Methanol In Alkaline Solution Research Articles

Copper selenide - Porous carbon derived from metal-organic frameworks as an efficient electrocatalyst for methanol oxidation

In the present study, a metal-organic framework (Cu-MOF) was used as the precursor for synthesis of carbon-encapsulated copper selenides (namely, Cu2-xSe@PCs). After carbonization of Cu-MOF to Cu/Cu2O@PCs, the selenidation process was applied by selenium powder at 500 °C to form Cu2-xSe@PCs. Scanning electron microscopy showed the maintenance of the initial octahedral structure of Cu-MOF after carbonization and selenidation. Nickel foam (NF) was modified with the prepared composite and used as anode in electrochemical cells. Cyclic voltammetric study in alkaline solution (in the absence of methanol) showed highly increased peak currents (∼4 times) on Cu2-xSe@PCs/NF compared to that on Cu/Cu2O@PCs/NF. The electrocatalytic oxidation of methanol in alkaline solution showed lower overpotential and much higher catalytic currents (629.3 mA cm−2 in methanol 0.5 M) on Cu2-xSe@PCs/NF compared to that on Cu/Cu2O@PCs/NF (204.6 mA cm−2). The long-term stability of the proposed electrocatalyst was studied by chronopotentiometry and chronoamperometry. High potential stability was observed when a constant current (22.3 mA cm−2) was drawn from the cell (>4 h). Similar stability was observed for the catalytic current when a constant voltage (1.62 V vs. RHE) was imposed on the electrode in chronoamperometry. In addition, more than 88.5 % of the catalytic current remained after the application of 300 consecutive potential cycles to Cu2-xSe@ PCs/NF in the alkaline solution of methanol. The electrocatalyst was also used in a two-electrode system. Polarization and power density plots showed improved catalytic methanol oxidation by using Cu2-xSe@PCs/NF compared to Cu/Cu2O@PCs/NF. Excellent electrocatalytic properties of the proposed composite towards methanol, long-term stability and the simple synthetic route of the mono-metal electrocatalyst make it a good candidate as the anode of direct methanol fuel cells.

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.

The Tunable and Efficient Nanoporous CuAg Alloy Catalysts Toward Methanol Oxidation Reaction Synthesized by Electrochemical Dealloying of Metallic Glassy Precursors.

Three-dimensional (3D) nanoporous CuAg (NPCuAg) alloy catalysts with various Cu/Ag ratios are prepared by electrochemical dealloying of metallic glassy (MG) precursors. All dealloyed samples exhibit homogenous nanoporous structure and element composition distribution. After systematically evaluating their electrocatalytic performance toward MOR, it was found that the catalytic activity of the NPCuAg catalysts is enhanced along with the increase of Cu/Ag ratio, which may be attributed to the more exposed active reaction sites derived from high surface area of nanoporous structure and the optimal synergistic effect. Thus, the NPCu1.75 Ag alloy catalyst presents the best methanol electro-oxidation properties, including a high current density of 397.2 mA cm-2 and good operation stability that retaining 84.5 % catalytic activity even after 7200 s. These results outperform most reported copper-based MOR catalysts in alkaline methanol solution. Considering these advantages, the designed electrodes are expected to be promising catalysts for alkaline DMFCs applications.

A Novel Chemosensor for Selective Detection of L‐Arginine and L–Cysteine via Macroscopic Sol‐Gel Transition

AbstractTo develop chemosensors for biomolecule recognition, a multi stimuli responsive supramolecular gelator, [(E)‐4‐((4‐(benzyloxy)phenyl)diazenyl)benzaldehyde], comprised of azo and formyl units, was designed and synthesized from readily available starting materials. The gelator was found to be capable of forming gels in light alcohols and alcohol/water mixtures at low concentrations (0.7–1.5 g/100 mL). The gel rheological analyses showed the dominance of storage modulus (G′) values (ca 5000 Pa) within the range of analysis, confirming the gel stiffness. The xerogel scanning electron microscopy (SEM) studies showed a flake‐like pattern of thin sheets. Our investigations on the gelator sensing abilities revealed that, in addition to the photo‐responsive function due to the presence of azo moiety, its ethanol/water gel exhibited excellent ability to detect l‐arginine among 19 various amino acids, via gel to sol transition and colour change. Furthermore, the gelator could successfully recognize l‐cysteine among 19 amino acids, through macroscopic sol to gel transition and colour change of its alkaline methanolic solution. Moreover, the photo‐ and chemo‐responsive functions of the gelator were demonstrated as two combinational logic gates.

Ultralong PtPd Alloyed Nanowires Anchored on Graphene for Efficient Methanol Oxidation Reaction.

The rational synthesis of Pt-based alloyed nanowires still remains a great challenge because of the different reduction potentials between Pt and another metal and the intrinsic feature of isotropic growth in face-centered cubic (fcc) structured Pt. In this work, PtPd alloyed nanowires with ultrahigh aspect ratio anchored on graphene (PtPd NWs/graphene) were synthesized by a facile solvothermal method without the use of any templates or surfactants. Due to the integration of ultralong PtPd nanowires and stable graphene support, PtPd NWs/graphene exhibited outstanding electrochemical activity toward methanol oxidation reaction (MOR) in comparison with pure Pt NWs/graphene and commercial Pt/C catalysts. Meanwhile, PtPd NWs/graphene had a much higher current density than Pt NWs/graphene and commercial Pt/C catalysts at a constant potential for 7200s in alkaline methanol solution. Moreover, after 1000 cycles of durability testing, PtPd NWs/graphene retained 89.2% of its initial mass activity, much superior to the 63.7% retained for commercial Pt/C.

A nickel ion-incorporating zinc-mesoporous metal organic framework thin film nanocomposite modified glassy carbon electrode for electrocatalytic oxidation of methanol in alkaline media

In this work, we have successfully synthesized a nickel ion-incorporating zinc-mesoporous metal–organic framework thin films (Zn-mMOFTFs) modified glassy carbon electrode (GCE), Ni/Zn-mMOFTFs/GCE, for electrooxidation of methanol in alkaline solution.

Robust copper nanocrystal/nitrogen-doped carbon monoliths as carbon monoxide-resistant electrodes for methanol oxidation reaction

Noble metal-based electrocatalysts present high activities for methanol oxidation reaction (MOR), but are limited by their high cost, low stability and poor resistance to carbon monoxide (CO) poisoning. The development of active and stable non-noble metal electrocatalysts for MOR is desired, but remains a challenge. Herein, we report a simple strategy to make copper nanocrystal/nitrogen-doped carbon (Cu/N-C) monoliths, which can serve as active and robust electrodes for MOR. Copper nanocrystals were electrochemically deposited onto a conductive polyaniline hydrogel and calcined to form Cu/N-C monolith, where the active copper nanocrystals are protected by nitrogen-doped carbon. Owing to their extremely high electrical conductivity (1.25 × 105 S cm−1) and mechanical robustness, these Cu/N-C monoliths can be directly used as electrodes for MOR, without using substrates or additives. The optimal Cu/N-C (FT) @500 monolith shows a high MOR activity of 189 mA cm−2 at 0.6 V vs. SCE in alkaline methanol solution, superior to most of reported Cu-based MOR catalysts. Cu/N-C (FT)@500 also presents a better stability than Pt/C catalyst in the long-term MOR test at high current densities. Upon carbon monoxide (CO) poisoning, Cu/N-C (FT)@500 retains 96% of its MOR activity, far exceeding the performance of Pt/C catalyst (61% retention). Owing to its facile synthesis, outstanding activity, high stability and mechanical robustness, Cu/N-C (FT)@500 monolith is promising as a low-cost, efficient and CO-resistant electrocatalyst for MOR.

In situ facile fabrication of Ni(OH)2 nanosheet arrays for electrocatalytic co-production of formate and hydrogen from methanol in alkaline solution

Ni(OH)2 nanosheet arrays are in situ prepared on Ni foam through very straightforward ultrasonication in HCl solution and the following rinsing and drying procedures. Value-added formate and hydrogen could be co-produced by selective oxidation of methanol without carbon dioxide emissions and water reduction over Ni(OH)2 nanosheet arrays bifunctional electrocatalysts. Energy depletion for hydrogen evolution from water could be reduced by integrating with selective methanol oxidation rather than oxygen evolution. The prepared Ni(OH)2 nanosheet arrays exhibits high activity for selective methanol oxidation in alkaline methanol-water solution. It gives a low potential of only 1.36 V (vs. reversible hydrogen electrode) to drive the current density of 100 mA cm−2. The faradaic efficiencies of formate are approximately 100% with the current densities from 10 mA cm−2 to 100 mA cm−2. Moreover, it is easy to separate the anodic and cathodic products without help of any membrane, which greatly simplifies the electrolysis system.

Eggshell-membrane-templated synthesis of C, S Doped Mesoporous NiO for methanol oxidation in alkaline solution

An interwoven hollow fiber structured mesoporous NiO catalyst doped with C, S was fabricated by the vacuum impregnation and thermal decomposition methods using eggshell membrane as template. The structure of the catalyst was characterized by X-ray diffraction, thermo-gravimetric analysis, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and specific surface area test. Under a high vacuum condition, the synthesized NiO material has a better interwoven fiber and mesoporous structure, which effectively increases the specific surface area of the material. C and S were doped into NiO via eggshell membrane pyrolysis, which then formed C–OH and SO42− species on the surface of the material. The electrocatalytic performance of the catalyst for the oxidation of methanol in alkaline solution was studied by cyclic voltammetry and chronoamperometry. The C, S doped mesoporous NiO material exhibits much higher catalytic efficiency and anti-poisoning ability than that of NiO nanoparticles due to the synergistic catalysis of NiO and doping C–OH and SO42− species.

A novel sandwich shaped {CoCoMo} cluster with a Co triangle encapsulated in two capped CoIIICoMoO40 fragments.

A novel discrete {Co14Mo24} nanoscale cluster, {CoIII2CoII10Cl2(dpbt)3(H2O)2[CoIIMoV12O31(CH3O)9]2}·24CH3OH (1) (here, dpbt = 5,5'-di(pyridin-2-yl)-3,3'-bi(1,2,4-triazole)), with a triangular Co4 core encapsulated in two novel capped Co-substituted Keggin-type Co5Mo12O40 anions, has been isolated from alkaline methanol solution. The high-resolution electrospray ionization mass spectrum (HRESI-MS) of microcrystalline 1 in MeOH/CH2Cl2 (v : v = 2 : 1) was recorded. Two prominent overlapping peaks in the range of m/z = 2740-2840 and 1820-1880 for the discrete fragments of [CoIII2CoII12MoV24O62Cl2(dpbt)3(H2O)2(CH3O)x(OH)18-x-2H]2- (x = 9-18, F1) and [CoIII2CoII12MoV24O62Cl2(dpbt)3(H2O)2(CH3O)x(OH)19-x-2H]3- (x = 6-13, F2), respectively, are obtained, confirming the {Co14Mo24} composition in 1. In addition, weak anti-ferromagnetic interactions in 1 are observed.

Chromium phosphide CrP as highly active and stable electrocatalysts for oxygen electroreduction in alkaline media

Catalysts for oxygen reduction reaction (ORR) are key components in emerging energy technologies such as fuel cells and metal-air batteries. Developing low-cost, high performance and stable electrocatalysts is critical for the extensive implementation of these technologies. Herein, we present a procedure to prepare colloidal chromium phosphide CrP nanocrystals and we test their performance as ORR electrocatalyst. CrP-based catalysts exhibited remarkable activities with a limiting current density of 4.94 mA cm−2 at 0.2 V, a half-potential of 0.65 V and an onset potential of 0.8 V at 1600 rpm, which are comparable to commercial Pt/C. Advantageously, CrP-based catalysts displayed much higher stabilities and higher tolerances to methanol in alkaline solution. Using density functional theory calculations, we demonstrate CrP to provide a very strong chemisorption of O2 that facilitates its reduction and explains the excellent ORR performance experimentally demonstrated.

Preparation and characterization of Grafoil/Ni and polyaniline/Ni composites from the controlled electrochemical reduction of NiCl42-

The controlled reduction of a nickel metal anion, NiCl42−, at a carbon (Grafoil) and Polyaniline (PANI) electrode is explored. The incremental increase of Ni deposits is achieved from the reduction of the metal precursor at both electrodes. The normal oxidation/reduction was used to facilitate the uptake and dispersion of the precursor using electrostatic interactions with the positively charged PANI. The controlled in-situ reduction of the dispersed Ni precursor in the polymer was utilized to produce PANI/Ni composites with variable metal content. Scanning electron microscope (SEM) analysis and energy dispersive x-ray (EDX) spectroscopy of both substrates confirm the reduction of the Ni metal precursor at both electrodes. The chemical reactivity of the Ni metal deposited was also confirmed for both substrates using surface specific electrochemical reactions including the formation/reduction of oxidized nickel species and the catalytic oxidation of methanol in alkaline solutions (pH ≈ 14). The electrochemistry associated with NiOOH/Ni(OH)2 and the catalytic oxidation of methanol is resolved in alkaline solution for both electrodes. Furthermore, the electrochemical activity of PANI/Ni composite materials is maintained without acid doping the polymer. Finally, an alternative pathway for the inclusion of anionic transition metal species in PANI that eliminates the competitive uptake of proton and metal cation precursors commonly used in traditional acidic environments is demonstrated.

Multiwall carbon nanotubes loaded with MoS2 quantum dots and MXene quantum dots: Non–Pt bifunctional catalyst for the methanol oxidation and oxygen reduction reactions in alkaline solution

We synthesized a novel composite of multiwall carbon nanotubes (MWCNTs) decorated with MoS2 quantum dots (MoS2 QDs) and Ti3C2Tx QDs (denoted by MoS2QDs@Ti3C2TxQDs@MWCNTs), of which MoS2 QDs and Ti3C2Tx QDs were separately prepared by exfoliating MoS2 and Ti3C2Tx MXene nanosheets by the hydrothermal method. It showed that the as–prepared MoS2QDs@Ti3C2TxQDs@MMWCNTs composite was rich in functional groups and exhibited homogeneous nanotube nanostructure by coupling with good electrochemical activity. Of note, the MoS2QDs@Ti3C2TxQDs@MWCNTs composite exhibited outstanding bifunctional electrocatalytic performances for oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) in alkaline solution by combining the superior electrocatalytic activity of MoS2 QDs and Ti3C2Tx QDs and the excellent electrochemical performance of MWCNTs. The MoS2QDs@Ti3C2TxQDs@MMWCNTs catalyst exhibited a superior ORR activity to other non-Pt catalysts, giving a low Tafel slope (90 mV dec−1) and high half potential (E1/2, 0.75 V), which was close to those of the commercial Pt/C (20%) catalyst (Tafel slope of 89 mV dec−1, E1/2 of 0.80 V). Additionally, the MoS2QDs@Ti3C2TxQDs@MMWCNTs also possessed good electro–oxidation performance for methanol in alkaline solution, giving a maximum methanol oxidation current density at 2.2 V of 160 A·g−1. The results indicated that the combination of MoS2 and Ti3C2Tx QDs with MWCNTs can supply a potential for fabricating the bifunctional electrocatalysts for ORR and MOR.

Novel electroactive nanocomposite of POAP for highly efficient energy storage and electrocatalyst: Electrosynthesis and electrochemical performance

In this work, we presented facile route for fabrication of poly ortho aminophenol (POAP) POAP and POAP/ZnO nanocomposite on the surface of the working electrode. The fractal dimension of nanocomposite films in the presence of counter ions was investigated. Surface morphology of the composite film was studied by surface microscopy techniques (SEM). The presence of ZnO in the films was confirmed by EDS analysis. The results indicate that a strong interaction exist at the interface of POAP and nano-ZnO. Different electrochemical methods including galvanostatic charge discharge experiments and cyclic voltammetry have been applied to study the system performance. This work introduces new nanocomposite materials for electrochemical redox capacitors with such advantages as the ease of synthesis, high active surface area and stability in an aqueous electrolyte. Furthermore, comparison with a Ni-POAP the Ni-POAP/ZnO electrode shows a better catalytic performance for the electrocatalytic oxidation of methanol in alkaline solution. It is observed that the in the presence of ZnO nanoparticles current density of electro-oxidation of methanol is almost constant in 400 cycles due to the stability of electrocatalyst in this cycle number and indicating that methanol reacted with the surface and no poisoning effect on the surface was observed.

Graphene quantum dot functionalized by chitosan and beta-cyclodextrin as a new support nanocomposite material for efficient methanol electrooxidation

Current needs for sustainable energy have popularized the development and use of fuel cell technology. Catalysts are vital fuel cell components, and in recent years research efforts have focused on the development new types of catalysts. This work describes application of a novel nanocatalyst based on graphene quantum dot functionalized by chitosan (GQD-CS) and β-cyclodextrin (GQD-β-CD) towards electrooxidation of methanol in alkaline solution. The catalysts were prepared by cycling the glassy carbon electrode in solutions containing graphene quantum dot and chitosan. The synergistic effects and catalytic activity of the modified electrodes were investigated by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). It was found that, in the presence of methanol, the modified electrodes [(GQD-CS-GCE) and (GQD-β-CD-GCE)] exhibited a significantly higher catalytical response for methanol oxidation compared to the other samples. The anodic peak currents showed a linear dependency on the square root of the scan rate, which is a characteristic of a diffusion controlled process. The graphene quantum dots functionalized with chitosan and β-CD electrodes is further extended to the demonstration of novel electrocatalyst through the transfer of the electrode fabricated by bare GQDs. For comparison of the recognition efficiency, other electrodes including bare GCE, and GQDs-GCE were used for the control experiments. Comparison of recorded CVs and CHs in the presence of methanol using GQD-CS-GCE, β-CD-GQDs-GCE shows ΔEp was decreased as GQD-CS-GCE > GQDs-β-CD-GCE > GQDs-GCE. The higher peak current observed in the presence of GQD-CS-GCE, GQDs-β-CD-GCE clearly indicates β-CD and CS essential roles in the observed electrocatalytical behavior. In general, the attachment of chitosan and β-cyclodextrin to structure of GQDs provides new opportunities towards the direct methanol fuel cell application.

Application of phosphotungstic acid–nickel composite-modified carbon paste electrode for electrocatalytic oxidation of methanol in alkaline solution

Phosphotungstic acid (PWA) was used for accumulation of nickel ions at the carbon paste electrode for preparation of PWA-modified CPE (PWA/CPE). The PWA was evenly mixed with graphite powder and paraffin oil. Then, for preparation of Ni/PWA/CPE, Ni ions were included onto the PWA/CPE surface through immersion method at open circuit condition. The scanning electron microscopy (SEM), energy-dispersive spectroscopy and electrochemical methods were used to verify the prepared electrodes. The SEM images reveal that morphology of the CPE was influenced by PWA addition. Application of the Ni/PWA/CPE for methanol oxidation was explored by various electrochemical techniques. Electrochemical response of methanol oxidation at the surface of Ni/PWA/CPE was 2.5 times higher than that Ni/CPE. The obtained results indicated that the modified electrode exhibited high electrocatalytic activity toward methanol oxidation. Then, catalytic rate constant was found to be 8.25 × 104 cm3 mol −1 s−1 using chronoamperometry method. Furthermore, the effects of several parameters, such as PWA loading, NiSO4 concentration, accumulation time and methanol concentration toward methanol oxidation at the surface of this modified electrode as well as stability, have been investigated.

A simple, cheap and effective methanol electrocatalyst based of Mn(II)-exchanged clinoptilolite nanoparticles

Clinoptilolite nanoparticles (NClin), prepared via ball-mill mechanical method, were ion-exchanged in Mn(II) solutions with different concentrations ranging from 0.1 to 1 mol L−1. After characterization of samples by XRD, TEM and BET techniques, the resulted Mn-exchanged nano-particles (Mn(II)-NClin) (and also Mn-exchanged micronized one: Mn(II)-MClin) were used for modification of carbon paste electrode (Mn(II)-NClin-CPE). These modified electrodes were applied in methanol oxidation reaction as a catalyst in strong basic pHs which caused to a significant decrease (920 mV) in overvoltage of the process with respect to the bare CPE. The best voltammetric response (CV) was obtained for the catalyst ion exchanged in 1 mol L−1 Mn(II) solution and also by using clinoptilolite nanoparticles with respect to micronized one (MClin). In the chronoamperometris studies, the average diffusion coefficients of 8.73 × 10−3 and 8.6 × 10−5 cm2 s−1 and also the mean ks values of 150 M−1 s−1 and 99 M−1 s−1 were obtained for Mn(II)-NClin/CPE and Mn(II)-MClin/CPE, respectively. CV behavior of the modified electrode was a diffusion controlling process in the absence of methanol, while it was controlled by surface confined process in the presence of methanol, confirming the important role of Mn(OH)2/MnOOH system in electrocatalysis of methanol in alkaline solutions.

Synthesis and Electrocatalytic Activity of Nitrogen and Phosphorus Co-Doped Graphene for Oxygen Reduction

The oxygen reduction reaction (ORR) at the cathode plays an important role in the performance of fuel cells and metal-air batteries. Due to the high cost and scarcity of Pt-based electrocatalysts, intensive efforts have been focused on reducing or replacing Pt catalyst in fuel cells and metal-air batteries. [1-4] Graphene, single-atom-thick layer of sp2-hybridized carbon atoms packed into two-dimension hexagonal lattice, has been rapidly developed in recent years. Recently, both theoretical and experimental studies show that the electrical and physicochemical properties of graphene can be significantly modified by incorporation foreign atoms into graphene. [5-8] Especially for catalytic applications, doping pristine graphene with heteroatoms, such as N, B, S, I and P, is an effcient approch to alter the electron-donor property and consequently increase the electrocatalytic performance for ORR. [9-12] Particularly, co-doping multiple heteroatoms endows graphene much imrpoved ORR activity than doping with single atom. Such multiple-doped graphene can create a unique electronic structure with a synergistic effect in these heteroatoms, efficiently enhancing the ORR activity. In this work, for the first time, we have successfully synthesized P and N binary-doped graphene (PNG) through a facile thermal annealing method by using urea and tetraphenylphosphonium bromide (C24H20BrP) as N and P precursors, respectively. The as-prepared PNG catalysts with a large specific surface area up to 1207.03 m2 g-1 act as efficient metal-free electrocatalysts for ORR, showing remarkable electrocatalytic activity and excellent long-term stability as well as high tolerance to methanol in alkaline solution. The content of N and P has a significant impact on the activity of the PNG as shown in Figure 1.The outstanding electrocatalytic activity and long-term durability of PNG toward ORR are primarily attributed to the synergetic effect arising from co-doping graphene with both P and N. This work may provide an efficient approach for the synthesis of heteroatom multiple-doped graphene. Acknowledgements This work is supported by National Natural Science Foundation of China (Nos.51272167, 21206101 and 51572181 ).

Electrochemical properties, optical modeling and electrocatalytic activity of pulse-electropolymerized ternary nanocomposite of poly (methylene blue) in aqueous solution

This paper aims to investigate the relationship between surface morphology of poly (methylene blue) (PMB) films and pulse synthesis conditions. A simple and general strategy, namely in situ electropolymerization has been used for electrosynthesis of PMB on the Indium Tin Oxide (ITO) substrates by pulse galvanostatic method. The obtained surface analysis results revealed that the morphology and particle sizes of PMB strongly depended on the synthetic conditions. PMB nanoparticles with good electrochemical stability were obtained by optimization of synthetic conditions. Then, Ni (II) and Mn (II) ions were incorporated to electrode by immersion of the polymerically modified electrode in a stirred solution containing Ni and Mn ions to form Ni–Mn/PMB films. Furthermore, the experimental absorbance spectra of nanocomposite were compared with the results from the Maxwell-Garnett theory (MGT) and the value of energy, Eg, of composite obtained. Modified electrodes (Ni–Mn/poly methylene blue) were examined for their redox and electrocatalytic activities in the oxidation of methanol in alkaline solutions. The electrochemical results reveal that Ni–Mn/poly methylene blue modified electrode shows a significantly higher response for methanol oxidation in alkaline solution.

Application of nano-sized nanoporous zinc 2-methylimidazole metal-organic framework for electrocatalytic oxidation of methanol in alkaline solution

In this work, a novel non-platinum group metals (non-PGM) catalyst based on modified zinc 2-methylimidazole metal-organic framework (ZIF-8) is proposed and used for electrooxidation of methanol. Nano-sized particles of nonporous ZIF-8 are synthesized at room temperature using a simple template-free method. The synthesized ZIF-8 nanoparticles are characterized by X-ray diffraction, scanning electronic microscopy and nitrogen adsorption-desorption techniques. In order to decrease the overvoltage of methanol oxidation on carbon paste electrode (CPE), nickel species doped ZIF-8 modified carbon paste electrode (Ni/ZIF-8CPE) is fabricated as a modified electrode. Electrochemical techniques such as cyclic voltammetry and chronoamperometry are used to investigate the electrocatalytic activity of Ni/ZIF-8CPE toward methanol oxidation in alkaline solution. Cyclic voltammetry results show that oxidation current is considerably increased using Ni/ZIF-8CPE in comparison with unmodified CPE. Catalytic rate constant of methanol oxidation on Ni/ZIF-8CPE is obtained using chronoamperometric studies. Besides the good catalytic activity of the modified electrode toward methanol oxidation, it has other advantages such as simple preparation, ease of operation, good stability and low cost, which can be promising in the field of preparation of non-PGM electrocatalysts for application in fuel cells.