Performance Of Direct Methanol Fuel Cell Research Articles

N-doped titanium oxide/carbon composite as supports for platinum catalysts in highly efficient methanol oxidation

The commercialization of direct methanol fuel cells (DMFCs) faces significant challenges due to the susceptibility of conventional platinum-based catalysts to poisoning by intermediates such as CO and HCOO− generated during the methanol oxidation reaction (MOR). This study details the synthesis of a highly porous titanium dioxide/carbon composite (TCC) using NH2-MIL-125(Ti) (MIL = Matérial Institut Lavoisier) as a precursor. To enhance the conductivity and catalytic properties of TCC, a nitriding reaction is conducted in an NH3 atmosphere, producing a nitrogen-doped titanium oxide/carbon composite (N-TCC). The resulting N-TCC is employed as a support for a platinum catalyst to improve MOR performance in DMFCs. The Pt/N-TCC catalyst demonstrates high catalytic performance, achieving a mass activity of 537 mA mg−1 for the MOR, marking a 39 % increase over the commercial Pt/C catalyst. Furthermore, the Pt/N-TCC catalyst exhibits a low onset potential for CO oxidation, a higher If/Ib ratio, and greater stability in chronoamperometry test, indicating high resistance to CO poisoning and enhanced chemical stability. Therefore, N-TCC can be used as a promising support for Pt-based catalysts in DMFC applications.

Constructing hollow cobalt sulfide nanocages strung by manganese molybdate nanorods for high-efficiency supercapacitors and electrocatalytic methanol oxidation

Constructing core-shell heterostuctures with rationally designed nanoarchitectures and components is a promising strategy to pursuit high-efficiency energy storage and conversion in supercapacitors (SCs) and direct methanol fuel cells (DMFCs). Herein, a multi-dimensional MnMoO4@CoS core-shell heterostructure is designed and synthesized by stringing metal-organic framework-derived hollow CoS nanocages with MnMoO4 nanorods. Such heterostructure provides more electroactive sites and enhanced structural stability. Theory calculations unveil that the work function difference between MnMoO4 and CoS induces the charge redistribution and modulate interfacial electronic configuration in the MnMoO4/CoS heterojunction. Meanwhile, a interfacial built-in electrical field is established, enhancing interfacial charge transfer efficiency and promoting the surface adsorption of electrolyte ions. By integrating all these advantages, the MnMoO4@CoS electrode demonstrates enhanced rate capacities (933 C g−1 at 1 A g−1 and 623 C g−1 at 10 A g−1) and cycling durability (90.3 % capacity retention after 10,000 cycles) compared to bare MnMoO4 and CoS electrodes. Moreover, the MnMoO4@CoS electrode exhibits an appreciable electrocatalytic performance for methanol oxidation, with a current density of 294.8 mA cm−2 at 10 mV s−1 and 96.6 % current retention after 10,000 s. Our work offers a fundamental guideline for designing and engineering core-shell heterostructures with desirable electrochemical performance for SCs and DMFCs.

Tuning d-band center of Pt via Pt-Pt5La heterostructure interface as efficient and stable electrocatalyst for oxygen reduction and methanol oxidation reactions in DMFCs

Developing Pt-based electrocatalysts with superior activity and durability is essential for direct methanol fuel cells (DMFCs), and regulating the interfacial electronic interaction for Pt-based composites can significantly modulate the electrocatalytic performances. Herein, the Pt-Pt5La/C heterostructure catalyst was developed to enhance the catalytic property towards oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). Experimental analyses and theoretical calculations demonstrated the electron redistribution at the interface and reduction of the d-band center of Pt for this unique Pt-Pt5La/C heterostructure. As the results, Pt-Pt5La/C exhibited 5.0- and 6.4-times higher mass activity and specific activity towards alkaline ORR compared to Pt/C, and the excellent electrocatalytic MOR performance due to the interfacial interaction. These superior electrocatalytic property promoted Pt-Pt5La/C as the bifunctional catalyst for DMFC application with outstanding power density and durability. Consequently, this work proposed a novel interfacial regulation strategy for designing Pt-rare earth (RE) alloy heterostructures and their reliable operation of DMFCs.

An investigation into the effect of anode platinum loading on Direct Methanol Fuel Cell performance

An investigation into the effect of anode platinum loading on Direct Methanol Fuel Cell performance

Development of novel proton exchange membranes based on cross-linked polyvinyl alcohol (PVA)/5-sulfosalicylic acid (SSCA) for fuel cell applications

The proton-conducting and methanol permeation behaviors of polymeric electrolyte membranes (PEMs), as well as the expensive nature of direct methanol fuel cell (DMFC) components, pose major concerns in DMFC performance and commercialization. As a result, this research aimed to develop low-cost polyelectrolyte membranes based on cross-linked poly(vinyl alcohol)/5-sulfosalicylic acid dehydrate (PVA/SSCA) composite. Chemical cross-linkers and modifiers offer the essential chemical and mechanical stability of the developed membranes for usage as polyelectrolyte membranes (PEMs). The manufactured composite proton exchange membranes provide several benefits, including significant thermal, chemical, and mechanical stability. The results revealed that extending the SSCA molar concentration increased IEC outcomes of the synthesized membranes, reaching an elevated level of (3.31 meq g−1) compared to (0.91 meq g−1) for the Nafion 117 membrane. The proton conductivity of a composite membrane (102 μm thick) measured by impedance spectroscopy was relatively (0.078 S cm−1) and found comparable to other PVA-based composite membranes reported in the literature. Other key parameters, such as methanol permeability, were measured for constructed composite proton exchange membranes (2.52 × 10–7 cm2 s−1), which were much lower than Nafion 117 (3.39 × 10–6 cm2 s−1). The Fourier transform infrared (FT-IR), Raman scattering spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, elemental analysis, and thermal gravimetric analysis (TGA) were among the techniques used to characterize the synthesized membranes. These characterizations confirm the structural interaction between the membrane components’ crystalline nature, and no signs of phase separation or cracks were found; surface morphology and good membrane homogeneity, elemental analysis, and the membranes’ thermal stability (up to 290 °C). The membranes were also mechanically characterized using a universal testing machine (UTM), which revealed good mechanical stability. The findings demonstrate that a low-cost proton exchange membrane could potentially be synthesized for DMFC applications.

Sulfonated poly (ether ether ketone)/MOF hybrid polymer electrolyte membrane with ultra‐low methanol permeability for enhanced direct methanol fuel cell performance

AbstractA novel hybrid polymer electrolyte membrane (PEM) was developed for direct methanol fuel cell (DMFC) applications by incorporating sulfonated poly (ether ether ketone) (SPEEK) with a chromium‐based metal–organic framework (MOF), namely, BUT‐8(Cr). The incorporation of BUT‐8(Cr) significantly improved the dispersion of the MOF within the SPEEK matrix, leading to alterations in surface morphology and the creation of hydrophilic channels, as confirmed by SEM. Furthermore, the presence of an excess of sulfonic groups and the flexible structure of the MOF enhanced the physicochemical properties of the membrane, such as water uptake, proton conductivity and ion exchange capacity. Importantly, well‐defined rigid coordination structure of MOF effectively blocks methanol migration, resulting in a notably low methanol permeability value of 1.6 × 10−7 cm2 s−1, compared to Nafion 117 (20 × 10−7cm2s−1). For practical DMFC operation, the hybrid membrane (~0.75 wt.% MOF) exhibited a maximum power density of 88.6mWcm−2 with current density of 434.04 mAcm−2, outperforming Nafion 117 (73.4mWcm−2 and 380 mAcm−2 respectively) at same conditions. Our results suggest that the prepared SPEEK‐0.75 hybrid membrane holds a great promise as a PEM material for DMFC applications.

Investigating the Impact of Methanol Concentration and Implementation of a Coefficient Diagram-Based Control System for Direct Methanol Fuel Cell Operation

Investigating the Impact of Methanol Concentration and Implementation of a Coefficient Diagram-Based Control System for Direct Methanol Fuel Cell Operation

Chitosan Incorporated with Titanium (IV) Oxide Membrane for Direct Methanol Fuel Cell Application

The direct methanol fuel cell (DMFC), a type of promoted polymer electrolyte membrane fuel cell (PEMFC), has received tremendous attention in the past two decades because of its potential as a promising technology for clean and efficient power generation in the twenty-first century. Over the past four decades, the dominancy of perfluorinated proton exchange membranes (PEM) such as Nafion is prolonging in the current PEM technology due to its chemical stability, high proton conductivity and high mechanical strength in the low operating temperatures. However, the Nafion membrane also has several weaknesses, such as high methanol permeability, high manufacturing cost, and dehydration with low proton conductivity at elevated temperatures > 100°C. This study fabricated a novel composite membrane by blending the pristine chitosan (CS) and titanium oxide (TiO2) at various loadings, 0.5, 1.0, 1.5 and 2.0 wt% to obtain high performance in DMFC. SEM and FTIR analysis showed that the grafting of (O-Ti-O) successfully incorporated into the CS polymer matrix. Water and methanol uptake of CS/TiO2 composite membrane decreased with increase of TiO2 loadings, but proton conductivity value increased. The CS/TiO2 membrane with 1.5wt.%TiO2 loading exhibited highest proton conductivity (0.41mScm-1) and lowest methanol permeability (17.18E-08cm2/s) characteristics among other membranes this due to the hydrophilic TiO2 raised the membrane hydrophilic character by increasing the number of hydrophilic sites, such as OH-, COO- and O-. The results obtained from the study can be used to conclude that chitosan membrane with TiO2 filler is a promising high performance PEM candidate for DMFC applications.

TiO2 Nanolayer–Coated Carbon as Pt Support for Enhanced Methanol Oxidation Reaction

Abstract To facilitate the large-scale application of direct methanol fuel cells (DMFCs), the issue of low Pt/C durability due to Pt degradation and carbon corrosion in harsh DMFC operating conditions must be addressed. A promising strategy is to hybridize metal oxides with carbon materials, resulting in a durable and conductive support that exhibits a strong metal-support interaction (SMSI) effect on platinum nanoparticles (Pt NPs). In this study, we introduced a TiO2 coating on carbon black, creating a TiO2 nanolayer between Pt and carbon black. The nanolayer not only protects the carbon black but also activates the SMSI effect on Pt. The resulting Pt/C@TiO2 electrocatalyst exhibits superior durability than commercial Pt/C. After the accelerated durability test, the mass activity loss of the methanol oxidation reaction (MOR) of Pt/C@TiO2 (32%) is significantly lower than that of Pt/C (46.8%). Moreover, the MOR activity of Pt/C@TiO2 is higher than Pt/C as well. It suggests that Pt/C@TiO2 shows great potential as a highly durable and active electrocatalyst for DMFCs.

Self-Healing Sulfonated Poly(ether ether ketone)-Based Polymer Electrolyte Membrane for Direct Methanol Fuel Cells: Effect of Solvent Content.

Proton exchange membranes (PEMs) with superior characteristics are needed to advance fuel cell technology. Nafion, the most used PEM in direct methanol fuel cells (DMFCs), has excellent proton conductivity but suffers from high methanol permeability and long-term performance degradation. Thus, this study aimed to create a healable PEM with improved durability and methanol barrier properties by combining sulfonated poly(ether ether ketone) (SPEEK) and poly-vinyl alcohol (PVA). The effect of changing the N,N-dimethylacetamide (DMAc) solvent concentration during membrane casting was investigated. Lower DMAc concentrations improved water absorption and, thus, membrane proton conductivity, but methanol permeability increased correspondingly. For the best trade-off between these two characteristics, the blend membrane with a 10 wt% DMAc solvent (SP10) exhibited the highest selectivity. SP10 also showed a remarkable self-healing capacity by regaining 88% of its pre-damage methanol-blocking efficiency. The ability to self-heal decreased with the increasing solvent concentration because of the increased crosslinking density and structure compactness, which reduced chain mobility. Optimizing the solvent concentration during membrane preparation is therefore an important factor in improving membrane performance in DMFCs. With its exceptional methanol barrier and self-healing characteristics, the pioneering SPEEK/PVA blend membrane may contribute to efficient and durable fuel cell systems.

Critical analysis for evaluating maximum power point tracking strategy in photovoltaics and fuel cells using key performance metrics

This study performs detailed analyses to investigate and justify the utilization of maximum power point tracking (MPPT) algorithm in photovoltaics (PV) and fuel cells. Two devices are parallelly analyzed to establish a comparative and contrasting study on the performance of the two technologies at MPP regime for a given operational condition. Direct methanol fuel cell (DMFC) is chosen as a representative of the hydrogen fuel cells family. The operational variables affecting the electrical power in the devices, including temperature (for both devices), solar irradiance (for PV cells), and methanol concentration (for DMFC) are discussed, along with their similarities and differences. Voltage losses are addressed to gain insights into the electrical quality of each device at MPP regimes. Due to their pivotal role, fuel availability and cost, energy losses, overall efficiency, and cathode flooding are selected as crucial performance metrics to compare the two technologies at MPP. The results demonstrate that PV cells have a good voltage quality at MPP with an average retention of 87% from open-circuit voltage VOC, whereas DMFC performance deteriorates at MPP, resulting in a significant decline with a loss of 61% from VOC . Consistent with voltage loss results, fill factor analysis at MPP zones lead to the same conclusion wherein photovoltaics offer high fill factor of approximately 82%, whereas DMFC has lesser values that are below 40%. The maximum overall efficiency of PV cells is attained at the MPP zones, whereas optimal efficiencies do not match the MPP loci in fuel cells. Simulations show that DMFC is extremely prone to cathode flooding at MPP zones, where approximately 90% of pore spaces in the liquid distribution layer are occupied with water. Conversely, PV cells are completely free from such issues. Some recommendations for further advancement and investigation on the use of MPPT in both technologies are provided.

In situ shaped PtPd nanocubes on common carbon powder for efficient methanol electrooxidation in practical fuel cells

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.

Polyelectrolyte Membranes Based on Nafion/Chitosan Blends for Direct Methanol Fuel Cell Application

In this study, polyelectrolyte membranes (PEMs) were fabricated by blending chitosan and Nafion with various compositions for direct methanol fuel cell (DMFC) application. The incorporation of Nafion caused increasing the glass transition temperature (Tg), as well as decreasing the crystallinity of chitosan based matrix, which has roots in the attractive interaction between –SO3H groups in Nafion and –NH2 groups in chitosan structure. In addition, the proton conductivity, as well as the methanol permeability of the studied membranes increased with an increase in the loading weight of Nafion. The selectivity parameter (the ratio of proton conductivity to methanol permeability) of the membrane containing 25 wt% of Nafion was comparable to neat Nafion. In parallel, the results of the DMFC performance test showed a maximum power density of 39 mW cm−2 at 319 mA cm−2 current density (at 5 M methanol concentration and 75 °C) for the mentioned membrane which is near to that for recast Nafion. The results showed that the chitosan/Nafion complex can be considered as a PEM for DMFC application.

Optimization of Multiple Reactants in a Membrane-Less Direct Methanol Fuel Cell (DMFC).

Membrane-less fuel cells are a promising power source for portable applications that enable the solving of membrane-related issues, such as water management and high cost, in conventional fuel cells. Apparently, research on this system uses a single electrolyte. This study focused on enhancing the performance of membrane-less fuel cells by introducing multiple reactants that are dual electrolytes with hydrogen peroxide (H2O2) and oxygen as oxidants in membrane-less direct methanol fuel cells (DMFC). The conditions tested for the system are (a) acidic, (b) alkaline, (c) dual medium with oxygen as an oxidant, and (d) dual medium and dual oxygen and hydrogen peroxide as an oxidant. Additionally, the effect of fuel utilization on different electrolyte and fuel concentrations was also studied. It was found that the fuel utilization decreases dramatically with the increasing of the fuel concentration, but it improved with the increasing of the electrolyte concentration until 2M. The performance of the dual oxidants in dual-electrolyte membrane-less DMFCs was 15.5 mW cm-2 of the power density achieved before optimization. Later, the system was optimized, and the power density increased to 30 mW cm-2. Finally, this work presented the stability of the cell using the suggested parameters from the optimization process. This study indicated that the performance of the membrane-less DMFC increased for dual electrolytes with mixed oxygen and hydrogen peroxide as oxidants compared to a single electrolyte.

Toward Electrocatalytic Methanol Oxidation Reaction: Longstanding Debates and Emerging Catalysts.

The study of direct methanol fuel cells (DMFCs) has lasted around 70 years, since the first investigation in the early 1950s. Though enormous effort has been devoted in this field, it is still far from commercialization. The methanol oxidation reaction (MOR), as a semi-reaction of DMFCs, is the bottleneck reaction that restricts the overall performance of DMFCs. To date, there has beenintense debate on the complex six-electron reaction, but barely any reviews have systematically discussed this topic. To this end, the controversies and progress regarding the electrocatalytic mechanisms, performance evaluations as well as the design science toward MOR electrocatalysts are summarized. This review also provides a comprehensive introduction on the recent development of emerging MOR electrocatalysts with a focus on the innovation of the alloy, core-shell structure, heterostructure, and single-atom catalysts. Finally, perspectives on the future outlook toward study of the mechanisms and design of electrocatalysts are provided.

Self-Standing, Ultrasonic Spray-Deposited Membranes for Fuel Cells.

The polymer electrolyte membrane and its contact with electrodes has a significant effect on the performance of fuel and electrolysis cells but the choice of commercially available membranes is limited. In this study, membranes for direct methanol fuel cells (DMFCs) were made by ultrasonic spray deposition from commercial Nafion solution; the effect of the drying temperature and presence of high boiling solvents on the membrane properties was then analyzed. When choosing suitable conditions, membranes with similar conductivity, water uptake, and higher crystallinity than comparable commercial membranes can be obtained. These show similar or superior performance in DMFC operation compared to commercial Nafion 115. Furthermore, they exhibit low permeability for hydrogen, which makes them attractive for electrolysis or hydrogen fuel cells. The findings from our work will allow for the adjustment of membrane properties to the specific requirements of fuel cells or water electrolysis, as well as the inclusion of additional functional components for composite membranes.

Nickel-doped molybdenum diselenide/functionalized multiwalled carbon nanotube as highly efficient non-Pt electrocatalyst toward methanol oxidation reaction

Designing a highly active, cost-effective, poison-resistant, and durable noble-metal-free electrocatalyst is essential for improvement of direct methanol fuel cells performance. In this work, Ni-doped MoSe2 nanosheets were successfully synthesized and integrated with carboxylated multiwalled carbon nanotube (f-MWCNT). The formation of Ni-doped MoSe2/f-MWCNT was confirmed with field emission scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy techniques. The prepared nanocomposite was used as an electrochemical catalyst for methanol electro-oxidation. The Ni-doped MoSe2/f-MWCNT electrocatalyst displayed a low onset potential of 0.33 V and methanol oxidation reaction (MOR) activity of 630 mA/cm2 at 0.8 V vs. Ag/AgCl after addition of 1 M methanol in alkaline solution. The proposed electrocatalyst also presented outstanding stability with 90% of its MOR activity retention even after 8000 s. With its facile synthesis, excellent catalytic performance and high stability, Ni-doped MoSe2/f-MWCNT is promising as an inexpensive, CO-resistant and efficient anode catalyst for MOR.

Assessment of innovative graphene oxide composite membranes for the improvement of direct methanol fuel cells performance

The main objective of the study was to verify potential of GO-PEM and its best effective usage in a Direct Methanol Fuel Cells (DMFC) application so investigating the effect of this filler on cell performance, varying several operating conditions, without affecting the mechanical and electric properties of the baseline PEM. In this work, GO was added to the Nafion polymer using a weight percentage varying from 0.5 to 1.5%. The present analysis showed that the GO-membranes have higher tensile strength, greater water, and methanol uptake. It was also demonstrated that the presence of carbon compounds slightly reduced the proton conductivity suggesting that an optimal GO-content must be determined. Comparing several physical and electrochemical properties, we concluded that the 1 wt. %GO-loading PEM represents the most effective solution. Later, the advantages of adopting GO-PEMs in DMFCs were also assessed. A comparative analysis of a GO-DMFC and a standard DMFC was carried out by changing the relevant control parameters, such as anode flow rate, temperature, and methanol concentration obtaining that: a) the GO-DMFC performance enhanced when increasing the temperature and the anode flow rate; b) an increase in methanol concentration had a beneficial effect on DMFC performance only up to a peak value after that a rapid reduction was noticed. Optimal conditions were obtained for an anode flow rate of 7 µl min−1, a temperature of 60 °C and a 1 M methanol concentration.

Modified Cellulose Proton-Exchange Membranes for Direct Methanol Fuel Cells.

A direct methanol fuel cell (DMFC) is an excellent energy device in which direct conversion of methanol to energy occurs, resulting in a high energy conversion rate. For DMFCs, fluoropolymer copolymers are considered excellent proton-exchange membranes (PEMs). However, the high cost and high methanol permeability of commercial membranes are major obstacles to overcome in achieving higher performance in DMFCs. Novel developments have focused on various reliable materials to decrease costs and enhance DMFC performance. From this perspective, cellulose-based materials have been effectively considered as polymers and additives with multiple concepts to develop PEMs for DMFCs. In this review, we have extensively discussed the advances and utilization of cost-effective cellulose materials (microcrystalline cellulose, nanocrystalline cellulose, cellulose whiskers, cellulose nanofibers, and cellulose acetate) as PEMs for DMFCs. By adding cellulose or cellulose derivatives alone or into the PEM matrix, the performance of DMFCs is attained progressively. To understand the impact of different structures and compositions of cellulose-containing PEMs, they have been classified as functionalized cellulose, grafted cellulose, acid-doped cellulose, cellulose blended with different polymers, and composites with inorganic additives.

Oxygen Reduction at PtNi Alloys in Direct Methanol Fuel Cells—Electrode Development and Characterization

Catalyst layers made from novel catalysts must be fabricated in a way that the catalyst can function to its full potential. To characterize a PtNi alloy catalyst for use in the cathode of Direct Methanol Fuel Cells (DMFCs), the effects of the manufacturing technique, ink composition, layer composition, and catalyst loading were here studied in order to reach the maximum performance potential of the catalyst. For a more detailed understanding, beyond the DMFCs performance measurements, we look at the electrochemically active surface area of the catalyst and charge-transfer resistance, as well as the layer quality and ink properties, and relate them to the aspects stated above. As a result, we make catalyst layers with optimized parameters by ultrasonic spray coating that shows the high performance of the catalyst even when containing less Pt than commercial products. Using this approach, we can adjust the catalyst layers to the requirements of DMFCs, hydrogen fuel cells, or polymer electrolyte membrane electrolysis cells.