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• CQDs were synthesized by facile and affordable electrochemical method • One step electrochemical method was employed to synthesis and deposition of electrodes. • CQDs caused to enhanced active surface area for deposition of metal nanoparticles. • The Pd-NPs/RCQD nanocomposite, offers promising option for wide catalytic applications such as high stability, low activation energy, high current density and good electric conductivity for MOR and HER. Glassy carbon electrode, GCE, is decorated with an electrochemically-deposited layer of reduced carbon quantum dots, RCQDs. The Pd nanoparticles are then electrodeposited on RCQDs and the Pd-NPs/RCQDs/GCE is fabricated. The fabricated electrodes are characterized by some characterization techniques. The electrocatalytic performance of the electrodes for methanol oxidation reaction, MOR, and hydrogen evolution reaction, HER, are investigated using different electrochemical measurement techniques in alkaline and acidic media, respectivly. Cyclic voltammetry, CV, Linear sweep voltammetry, LSV, Chronoamperometry, CA, and electrochemical impedance spectroscopy, EIS, measurements are used to evaluate the bifunctional catalytic behavior of the Pd-NPs/RCQDs/GCE. All results are compared with Pd-NPs/GCE and the effect of decorating the GCE substrate with RCQDs is discussed. The results indicate that modification of GCE with a layer of RCQDs increases the active surface area from 0.12 for Pd-NPs/GCE to 0.22 cm2 for Pd-NPs/RCQDs/GCE. Also E onset and EIS parameters are calculated. [ABSTRACT FROM AUTHOR]

Platinum-free electrocatalysts have been considered recently due to their low costs and high resistances against poisoning with reaction intermediates. In this work different electrocatalysts based on a matrix of polypyrrole, PPy, were examined for catalysis of methanol oxidation reaction, MOR. The copper substrates were covered by a PPy layer and NiOx nanoparticles were deposited electrochemically on it. The Cu/PPy/NiOx electrodes indicated catalytic performance for MOR. However, it was shown that the modification of the morphology of PPy, influenced its catalytic behavior. The self-assembly of pyrrole monomers on copper, prior to polymerization, led to the formation of tiny PPy nanoparticles between the common cauliflowers shaped PPy masses. The overoxidation was then carried out electrochemically and the PPy matrix encountered changes in morphology with micro/nano cracks. These changes in PPy morphology facilitated the diffusion of methanol electroactive species, which was verified by the cyclic voltammetry and electrochemical impedance spectroscopy results. The enhancement of active surface area and reduction of diffusion resistance for modified electrodes caused significant increment of their electrocatalytic performance. Scanning electron microscopy, energy dispersive X-ray analysis and X-ray diffraction patterns were used for the characterization of the surface layers. [ABSTRACT FROM AUTHOR]

Tin oxide nanoparticles were synthesized through a galvanostatic pathway on polypyrrole, PPy, coated nanoporous copper. The morphology and surface analysis of the assemblies were evaluated by field emission scanning electron microscopy, FESEM, and energy dispersive X-ray, EDX, analysis, respectively. The electrocatalytic behavior of electrodes was studied by cyclic voltammetry and chronoamperometry tests in methanol solution. FESEM results showed that uniformly distributed nanoparticles with diameters of about 20–30 nm have been dispersed on PPy matrix. Cyclic voltammetry and chronoamperometry tests in methanol solution showed a significant enhancement in the catalytic action of PPy after decoration of tin oxide nanoparticles. Porous Cu/PPy/SnO x electrodes showed enhanced anodic peak current density for methanol oxidation compared to smooth Cu/PPy/SnO x and porous Cu/PPy. The effects of synthesis current density and time on the electrocatalytic behavior of the electrodes were evaluated. The significant enhancement of electrocatalytic behavior of the Cu/PPy electrode after decoration of SnO x overlayer was attributed to the effect of tin oxide on the adsorption of intermediates of methanol oxidation as well as oxidation of bi-products such as CO; huge tendency of tin oxides for dehydrogenation of the alcohols and the increase in microscopic surface area of the electrodes were introduced as other affecting factors. [ABSTRACT FROM AUTHOR]

The direct methanol fuel cell (DMFC), as the ideal fuel cell system which produces the electric power by the direct conversion of the methanol fuel at the fuel cell anode. The main advantage of this kind of fuel cell is the ease of fuel transportation, an energy-dense yet reasonably stable liquid at all environmental conditions. The DMFC relies upon the oxidation of methanol on a catalyst layer to form carbon dioxide. Up to now, different particles ad nanoparticles have been used as an anodic catalysts in various researches. In this work, bimetallic nanoparticles of Ni Cu dispersed on reduced carbon quantum dots (RCQDs) were prepared using the facile electrochemical procedure. The electrochemical oxidation of methanol on a Ni–Cu/RCQDs/GCE electrode was studied in 0.50 M KOH using cyclic voltammetry (CV), chronoamperometry (CA), and impedance spectroscopy (EIS). The beginning potential for electro-oxidation of methanol was observed at lower voltages for Ni-Cu/RCQD/GCE related to Ni-Cu/GCE and Ni-NPs/GCE. Also, the peak current density for the oxidation of methanol for Ni-Cu/RCQD/GCE showed a high amount of 90.41 mA.cm-2, which is threefold of Ni-Cu/GCE catalyst. EIS studies were applied to study the charge transfer rate. The charge transfer resistance for the electrochemical oxidation of methanol for Ni-Cu/RCQD/GCE was obtained 25 Ω while this amount for Ni-Cu/GCE was ca. 313 Ω. [Display omitted] • CQDs were synthesized by facile and one-step electrochemical method. • One-step electrochemical method was employed for deposition of CQDs. • A green, low-cost and electrochemically- synthesized electrocatalyst was introduced. • Enhancement of methanol oxidation reaction was evaluated. • The Ni-Cu/RCQD nanocomposite as a novel non‑platinum bimetallic catalyst, offers promising option as anodic electrode for MOR [ABSTRACT FROM AUTHOR]

• CQDs were synthesized by facile and cost-effective electrochemical method. • CQDs that deposited by one step electrochemical method, caused to increases of electrochemical active surface area and good dispersion of nanoparticles on it. • A green, low-cost and electrochemically-synthesized electrocatalyst was introduced. • The Ni-NPs/RCQD nanocomposite as a novel non-platinum catalyst, offers promising option for wide catalytic applications. The methanol oxidation reaction (MOR) is catalyzed by non- platinum catalysts of nickel nanoparticles (Ni-NPs) that deposited on a modified glassy carbon electrode by reduced carbon quantum dots (RCQD). The cyclic voltammetry (CV), and chronoamperometry (CA) techniques are used for the electrodeposition process. Then the morphology and structure of electrodeposited materials are characterized by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM). Results showed that Ni-NPs are homogeneously electrodeposited on the surface of CQDs. Also, the catalysis of MOR on electrodes is investigated by different electrochemical techniques like CV and CA, and electrochemical impedance spectroscopy (EIS). The electrochemical behavior of electrodes for MOR has been informed with several parameters. For example, for Ni-NPs/RCQDs/GCE, the peak current density at E = 0.56 V, vs. Ag/AgCl was 32 mA·cm−2 that is higher than of Ni-NPs/GCE. Also, the this catalyst shows excellent stability and high current at constant voltage. [ABSTRACT FROM AUTHOR]