Performance Of Direct Methanol Fuel Cell Research Articles

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.

Synthesis of graphene anchored with atomically isolated cobalt from a promising graphite-like supramolecule.

The application of heteroatom-doped graphene for photochemical and electrochemical reactions is primarily hindered by the lack of a controllable and facile synthesis strategy. In this work, few-layer CoN-graphene (1.8 nm thickness) with atomic Co has been fabricated via pyrolysis exfoliation. The half wave potential of CoN-graphene reaches 0.875 V vs. RHE, and the corresponding direct methanol fuel cell performance is 100% (higher than that of the commercial Pt/C catalyst), demonstrating potential for practical application in energy conversion devices.

A Tortuosity Engineered Dual-Microporous Layer Electrode Including Graphene Aerogel Enabling Largely Improved Direct Methanol Fuel Cell Performance with High-Concentration Fuel

Methanol crossover is an important factor affecting the performance of direct methanol fuel cells (DMFCs). In this work, a novel membrane electrode assembly (MEA) is designed and prepared by adding a layer of graphene aerogel (GA) between the carbon powder microporous layer and the catalytic layer, which optimizes the methanol transport and improves the output performance of DMFC at high methanol concentrations. Compared to conventional carbon powder, the addition of GA increases the tortuosity of the anode in the through-plane direction; hence, methanol is diluted to a suitable concentration when it reaches the catalyst. The maximum power density of the novel MEA can reach 27.4 mW·cm−2 at a condition of 8 M methanol, which is 234% higher than that of the conventional electrode. The test results of electrochemical impedance spectroscopy (EIS) indicate that the addition of GA does not increase the internal resistance of the novel MEA and that the mass transfer resistance at high concentrations is significantly lower. The experimental results indicate that the output performance at high concentration can be significantly improved by adding a GA layer, and its practicability in portable devices can be improved. It also improves the stability of DMFC under long-term testing.

Polyoxometalate-polymer nanocomposites with multiplex proton transport channels for high-performance proton exchange membranes

Multiplex ion channels play a critical role in life processes and are highly desired for advanced electrolytes due to the synergistic effect on ion transport. However, it is a challenge to integrate different types of proton transport channels in the same membrane system while keeping their intrinsic structural stability. Here, we report a facile strategy for the preparation of nanostructured polymer composite membranes with multiplex proton transport channels based on the supramolecular co-assembly of sulfonated poly(ether-ether-ketone) (SPEEK), poly(ether-ether-ketone)-grafted-poly(vinyl pyrrolidone) (PGP) and polyoxometalate H3PW12O40 (PW). The spherical ionic domains from SPEEK and the bicontinuous ionic domains from the electrostatically assembled PGP/PW components were fabricated in the membranes simultaneously, which co-construct the multiplex channels for proton conduction. The optimized membranes exhibit a high proton conductivity of ∼130 mS/cm and a high modulus of ∼4.3 GPa, which are ∼2.2 and ∼1.3 times higher than the pristine SPEEK, respectively. Furthermore, the direct methanol fuel cell performance based on these membranes is enhanced by 50.4% compared to SPEEK. This approach can provide a paradigm to design advanced polymer electrolyte membranes with highly efficient ion-conducting channels for energy applications.

Comparative study for electrochemical and Single-Cell performance of a novel MXene-Supported Platinum–Ruthenium catalyst for Direct methanol fuel cell application

• Novel formulation of bimetal embedded on MXene structure. • Latest two dimensional materials with ceramic and metal-like category. • Comparative study on electrochemical and DMFC single cell performance. • Promising anodic electrocatalyst for methanol oxidation reaction. • High electrochemical surface area and intrinsic activity leads to high performance. Direct methanol fuel cell (DMFC) is one of the reliable sources of energy owing to numerous benefits it offers and its suitability for portable electronic applications. Therefore, this study aims to overcome the main issues confronting anodic electrocatalyst part by introducing the novel formulation of platinum–ruthenium (PtRu) bimetal into the 2D Ti 3 C 2 T x structure to boost the electrocatalytic activity and single-cell performance. A comparative study for electrochemical measurement and DMFC performance is conducted between as-synthesized electrocatalyst PtRu/Ti 3 C 2 T x and two other electrocatalysts, PtRu/C and Pt/C. This comparative study between electrocatalyst revealed that PtRu/Ti 3 C 2 T x exhibits the highest electrochemical surface area (55 m 2 g -1 ), electrocatalytic and intrinsic activity (449 mA mg PtRu −1 / 1.36 mA cm ECSA −2 ), carbon monoxide tolerance (1.56), and smallest charge-transfer resistance (2.66 Ω) compared with other electrocatalysts. Furthermore, the validation by DMFC single-cell test showed that PtRu/Ti 3 C 2 T x electrocatalyst improves the performance almost 70 % compared to the Pt/C electrocatalyst. This excellent electrochemical and single-cell performance of PtRu/Ti 3 C 2 T x electrocatalyst validates its potential to be one of the promising candidates for the anodic electrocatalyst in DMFC application.

Passive direct methanol fuel cells acting as fully autonomous electrochemical biosensors: Application to sarcosine detection

This work describes an innovative electrochemical biosensor that advances its autonomy toward an equipment-free design. The biosensor is powered by a passive direct methanol fuel cell (DMFC) and signals the response via an electrochromic display. Briefly, the anode side of the DMFC power source was modified with a biosensor layer developed using molecularly imprinted polymer (MIP) technology to detect sarcosine (an amino acid derivative that is a potential cancer biomarker). The biosensor layer was anchored on the surface of the anode carbon electrode (carbon black with Pt/Ru, 40:20). This was done by bulk radical polymerization with acrylamide, bis-acrylamide, and vinyl phosphonic acid. This layer selectively interacted with sarcosine when integrated into the passive DMFC (single or multiple, in a stack of 4), which acted as a transducer element in a concentration-dependent process. Serial assembly of a stack of hybrid DMFC/biosensor devices triggered an external electrochromic cell (EC) that produced a colour change. Calibrations showed a concentration-dependent sarcosine response from 3.2 to 2000 µM, which is compatible with the concentration of sarcosine in the blood of prostate cancer patients. The final DMFC/biosensor-EC platform showed a colour change perceptible to the naked eye in the presence of increasing sarcosine concentrations. This colour change was controlled by the DMFC operation, making this approach a self-controlled and self-signalling device. Overall, this approach is a proof-of-concept for a fully autonomous biosensor powered by a chemical fuel. This simple and low-cost approach offers the potential to be deployed anywhere and is particularly suitable for point-of-care (POC) analysis.

Improved the Methanol Electro-Oxidation and Carbon Monoxide Tolerance for Direct Methanol Fuel Cells Using Strontium Molybdate

A high methanol electro-oxidation (MOR) and carbon monoxide (CO) tolerance satisfied the electrochemical requirements of direct methanol fuel cells (DMFCs). The study investigated strontium molybdate (SrMoO4) mixed with Vulcan XC-72, carbon-loaded with 20% Pt. The electrochemical performance was confirmed by MOR and CO tolerance activities measured via cyclic voltammetry (CV). The synergistic effect between Pt and SrMoO4 is essential to affect the electrochemical characteristic. SrMoO4 can help remove CO-like intermediate products on the Pt surface, enhancing electrochemical performance for DMFCs. In addition, HxMoO3/HyMoO3 existence in Sr0.5Mo0.5O4−δ can quickly remove intermediates from Pt surfaces and accelerate the transformation of adsorbed intermediates to CO2. The results obtained showed that 20%-Pt/uncalcined Sr0.5Mo0.5O4−δ-C electrocatalyst has higher MOR and CO tolerance ability in DMFCs. Furthermore, the fabricated DMFC shows excellent long-term electrochemical stability after 1000 cycles and a maximum power density (1.42 mW/cm2) higher than commercial 20%-Pt/C (1.27 mW/cm2).