Methanol Fuel Cell Applications Research Articles

A versatile non-precious metal based electrode material endowed by layer-on-layer structure for methanol oxidation and supercapacitor applications

A high-performance non-noble metal-based electrode is the need of the hour to resolve the challenge of huge energy demand. Energy conversion and storage devices are the two ways to tackle this challenge. In this context, porous and non-noble metal-based electrodes NiCo2O4 (NCO), NiCo2O4/NiO (CNO) and NiCo2O4/NiO/rGO (CNOG) are developed as a bifunctional electrode for supercapacitor and methanol fuel cell applications. The binary composite of NiCo2O4 with NiO increases the redox sites and enhances its electrochemical activity. The low conductivity and problem of aggregation of transition metal oxides are overcome by developing a hybrid nanocomposite of NiCo2O4/NiO with reduced graphene oxide (rGO). The layer-on-layer morphology of CNOG, and the interfacial interactions among NiCo2O4 nanoflakes, NiO nanoparticles and rGO nanosheets increase the specific surface area of the hybrid, which leads to enhanced ion penetration into the active sites. CNOG acts as a potential anode catalyst for methanol oxidation with excellent structural stability. It exhibits a high methanol oxidation current density with low onset potential and faster kinetics. Symmetric supercapacitor CNOG//CNOG delivers specific capacitance of 59.4989 F/g, energy and power density of 6.69 Wh/kg and 698 W/kg respectively at 3 M KOH aqueous electrolyte. The solid-state symmetric supercapacitor (SSSC) using PVA/KOH electrolyte allows broader potential window, thereby outperforming the aqueous electrolyte. The SSSC exhibits specific capacitance of 88.8 F/g, energy and power density 20.84 Wh/kg and 1003 W/kg respectively at the same current density.

Sheet-Isolated MoS2 Used for Dispersing Pt Nanoparticles and its Application in Methanol Fuel Cells.

It is highly challenging to activate the basal plane and minimize the π-π stacking of MoS2 sheets, thus enhancing its catalytic performance. Here, we display an approach for making well-dispersed MoS2 . By using the N-doped multi-walled carbon nanotubes (NMWCNTs) as an isolation unit, the aggregation of MoS2 sheets was effectively reduced, favoring the dispersion of Pt nanoparticles (noted as Pt/NMWCNTs-isolated-MoS2 ). Excellent bifunctional catalytic performance for methanol oxidation and oxygen reduction reaction (MOR/ORR) were demonstrated by the produced Pt/NMWCNTs-isolated-MoS2 . In comparison to Pt nanoparticles supported on MoS2 (Pt/MoS2 ), the MOR activity (2314.14 mA mgpt -1 ) and stability (317.69 mA mgpt -1 after 2 h of operation) on Pt/NMWCNTs-isolatedMoS2 were 24 and 232 times higher, respectively. As for ORR, Pt/NMWCNTs-isolated-MoS2 holds large half-wave potential (0.88 V) and high stability (92.71 % after 22 h of operation). This work presents a tactic for activating the basal planes and reducing the π-π stacking of 2D materials to satisfy their applications in electrocatalysis. In addition, the proposed sheet-isolation method can be used for fabricating other 2D materials to promote the dispersion of nanoparticles, which assist its application in other fields of energy as well as the environment.

Ultrasonication-Assisted Synthesis of Nickel Tungstate Decorated on Polydimethoxyaniline Nanocomposite Catalyst for Potential Direct- Methanol Fuel-Cell Application

Ultrasonication-Assisted Synthesis of Nickel Tungstate Decorated on Polydimethoxyaniline Nanocomposite Catalyst for Potential Direct- Methanol Fuel-Cell Application

Bi-Mn diatomic interaction on SOD zeolite substrate promotes electrochemical methanol oxidation

The strategy of diatomic synergy is applied to the in-situ synthesis of electrode catalyst material for methanol fuel cells. During the one-pot synthesis in hydrothermal conditions, the doped Bi and Mn atoms are highly dispersed on and immobilized into the SOD zeolite cage structure as nanocrystals with trace amounts to form the novel Bi/Mn/SOD composite catalyst. The as-synthesized Bi and Mn NPs were confined in a rigid SOD nano-cage to maintain the stability and catalytic activity of the monodisperse state. Several key problems to be solved in methanol fuel cell applications are its energy density, catalytic efficiency, stability, and cost. Through the combined action of Mn and Bi, the composite electrode performed high activity in the methanol oxidation reaction (MOR) with a high current density of 45.9 mA cm−2 without precious metal and with high stability in 10 M methanol without any catalyst poisoning.

Synthesis and Characterization of Chitosan/κ-Carrageenan/Mesoporous Phosphotungstic Acid (mPTA) Electrolyte Membranes for Direct Methanol Fuel Cell (DMFC) Applications

A new biopolymer based on chitosan and k-carrageenan with the addition of mesoporous phosphoric acid (mPTA) filler was used as an electrolyte membrane for Direct Methanol Fuel Cell (DMFC) applications. Electrolyte membranes of pure solution of chitosan, k-carrageenan, and various compositions of chitosan/k-carrageenan (Cs/k-Car) (80/40, 90/30, 100/20 mL) were carried out to determine the composition of chitosan/k-carrageenan optimal. The optimum chitosan/k-carrageenan membrane is Cs/k-Car 80/40 which has a tensile strength of 22.00 MPa and a methanol permeability of 14.33 x 10-6 cm2/s. Membrane Cs/k-Car 80/40 was then added with variations of mesoporous phosphotungstic acid (mPTA) filler (0.05, 0.1, 0.15, 0.2 and 0.25 %) to determine the optimum membrane electrolyte. The chitosan/k-carrageenan/mPTA 0,2% (Cs/k-Car/mPTA 0.2%) electrolyte membrane is the most optimum electrolyte membrane which has a proton conductivity of 12 x 10-3 S/cm and a methanol permeability of 7.64 x 10-6 cm2/s so it is expected to be the most suitable electrolyte membrane for DMFC application. Key words : Electrolyte membrane, chitosan, k-carrageenan, mesoporous phosphoric acid (mPTA), DMFC

Highly exposed Fe-N4 active sites in porous poly-iron-phthalocyanine based oxygen reduction electrocatalyst with ultrahigh performance for air cathode.

Progress in the development of efficient electrocatalysts for oxygen reduction reactions is imperative for various energy systems such as metal-air batteries and fuel cells. In this paper, an innovative porous two-dimensional (2D) poly-iron-phthalocyanine (PFe-Pc) based oxygen reduction electrocatalyst created with a simple solid-state chemical reaction without pyrolysis is reported. In this strategy, silicon dioxide nanoparticles play a pivotal role in preserving the Fe-N4 structure during the polymerization process and thereby assist in the development of a porous structure. The new polymerized phthalocyanine electrocatalyst with tuned porous structure, improved specific surface area and more exposed catalytic active sites via the 2D structure shows an excellent performance towards an oxygen reduction reaction in alkaline media. The onset potential (E = 1.033 V) and limiting current density (I = 5.58 mA cm-2) are much better than those obtained with the commercial 20% platinum/carbon electrocatalyst (1.046 V and 4.89 mA cm-2) and also show better stability and tolerance to methanol crossover. For practical applications, a zinc-air (Zn-air) battery and methanol fuel cell equipped with the PFe-Pc electrocatalyst as an air cathode reveal a high open circuit voltage and maximum power output (1.0 V and 23.6 mW cm-2 for a methanol fuel cell, and 1.6 V and 192 mW cm-2 for the liquid Zn-air battery). In addition, using the PFe-Pc electrocatalyst as an air cathode in a flexible cable-type Zn-air battery exhibits excellent performance with an open-circuit voltage of 1.409 V. This novel porous 2D PFe-Pc has been designed logically using a new, simple strategy with ultrahigh electrochemical performances in Zn-air batteries and methanol fuel cell applications.

Preparation of Poly Eter Eter Keton as Alternative Membrane for Direct Methanol Fuel Cell (DMFC)

The objective of this study focuses on the characterization of polyetheretherketone (PEEK) membranes for direct methanol fuel cells (DMFC) application. The PEEK membrane was modified with sulfonation and charged surface modifying macromolecule (cSMM) using MDI, DEG and HBS in NMP solvent. The characterized of membrane were done using Scanning Electron Microscopy (SEM), water uptake, contact angle, thermal stability, methanol permeability, proton conductivity and DMFC test. DMFC tests were performed at room temperature to obtain polarization curves that show voltages and power density of each variable. The results showed that the cSMM methode of the polymer increases water uptake, thermal stability, methanol permeability and proton conductivity. In terms of morphology, it was found that cSMM method can be applied for membrane modification for DMFC application. In terms of the DMFC tests of the membranes, SPEEK without modification proved to have the best performance in stability because of its low methanol permeability. In contrast, the best performance was achieved by the SPEEK/cSMM (with modification) in highest voltage and power density because of its high proton conductivity.

The Influence of Chitosan Membrane Properties for Direct Methanol Fuel Cell Applications

The chitosan membranes with different degrees of deacetylation (dda), prepared from Cape rock lobster collected from the surroundings of Cape Town, South Africa were characterized for suitability in methanol fuel cell applications. A comparison of chitosan membranes characteristics and that of conventional Nafion 117 membranes were made. Following this, the chitosan membranes were chemically modified with sulfuric acid to improve its proton conductivity and mechanical properties. A mass balance on proton transfer across the membrane resulted in a second order differential equation. Experimental data fitted into the equation gives a linear curve that was used to determine the membrane resistance. It was found that the dda of the chitosan membranes affected the water uptake, thereby affecting the proton flow. At a temperature of 20°C, chitosan membranes with a difference of 10% dda have a difference of about 5% water content. Chitosan membranes with a lower dda were found to have higher water content resulting in lower membrane resistances to proton flow. The water content of chitosan membranes was higher than Nafion membranes. The average resistance to proton flow for chitosan membrane was 53 min/cm and a Nafion membrane was 78 min/cm. Thermogravimetry analysis shows that chitosan membrane with higher dda is more thermally stable than chitosan with lower dda, Nafion membranes were more stable at higher temperature than chitosan membranes, Nafion membranes could decompose at temperature of 320 °C while chitosan membranes at 230 °C. Methanol permeability through chitosan membrane of higher dda was more than with one lower dda, however, the permeability through chitosan was three times lower when compares to Nafion membranes under the same temperature and pressure conditions. The performance of chitosan membranes and Nafion 117 membranes measured from a single cell DMFC with Pt-Ru/C anode catalysts and Pt/C cathode catalysts showed that Nafion membranes have a better performance. This was because the current and peak power densities determined for Nafion membranes were 0.56 A/cm2 and 0.075 W/cm2, respectively, and for Chit-I, were 0.22 A/cm2 and 0.0274 W/cm2, respectively, and for Chit-II membrane, were 0.26 A/cm2 and 0.0424 W/cm2, respectively.

Preparation of Proton Exchange Membranes by a Plasma Polymerization Method and Application in Direct Methanol Fuel Cells (DMFCs)

Preparation of Proton Exchange Membranes by a Plasma Polymerization Method and Application in Direct Methanol Fuel Cells (DMFCs)

Application of Green Chemistry Techniques to Prepare Electrocatalysts for Direct Methanol Fuel Cells

A series of green techniques for synthesizing carbon nanotube-supported platinum nanoparticles and their high electrocatalytic activity toward methanol fuel cell applications are reported. The techniques utilize either the supercritical fluid carbon dioxide or water as a medium for depositing platinum nanoparticles on surfaces of multiwalled or single-walled carbon nanotubes. The catalytic properties of the carbon nanotubes-supported Pt nanoparticle catalysts prepared by four different techniques are compared for anodic oxidation of methanol and cathodic reduction of oxygen using cyclic voltammetry. One technique using galvanic exchange of Pt(2+) in water with zerovalent iron present on the surfaces of as-grown single-walled carbon nanotubes produces a Pt catalyst that shows an unusually high catalytic activity for reduction of oxygen but a negligible activity for oxidation of methanol. This fuel-selective catalyst may have a unique application as a cathode catalyst in methanol fuel cells to alleviate the problems caused by crossover of methanol through the polymer electrolyte membrane.

SPEEK-based Composite Membranes for Direct Methanol Fuel Cells

AbstractSulfonated polyether ether ketone (SPEEK)-based composite membranes doped with 23 and 50 wt% of hydrated tin oxide (SnO2·nH2O) were prepared and characterized for Direct Methanol Fuel Cell (DMFC) applications . The composite membranes were characterized in terms of ion exchange capacity (IEC), tensile tests, water uptake measurements, electrochemical impedance spectroscopy (EIS), and Pulsed-field-gradient spin-echo nuclear magnetic resonance (PFGSE NMR) spectroscopy. The body of results indicated the involvement of hydrated tin oxide in the proton conduction mechanism, the inorganic phase providing additional paths between the water clusters for proton transport. NMR measurements evidenced that SnO2·nH2O particles not only facilitate the proton transport but also hinder water diffusion. Therefore, due to the selectivity of SnO2·nH2O for proton diffusion, the filler effect was found to be also beneficial for the reduction of methanol crossover through the SPEEK membrane and for improving the performance of the SPEEK membrane when used as electrolyte in a DMFC test station.

Reactions of methanol and water over carbide-modified Mo( [formula omitted

The reactions of methanol and water over clean and carbide-modified Mo(1 1 0) have been studied using temperature-programmed desorption, high-resolution electron energy loss spectroscopy, and Auger electron spectroscopy. The product selectivity of methanol on unmodified Mo(1 1 0) is 84% toward complete decomposition and 16% toward the production of CO. After the Mo(1 1 0) surface is modified by carbon, the complete decomposition pathway decreases to 63%, with the remaining methanol dissociating to produce CO. The absence of a reaction pathway to produce methane on the C/Mo(1 1 0) surface is distinctly different from that on the C/W(1 1 1) and C/W(1 1 0) surfaces. On Mo(1 1 0), the amount of H 2O undergoing dissociation is determined to be 0.25 molecules per Mo atom. Upon carbon modification, the activity of water decreases slightly to 0.20 molecules per Mo atom. These results indicate that the C/Mo(1 1 0) surface is more active toward the dissociation of H 2O than either C/W(1 1 1) or C/W(1 1 0). Overall, the comparison of the current study to our previous investigations on C/W(1 1 1) and C/W(1 1 0) provides insights into the possible role of molybdenum carbides as promoters for tungsten carbide electrocatalysts in methanol fuel cell applications.

Pervaporation membranes in direct methanol fuel cells

The membranes in direct methanol fuel cells must both conduct protons and serve as a barrier for methanol. Nafion, the most common fuel cell membrane, is an excellent conductor but a poor barrier. Polyvinyl alcohol pervaporation membranes are good methanol barriers but poor conductors. These and most other pervaporation membranes offer no significant advantages over Nafion in methanol fuel cell applications. However, polybenzimidazole membranes have demonstrated characteristics that suggest up to a 15-fold improvement in direct methanol fuel cells. This improvement may be due to an alternate form of proton conduction in which protons travel via a Grotthus or “hopping” mechanism.