐C cathodes provides a more unique porous structure. DMFC tests with various methanol concentrations are systematically studied using the best performing Fe‐N‐C catalyst. At feed concentrations greater than 2.0 M, the obtained DMFC performance from the Fe‐N‐C cathode is found to start exceeding that of a Pt/C cathode. This work will open a new avenue to use PGM-free cathode for advanced DMFC technologies with increased performance and at significantly reduced cost.

Fabrication of electrospun sulfonated poly(ether sulfone) nanofibers with amino modified SiO2 nanosphere for optimization of nanochannels in proton exchange membrane

Nanofibers have been widely used for the construction of proton channels in proton exchange membranes (PEMs), and the optimization and control of proton channels have become a focus in this research area. In this work, we design and fabricate optimized and efficient proton transport channels in PEMs by introducing of sulfonated poly (ether sulfone) nanofiber with amino–modified SiO2 protuberance structures. The protuberance structures improve the strong interactions between the functional groups of nanofibers and matrix, resulting in an increased density of proton-conducting sites and improvement in membrane properties. Notably, Nafion/SPES/SiO2–3% possesses a low methanol permeability of 7.22 × 10−7 cm2s−1 and a high proton conductivity of 0.23 S cm−1 at 80 °C in water. Consequently, the Nafion/SPES/SiO2 membrane demonstrates a maximum power density of 77.22 mW cm−2 in a direct methanol fuel cell test system, which is 42.34% higher compared to the value of Nafion membrane (54.25 mW cm−2). This study successfully explores the preparation route of nanofiber with protuberance structures successfully, and highlights the potential benefits of this novel nanofiber structure in the PEM field.

Layered double hydroxide-coated silica nanospheres with 3D architecture-modified composite anion exchange membranes for fuel cell applications

A flower-like hierarchical structure consisting of a hydroxide ion conductor (layered double hydroxide, LDH) wrapped on hydrophilic SiO2 nanospheres (LDH@SiO2) was first prepared by an in situ co-precipitation method and then quaternized. This resulting nanocomposite (QLDH@SiO2) was used as a multifunctional additive to modify a quaternized chitosan/polyvinyl alcohol (QCS/PVA) blend matrix to prepare composite membranes. The surface modification of LDH@SiO2 with the silane coupling agent facilitates its dispersion within the blend matrix, which leads to the decreased degree of crystallinity and significant enhancement of mechanical properties of the composite membranes. Furthermore, in situ vertical growth of LDH on the surface of SiO2 cores can effectively avoid the ab-face stacking aggregation of LDH, which can take full advantage of the intrinsic hydroxide-conducting ability of LDH nanosheets. Compared to the ion exchange capability (only 2.09 mmol g−1) and effective ionic mobility (1.23×10−5 cm2 s−1 V−1) of the pristine membrane, the two values for the composite membrane containing 6 wt% of QLDH@SiO2 increased to 2.63 mmol g−1 and 1.50×10−5 cm2 s−1 V−1, respectively. In alkaline direct methanol fuel cell tests at 60 °C, the QCS/PVA-6% QLDH@SiO2 composite membrane demonstrates peak power density of 64 mW cm−2 which is 82% higher than that of the pristine membrane (only 35 mW cm−2). Moreover, the increased alkaline stability and decreased methanol permeability of the composite membranes also guarantee their satisfactory fuel cell stability.

Mechanically robust and highly methanol-resistant sulfonated poly(ether ether ketone)/poly(vinylidene fluoride) nanofiber composite membranes for direct methanol fuel cells

As a key component of direct methanol fuel cells (DMFCs), proton exchange membranes (PEMs) are required to be mechanically robust, methanol-resistant, and conductive to protons. In this work, a novel sulfonated poly(ether ether ketone) (SPEEK) impregnated poly(vinylidene fluoride) (PVDF) electrospun nanofiber membrane was prepared. To avoid the collapse of PVDF fiber framework by the solvent of SPEEK, we designed a SPEEK/solvent/nonsolvent ternary filling system through the cloud point titration curves. Meanwhile, polydopamine (PDA), an extraordinarily adhesive and hydrophilic material, was coated on the surface of PVDF nanofibers to further improve the interface bonding between SPEEK and PVDF. The introduction of PVDF nanofibers completely changed the rigidity of SPEEK thus achieving a 5.4-fold increase of toughness when compared with that of pure SPEEK at dry state. Notably, significantly improved methanol barrier ability was also obtained due to the tortuous methanol crossover pathways caused by the embedded PVDF nanofibers. In the DMFC tests, the ultra-low methanol permeability and relatively high proton conductivity of the obtained composite membrane made it could be operated with 5 M methanol fuel and showed a peak power density of 104.0 mW cm−2, which was higher than the values of 89.3 mW cm−2 (2 M methanol) and 84.0 mW cm−2 (5 M methanol) recorded with commercial Nafion 115 membrane.

Enhanced properties of SPEEK with incorporating of PFSA and barium strontium titanate nanoparticles for application in DMFCs

Novel blend nanocomposite proton-exchange membranes were prepared using sulfonated poly (ether ether ketone) (SPEEK), perfluorosulfonic acid (PFSA), and Ba0.9Sr0.1TiO3 (BST) doped-perovskite nanoparticles. The membranes were evaluated by attenuated total reflection, X-ray diffraction spectroscopy, water uptake, proton conductivity, methanol permeability, and direct methanol fuel cell test. The effect of two additives, PFSA and BST, were investigated. Results indicated that both proton conductivity and methanol barrier of the blend nanocomposite membranes improved compared with pristine SPEEK and the as-prepared blend membranes. The methanol permeability and the proton conductivity of the blend membrane containing 6 wt% BST obtained 3.56 × 10−7 cm2 s−1 (at 25 °C) and 0.110 S cm−1 (at 80 °C), respectively. The power density value for the optimum blend nanocomposite membrane (15 wt% PFSA and 6 wt% BST) (54.89 mW cm-2) was higher than that of pristine SPEEK (31.34 mW cm-2) and SPF15 blend membrane (36.12 mW cm-2).

Chemically tethered functionalized graphene oxide based novel sulfonated polyimide composite for polymer electrolyte membrane

Novel sulfonated diamine (NSDA) having pendant sulfonic acid group was synthesized. Polycondensation reaction of this NSDA, dianhydride, and graphene oxide (GO) yielded sulfonated imidized graphene oxide (SIGO). Sulfonated imidized graphene oxide(SIGO) along with NSDA, 4,4′-oxydianiline (ODA) and 1,4,5,8-naphthalene tetracarboxylic dianhydride dianhydride(NTDA) were used for the preparation of polymer electrolyte membranes (PEMs). High temperature proton conduction due to the hydrophobic- hydrophilic phase separation resulted from the incorporation of SIGO. 2.28 meq/g of ion exchange capacity (IEC), 11.18 × 10−2 S/cm of proton conductivity at room temperature and bound water of worth 5.1% between temperature ranges of 100 °C to 150 °C were exhibited by NSPI/3 wt%SIGO composite membrane. Maximum power density of 74.9 mWcm−2 was achieved at 70 °C by NSPI/ 3% SIGO in single cell direct methanol fuel cell test. All these results make these composite membranes suitable candidate to be used as PEM.

Long-term degradation behaviors research on a direct methanol fuel cell with more than 3000h lifetime

This paper focuses on the gradual performance and durability degradation behaviors of a direct methanol fuel cell (DMFC) with more than 3000 h lifetime. This work adopted a new DMFC test strategy and the entire lifetime test consisted of No.1-No.166 single operation. Stage-failure phenomenon occurred in the lifetime test, which indicated the existence of recoverable and non-recoverable degradations during the entire operation process. In-situ electrochemical tests were applied to the DMFC to analyse causes of durability and performance loss. When single cell came to failure, some recoverable methods were conducted to realize the recovery and improvement of DMFC performance and durability. As a result, during each single operation, continuous lifting pressure operation can realize the improvement of catalyst activity and optimization of mass transfer channel. Proton (H+) recovery method and increasing operation temperature can effectively solve the problem of internal resistance enlargement. According to the results of electrochemical monitoring, higher temperature results in the rapid degradation of catalytic layer activity, and lower temperature causes the increase of membrane resistance. N2 purging works as an effective method to eliminate the concentration polarization caused by cathode “water flooding” phenomenon. Based on these results, it can be concluded that the main degradation of DMFC successively changes with operation time, which mainly comes from internal resistance enlargement, cathode concentration polarization and final deactivation of catalyst at different operation stages. This work well explains the real long-term degradation behaviors of DMFC along with operation time, and provides several practicable methods for recovering DMFC performance and durability.

Poly(vinylidene fluoride-co-chlorotrifluoro ethylene) Nanohybrid Membrane for Fuel Cell.

Through nanochannels are created in the polymer/hybrid films by irradiating swift heavy ions followed by selective chemical etching of the amorphous latent track caused by irradiation. The dimensions of the nanochannels are varied from 30 to 100 nm by either using small (lithium) and large (silver) size of swift heavy ions with high energy (80 MeV) or by embedding few percentage of two-dimensional nanoparticle in the polymer matrix. The side walls of the nanochannels are grafted with polystyrene using the free radicals created during irradiation. Polystyrene graft is functionalized by tagging sulfonate group in the benzene ring of polystyrene to make the nanochannels conducting and hydrophilic. The proof of grafting and functionalization is shown through various spectroscopic techniques. The relaxation behavior and thermal stability of graft polymer within the nanochannel are shown through different thermal measurements. Nanoclay in nanohybrid nucleates the piezoelectric phase in the polymer matrix whose extent is further increased in grafted and functionalized specimen. Functionalized nanochannels exclusively facilitate proton conducting, whereas the remaining part of the film is electroactive, making it as a smart membrane. Greater water uptake, ion exchange capacity (IEC), high activation energy (8.3 × 103 J mol–1), and high proton conduction (3.5 S m–1) make these functionalized nanohybrid film a superior membrane. Membrane electrode assembly has been made to check the suitability of these membranes for fuel cell application. Open circuit voltage and potential are significantly high for nanohybrid membrane (0.6 V) as compared to pure polymer (0.53 V). Direct methanol fuel cell testing using the membrane assembly exhibit a considerable high power density of ∼400 W m–2, making these developed membranes suitable for fuel cell application and providing the ability to replace standard membrane like Nafion, as the methanol permeability is low, thus raising the higher selectivity parameter of the nanohybrid membrane.

Fe-Mn bimetallic oxides-catalyzed oxygen reduction reaction in alkaline direct methanol fuel cells.

Two Fe–Mn bimetallic oxides were synthesized through a facile solvothermal method without using any templates. Fe2O3/Mn2O3 is made up of Fe2O3 and Mn2O3 as confirmed via XRD. TEM and HRTEM observations show Fe2O3 nanoparticles uniformly dispersed on the Mn2O3 substrate and a distinct heterojunction boundary between Fe2O3 nanoparticles and Mn2O3 substrate. MnFe2O4 as a pure phase sample was also prepared and investigated in this study. The current densities in CV tests were normalized to their corresponding surface area to exclude the effect of their specific surface area. Direct methanol fuel cells (DMFCs) were equipped with bimetallic oxides as cathode catalyst, PtRu/C as the anode catalyst and PFM as the electrolyte film. CV and DMFC tests show that Fe2O3/Mn2O3(3 : 1) exhibits higher oxygen reduction reaction (ORR) activity than Fe2O3/Mn2O3(1 : 1), Fe2O3/Mn2O3(1 : 3), Fe2O3/Mn2O3(5 : 1) and MnFe2O4. The much superior catalytic performance is due to its larger surface area, the existence of numerous heterojunction interfaces and the synergistic effect between Fe2O3 and Mn2O3, which can provide numerous catalytic active sites, accelerate mass transfer, and increase ORR efficiency.

Pt-Ru/C Catalyst Performance during Direct Methanol Fuel Cell Operation

A methodology for the electroless deposition (ED) of ruthenium (Ru) on a commercial, carbon-supported Platinum (Pt) catalyst has been developed for electrochemical and fuel cell applications [1, 2]. Several different bimetallic catalysts composed of Pt and Ru have been produced using this methodology with promise of having better catalytic activity. Figure 1 shows how the SEA/ED method produces a finer, more evenly dispersed bimetallic distribution with less monometallic clustering [1]. These bimetallic catalysts have shown higher activities compared to both commercially-available Pt-Ru/C catalysts and monometallic Pt or Ru catalysts [3, 4]. This method’s bimetallic catalyst is proven to show better resistance to CO poisoning as well [3, 5, 6]. In application, this Pt-Ru/C catalyst has promise to be an optimal catalyst for use in a Direct Methanol Fuel Cell (DMFC). The objective for this study is to test the performance of the new Pt-Ru/C catalyst within a DMFC and compare the results to the commercially-available catalyst. This includes synthesis of the SEA/ED, Pt-Ru/C catalyst, characterization of the commercially-available and newly-synthesized catalyst with analysis, and finally, testing of each catalyst within a DMFC testing station and analyzing performance results. The DMFC testing and comparison is important to help show the catalysts’ real-world performance as well as effects of possible CO-poisoning during operation. The newly-synthesized catalyst has an increased electrochemical area as well as a better bi-metallic dispersion, to allow ruthenium to better prevent any platinum from being poisoned, causing the catalyst to perform better and last longer. 1. Diao, W., et al., Preparation and Characterization of Pt–Ru Bimetallic Catalysts Synthesized by Electroless Deposition Methods. ACS Catalysis, 2015. 5(9): p. 5123-5134. 2. Cho, H.-R. and J.R. Regalbuto, The rational synthesis of Pt-Pd bimetallic catalysts by electrostatic adsorption. Catalysis Today, 2015. 246: p. 143-153. 3. Garrick, T.R., et al., The Effect of Bimetallic Surface Composition for Methanol Oxidation. Student Posters (General) - 223rd Ecs Meeting, 2013. 53(29): p. 79-84. 4. Garrick, T.R., et al., The Effect of the Surface Composition of Ru-Pt Bimetallic Catalysts for Methanol Oxidation. Electrochimica Acta, 2016. 195: p. 106-111. 5. Galhenage, R.P., et al., Platinum–ruthenium bimetallic clusters on graphite: a comparison of vapor deposition and electroless deposition methods. Physical Chemistry Chemical Physics, 2015. 17(42): p. 28354-28363. 6. Kabbabi, A., et al., In situ FTIRS study of the electrocatalytic oxidation of carbon monoxide and methanol at platinum–ruthenium bulk alloy electrodes. Journal of Electroanalytical Chemistry, 1998. 444(1): p. 41-53. Figure 1

Fault-tolerant model predictive control of a direct methanol-fuel cell system with actuator faults

This paper investigates fault tolerant model predictive control (MPC) of a direct methanol fuel cell (DMFC) system with several faults in the methanol feeding pump. An active FTMPC strategy with a hierarchal structural design is developed. The focus here is on fault detection and isolation (FDI) and the implementation of fault-tolerant strategies within the control algorithm. To this end, a model-based FDI scheme with virtual sensors is first developed by means of the real-time diagnosis of fault occurrence during operation. Thereby, several faults in the methanol pump are characterized and the information integrated into the MPC algorithm in each fault case. Strategies are presented to reconfigure the active fault-tolerant MPC to keep the DMFC system stable in case of a feeding failure. Moreover, economic, stability and lifetime characteristics are also integrated into the active fault-tolerant MPC. The proposed FDI and FTMPC scheme is tested experimentally in a DMFC test rig with a 5-cell DMFC stack to demonstrate the effectiveness and robustness of the designed approach. Several fault scenarios with the FTMPC are shown. Particularly in the case of fuel cells, fault tolerance is necessary to meet the goals of long-lasting system stability and efficiency.

Enhanced oxygen reduction reaction activity of iron-containing nitrogen-doped carbon nanotubes for alkaline direct methanol fuel cell application

Abstract Non-precious metal catalysts for electrochemical oxygen reduction reaction are synthesised by pyrolysis of multi-walled carbon nanotubes in the presence of nitrogen and iron precursors. For the physico-chemical characterisation of the catalysts transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction are used. The electrocatalytic activity of the catalysts for oxygen reduction is studied in 0.1 M KOH solution using the rotating disk electrode method. The Fe-containing nitrogen-doped carbon nanotubes exhibit an enhanced electrocatalytic performance as compared to metal-free counterparts and their electrocatalytic activity is comparable to that of commercial Pt/C catalyst. Alkaline direct methanol fuel cell tests also show performance close to Pt/C. Thus, these materials can be considered as promising cathode catalysts for application in alkaline fuel cells.

High-Performance Direct Methanol Fuel Cells with Precious-Metal-Free Cathode.

Direct methanol fuel cells (DMFCs) hold great promise for applications ranging from portable power for electronics to transportation. However, apart from the high costs, current Pt‐based cathodes in DMFCs suffer significantly from performance loss due to severe methanol crossover from anode to cathode. The migrated methanol in cathodes tends to contaminate Pt active sites through yielding a mixed potential region resulting from oxygen reduction reaction and methanol oxidation reaction. Therefore, highly methanol‐tolerant cathodes must be developed before DMFC technologies become viable. The newly developed reduced graphene oxide (rGO)‐based Fe‐N‐C cathode exhibits high methanol tolerance and exceeds the performance of current Pt cathodes, as evidenced by both rotating disk electrode and DMFC tests. While the morphology of 2D rGO is largely preserved, the resulting Fe‐N‐rGO catalyst provides a more unique porous structure. DMFC tests with various methanol concentrations are systematically studied using the best performing Fe‐N‐rGO catalyst. At feed concentrations greater than 2.0 m, the obtained DMFC performance from the Fe‐N‐rGO cathode is found to start exceeding that of a Pt/C cathode. This work will open a new avenue to use nonprecious metal cathode for advanced DMFC technologies with increased performance and at significantly reduced cost.

Investigation of methanol oxidation on a highly active and stable Pt–Sn electrocatalyst supported on carbon–polyaniline composite for application in a passive direct methanol fuel cell

Polyaniline fiber (PANI) was synthesized and utilized to fabricate a vulcan–polyaniline (C-PANI) composite. Pt/C-PANI and PtSn/C-PANI electro-catalysts with different Pt:Sn atomic ratios were prepared by the impregnation method. These electro-catalysts, along with commercial PtRu/C (Electrochem), were characterized with respect to their structural and electrochemical properties in methanol oxidation reaction (MOR). PtSn(70:30)/C-PANI showed excellent performance in MOR, the obtained maximum current density being about 40% and 50% higher than that for PtRu/C and Pt/C-PANI, respectively. It was also found that the CO tolerance and stability of PtSn(70:30)/C-PANI was considerably higher than that of PtRu/C. Finally, the performance of these two materials was compared in a passive direct methanol fuel cell (DMFC). The DMFC test results demonstrated that the membrane electrode assembly (MEA) prepared using PtSn(70:30)/C-PANI anode catalyst performed more satisfactorily in terms of maximum power density and lower methanol crossover.

Effect of filler surface functionalization on the performance of Nafion/Titanium oxide composite membranes

The phenylsulfonic functionalized nanometric titania (TiO2-PhSO3H) was synthesized to be used as filler in Nafion-based composite membranes for direct methanol fuel cell (DMFC) applications. The organic moieties were covalently bound on the surface of TiO2 nanoparticles and the hybrid product was characterized by Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric and differential thermal analysis (TG/DTA), field emission scanning electron microscopy (FE-SEM), and X-ray diffraction (XRD) analysis. TiO2-PhSO3H showed higher ion exchange capacity (IEC) and proton conductivity values with respect to those of TiO2. The incorporation of TiO2-PhSO3H in Nafion led to a mechanical reinforcement of the membranes and higher conductivity than that obtained with unfilled Nafion. The composite membrane containing 10wt.% of TiO2-PhSO3H showed an increased crystallinity and the highest conductivity, reaching 0.11Scm−1 at 140°C. DMFC tests were carried out showing that the use of the organic-inorganic hybrid filler leads to a general improvement in the cell performance, in terms of higher current and power density and reduced methanol crossover.