Methanol Electrooxidation In Alkaline Media Research Articles

Unlocking efficient methanol electro-oxidation in alkaline medium with non-stoichiometric 3D sphere-like Cu3Mo2O9@CoMoO4 heterostructure

In order to unlock the full potential of direct methanol fuel cells (DMFCs), there is a pressing need for the development of cost-effective catalysts that don't rely on precious metals. Within this context, we have successfully synthesized a non-stoichiometric three-dimensional (3D) sphere-like Cu3Mo2O9@CoMoO4 heterostructure using a straightforward two-step hydrothermal process. A range of analytical techniques was utilized to explore the physical and chemical properties of this Cu3Mo2O9@CoMoO4 in comparison to their constituents' parts, one-dimensional (1D) rod-like Cu3Mo2O9 and CoMoO4 microstructures. X-ray photoelectron spectroscopy (XPS) was employed for the quantitative assessment of the non-stoichiometric composition of elements such as Cu, Co, and Mo within the heterostructure. This outcome was additionally corroborated by data obtained through analysis using field emission scanning electron microscopy (FESEM) with energy-dispersive X-ray spectroscopy (EDS). The heterostructure showed highly porous characteristics and displayed a large surface area of 42.54 m2 g−1 compared to Cu3Mo2O9 and CoMoO4. This configuration yields a notably preeminent current response for methanol electro-oxidation (MOR), reaching 202.8 mA cm−2 at a scan rate of 50 mV s−1 within the voltage range of 0.0–0.7 V (vs. Hg/HgO). In comparison, both Cu3Mo2O9 and CoMoO4 exhibit lower methanol electro-oxidation currents of 154.9 mA cm−2 and 120 mA cm−2, respectively. After examination by chronoamperometry for 10 h, the Cu3Mo2O9@CoMoO4 exhibited good stability performance. This research illustrates that the synergistic effects between Cu3Mo2O9 and CoMoO4 within Cu3Mo2O9@CoMoO4 heterostructure can significantly boost electrocatalytic capabilities. This enhancement opens extensive avenues for advancing cost-effective electrocatalyst materials for the broader advancement of efficient MOR processes.

Electrodeposited Nickel Sulfide Nanoparticles Incorporated Carbon Nanofibers as Effective Non‐Precious Catalyst for Methanol Electrooxidation in Alkaline Medium

AbstractFor direct methanol fuel cells, developing low‐cost, highly efficient, and long‐term stable electrocatalysts is crucial. In this work, we report easy and single‐step electrodeposition of nickel sulfide thin film incorporating carbon nanofibers on indium tin oxide (denoted as Ni4S3‐CNF/ITO). The electrodeposited materials were characterized by X‐ray Diffraction, Scanning Electron Microscopy, and Energy Dispersive X‐ray spectroscopy. The electrocatalytic activity toward Methanol Oxidation Reaction (MOR) was investigated using Cyclic Voltammetry, Chrono‐Amperometry, and Electrochemical Impedance Spectroscopy. The electrocatalyst exhibited good electrocatalytic activity regarding methanol electrooxidation in an alkaline medium with retention of its activity over a significant period of time. These results indicate that the incorporation of carbon nanofibers into nickel sulfide allows the electrocatalyst to gain higher surface area and high tolerance to the catalyst‐poising species generated during MOR. The electrocatalytic activity of electrodeposited Ni4S3‐CNF/ITO makes it a promising electrocatalyst for low‐cost, high‐efficient fuel cells.

Electrochemical properties of NiO–Ni electrocatalyst synthesized via solution combustion for methanol oxidation in alkaline media

Transition metal oxides have been recently considered as the anode catalyst in direct methanol fuel cells to reduce the anodic overpotential of methanol electrooxidation in alkaline media. In this work, the NiO–Ni catalyst is synthesized via solution combustion synthesis process to reach an appropriate nanomorphology with high effective surface area and electrocatalytic activity. The influence of the fuel type (glycine and urea) and the fuel to oxidizer (F/O) ratio are investigated. The composition and phase analysis, crystallite size, particle size, specific surface area, and morphology of the nanoparticles are assessed. Moreover, electrochemical characteristics of the products are evaluated. The catalytic activity of the product towards methanol oxidation is found to vary with the fuel type and F/O ratio. The dependence of the oxidation current on the adiabatic temperature and morphological characteristics of the product is discussed. It is found that solution combustion synthesis is a confident technique that provides a considerable improvement in catalytic performance. Moreover, it is concluded that samples with dominant NiO show lower onset potential and higher current density. Synthesis by glycine in the most explosive condition (i.e., F/O = 0.83) results in more desirable catalytic activity.

Improved methanol electro-oxidation reaction on PdRh-PVP/C electrodes

Here we report on the organometallic synthesis of polyvinylpyrrolidone (PVP)-stabilized palladium-rhodium nanostructures that display high electrochemical properties when used as carbon-supported electrodes (PdxRh1-x-PVP/C) for methanol oxidation reaction (MOR). These nanostructures were synthesized by hydrogenation of the tris(dibenzylideneacetone)dipalladium(0) (Pd2(dba)3) and tris(allyl) rhodium (Rh(η3-C3H5)3) complexes, in tetrahydrofuran (THF) under mild reaction conditions (room temperature and 3 bar H2) and in the presence of PVP as stabilizer. The influence of methanol concentration (0.5, 1.0 and 2.0 M) as well as different scan rates (5–100 mV s−1) was evaluated to determine changes in the stability and catalytic activity. The organometallic approach and the use of PVP for the preparation of PdRh electrode materials promoted the formation of highly dispersed nanostructures, that led to a remarkably enhanced methanol electro-oxidation in alkaline medium. This high catalytic behavior can reasonably arise from a synergistic effect between Pd and Rh metals as, under the applied conditions, Rh is expected to enhance the Pd ability to oxidize methanol to CO2 (oxophilic character) as well as the catalyst stability. From all the evaluated electrode materials, Pd8Rh2-PVP/C electrode showed the highest mass activity at high methanol concentration (2.0 M) and low scan rate (10 mV s−1). This catalyst showed a performance up to 26 times higher than that of Pd-PVP/C and interestingly an electroactivity superior to that of previously reported PdRh catalysts.

Comparative study of Pd-based electrocatalysts decorated on hybrid carbon supports towards methanol oxidation

One suitable strategy to improve the utilisation and performance of Pd-based catalysts in direct methanol fuel cells (DMFCs) is by combining or blending carbon supports. In this study, Pd nanoparticles (NPs) were decorated on bi-hybrid carbon supports consisting of carbon nanotubes (CNTs), graphene nanoplates (GNPs) and carbon black (XC-72) with varying ratios of CNTs: GNPs, CNTs: XC-72 and XC-72: GNPsthrough microwave-assisted ethylene glycol (EG) reduction. All as-prepared catalysts were characterisedby Transmission Electron Microscope (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and their electrocatalytic activities towards methanol oxidation reaction (MOR) in alkaline solution were investigated by electrochemical measurements. Results indicated that the use of hybrid supports for catalysts substantially increases the electrochemical surface area, reduces the overpotential to methanol oxidation and improves kinetic performance. These effects can be attributed to the unique structure formed after mixing that allows for complete surface utilisation.Among the bi-hybrid electrocatalysts, Pd/CNT-GNP (1:0.1), Pd/CNT-XC-72(1:0.2) and Pd/XC-72-GNP (1:0.2) catalysts have higher activity and better performance.Particularly, Pd/CNT-GNP (1:0.1) catalyst shows a superior activity and the highest oxidation peak current density towards MOR at 57.34 mA/cm2.TEM and XRD results show that the catalyst nanoparticles on the bi-hybrid carbon support have good dispersion, are not agglomerated and havea small particle size. Hence, the catalyst exhibits an optimised performance and long stability towards methanol electrooxidation in alkaline media.

Comparative Study of the Synthesis of sub‐10 nm Carbon‐Supported Gold Nanoparticles and their Suitability for Methanol Electrooxidation in Alkaline Media

AbstractGold nanoparticles where synthesized and supported on carbon, or directly synthesized on carbon according to five different methods reported in literature, aiming at particles<10 nm. Characterization was done with transmission electron microscopy and thermogravimetric analysis. Although all syntheses yielded particles with an average diameter<10 nm, the formation of few very large particles, where a relatively large amount of Au is buried, as well as loss during the supporting procedure led to the exclusion of four of the five tested methods for further studies. The most promising AuNPs supported on carbon where tested for the methanol electrooxidation (MEO) in alkaline media. Four different Au‐loadings where realized, and supporting led to moderate particle growth depending on the loading. To compare MEO activity of the samples with different Au‐loadings a conversion factor was developed where the MEO activity can be compared in terms of NP size and Au‐loading.

Liquid Metal Interfacial Growth and Exfoliation to Form Mesoporous Metallic Nanosheets for Alkaline Methanol Electroreforming

Two-dimensional (2D) materials have spurred great interest in the field of catalysis due to their fascinating electronic and thermal transport properties. However, adding uniform mesopores to 2D metallic materials has remained a great challenge owing to the inherent high surface energy. Here, we introduce a generic liquid metal interfacial growth and exfoliation strategy to synthesize a library of penetrating mesoporous metallic nanosheets. The formation of liquid-metal/water interface promotes the adsorption of metal ion-encapsulated copolymer micelles, induces the self-limiting galvanic replacement reaction, and enables the exfoliation of products under mechanical agitation. These 2D mesoporous metallic nanosheets with large lateral size, narrow thickness distribution, and uniform perforated structure provide facilitated channels and abundant active sites for catalysis. Typically, the generated mesoporous PtRh nanosheets (mPtRh NSs) exhibit superior electroactivity and durability in hydrogen evolution reaction as well as methanol electrooxidation in alkaline media. Moreover, the constructed symmetric mPtRh NSs cell requires only a relative low electrolysis voltage to achieve methanol-assisted hydrogen production compared with traditional overall water electrolysis. The work reveals a specific growth pattern of noble metals at the liquid-metal/water interface and thus introduces a versatile strategy to form 2D penetrating mesoporous metallic nanomaterials with extensive high-performance applications.

Performance Improvement of Gold Electrode towards Methanol Electrooxidation in Akaline Medium: Enhanced Current Density Achieved with Poly(aniline-co-2-hydroxyaniline) Coating at Low Overpotential.

Electronically conducting poly (aniline-co-2-hydroxyaniline) (PACHA), a copolymer of aniline and 2-hydroxyaniline (2HA), was electrochemically coated on gold substrate for methanol electrooxidation in alkaline media. The electrochemical behavior of PACHA coated gold electrode towards methanol electrooxidation was investigated via cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) for application in an alkaline fuel cell. Methanol electrooxidation was observed at two different electrode potentials depending on the concentration of the base. At the PACHA coated gold electrode, the methanol oxidation peak was observed at lower overpotential (at 0.19 V) in a solution of high base concentration (1.8 M NaOH), which was 30 mV lower than the peak for the uncoated gold electrode. In addition, the Faradic current Imax obtained on the PACHA coated electrode (20 mA) was two times higher as compared to the Faradic current Imax of the un-modified gold electrode (10 mA). In solution of lower base concentration (0.06 M NaOH), the electrooxidation of methanol became sluggish on both electrodes, as indicated by peak shifting towards positive potential and with reduced faradaic current (at 0.74 V on PACHA coated electrode; Imax 10 mA). The electrooxidation of methanol at both lower and higher electrode potentials was analyzed mechanistically and discussed in light of the literature. EIS results were interpreted using Nyquist and Bode plots. The charge transfer resistance was decreased and pseudo-capacitive behavior changed to conductive behavior when external applied potential was increased from 0.1 V to 0.4 V.

Synthesis and characterization of Nickel sulfide and Nickel sulfide/Molybdenum disulfide nanocomposite modified ITO electrode as efficient anode for methanol electrooxidation

The synthesis of cheap and efficient materials for developing fuel cells is challenging for researchers. In this study, nickel sulfide nanoparticles (NiS NPs) and nickel sulfide/molybdenum disulfide (NiS/MoS2) nanocomposite modified ITO electrodes were synthesized based on a simple and facile hydrothermal method. Raman spectroscopy, X-ray diffraction, SEM, FTIR, and energy dispersive X-ray spectroscopy analysis were used to study the morphologies, structures, and phase identification of the electrocatalysts. The electrocatalytic activities of the modified electrodes towards the methanol oxidation reaction were also evaluated based on the cyclic voltammetry technique. The results indicated that NiS/MoS2 exhibited higher electrocatalytic activity towards the methanol electrooxidation in alkaline media that could be attributed to the uses of MoS2 with high surface area, which facilitates the diffusion of methanol molecules. Thus, the NiS/MoS2 is a good candidate for application in the direct methanol fuel cell.

Highly Stable NiCoZn Ternary Mixed-Metal-Oxide Nanorods as a Low-Cost, Non-Noble Electrocatalyst for Methanol Electro-Oxidation in Alkaline Medium

There is an imperative necessity to develop low-cost and efficient nanocatalysts as a substitute for expensive and rare noble-metal catalysts such as platinum (Pt) and gold (Au) in overcoming the limitations of carbon monoxide and intermediate poisoning in direct methanol fuel cells (DMFCs). Herein, we report a simple, one-step hydrothermal synthesis of NiCoZn ternary mixed-metal-oxide nanorod (NCZMMO)-modified glassy carbon electrode (NCZMMO/GCE) for DMFC application. The NCZMMO/GCE electrode exhibits outstanding electro-oxidation of methanol (MeOH) at a low onset potential of 0.30 V (vs Ag|AgCl) with a high current density of 414 mA/mg in an alkaline medium (1 M KOH). This outstanding performance of the electrode is ascribed to the synergistic outcome of NCZMMO nanorods, where Ni imparts the electrocatalytic active sites for methanol oxidation reaction (MOR) through its multiple oxidation states while the excellent mechanical and chemical stability of the electrode is attributed to the oxides of Co and Zn. The electrode exhibits outstanding durability with 75% retention even at 5000 s of chronoamperometry analysis in the presence of 0.5 M MeOH, which is far superior to other reported noble-metal electrocatalysts. This superior performance of NCZMMO frontlines it as a promising non-noble, low-cost electrocatalyst for various energy conversion applications.

The Effect of Tin Addition to Platinum Catalysts with Different Morphologies towards Methanol Electrooxidation in Alkaline Media

Direct methanol fuel cells (DMFCs) using anion exchange membranes have been attracting great interest. Thus, it is very important to develop electrocatalysts for methanol electrooxidation reaction (MEOR) in alkaline media. In this study, the effects of platinum nanoparticle morphology and presence of tin oxide in the electrocatalysts were investigated. Platinum and platinum-tin nanoparticles with cubic-like shape and (100) preferential orientation supported on carbon, Pt/C(100) and PtSnO2/C(100), were synthesized by the alcohol-reduction process using KBr as the shape-directing agent. Polycrystalline nanoparticles supported on carbon, Pt/C, and PtSnO2/C were also synthesized. The catalytic activity of the nanomaterials toward MEOR in alkaline media was investigated by cyclic voltammetry (CV) and chronoamperometry (CA). High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) analysis showed cubic Pt nanoparticles and SnO2 dispersed on the carbon support. X-ray diffraction (XRD) showed peaks of SnO2 cassiterite and peaks of the face-centered cubic (FCC) structure of Pt. CV experiments showed that the maximum current density from MEOR on Pt/C(100) (current density of about 108 mA cm–2 mg–1 of Pt) is about 2.4, 2.1, and 1.1 times higher than on Pt/C, PtSnO2/C, and PtSnO2/C(100), respectively. The same trend was observed in CA experiments. The higher catalytic activity of Pt(100) might be related to the OHads species coverage on it. SnO2 increases the catalytic activity on polycrystalline platinum, probably due to the OHads species provided by it. On the other hand, for Pt(100), the presence of SnO2 results in a decrease of the catalytic activity towards MEOR.

NiPd Supported on Mesostructured Silica Nanoparticle as Efficient Anode Electrocatalyst for Methanol Electrooxidation in Alkaline Media

The direct methanol fuel cell (DMFC) is a portable device and has the potential to produce 10 times higher energy density than lithium-ion rechargeable batteries. It is essential to build efficient methanol electrooxidation reaction electrocatalysts for DMFCs to achieve their practical application in future energy storage and conversion. A catalyst consisting of nickel–palladium supported onto mesostructured silica nanoparticles (NiPd–MSN) was synthesized by the wet impregnation method, while MSN was synthesized using the sol-gel method. MSN act as a catalyst support and has very good characteristics for practical support due to its large surface area (>1000 m2/g) and good chemical and mechanical stability. The microstructure and catalytic activity of the electrocatalysts were analyzed by X-ray diffraction (XRD), Fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM), Brunauer–Emmet–Teller (BET) theory, X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and chronoamperometry (CA). XRD showed that the NiPd–MSN electrocatalysts had a high crystallinity of PdO and NiO, while FESEM displayed that NiPd was dispersed homogeneously onto the high surface area of MSN. In alkaline media, the catalytic activity toward the methanol oxidation reaction (MOR) of NiPd–MSN demonstrated the highest, which was 657.03 mA mg−1 more than the other electrocatalysts. After 3600 s of CA analysis at −0.2 V (vs. Ag/AgCl), the MOR mass activity of NiPd–MSN in alkaline media was retained at a higher mass activity of 190.8 mA mg−1 while the other electrocatalyst was significantly lower than that. This electrocatalyst is a promising anode material toward MOR in alkaline media.

Electrocatalysis of Pd–Er bimetallic catalysts for methanol oxidation in alkaline media

The Pd–Er/C catalysts with different Pd/Er ratios were synthesized through a simple simultaneous reduction reaction with sodium borohydride in aqueous solution. The structural and morphological features were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The electrocatalytic performance of those catalysts for methanol oxidation in alkaline media was tested using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). It is found that the Pd-4Er/C catalyst has a higher catalytic activity than the Pd/C catalyst. CO stripping experiments show its good resistance to CO poisoning, which can be explained by a bifunctional mechanism. According to the results from the X-ray photoelectron spectroscopy (XPS), the higher content of metallic Pd caused by the doping of metal Er also accounts for the improvement of catalytic performance. This work provides a highly efficient catalyst for methanol electrooxidation in alkaline media.

Efficient stabilization of in situ fabrication of PtxPd1-x nanostructures for electro-oxidation of methanol in alkaline medium

Different binary PtxPd1-x alloys supported on Vulcan carbon XC-72R were synthesized by the displacement of ligands from organometallic compounds to be used as anodic electrode for methanol electro-oxidation in alkaline medium. The influence of the Pd addition during the synthesis of PtxPd1-x alloys in presence of octylamine as stabilizer was analyzed in terms of structure, chemical composition and electroactivity in the methanol oxidation reaction. The X-ray photoelectron spectroscopy analysis showed that the surface of the electrodes consisted of a metallic mixture and oxide states, which confirmed the change in the electronic properties during the alloy formation. The current density of Pt30Pd70/C during CV measurements was about 2.1 times higher than the one observed with Pt/C electrodes. The CO tolerance was also slightly improved under similar conditions. The work findings indicate that stabilized Pt30Pd70/C binary alloys can be used to design highly active anodic catalysts with potential applications in direct methanol fuel cells (DMFCs).

Synthesis of ternary electrocatalysts for exploration of methanol electro-oxidation in alkaline media

In the quest for alternate and efficient electrode materials, ternary metal electrocatalysts (TMEs), part of the perovskite family, were synthesized and tested for methanol electro-oxidation in alkaline media. La0.5Ca0.5MO3 (M = Ni, Co, or Mn) was synthesized via sol-gel method. X-ray diffraction analysis revealed that the perovskite crystal structure possesses characteristic sharp and crystalline peaks for all synthesized ternary electrocatalysts. The average particle size calculated using Debye–Scherrer equation was in the order of La0.5Ca0.5NiO3 (LCNO) > La0.5Ca0.5CoO3 (LCCO)> La0.5Ca0.5MnO3 (LCMO). The elemental composition of as prepared sample, LCCO was investigated via x-ray fluorescence spectroscopy. The qualitative and quantitative analysis revealed the presence of La, Ca and Co in parent crystal structure with percentage compositions of 9.0, 3.12 and 87.82% respectively. The particle size distribution was homogenous, as determined by scanning electron and transmission electron microscopes. The electrocatalytic activity of the synthesized ternary electrocatalysts was studied electrochemically by cyclic voltammetry. The calculated diffusion coefficient values showed that electrode surface of LCNO and LCCO have limited efficiency for diffusion related phenomenon. The heterogeneous rate constants inferred better electrode kinetics of LCCO and LCNO which exhibited good electrocatalytic behavior; sharp anodic peaks were observed in the potential range of +0.3 to 0.6 V and +0.6 to 0.8 V, respectively. Methanol electro-oxidation was found minimal in case of LCMO sample. We have observed that Co substitution at B-site of perovskite electrode materials attains better electrochemical properties, thus in relation with reported literature.

CuWO₄ Nanoparticles: Investigation of Dielectric, Electrochemical Behaviour and Photodegradation of Pharmaceutical Waste.

The hydrothermally synthesized CuWO₄ nanoparticles (NPs) were characterized with different analysis such as X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM), Energy Dispersive X-ray Spectroscopy (EDX), Cyclic Voltammetry (CV), UV-Visible and Photoluminescence (PL) analysis. The prepared CuWO₄ NPs were examined with Electrochemical Impedance Spectroscopy (EIS). SEM images show that CuWO₄ NPs are highly spherical shaped morphology and porous in nature. The optical band gap of prepared CuWO₄ NPs is found to be 2.12 eV. Photodegradation of diclofenac sodium (DFS) (medical waste) in the aqueous medium with CuWO₄ NPs under visible light irradiation shows 98% degradation. The CuWO₄ NPs was stable up to 5th cycle it can be used as a reusable photocatalyst for the DFS degradation. The electrical conductivity and dielectric properties of the CuWO₄ NPs at room temperature is analyzed by EIS studies. The bulk conductivity value of the prepared nanoparticles is 1.477×10-5 S/cm at room temperature. The conductivity of CuWO₄ NPs is found to be due to electrons movement. The CuWO₄ NPs shows higher photocatalytic and electrocatalytic activity for decomposition of DFS and methanol electro-oxidation in alkaline medium respectively.

Electrochemical Study of Palladium-Based Bimetallic Electrocatalysts Supported on Carbon Vulcan XC72R for Methanol Electro-Oxidation in Alkaline Media

Palladium-based electrocatalysts supported on carbon Vulcan XC72R were synthesized by combustion to step up the methanol electro-oxidation reaction (MER) in alkaline media and physico-chemically characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) to establish composition, crystallite and particle sizes, respectively. The catalytic activity was evaluated by electrochemical techniques, namely, cyclic voltammetry (CV) and chronoamperometry (CA) using the well-known electrochemical parameter: steady state anodic current density (j ss).

Remarkably enhanced activity of 4A zeolite modified Pt/reduced graphene oxide electrocatalyst towards methanol electrooxidation in alkaline medium

A novel 4A zeolite modified platinum/reduced graphene oxide (Pt/RGO-4A zeolite) electrocatalyst has been successfully synthesized by one-step chemical co-reduction method. The electrocatalytic performances of Pt/RGO-4A zeolite electrocatalyst for methanol electrooxidation are investigated in 1.0 M CH3OH containing 1.0 M KOH solution. The results demonstrate that, with loading of 10% of 4A zeolite, Pt/RGO-4A zeolite electrocatalyst shows higher current density of 319.40 mA mg−1 than Pt/RGO electrocatalyst (88.64 mA mg−1) at the potential of 0.70 V. In addition, Pt/RGO-4A zeolite electrocatalyst still exhibits high electrocatalytic activity even after 4000-s operation, suggesting satisfactory long-term durability. The remarkably enhanced electrocatalytic performances are attributed to the nanoporous structure of 4A zeolite, which significantly promotes the dispersion of Pt nanoparticles and provides substantial fast flow paths for reactants. The results suggest a potential application of Pt/RGO-4A zeolite electrocatalyst to methanol electrooxidation.

Methanol Electro-Oxidation in Alkaline Medium by Ni Based Binary and Ternary Catalysts: Effect of Iron (Fe) on the Catalyst Performance

Pt free methanol electro oxidation catalysts with stable response are of interest to reduce the overall cost of the direct methanol fuel cell (DMFC). Here, nickel based bi and tri metallic catalysts have been prepared on multiwall carbon nanotube (MWCNT) support by incipient wetness impregnation method. Methanol oxidation performance was investigated in 1 M KOH by cyclic-voltammetry (CV) and chronoamperometry (CA). The results of electrochemical tests showed that among all the catalysts tested, catalyst sample, CAT-3 exhibited the highest current density of 125.5 mA/cm2 and have stable electrochemical response, which is very promising. These catalysts have been characterized by field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray-(EDX), transmission electron microscopy (TEM), X-ray diffraction XRD and X-ray photoelectron spectroscopy (XPS) to study the structural and morphological properties. Characterization results revealed small and uniform particle size distribution and better homogeneity in CAT-3. It was also observed that addition of ‘Fe’ in tri metallic catalyst lowers the Cu contents in the catalysts and in the contrary lowers the electro-catalytic performance. All the catalyst found to be quite stable and CAT-3 gave the highest oxidative current response, which is attributed to higher Cu contents.

Synthesis and characterization of (Co, Fe, Ni)9 S8 nanocomposite supported on reduced graphene oxide as an efficient and stable electrocatalyst for methanol electrooxidation toward DMFC

In this study, Co4S3, Fe3S4, and NiS nanoparticles as a nanocomposite in the form of a new composite called (CoFeNi)9 S8 (CFNS) were synthesized by a facile hydrothermal method. Then, graphene oxide supported (CoFeNi)9 S8 nanoparticles (CFNS/rGO) were prepared and methanol oxidation reaction evaluated on CFNS/rGO electrocatalyst. X-ray diffraction and energy dispersive X-ray spectroscopy analysis were used to investigate the structure and phase identification of electrocatalyst. Homogenous dispersion of CFNS nanoparticles on rGO was confirmed by FESEM and HRTEM images. The electrocatalytic activity of CFNS/rGO hybrid was assessed by cyclic voltammetry, linear sweep voltammetry and electrochemical impedance spectroscopy techniques. The CFNS/rGO exhibited high electrocatalytic activity for methanol electrooxidation in alkaline media. The significant activity of CFNS/rGO assigned to synergistic effects between Co, Fe, and Ni, suitable dispersion of CFNS nanoparticles on rGO, high surface area, and porous structure of rGO that comforts the diffusion of methanol. Therefore, the CFNS/rGO catalyst has enough potential for application in the direct methanol fuel cell.