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In this work, an anode current collector with a scaled step-hole structure (called SF-type) and a cathode current collector with a perforated cross-tilt structure (called X-type) were designed and fabricated for application in passive direct methanol fuel cells (DMFCs). A whole-cell test showed that the combination of an anode SF-type current collector and cathode conventional current collector increased the optimal methanol concentration from 6 M to 8 M and the maximum power density to 5.40 mW cm−2, which improved the cell performance by 51.6% compared to that of the conventional design under ambient testing conditions. The combination of the anode conventional current collector and cathode X-type current collector achieved a maximum power density of 5.65 mW cm−2 with a 58.7% performance improvement, while the optimal methanol concentration was increased to 10 M. Furthermore, the combination of anode SF-type and cathode X-type obtained the highest power density at 6.22 mW cm−2. Notably, the anode and cathode catalyst loadings used in this study were 2.0 mg cm−2, which is lower than the commonly used loading, thus reducing the fuel cell cost. [ABSTRACT FROM AUTHOR]

In this work, a poly (vinylidene fluoride) (PVDF) and cellulose acetate (CA) blend membrane is developed using the solution casting method for a direct methanol fuel cell (DMFC). The CA addition in PVDF polymer reduces the dense structure of the polymer and creates a porous surface by increasing the amorphous region that is confirmed by surface morphology and crystallinity examination tests. The high glass transition temperature of CA boosts the protection from the melting of PVDF membrane and increases the thermal shrinkage that reduces the probability of a short circuit. PVDF and CA with abundant hydroxyl groups and carboxylic groups enhance the water uptake, also the hydrogen bonding in between them promotes the mechanical strength and develops a tortuous structure that allows protons to pass through them and block the methanol crossover. The 60% PVDF and 40% CA blend membrane shows an ion exchange capacity value of 0.91 and a methanol permeability value of 4.21 × 10–7 cm2 s−1, which is lower than that of the conventional Nafion 117 membrane (19.5 × 10–7 cm2 s−1). A direct methanol fuel cell with this membrane represents a power density value of 16.5 mW cm−2 with a voltage and current density values of 0.178 V and 165 mA cm−2 at 1 M methanol concentration and room temperature. Moreover, it shows a 70% voltage retention after 20 h of testing of the cell at room temperature that is superior to that of the commercial Nafion 117 membrane (48% voltage retention). [ABSTRACT FROM AUTHOR]

Based on a novel unsaturated polyester, polybutylene fumarate (PBF), a series of sulfonated proton exchange membranes were prepared and characterized for direct methanol fuel cell application. In this work, PBF underwent sulfonation at different degrees, and the optimum degree of sulfonation (DS) was identified by assessing the hydrolytic stability. In the second step, an effective strategy to enhance the membranes' proton conductivity was adopted by the addition of the 2‐(1H‐Imidazol‐2‐yl) acetic acid (Im‐COOH) compound as a proton‐conducting agent to the sulfonated PBF (SPBF) matrix with the optimum DS. The results unveiled significant alterations in the physicochemical properties of PBF due to sulfonation, including an elevation in water uptake and the glass transition temperature (Tg), accompanied by the disappearance of the crystallinity within SPBF. In terms of electrochemical characteristics, the SPBF‐17.5 PEM demonstrated a proton conductivity of 3.36 × 10−3 S cm−1 and a methanol permeability of 1.068 × 10−7 cm2 s−1, yielding a selectivity of approximately 31,460 S s cm−3. Furthermore, the attractive interactions between SO3H and NH groups further elevated proton conductivity to 4.12 × 10−3 S cm−1, accompanied by a decrease in methanol permeability to 0.942 × 10−7 cm2 s−1, enhancing the selectivity parameter to 43,736 S s cm−3. [ABSTRACT FROM AUTHOR]

[Display omitted] • A strategy for MOF-composite nanofiber with synergistic architecture is proposed. • PU@PAN/UiO-66 core/shell nanofiber is prepared by coaxial electrospinning. • 3D proton-conduction networks are constructed in proton exchange membrane. • Sulfamic acid is successfully introduced on nanofiber. • The maximum power density of Nafion/S@NF-50 exhibits 182.6 mW cm−2. Proton exchange membranes (PEMs) play an important role in fuel cells. For realizing a nanofiber (NF) structure design in PEMs, the material should have tunable pores and a high specific area. In this study, we attempt to design a novel NF with synergistic architecture doped MOF for constructing three-dimensional (3D) proton conduction networks in PEMs. In this framework, UiO-66-COOH serves as a platform for proton sites to synergistically promote proton conductivity via polyvinylpyrrolidone dissolution, hydrolyzation of polyacrylonitrile, and sulfamic acid functionalization of the shell-layer NF. Benefiting from enriched proton-transfer sites in NFs, the obtained composite membrane overcomes the trade-off among proton conductivity, methanol permeability, and mechanical stability. The composite membrane with 50 % fiber (Nafion/S@NF-50) exhibited a high proton conductivity of 0.212 S cm−1 at 80 °C and 100 % relative humidity, suppressed methanol permeability of 0.66 × 10−7 cm2 s−1, and the maximum power density of direct methanol fuel cell is 182.6 mW cm−2. Density functional theory was used to verify the important role of sulfamic acid in proton transfer, and the activation energy barriers under anhydrous and hydrous conditions are only 0.337 and 0.081 kcal, respectively. This study opens up new pathways for synthesizing NF composite PEMs. [ABSTRACT FROM AUTHOR]

A hybrid chitosan-based nanocomposite was fabricated by chitin nanowhiskers coupled with silanized Fe3O4 nanoparticles as a polyelectrolyte membrane for direct methanol fuel cells (DMFCs). The morphological evaluations articulated that the magnetite nanoparticles were uniformly attached to the chitin nanowhiskers. After characterization of the synthesized nanowhiskers, they were incorporated into the chitosan, as a polycationic electrolyte, to investigate the performance of nanocomposite for DMFC applications. An external magnetic field was applied to the magnetic chitin nanowhiskers to induce alignment, and the effects of aligned nanowhiskers, as well as random ones, were also studied. The magnetic chitin nanowhiskers positively influenced the water uptake and proton conductivity due to the formation of hydrogen bonds between the surface functional groups of nanowhiskers and free water molecules. On the other hand, methanol permeation of the chitosan nanocomposites was reduced regarding the tortuous pathways and narrower transportation channels by the presence of nanowhiskers. [ABSTRACT FROM AUTHOR]

At present, commercial Nafion membrane is not suitable for proton exchange membrane used in direct methanol fuel cell (DMFC) due to the severe methanol permeation phenomenon. This work reported the preparation and characterization of azide‐substituted polysulfone (PSU‐N3) and alkynyl‐substituted sulfonated polyvinyl alcohol (SAPVA) crosslinked in the matrix of Nafion membrane base on click chemistry applied in DMFC. The compatibility between PSU‐N3 and SAPVA is promoted due to the formation of crosslinked network structure. Key properties, including dimensional stability, oxidative stability, mechanical behavior, methanol permeability and proton conductivity, are compared with those of the recast Nafion membrane. The prepared blend membranes exhibit lower methanol permeability due to the crosslinked network and well‐dispersed microphase structure of PSU‐PVA in the Nafion matrix. The proton selectivity of the Nafion‐PSU‐PVA‐3 membrane is 9.16 × 104 S s/cm3, much higher than that of the recast Nafion membrane (2.82 × 104 S s/cm3). In DMFC single cell tests, the maximum power density of the Nafion‐PSU‐PVA‐3 membrane is 4.6 mW/cm2, about 58.6% higher than that of the recast Nafion membrane. All the results indicate that the prepared blend membranes have the potential to be applied in DMFC. [ABSTRACT FROM AUTHOR]

In order to improve the output performance of direct methanol fuel cell, the finite-time thermodynamic model of direct methanol fuel cell is developed in this paper. Then, mathematical expressions for energy efficiency, power density, exergy efficiency and exergy coefficient of performance are derived. In addition, the effects of operating temperature, inlet pressure and membrane thickness on the performance of direct methanol fuel cells are considered. The results show that the exergetic performance coefficient not only considers the exergy loss rate to minimize the loss, but also the power density of the direct methanol fuel cell to maximize its power density and improve its efficiency. Therefore, the exergetic performance coefficient is a better performance criterion than conventional power and efficiency. In addition, increasing the inlet pressure and decreasing the membrane thickness can significantly improve the exergetic performance coefficient and energy efficiency. [ABSTRACT FROM AUTHOR]

The synergistic effect of metal-carrier introduces novel possibilities for the potential application of non-precious metal electrocatalysts in direct methanol fuel cell (DMFC). Electrostatically spun nanofibers with a uniquely graded porous structure and efficient electrolyte and electron transfer channels exhibit enhanced synergistic catalytic performance as carriers. In this study, we report a metal-organic frameworks (MOFs)-derived nitrogen-doped carbon nanofibers (CNFs) CoCu nanocrystalline catalysts. The oxyphilicity of Co facilitates the adsorption of hydroxyl (OH) radicals, thereby enhancing the removal of carbon monoxide (CO). Additionally, Cu acts as a methanol adsorption center in the adsorption experiments, promoting the acceleration of reaction pathways. The optimized Co 2 Cu 1 /N-CNFs demonstrated comparable power densities to commercial Pt/C catalysts in single-cell tests, showcasing their potential as a promising non-precious metal catalyst for the DMFC field. This study highlights the significant contribution of both structural and compositional synergistic effects, along with the assembly effect of electrospinning, towards enhancing methanol oxidation reaction (MOR) activity and anti-CO poisoning performance. [Display omitted] • Carbon nanofiber loaded hyperdispersed CoCu nanocrystalline catalysts were prepared. • Adsorption experiments indicate that Cu can act as the methanol adsorption site. • Oxyphilicity of Co promoted efficient CO ads removal through OH radical adsorption. • Co 2 Cu 1 /N-CNFs exhibited excellent single-cell performance in alkaline DMFC. [ABSTRACT FROM AUTHOR]

Nafion membranes are commercially available for the application of direct methanol fuel cells (DMFCs) due to their unique nano-porous structure, high wettability, high ion exchange capacity due to sulfonic groups and high mechanical strength. However, its high cost and high swelling in water result in high methanol crossover, low chemical stability and low ion conductivity at elevated temperatures that limit its usage. Moreover, in commercial membranes when the thickness increases, the ion conductivity compromises and when the thickness decreases, the fuel crossover increases which disrupts the performance of the fuel cell. The modification of pre-existing Nafion membrane such as Nafion 115, Nafion 117, Nafion 212, Nafion 112 and laboratory recasted Nafion membrane is a promising requirement for their future applications. Additives such as organic, inorganic nanoparticles and polymers apply to the Nafion membrane that not only tune the physical aspects of the membrane but also improve the electrochemical properties of the membrane. This review article focuses on advances in different Nafion commercial membranes and laboratory recasted non-commercial Nafion membrane that make under special conditions after modifications. This paper provides challenges, advantages, and disadvantages, as well as future advances in the application of composite membranes in direct methanol fuel cells. [ABSTRACT FROM AUTHOR]

The open ratio of a current collector has a great impact on direct methanol fuel cell (DMFC) performance. Although a number of studies have investigated the influence of the open ratio of DMFC current collectors, far too little attention has been given to how geometry (including the shape and feature size of the flow field) affects a current collector with an equal open ratio. In this paper, perforated and parallel current collectors with an equal open ratio of 50% and different feature sizes are designed, and the corresponding experimental results are shown to explain the geometry effects on the output power of the DMFC. The results indicate that the optimal feature sizes are between 2 and 2.5 mm for both perforated and parallel flow field in the current collectors with an equal open ratio of 50%. This means that for passive methanol fuel cells, to achieve the highest output power, the optimal feature size of the flow field in both anode and cathode current collectors is between 2 and 2.5 mm under the operating mode of this experiment. The effects of rib and channel position are also investigated, and the results indicate that the optimum pattern depends on the feature sizes of the flow field. [ABSTRACT FROM AUTHOR]

The type of catalyst support affects platinum activity and durability in direct methanol fuel cells (DMFCs). In this study, Sb with 0, 4, 8 and 12% doped SnO2 on carbon cloth (CC) support at ultra-low platinum loading (0.04 mg cm−2) is prepared. The results show that the modification of support and the use of Sb-doped SnO2 improve the electrochemical activity of the prepared electrodes. Scanning electron microscopy (SEM) indicates that the doping of SnO2 with Sb decreases the average particle size of Pt. The X-ray diffraction (XRD) patterns show that incorporating Sb and Pt nanoparticles into SnO2 would not damage the tetragonal rutile structure. The highest electrochemical surface area (ECSA) of electrodes in the acidic environment is obtained in Sb of 4%. The highest current density of 15.5 mA cm−2 is obtained at the peak potential of 0.71 V for Pt@Sb4-SnO2-CC electrode in the methanol oxidation reaction while its value is 1.2 times higher than Pt@CC. The chronoamperometry analysis and CO stripping voltammetry show that this electrode has the highest tolerance to CO. The electrochemical impedance spectroscopy demonstrates that the minimum charge transfer resistance of 17.6 (Ω cm2) is acquired for the Pt@Sb4-SnO2-CC electrode. In the active DMFC test, the high power and current density of this electrode are 11 mW cm−2 and 66 mA cm−2, respectively, at the cell voltage of 0.2 V. [ABSTRACT FROM AUTHOR]

The composite membrane is synthesized using chitosan as a matrix membrane with montmorillonite (MMT) as a filler and modified using polyvinyl alcohol (PVA). The main aim of this study is to find out the influence of PVA concentration and the working temperature toward the permeability of chitosan-MMT/PVA composite membrane. Fourier transform infrared spectroscopy (FTIR) characterization is performed in order to identify the interaction between the chitosan matrix and the modified MMT with PVA. The presence of new absorption at 1116.82 and 619.17 cm-1 indicated the interaction between MMT and PVA. Further, the widening of OH absorption indicated the hydrogen bond which is formed between chitosan matrix and PVA. This interaction is also demonstrated by the evenly distributed surface on scanning electron microscope (SEM) topography analysis. The thermal stability of composite membrane is determined by thermal gravimetry analysis (TGA). In addition, the composite membrane containing PVA has four patterns decomposed. When the TVA is absent from the composite membrane, it has three decomposition patterns, which are shown by TGA analysis. Based on its tensile strength, the composite membrane has good mechanical properties. The proton conductivity of the composite membranes are directly proportional to the PVA concentration. On the other hand, the methanol permeability of composite membranes is inversely proportional with the PVA concentration. The highest proton conductivity was obtained with the addition of 2 % PVA of 2.94×10-4 S cm-1. Further, it also has the lowest methanol permeability with the value of 5.05×10-6 cm2 s-1. As a result, the crosslinked composite membrane chitosan- -MMT prepared by PVA-crosslinking technique has the potential to be exploited for the direct methanol fuel cell application. [ABSTRACT FROM AUTHOR]

Proper regulating morphology and rationally distributing of active sites in a catalyst is crucial for improving its electrocatalytic performance. In this study, we synthesized a series of porous urchin-like NiCo 2 O 4 structures through hydrothermal reaction and adjusted their morphologies and oxygen vacancies concentration by annealing them under different conditions. The resulting structure has interconnected pores that facilitate the fast transport of active species, assembled from many nanoneedles containing nanoparticles. Our results show that the porous urchin-like NiCo 2 O 4 structure obtained after annealing at 400 °C under an argon atmosphere has the largest surface coverage area for redox species and the richest oxygen vacancies. This configuration demonstrates excellent performance in both methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) in alkaline solution. Our findings offer a facile pathway to optimizing active sites on urchin-like NiCo 2 O 4 structures, which could serve as bifunctional electrocatalysts for direct methanol fuel cells (DMFCs). [Display omitted] • Porous urchin-like NiCo 2 O 4 structures were fabricated by the hydrothermal method. • Morphology and oxygen vacancies were tuned by annealing conditions simultaneously. • Optimized structure shows excellent performance in MOR and ORR in alkaline solution. [ABSTRACT FROM AUTHOR]

[Display omitted] Direct methanol fuel cell (DMFC) is hampered by the sluggish methanol oxidation reaction. In this work, we have invited rhodium phosphides (Rh 2 P) to platinum (Pt) as robust MOR electrocatalyst ascribing the excellent water dissociation capability of Rh 2 P to generate Pt(OH) ads species to mitigate the CO poisoning. MOR mass activity of Rh 2 P-Pt/C is enhanced by 2- and 3.5-time with relative to commercial Pt/C and PtRu/C, respectively; additionally, the CO anti-poisoning ability is also boosted by 2.4 folds than Pt/C. The in-situ electrochemical impedance spectroscopy test reveals that the water dissociation is accelerated by Rh 2 P; moreover, the mutual electronic interplay between Pt and Rh 2 P contributes to a superior resistance towards electrochemical dissolution and coalescence. The theoretical investigation also indicates that d band center of Pt in Rh 2 P-Pt is downshifted resulting in a lower CO binding strength. [ABSTRACT FROM AUTHOR]

This paper presents a membrane electrode assembly (MEA) with a double-catalytic layered structure to improve the performance of the micro direct methanol fuel cell. The inner and outer parts of the double-catalytic layer comprise an unsupported and carbon-supported catalyst, respectively. A two-dimensional two-phase model of mass transport and electrochemical reaction is established and simulated to analyze the superiority of the double-catalytic layered structure. Simulation results show that this structure has a more uniform current density distribution and less over-potential across the catalyst layer. Methanol crossover is also reduced. Experimental results confirm that the MEA with the double-catalytic layered structure exhibits better performance than the traditional MEA. The adoption of a gas diffusion electrode as the outer catalytic layer and a catalyst-coated membrane as the inner layer of the double-catalytic layered structure can further improve the performance of the MEA. Both simulation and experimental results show the existence of an optimum number of metal loadings of the inner and outer parts of the double-catalytic layer. [ABSTRACT FROM AUTHOR]

The successful commercialization of direct methanol fuel cells (DMFCs) is hindered by inadequate methanol oxidation activity and anode catalyst longevity. Efficient and cost-effective electrode materials are imperative in the widespread use of DMFCs. While Platinum (Pt) remains the primary component of anodic methanol oxidation reaction (MOR) electrocatalysts, its utilization alone in DMFC systems is limited due to carbon monoxide (CO) poisoning, instability, methanol crossover, and high cost. These limitations impede the economic feasibility of Pt as an electrocatalyst. Herein, we present the use of powdered activated carbon (PAC) and granular activated carbon (GAC), both sourced from macadamia nut shells (MNS), a type of biomass. These bio-based carbon materials are integrated into hybrid supports with reduced graphene oxide (rGO), aiming to enhance the performance and reduce the production cost of the Pt electrocatalyst. Electrochemical and physicochemical characterizations of the synthesized catalysts, including Pt-rGO/PAC-1:1, Pt-rGO/PAC-1:2, Pt-rGO/GAC-1:1, and Pt-rGO/GAC-1:2, were conducted. X-ray diffraction analysis revealed crystallite sizes ranging from 1.18 nm to 1.68 nm. High-resolution transmission electron microscopy (HRTEM) images with average particle sizes ranging from 1.91 nm to 2.72 nm demonstrated spherical dispersion of Pt nanoparticles with some agglomeration across all catalysts. The electrochemical active surface area (ECSA) was determined, with Pt-rGO/GAC-1:1 exhibiting the highest ECSA of 73.53 m2 g−1. Despite its high ECSA, Pt-rGO/GAC-1:1 displayed the lowest methanol oxidation reaction (MOR) current density, indicating active sites with poor catalytic efficiency. Pt-rGO/PAC-1:1 and Pt-rGO/PAC-1:2 exhibited the highest MOR current densities of 0.77 mA*cm−2 and 0.74 mA*cm−2, respectively. Moreover, Pt-rGO/PAC-1:2 and Pt-rGO/PAC-1:1 demonstrated superior electrocatalytic mass (specific) activities of 7.55 mA/mg (0.025 mA*cm−2) and 7.25 mA/mg (0.021 mA*cm−2), respectively. Chronoamperometry tests revealed Pt-rGO/PAC-1:2 and Pt-rGO/PAC-1:1 as the most stable catalysts. Additionally, they exhibited the lowest charge transfer resistances and highest MOR current densities after durability tests, highlighting their potential for DMFC applications. The synthesized Pt supported on PACs hybrids demonstrated remarkable catalytic performance, stability, and CO tolerance, highlighting their potential for enhancing DMFC efficiency.

Direct methanol fuel cell (DMFC) is a device which converts chemical potential energy into electrical energy through the electrochemical reaction that involves oxidation of methanol. This study investigates the underlying voltage loss mechanism and determines how a change in process conditions will affects the resulting voltage loss, through the development of a one-dimensional mathematical DMFC model in software (MATLAB). The one-dimensional mathematical model has adopted a modelling approach that is simple and relatively easy to be constructed, thus providing a method for simple yet accurate estimation of the DMFC voltage loss curve. The study is conducting in three stages, which include the construction of preliminary model, model parameter fitting and model simulation. Based on the developed DMFC model, the polarization curve of a DMFC are dividing into three regions, including activation polarization-controlled region, ohmic drop controlled region and concentration polarization-controlled region. In each of these regions, one of the voltage loss mechanisms is the dominant mechanism that causes the greatest voltage loss. Voltage loss from all three mechanisms are finding to be reduced at higher temperature. The simulated DMFC can operate at a maximum power density of 0.15 W/cm2, with a voltage efficiency of 33.9%. This model operates at temperature of 343K and uses 2M methanol concentration.

In this work, an anode current collector with a scaled step-hole structure (called SF-type) and a cathode current collector with a perforated cross-tilt structure (called X-type) were designed and fabricated for application in passive direct methanol fuel cells (DMFCs). A whole-cell test showed that the combination of an anode SF-type current collector and cathode conventional current collector increased the optimal methanol concentration from 6 M to 8 M and the maximum power density to 5.40 mW cm−2, which improved the cell performance by 51.6% compared to that of the conventional design under ambient testing conditions. The combination of the anode conventional current collector and cathode X-type current collector achieved a maximum power density of 5.65 mW cm−2 with a 58.7% performance improvement, while the optimal methanol concentration was increased to 10 M. Furthermore, the combination of anode SF-type and cathode X-type obtained the highest power density at 6.22 mW cm−2. Notably, the anode and cathode catalyst loadings used in this study were 2.0 mg cm−2, which is lower than the commonly used loading, thus reducing the fuel cell cost.

A direct methanol fuel cell (DMFC) is one prominent alternative energy technology. However, there are many problems that prevent the commercialization of DMFC, such as methanol crossover, low power density, and degradation of the membrane. To resolve these issues, functionalized graphene oxide (GO) and calcium hydroxy phosphate (CHP) were incorporated into the Nafion membrane to make a composite membrane. The content of the CHP was varied to determine and further investigation involved spraying the same amount of CHP onto the Nafion membrane to compare with the composite membrane. The fillers were characterized using Fourier-transform infrared spectroscopy and X-ray Powder Diffraction. The ex-situ tests investigated water uptake, solubility, and chemical degradation, while the in-situ tests investigated electrochemical impedance (EIS), methanol permeability, fuel cell performance, and durability. Adding both 1 wt% of CHP and 0.05 wt% functionalized GO into the Nafion membrane, resulting in a 1.86-fold higher durability than that of recast Nafion. In addition, the maximum power density of the composite membrane was 1.34-fold higher (75.41 mW/cm2) than that of the recast Nafion (56.11 mW/cm2) at 1 M methanol and 70 °C. At 2 M methanol and 70 °C, the maximum power density of the composite membrane increased to 80.19 mW/cm2 but then decreased to 46.00 mW/cm2 when the methanol feed increased to 4 M, due to the large amount of methanol crossover. • 1 wt% CHP functionalized 0.05 wt% GO/Nafion was used for DMFC. • The composite membrane was 1.86-fold higher durability than that of recast Nafion. • Power density was 1.34-fold higher than that of Nafion at 1 M methanol and 70 °C. • At 2 M methanol and 70 °C was the optimum condition for DMFC. [ABSTRACT FROM AUTHOR]

Direct methanol fuel cell is an emerging energy transformation system with the prospect of substituting secondary batteries soon due to their exciting features. One of the most limitations is the weak catalytic activity of the expensive nonprecious Pt-based catalysts at the fuel cell's anode. In this work, a standalone Nickel layered double hydroxide of hierarchical nanosheet structure was effectively synthesized on the nickel foam's surface through facile hydrothermal treatment that subsequently converted into NiO without destroying the structure by heat treatment at 500 °C. The synthesized standalone electrodes demonstrated a significant activity for methanol oxidation with an onset potential of 0.35 V in KOH (1 M), which is attributed to the Ni(OH) 2 (Ni+2)/(Ni+3) NiOOH active site. The electrodes effectively discharged current at 0.5 V for more than 1 h with no performance degradation compared to the bare nickel foam. The better activity of the synthesized electrodes was attributed to the nanosheet structure layer's better charge and mass transfers, as confirmed by the morphological images (SEM images) and the electrochemical characteristics (electrochemical impedance spectroscopy, chronoamperometry, and cyclic voltammetry). [Display omitted] • Standalone Nickel layered double hydroxide (Ni-LDH) nanosheet structure was prepared. • Nickel oxide (NiO) was prepared by heat treatment of Ni-LDH at 500 °C. • The synthesized electrodes demonstrated a significant activity for methanol oxidation. • Nanosheet structure exhibited better charge and mass transfers, and thus activity. • The electrodes have high stability during long-term oxidation activity. [ABSTRACT FROM AUTHOR]

Open Cathode Direct Methanol Fuel Cell (OC-DMFC) stack performance is achieved at different methanol temperatures (25, 40, 55 and 70 °C), methanol concentrations (0.5, 1, 2 and 4 M) and air flow rates (3.5, 4.8 and 6.4 m/s). Each parameter, whose performance was tested separately, was presented by making comparisons within itself. The effect of performance changes on peak power densities under relatively low electromagnetic fields (4.7, 12.4, 28 and 35 mT) was investigated by exposing the 10-cell OC-DMFC stack to a magnetic field with the help of ferritic magnets. Ferritic magnets placed on the OC-DMFC stack anode and cathode surfaces, It is designed to create an electromagnetic field. Thus, the magnetic field affected both surfaces. When the magnetic field was 35 mT, the OC-DMFC reached a power density of 17.5 mW cm−2. When the DMFC stack is exposed to the magnetic field, its performance is increased by ∼16%. • An open-cathode DMFC stack consisting of 10 cells was developed. • A 16% improvement in maximum power was achieved with the magnetic field effect. • When the magnetic field was 35 mT, the power density of 17.5 mW cm−2. • CO2 bubbles are exposed to the Lorentz force and affect their removal from the active area. [ABSTRACT FROM AUTHOR]

Platinum-group-metal-based polyhedral nanostructures generally possess high catalytic activity for electrochemical reactions owing to their numerous edges, corners, and well-defined lattice planes. However, their direct synthesis on common carbon powder is difficult, which considerably hinders their applications in practical devices. Herein, we report PtPd nanocubes (NCs) grown in situ on commercial carbon powder (Vulcan XC-72R) using a facile one-pot method. The as-prepared PtPd NCs/C (∼20 wt% metal) possess Pt-enriched surfaces, enabling the mass activity (MA) of methanol oxidation reaction (MOR) up to 1.77 A mgPt−1, which is 3.34/3.69 times that of commercial PtRu/C and Pt/C, respectively. With an average size of 8–10 nm, the PtPd NCs/C exhibit high stability, retaining over 80% initial MA against MOR in an accelerated durability test. For practical direct-methanol fuel cell (DMFC) operation, the PtPd NC/C as an anode catalyst delivered a maximum power density of 0.232 W cm−2 with high-concentration methanol (10 M) flow, which is 1.6 times higher than that for commercial PtRu/C under the same conditions. Moreover, the PtPd NCs/C demonstrated excellent durability for DMFC operation with much lower voltage decay than commercial PtRu/C, indicating its excellent potential for practical DMFC applications. • PtPd nanocubes were prepared in situ on common carbon support. • PtPd NCs/C possesses Pt-enriched surface. • Pd NCs/C showed significantly improved MOR activity and durability. • Superior performance compared with commercial PtRu/C for practical DMFC operation. [ABSTRACT FROM AUTHOR]

In the present work, a novel poly(arylene ether ketone) with a unique molecular design that included concentrated flexible sulfoalkyl groups and a silane cross-linked network (C-SPAEK) was prepared and used as a PEM for DMFCs. The chemical structures, sulfonation degree and phase-separated morphology were characterized and identified by 1H NMR, FT-IR and SAXS. The resulting copolymers exhibited excellent thermal stability (T 5% >263.8 °C) and mechanical properties (tensile strength>52.88 MPa). Additionally, the high IEC values and obvious hydrophilic/hydrophobic phase-separated structure (d > 2.71 nm) ensured that the C-SPAEK membranes possessed high proton conductivities. The C-SPAEK PEMs also displayed enhanced methanol resistance and dimensional stability, which were much better than those of a recast Nafion membrane under the same conditions. The C-SPAEK-0.4 membrane maintained a low methanol absorption of less than 48.7%, even in 4 M methanol solution. In particular, the C-SPAEK-0.6 membrane exhibited the best comprehensive performance, with a high proton conductivity (0.164 S cm−1), low methanol uptake (52.1%) and permeability (3.63 × 10−7 cm2 s−1), and maximum power density (83.2 mW cm−2), when immersed in 2 M methanol at 80 °C in a DMFC single-cell. These results suggested that the C-SPAEK membranes were sufficiently tough and had the potential to overcome the problems caused by the high methanol permeability of PEMs. The unique molecular design of C-SPAEK guaranteed a rare combination of high proton conductivity and enhanced methanol resistance, which are the key determining factors for DMFC applications. The C-SPAEK based PEM with high proton conductivity, enhance methanol resistance, low permeability and high selectivity was prepared successfully. [Display omitted] • Novel densely sulfonated copolymer containing silane cross-linked network was prepared for PEMs. • High proton conductivity and enhanced methanol resistance were obtained simultaneously. • The PEMs exhibit low methanol absorption and excellent dimensional stability in high concentration methanol solution. [ABSTRACT FROM AUTHOR]

The present study looked into a sustainable approach for synthesizing sodium ion conducting cation exchange membrane, in addition to addressing the methanol permeability, ionic conductivity, and cost of the direct methanol fuel cell (DMFC). The polyvinyl alcohol (PVA)-based sodium ion conducting membranes were synthesized by the sustainable modified phase inversion technique using a green nonsolvent coagulation bath composed of sodium hydroxide and sodium sulfate. Alkaline medium operating sulfonated polyvinyl alcohol (SPVA)-montmorillonite clay (MMT) was developed to overcome the drawbacks of a proton exchange membrane working in an acidic medium and an anion exchange membrane used in an alkaline medium. The SPVA-MMT membrane exhibited ionic conductivity of 0.0751 S cm−1 due to the presence of inorganic salts in the coagulation bath and the cation exchange capacity of the clays. Passive alkaline DMFC studies conducted using SPVA-MMT membrane showed a peak power density of 7.51 mW cm−2 at ambient conditions. • Green membrane synthesis technique to produce clean energy. • The green synthesis technique reduces the risk of human repro-toxicity. • A green non-solvent coagulation bath and clay enhance the Na+ ion conductivity. • Composite membrane shows ionic conductivity of 0.0751 S cm−1 at ambient conditions. • A 62.90% increase in power density as compared to Nafion 117/Na+ membrane. [ABSTRACT FROM AUTHOR]

[Display omitted] • A facile strategy is developed for synthesizing 1D integrated functional catalysts. • The structure is optimized via adjusting the molar ratio of doped metal ions. • CoFe@NCNF/BCNT present improved ORR activity and superior methanol tolerance. • The DMFCs modified with CoFe@NCNF/BCNT exhibit high power and current densities. The exploration of cost-effective electrocatalysts with high catalytic activity and methanol tolerance to replace precious metal catalysts in the oxygen reduction reaction (ORR) is highly desirable for direct methanol fuel cells (DMFCs). Herein, we report a novel complex composed of a CoFe alloy with a modulated electronic structure confined to nitrogen-doped carbon nanofiber (NCNF) and bamboo-like carbon nanotube (BCNT) by tuning the molar ratio of Co and Fe (CoFe@NCNF/BCNT). The synthetized catalysts possess one-dimensional (1D) mesoporous structure, high specific surface area, and rich pyridinic-N content. Notably, the Co 1 Fe 1 @NCNF/BCNT and Co 1 Fe 3 @NCNF/BCNT (Co:Fe ≈ 1:1 and 1:3) exhibited enhanced oxygen reduction activity and methanol tolerance, compared to unmodified samples. In addition, alkaline DMFCs containing Co 1 Fe 1 @NCNF/BCNT and Co 1 Fe 3 @NCNF/BCNT presented high power density (29.10 and 31.11 mW cm−2), exceeding that of Pt/C-modified DMFC (27.23 mW cm−2). Furthermore, the Co 1 Fe 1 @NCNF/BCNT-catalyzed DMFC exhibited high stability. This improved catalytic activity can be attributed to the rich surface area, controllable alloy composition, optimized N configuration, and favorable electronic interaction. The as-developed CoFe@NCNF/BCNT with multifunctional components may open a new avenue for designing highly active cathode catalysts for various fuel cells. [ABSTRACT FROM AUTHOR]

Herein, we report sol-gel modified sulfonated poly(ether ether ketone) (SPEEK) organo-silane based composite proton exchange membranes for their suitability in direct methanol fuel cells (DMFCs). Different concentrations (0.2–1.5 wt%) of aminopropyl trimethoxysilane (APTES) are incorporated in SPEEK matrix by in-situ sol-gel method. Physico and electrochemical performances of composite membranes are enhanced by induced H-bonding interactions between free –NH 2 and –SO 3 H groups. With increase in APTES concentration to 0.8 wt%, the ionic conductivity illustrates improvement by ⁓80% while IEC and Proton conductivity (Pc) enhances by ∼21% and ∼70%, respectively than SPEEK. To further explore the feasibility of the membranes in DMFC. Methanol crossover resistance is calculated to as low as 5.30 × 10−7 cm2 s−1 and offers highest selectivity of 4.43 S s cm−3 in contrast to 12.55 × 10−7 cm2 s−1 and 0.31 S s cm−3 for SPEEK, respectively. This study reveals that the Si-SPEEK membrane is a potential alternate for DMFC. • SPEEK matrix is loaded with APTES to enhance membrane properties. • Organosilicon-based acid-base stable membranes are prepared. • 0.8 wt% APTES showed overall improved physiochemical and electrochemical properties. • H-bonding interaction improved thermal and mechanical stability. • Alternate cation exchange membrane for DMFC is prepared. [ABSTRACT FROM AUTHOR]

Nanocomposite polyelectrolyte membranes based on sulfonated polystyrene (SPS) /imidazole‐2‐acetic acid (Im) blend (SPSIm), incorporated with halloysite nanotubes (HNTs) were studied for direct methanol fuel cell (DMFC) applications. Firstly, PS was sulfonated at various degrees of sulfonation (DS), and the optimum DS was selected based on hydrolytic stability. Then, SPS was blended with Im as new proton conducting sites. In addition to increasing proton conductivity, methanol permeability decreased due to the attractive interaction between Im and SO3H groups in SPS. In the next step, to introduce tortuous diffusion pathways and hence decrease the methanol crossover, halloysite nanotubes were incorporated into the SPSIm matrix. The results show that the methanol permeability of the membrane incorporated with 1 wt% HNT (SPSIm/HNT) was around 0.527 × 10−7 cm2 s−1, which showed a significant decrease compared to SPS, causing an improvement in the membrane selectivity parameter in comparison to pristine SPS membrane. Furthermore, the thermal properties, ion exchange capacity (IEC), water uptake behavior, and performance of the membranes were evaluated. Based on the results, owing to the reduced methanol permeability, acceptable power density, ease of preparation, as well as low cost, SPSIm/HNT could be considered for DMFC applications. [ABSTRACT FROM AUTHOR]

Direct methanol fuel cells (DMFCs) are promising form of energy conversion technology that have the potential to take the role of lithium-ion batteries in portable electronics and electric cars. To increase the efficiency of DMFCs, many operating conditions ought to be optimized. Developing a reliable fuzzy model to simulate DMFCs is a major objective. To increase the power output of a DMFC, three process variables are considered: temperature, methanol concentration, and oxygen flow rate. First, a fuzzy model of the DMFC was developed using experimental data. The best operational circumstances to increase power density were then determined using the beetle antennae search (BAS) method. The RMSE values for the fuzzy DMFC model are 0.1982 and 1.5460 for the training and testing data. For training and testing, the coefficient of determination (R2) values were 0.9977 and 0.89, respectively. Thanks to fuzzy logic, the RMSE was reduced by 88% compared to ANOVA. It decreased from 7.29 (using ANOVA) to 0.8628 (using fuzzy). The fuzzy model's low RMSE and high R2 values show that the modeling phase was successful. In comparison with the measured data and RSM, the combination of fuzzy modeling and the BAS algorithm increased the power density of the DMFC by 8.88% and 7.5%, respectively, and 75 °C, 1.2 M, and 400 mL/min were the ideal values for temperature, methanol concentration, and oxygen flow rate, respectively. [ABSTRACT FROM AUTHOR]

In this investigation, we systematically explored the intricate relationship between the structural attributes of polyvinyl alcohol (PVA) membranes and their multifaceted properties relevant to fuel cell applications, encompassing diverse crosslinking conditions. Employing the solution casting technique, we fabricated crosslinked PVA membranes by utilizing phosphoric acid (PA) as the crosslinking agent, modulating the crosslinking temperature across a range of values. This comprehensive approach aimed to optimize the selection of crosslinking parameters for the advancement of crosslinked polymer materials tailored for fuel cell contexts. A series of meticulously tailored crosslinked PVA membranes were synthesized, each varying in PBTCA content (5–30 wt.%) to establish a systematic framework for elucidating chemical interactions, morphological transformations, and physicochemical attributes pertinent to fuel cell utilization. The manipulation of crosslinking agent concentration and crosslinking temperature engendered a discernible impact on the crosslinking degree, leading to a concomitant reduction in crystallinity. Time-resolved attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was harnessed to evaluate the dynamics of liquid water adsorption and ionomer swelling kinetics within the array of fabricated PVA films. Notably, the diffusion of water within the PVA membranes adhered faithfully to Fick's law, with discernible sensitivity to the crosslinking conditions being implemented. Within the evaluated membranes, proton conductivities exhibited a span of between 10−3 and 10−2 S/cm, while methanol permeabilities ranged from 10−8 to 10−7 cm2/s. A remarkable revelation surfaced during the course of this study, as it became evident that the structural attributes and properties of the PVA films, under the influence of distinct crosslinking conditions, underwent coherent modifications. These changes were intrinsically linked to alterations in crosslinking degree and crystallinity, reinforcing the interdependence of these parameters in shaping the characteristics of PVA films intended for diverse fuel cell applications. [ABSTRACT FROM AUTHOR]

The rapid depletion of traditional non-renewable fossil fuels has increased energy sustainability threats. Methanol is recognized as one of the viable alternatives to conventional fossil fuels mainly due to its high energy density and abundant raw materials. Direct methanol fuel cells (DMFCs) can convert the chemical energy of methanol into electricity in real time, which is one of the most effective ways to utilize methanol energy. However, DMFCs have undesirable performance, such as low fuel utilization, low cell voltage, and unstable output voltage, hindering the development of methanol energy technology. Herein, we design an energy storage system with high methanol energy efficiency based on passive micro DMFCs. This system with low power consumption (only uW scale) can extract the high chemical energy in methanol, efficiently convert it into electric energy, and store it to output a stable voltage for load. Moreover, application research on this system has been carried out. A self-powered methanol concentration sensor is designed and implemented on a printed circuit board. It can detect methanol solution with a concentration of 3 M–12 M, only requiring it to be tested as fuel without an additional power supply. The sensor has about 1.1 mW total power consumption and 0.34 s response time. This study on the energy conversion and storage of sustainable methanol fuel aims to provide a reference to explore the application of renewable energy.

Series of proton conductive membranes were prepared by mixing different weight ratio of 3-hexyl-1-methylimidazolium hydrogensulfite ([C6C1Imi][HSO3]), and N-hexyl-pyridinium hydrogensulfite ([C6Py][HSO3]) ionic liquids with poly vinyl alcohol (PVA) polymer. To characterize the PVA-ILs membranes, different methods have been used such as X-ray diffraction (XRD), Fourier-transform infrared (FTIR), and scanning electron microscope (SEM). Moreover, the water uptakes, ion exchange capacity, methanol permeability, and proton conductivity of prepared PVA membranes doped with different weight ratio of ILs have been investigated to find the optimum formulation to use as electrolytes membranes for direct methanol fuel cell. The proton conductivity and the ion exchange capacity were improved as the ILs content increased. At 25 °C, The PVA-60 wt.% of [C6C1Imi][HSO3] membrane had a maximum proton conductivity of 17,47 mS.cm−1, and a methanol permeability of 8.17 10−7 cm2.s − 1. Mechanical and thermal data confirmed that addition of ILs improve the membrane flexibility and thermal stability up to 200 °C.

In this work, plasma under different atmospheres is used to adjust the surface electronic and chemical structure of Fe/Co/N co-decorated hollow graphene spheres (FCNHGS) in order to create suitable conditions for the deposition of Pt 1 Ni 2 alloy nanoparticles (NPs). The results show that plasma treatment in specific atmospheres has different effects on the surface of FCNHGS, such as O 2 plasma is etching and oxidation, N 2 plasma and Ar plasma is etching, Ar/H 2 plasma is etching and reduction, Ar/NH 3 plasma is etching, doping and reduction. Therefore, changing the plasma treatment atmosphere can control the anchoring sites on FCNHGS for the deposition of Pt 1 Ni 2 NPs. When Ar/NH 3 plasma is used, the synthesized Pt 1 Ni 2 @Ar/NH 3 -FCNHGS exhibits the best bi-functional catalytic activity and the highest utilization efficiency of Pt in the oxygen reduction and hydrogen evolution reaction (ORR/HER) due to the strong interaction between loaded Pt 1 Ni 2 NPs and the Ar/NH 3 -FCNHGS. Moreover, when the Pt 1 Ni 2 @Ar/NH 3 -FCNHGS is used as cathode catalyst for direct methanol fuel cell, it exhibits superior open-circuit voltage (OCV = 730 mV) and similar peak power density (PPD = 62.8 mW cm−2) to 20 wt% Pt/C from 25 to 80 °C. More importantly, it showed better stability compared with 20 wt% Pt/C after about 72 h of stability testing. [Display omitted] • The well-dispersed Pt 1 Ni 2 NPs on FCNHGS was achieved by plasma with different atmospheres. • The plasma with different atmospheres produced different defect levels on FCNHGS. • The NPs size is related to the strength of the interaction between the substrate and the alloy NPs. • The OES deduce the formation of defects/functional groups on substrate materials. • The Pt 1 Ni 2 @Ar/NH 3 -FCNHGS is demonstrated to be a stable and efficient catalyst for ORR/HER. [ABSTRACT FROM AUTHOR]

Methanol oxidation reaction (MOR) in the direct methanol fuel cells involves six electron transfer processes, and noble metal based catalysts such as Pt and Pd are still recognized as efficient catalysts for MOR. It is generally accepted that the reaction is mainly related to the d states of precious metal-based catalysts. Transition metal carbides and noble metals exhibit similar d band structure and catalytic properties, among which molybdenum carbide is an effective catalyst. However, molybdenum carbide-based catalysts have not been used in methanol electrooxidation reactions until the present moment, and we tried to use Mo 2 C/MWCNT for the MOR reaction. Compared with MoO 2 /MWCNT and MoO 3 /MWCNT, it is found that Mo 2 C/MWCNT shows the highest electrocatalytic activity, and the current density of Mo 2 C/MWCNT is 185 mA cm−2 in 1 M KOH+1 M CH 3 OH at 0.70 V (vs. Hg/HgO). The current density is about 2.2 times and 1.4 times higher than those of MoO 2 /MWCNT and MoO 3 /MWCNT catalysts, respectively, and the electrochemical impedance also decreases markedly. The current density retains 76.19% of the initial catalytic activity after 10 h at the Mo 2 C/MWCNT electrode, indicating that the catalyst has superior stability for MOR. The reaction pathway of MOR on Mo 2 C/MWCNT is as follows: CH 3 OH∗ → CH 3 O∗→ CH 2 O∗ → CH 2 OOH∗ → CH 2 OO∗ → CHOO∗ → CO 2 ∗. The result not only expands the Mo 2 C application area, but also provides a new idea for the design of the MOR catalyst. [Display omitted] • The current density of Mo 2 C/MWCNT is 185 mA cm−2 at 0.70 V (vs. Hg/HgO). • Mo 2 C/MWCNT also shows high electrocatalytic stability. • Mo 4d orbit of Mo 2 C/MWCNT is similar to the d-band structure of precious metals. • The charge transfers from Mo 2 C to MWCNT. [ABSTRACT FROM AUTHOR]

The electrospinning method has been successfully employed to prepare various percentages of less expensive nickel/palladium (NP) nanofiber catalysts as an alternative to platinum in direct methanol fuel cells (DMFC). The chemical structure, morphological characteristics, and electrochemical (EC) properties have been investigated using a variety of analysis techniques. According to the scanning electron microscope (SEM), all prepared samples with different Pd concentrations exhibit good nanofiber form and a distinct nanoparticle look. Transmission electron microscopy (TEM) reveals an amorphous carbon nanofiber structure with imbedded crystalline spheres of nickel and palladium. The carbonized polyvinyl alcohol nanofibers (PVANFs) have a steady and even distribution of nickel and palladium with an accurate nickel and palladium content, according to the energy dispersive X‐ray mapping results. The lack of hydroxide or oxide phases in the X‐ray diffraction (XRD) pattern proves that Ni–Pd nanoparticles are present in the metallic phase. For the electrooxidation of methanol, urea, and an isopropanol‐methanol mixture, the electrocatalytic features of the fabricated samples have been examined. EC results show that methanol has the best electrocatalytic properties. Hence, NP nanofiber catalysts could be a promising candidate to replace platinum in DMFC. [ABSTRACT FROM AUTHOR]

Different nanostructured anode electrocatalyst using Pt, Al, Ti, ZnO, and carbon cloth (CC) including Pt@CC, Pt@ZnO-CC, Pt@Al-ZnO-CC, Pt@Ti-ZnO-CC, and Pt@Al-Ti-ZnO-CC are prepared for the purpose of application in direct methanol fuel cells (DMFCs). The effect of carbonaceous material modification and co-doping (Al/Ti) utilization in electrodes is investigated for methanol oxidation reaction (MOR). The results show that the incorporation of Al, Ti, and Pt nanoparticles into ZnO does not damage the hexagonal wurtzite structure. The doping ZnO with Al and Ti nanoparticles improves the dispersion of Pt catalysts and increases the current density by 1.6 times compare with Pt@CC electrode. Maximum electrochemical surface area of 98.6 m2 g−1, minimum amount of charge transfer resistance of 14 Ω cm2, and good CO tolerance and stability are found in Pt@Al-Ti-ZnO-CC electrode. This electrode in the active DMFC shows the maximum power and current density of 15.1 mW cm−2 and 83.4 mA cm−2, respectively, in the cell voltage of 0.2 V. In the EIS test, charge transfer resistance at the anode and cathode (Rct,a and Rct,c) values is decreased by 11.6 and 26.6% by reducing the cell voltage from 0.3 to 0.2 V, respectively. [ABSTRACT FROM AUTHOR]

This study proposes a hydrophobic and hydrophilic aliphatic diblock copolymer wherein the hydrophobic block contains glycidyl methacrylate (GMA) units that are distanced by poly(acrylonitrile) (PAN) segments to fabricate a proton exchange membrane (PEM). This diblock copolymer also known as ionomer due to the hydrophilic block comprising 3-sulfopropyl methacrylate potassium salt (SPM) block. The diblock copolymer was synthesized in the one-pot atom transfer radical polymerization (ATRP) synthesis. Subsequently, the membrane was fabricated by means of solution casting in which an organic diamine, e.g., ethylene diamine (EDA), was introduced to crosslink the diblock copolymer chains via the addition of amine to the epoxide group of GMA. As a result, the PEM attained possesses dual continuous phases, in which the hydrophobic domains are either agglomerated or bridged by the EDA-derived crosslinks, whereas the hydrophilic domains constitute the primary proton conducting channels. The in-situ crosslinking hydrophobic block by using a hydrophilic cross-linker represents the merit aspect since it leads to both improved proton conductivity and dimensional stability in alcohol fuel. To characterize the above properties, Nafion® 117 and random copolymer of P(AN-co-GMA-co-SPM) were used as control samples. The PEM with the optimized composition demonstrates slightly better fuel cell performance than Nafion 117. Lastly, this diblock ionomer is nonfluorinated and hence favors lowering down both material and environmental costs.

Sluggish kinetics of methanol oxidation reaction (MOR) and alkaline hydrogen evolution reaction (HER) even on precious Pt catalyst impede the large-scale commercialization of direct methanol fuel cell (DMFC) and water electrolysis technologies. Since both of MOR and alkaline HER are related to water dissociation reaction (WDR), it is reasonable to invite secondary active sites toward WDR to pair with Pt for boosted MOR and alkaline HER activity on Pt. Mo2C and Ni species are therefore employed to engineer NiPt–Mo2C active site pairs, which can be encapsulated in carbon cages, via an in-situ self-confinement strategy. Mass activity of Pt in NiPt–Mo2C@C toward HER is boosted to 11.3 A mgpt−1, 33 times higher than that of Pt/C. Similarly, MOR catalytic activity of Pt in NiPt–Mo2C@C is also improved by 10.5 times and the DMFC maximum power density is hence improved by 9-fold. By considering the great stability, NiPt–Mo2C@C exhibits great practical application potential in DMFCs and water electrolysers.

This paper presents a membrane electrode assembly (MEA) with a double-catalytic layered structure to improve the performance of the micro direct methanol fuel cell. The inner and outer parts of the double-catalytic layer comprise an unsupported and carbon-supported catalyst, respectively. A two-dimensional two-phase model of mass transport and electrochemical reaction is established and simulated to analyze the superiority of the double-catalytic layered structure. Simulation results show that this structure has a more uniform current density distribution and less over-potential across the catalyst layer. Methanol crossover is also reduced. Experimental results confirm that the MEA with the double-catalytic layered structure exhibits better performance than the traditional MEA. The adoption of a gas diffusion electrode as the outer catalytic layer and a catalyst-coated membrane as the inner layer of the double-catalytic layered structure can further improve the performance of the MEA. Both simulation and experimental results show the existence of an optimum number of metal loadings of the inner and outer parts of the double-catalytic layer.

This work presents the first integration of antibodies into one of the electrodes of a passive direct methanol fuel cell (DMFC) to create an autonomous immunosensor for cancer antigen 15–3 (CA15-3). The anode of the fuel cell was first made of carbon cloth with carbon black, platinum and ruthenium nanoparticles and then modified with anti-CA15-3, while the cathode was made of carbon cloth with carbon black and platinum nanoparticles. This hybrid DMFC (hDMFC), which works as an immunosensor, was fed with dilute methanol to generate a concentration-dependent current.The hDMFC device was calibrated in different media (buffer and serum), by incubating increasing concentrations of CA15-3 standard solutions, ranging from 47 to 750 U/mL. The linear response ranged from 188 to 563 U/mL, and the limit of detection (LoD) was 39.8 U/mL. The selectivity of the biosensor was also evaluated with competing cancer biomarkers, such as carcinoembryonic antigen (CEA), and cancer antigen 125 (CA-125), as well as with other compounds normally present in blood plasma (ascorbic acid, glucose, uric acid and urea), adjusted to the normal range of concentrations in serum. The results obtained indicate good selectivity of the immunosensor in the fuel cell.In general, the immunosensor showed a good response considering its integration into a passive DMFC. It is a good sensor for point-of-care (PoC) diagnosis because it has a good performance in human serum and, most importantly, it pursues electrical autonomy.

An adaptive control strategy for fuel cell stabilization is proposed to alleviate the coupling effects of power output variation and performance degradation in the whole service life. An improved semi-empirical model is firstly developed to describe and analyze the direct methanol fuel cell (DMFC) performance under different operating conditions while considering degradations. Multi-objective optimizations are then utilized for the adaptive generation of control strategy to stabilize the voltage. Experiments are implemented to validate the effectiveness of the adaptive control strategy at different time periods during long-term operation. The results show that the improved semi-empirical model can provide a dynamic description of DMFC I-V relationships with the time. The adaptive control strategy developed from this model is effective for voltage stabilization that the deviation could be constrained in ±10% at different power outputs during long-term operation. [ABSTRACT FROM AUTHOR]

Fuel cells have already demonstrated their potential for green energy generation. However, the low reaction performance becomes an obstacle in terms of large-scale commercial manufacturing. Accordingly, this work focuses on a new unique fabrication of three-dimensional pore hierarchy TiO2-graphene aerogel (TiO2-GA) supporting PtRu catalyst for anodic catalyst direct methanol fuel cell, which is facile, ecologically benign, and economical. In this work, a hydrothermal technique was used, followed by a freeze-drying technique and a microwave-assisted ethylene reduction technique. The structural properties of the studied materials were confirmed by UV/visible spectroscopy, XRD, Raman spectrum, FESEM TEM, and XPS. Based on existing structural advantages, the performance of PtRu/TiO2-GA has been investigated on DMFC anode catalysts. Furthermore, electrocatalytic stability performance with the same loading (~20%) was compared to commercial PtRu/C. Experimental outcomes show that the TiO2-GA support offered a significantly high surface area value of 68.44 m2g−1, mass activity/specific activity (608.17 mAmg−1/0.45 mA/cm2PtRu) that is higher than commercial PtRu/C (79.11 mAmg−1/0.19 mA/cm2PtRu). In passive DMFC mode, PtRu/TiO2-GA showed a maximum power density of 3.1 mW cm−2, which is 2.6 times higher than that of the PtRu/C commercial electrocatalyst. This suggests that PtRu/TiO2-GA has a promising possibility for methanol oxidation and may be used as an anodic element in DMFC. [ABSTRACT FROM AUTHOR]

The design and synthesis of novel electrode catalysts is an applicable strategy to improve the performance of direct methanol fuel cells (DMFCs). The catalyst is composed of molybdenum disulfide as the shell and nickel silicide-doped sodalite (MoS 2 /NiSi@SOD) as the core. A series of characterization results indicate that NiSi is highly dispersed in the nanosized SOD cage on the surface of the SOD zeolite at the crystal faces of (011), (102), and (201). A thin conductive protective cover is formed by MoS 2 on the surface of the zeolite. By the cyclic voltammetry (CV), the catalyst performs a maximum current density of 46.9 mA cm−2 (1250.1 A g Ni −1) with 10 M methanol while no remarkable catalyst poisoning and catalyst deactivation are observed. It is revealed that MoS 2 /NiSi@SOD under high catalysis activity protects the Ni from the drain in the alkaline electrolyte, leading to a broad application prospect as a noble-metals-free DMFC catalyst. The MoS 2 /NiSi@SOD composite material reveals high performance in MOR with an efficiency of 46.9 mA cm−2 and 1250.1 A g−1 in 10 M methanol. The novel electrochemical catalyst is composed of the NiSi NPs doped SOD structure nanocages as the core and the MoS 2 nano wafer as the shell and is as-synthesized under hydrothermal condition through a self-assembly process in a one-pot reaction. During the crystallization of the zeolite, the NiSi nanocrystals are generated and restricted in the nanosized SOD cages. And the MoS 2 shell near the zeolitic surface enhances the electronic transport efficiency and protects the NiSi NPs from the drain in the electrolyte during the electrocatalytic progress. The catalyst is characterized by high performance and low production cost, being a good candidate to replace noble metal catalysts in applications. [Display omitted] • The MoS 2 /NiSi@SOD catalyst has been synthesized in hydrothermal conditions. • NiSi nanoparticles are highly dispersed and located in the pore of the SOD zeolite. • The low-cost catalyst plays high performance in MOR without obvious catalyst poisoning and deactivation. [ABSTRACT FROM AUTHOR]

This work attempted to improve the catalytic performance of an anodic catalyst for use in direct methanol fuel cells by coating graphene aerogel (GA) with platinum nanoparticles. A hydrothermal, freeze-drying, and microwave reduction method were used to load Pt–Ru bimetallic nanoparticles onto a graphene aerogel. The mesoporous structure of a graphene aerogel is expected to enhance the mass transfer in an electrode. XRD, Raman spectroscopy, SEM, and TEM described the as-synthesized PtRu/GA. Compared to commercial PtRu/C with the same loading (20%), the electrocatalytic performance of PtRu/GA presents superior stability in the methanol oxidation reaction. Furthermore, PtRu/GA offers an electrochemical surface area of 38.49 m2g−1, with a maximal mass activity/specific activity towards methanol oxidation of 219.78 mAmg−1/0.287 mAcm−2, which is higher than that of commercial PtRu/C, 73.11 mAmg−1/0.187 mAcm−2. Thus, the enhanced electrocatalytic performance of PtRu/GA for methanol oxidation proved that GA has excellent potential to improve the performance of Pt catalysts and tolerance towards CO poisoning. [ABSTRACT FROM AUTHOR]

Various materials have been examined over the last several decades to fabricate proton exchange membranes (PEMs) for direct methanol fuel cells (DMFCs), with the objective of achieving high selectivity (i.e., the ratio of proton conduction to fuel permeability). Ideally, a PEM for DMFC must demonstrate higher proton conductivity, as well as lower methanol permeability, in comparison to the commercial Nafion membranes. With these objectives, this research paper reports the fabrication of a composite PEM comprising glutaraldehyde-crosslinked poly(vinyl alcohol-co-styrenesulfonic acid) and sulfonated polypropylene-based non-woven fabric (S-NWF) by deep coating technique. The resulting PEMs were thoroughly characterized to find physicochemical and electrochemical properties. Key findings obtained with these composite PEMs are (a) exhibition of dimensional stability in hot water (at 80 °C), (b) improved proton conductivity (i.e., 0.12 S·cm–1 at 80 °C), and reduced methanol permeability (i.e., 3.91·10–8 cm2·s–1) upon increasing the number of coating layers on the S-NWF, (c) achievement of a membrane selectivity value of 2.61·106 S·s·cm–3, and (d) the fact that 6 layers of coating resulted in producing the highest peak power density of 62.32 W·m–2 and a current density of 540 A·m–2.

Performance decay of direct methanol fuel cells hinders technology competitiveness. The cathode electrochemical surface area loss is known to be a major reason for performance loss and it is mainly affected by cathode potential and dynamics, locally influenced by water and methanol crossover. To mitigate such phenomenon, novel materials and components need to be developed and intensively tested in relevant operating conditions. Thus, the development of representative accelerated stress tests is crucial to reduce the necessary testing time to assess material stability. In the literature, the most diffused accelerated stress tests commonly enhance a specific degradation mechanism, each resulting in limited representativeness of the complex combination and interaction of mechanisms involved during real-life operation. This work proposes a novel accelerated stress test procedure permitting a quantifiable and predictable acceleration of cathode degradation, with the goal of being representative of the real device operation. The results obtained with a 200 h accelerated stress test are validated by comparing both in situ and post mortem measurements with those performed during a 1100 h operational test, demonstrating an acceleration factor equal to 6.25x and confirming the development of consistent cathode degradation. [ABSTRACT FROM AUTHOR]