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Electrocatalytic preparation of Pt-based nanocomposites has been investigated for improvement of direct ethanol fuel cells (DEFCs). In this study, new alternative catalysts of Pt-decorated cerium zirconium oxide-modified multiwalled carbon nanotubes (Pt/CeZrO4/MCNT) were successively prepared to improve the activity of the ethanol oxidation reaction (EOR). The prepared CeZrO4 with a face-centered cubic (fcc) structure compatibly dispersed onto MCNT provides abundant active Pt sites for highly active catalysts. The fcc-structured Pt was also satisfactorily decorated onto CeZrO4/MCNT, resulting in highly active Pt. The Ce4+/Ce3+ redox property can promote oxygen vacancies to improve the electrochemical activity for oxidation of carbonaceous species. An increase in roughness and a stabilized catalyst structure can also be produced by inserting Zr4+ into the ceria metal oxide. The prepared Pt/20%CeZrO4/MCNT catalysts present excellent electrochemical active surface area, mass activity, CO tolerance and high electron kinetic transfer with low resistance and high stability over commercial PtRu/C toward EOR. This promising catalyst material could be introduced to enhance the anodic oxidation reaction in DEFCs.

Electrocatalytic oxidation of methanol, ethanol, and formic acid has currently attracted research attention for low-temperature fuel cells. However, the efficiencies of these fuel cells mainly depend on the electrocatalytic activities of Pt-based anodic catalysts due to the problems of low kinetics for small organic molecule electro-oxidation. An anode catalyst can be developed by the addition of some metal oxides into a Pt-based catalyst, which can effectively promote the electro-oxidation of fuels based on small organic molecules. In this work, a nanocomposite catalyst consisting of multi-wall carbon nanotubes (CNTs), copper oxide (CuO) and Pt nanoparticles was synthesized and used to improve fuel cell oxidation. Due to its low cost and oxophilic character, the metal oxide can play a major role in the oxidation of CO. The synthesis of xPt−yCuO/CNT electrocatalysts was executed through two steps: supporting of CuO nanoparticles on CNTs by the alcothermal method followed by Pt loading onto the prepared CuO/CNT by chemical reduction. The as-prepared catalysts were physically characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and electrochemical measurements. The results demonstrate that CuO is well dispersed onto the CNTs and that this oxide can further interact with the active Pt present on the as-prepared catalyst composites. The activity of various xPt−yCuO/CNT electrocatalysts was determined by cyclic voltammetry (CV), where x and y are the mass ratios of Pt and CuO, respectively. The presence of CuO was found to significantly contribute to enhanced electroactivity towards oxidation reactions. The 1Pt–3CuO/CNT electrocatalyst is a capable catalyst for improving low-temperature fuel cell applications.

Catalyst composites based on Pt and CeO2 on carbon for methanol oxidation were successively prepared for application in direct-methanol fuel cells (DMFCs). In this work, the catalyst was modified by decoration of CeO2 onto several carbons, including carbon black (CB), carbon nanotubes (CNT), graphene oxide (GO), reduced graphene oxide (rGO) and mixed carbons, followed by the electrochemical deposition of Pt. The dispersal of CeO2 and Pt nanoparticles onto the carbon surfaces was confirmed with a face-centred cubic structure. The use of single and mixed carbons takes admirable advantage of the coexisting CeO2 and Pt nanoparticles, confirming the positive effect of various carbon structures for electrocatalytic enhancement towards methanol oxidation. The CeO2 also improves the ability for CO oxidation, resulting in a reduction of CO poisoning. The outcomes show an enhancement of the activity and stability so that such alternative as-prepared materials can be introduced to improve the anodic oxidation in DMFCs.

The modification of various carbons with various metal oxides and noble metal composites was performed to prepare electrocatalysts, and the catalysts were further investigated for ethanol electro-o...

Pd-rich Pd-Pt-Ru alloys, obtained by electrodeposition, were characterized by microscopic and electrochemical techniques at room temperature (298 K). The influence of the electrode potential and bulk composition on the amount of electrosorbed hydrogen was studied in 0.5 M H2SO4 aqueous solutions and compared with the behavior of Pd-Rh-Ru alloys under identical experimental conditions. The maximum hydrogen absorption capacities gradually decreased with increasing total amounts of both Pt and Ru in the alloy bulk. The effects of both Pd bulk content and the relative proportions between other components in Pd-Pt-Ru and Pd-Rh-Ru electrodes are also responsible for the changes in maximum hydrogen absorption capacity, the decrease in the potential of the alpha-beta phase transition, and the decrease in the absorption/desorption hysteresis. During voltammetric cycling in 0.5 M H2SO4 in the potential range − 0.1÷1.5 V vs. RHE (scan rate 0.1 V/s), the freshly obtained deposits became enriched with Pt due to electrodissolution of Ru and Pd, and the electrode morphology was also altered due to hydrogen electrosorption and surface oxidation.

A series of platinum nanoparticle-loaded carbon composites composed of reduced graphene oxide and multi-walled carbon nanotubes (rGO-CNT/Pt) was chemically synthesized at room temperature. The prepared catalysts were characterized using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results confirm that rGO mixed CNT composites were successfully prepared with small and highly dispersed Pt nanoparticles on the composite supports. The cyclic voltammetry (CV) and chronoamperometry (CA) electrochemical measurements indicated that the composite carbon catalyst increased the intensity and stability for the methanol oxidation reaction (MOR). In addition, fewer carbon intermediate species were observed in the CO stripping experiment. The incorporation of CNTs into rGO decreases the agglomeration between rGO sheets and increases the active surface of dispersed Pt nanoparticles, resulting in the enhanced oxidation activity of the as-prepared electrocatalysts. The combined characteristics of the highly active Pt nanoparticles and potent electron transfer of the rGO-CNTs enable excellent methanol oxidation with high stability. Consequently, this hybrid carbon material is a good candidate for MOR catalysis, which can be applied to direct methanol fuel cells.

To improve the electrocatalytic activity of alcohol oxidation, functionalized carbon nanotubes (CNTs) decorated with various compositions of metal alloy catalyst nanoparticles (PtxMy, where M = Au and Pd; x and y = 1–3) have been prepared via reduction. The CNTs were treated with an nitric acid solution to promote the oxygen-containing functional groups and further load the metal nanoparticles. X-ray diffraction (XRD) scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to probe the formation of catalyst microstructure morphologies. A uniform dispersion of the spherical metal particles with diameters of 2–6 nm was acquired. The catalytic properties of the catalyst for oxidation were thoroughly studied by electrochemical methods that involved in the cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). To maximize the electrocatalytic performance and minimize the metal integration of the loaded CNTs, various compositions of active catalysts with large active surface areas are expected to increase the activity of the enhanced catalysts for alcohol oxidation. Most of the prepared bimetallic catalysts have better alcohol oxidation kinetics than commercial PtRu/C. Among the prepared catalysts, the PtAu/CNTs and PtPd/CNTs catalysts with high electrochemically active surface area (ECSA) show excellent activities for alcohol oxidation resulting in their low onset potentials, small charge transfer resistances and high peak current densities and If/Ib ratios, stability, and better tolerance to CO for alcohol oxidation. The integration of Pt and different metal species with different stoichiometric ratios in the CNTs support affects the electrochemical active surface area achieved in the catalytic oxidation reactions.

The noble metals (Pt and Pd) loaded on polydopamine (PDA) modified graphene oxide (GO) as catalysts were prepared by a reduction. The catalysts were characterized by Fourier transform infrared spec...

By integrating the effects of alloying, chemical composition and support, a series of mono- and bi-metallic catalyst nanoparticles electrodeposited on α-manganese dioxide (MnO2)-modified carbon nanotube (CNT) supports were synthesized to improve the efficiency of direct alcohol fuel cells. Small and dispersed nanoparticles on the CNT/MnO2 surfaces with high electrochemically active surface area (ECSA) were successfully obtained in this work. The support materials were characterized by Fourier-transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD), while the as-prepared catalysts were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry (CV) and chronoamperometry (CA) were used to study the activity and stability of the catalysts, respectively. The results showed that a combination of Pt, Pd, Au and MnO2 on the CNTs significantly affected the topography of the composite catalyst surfaces, and their electrochemical measurements showed excellent electrocatalytic activity toward the reaction. For methanol and ethanol oxidation in acid solution, CNT/MnO2/1M3Pt (M = Pd or Au) catalysts revealed greater activity improvement compared to the other prepared catalysts. For the bimetallic CNT/MnO2/xMyPt catalysts, the values of the forward peak current (If)) and the ratio of the forward peak current to the reverse peak current (If/Ib) were higher, while their onset potentials (Eo) were lower compared to those of the monometallic CNT/MnO2/4Pt catalyst. Moreover, CO oxidation on these bimetallic catalysts was also confirmed to be poisoning resistant. These results indicate that our prepared catalyst showed excellent electrocatalytic performance, reliability, and stability. The catalytic activity improvement was based upon the unique integrated structural and functional properties and the synergistic effect of different compositions in the catalyst system.

New tungsten-doped CoMoO4 (W-CoMoO4) was successfully synthesized by a simple co-precipitation method and investigated for a possible application in oxygen evolution reaction (OER). The effect of W6+ doping on structure, morphology, and chemical compositions was investigated by X-ray diffraction spectroscopy, scanning electron microscopy, Fourier transform spectroscopy, Brunauer–Emmet–Teller surface area measurement, and X-ray photoelectron spectroscopy. Linear sweep voltammetry indicates that doping CoMoO4 with an optimum W6+ amount of 21 wt% provides higher current density at lower overpotential than other catalysts. Compared to undoped CoMoO4, the 21 wt% W-CoMoO4 also shows a remarkable activity and excellent long-term stability in alkaline media. This superior activity is ascribed to the synergistic effect of increased oxygen vacancy, enhanced surface area, and possibly improved electrical conductivity upon W6+ doping. The significances of this work are that the potential OER application of Co–W–Mo tertiary oxide, which has never been studied before, and the effect of non-3d high-valency metal (W) doping on OER activity enhancement are now being recognized.

Successive electropolymerization of dopamine and electrodeposition of Pd and/or Pt on a graphene oxide (GO) support were used to prepare anode catalysts for low-temperature fuel cells. Tran...

The orders of metal deposition (e.g. Pt, Au and Pd) on graphene oxide (GO) and their electrocatalytic properties were investigated. The mono-, bi- and tri-metallic nanoparticles were electrochemica...

The screen-printed carbon electrode (SPCE) modified with various nanoparticles has been studied for using as a working electrode in voltammetric technique. The electrochemical behavior of paraquat on different electrodes was studied by cyclic voltammetry (CV), and then differential pulse voltammetry (DPV) has been employed for trace analysis of paraquat based on redox reaction which the peak current was directly proportional to the concentration of paraquat in the solution. The SPCE modified with carbon nanotube dispersed in Nafion and ethanol (SPCE-CNT/Nafion) gave the best result. Sequential injection-differential pulse voltammetric (SI-DPV) method has been developed for more automated analysis and to reduce chemical consumption. The parameters affecting the SI-DPV system such as step potential, modulation amplitude, flow rate, and concentration of sodium chloride as an electrolyte were studied to improve the sensitivity. Under the optimum condition of the system, i.e., Nafion concentration of 1% (w/v), volume of CNT suspension of 2µL, flow rate of 100µLs-1, step potential of 5mV, modulation amplitude of 100mV and concentration of sodium chloride of 1M, a linear calibration graph in the range of 0.54-4.30µM with a good R2 of 0.9955 and a limit of detection of 0.17µM (0.03mgL-1) were achieved. The proposed system shows high tolerance to some possible interfering ions in natural water, surfactant, and other pesticides. The relative standard deviation (RSD) was 4.2% for 11 replicate measurements with the same electrode. The reproducibility for the preparation of 7 modified electrodes was 2.3% RSD. Recoveries of the analysis were obtained in the range of 82-106%. The developed system can be conveniently applied for analysis without pretreatment of the samples.

This paper proposes an approach for the fabrication of an anode electrocatalyst for application as a fuel cell catalyst. It comprises three components, multiwall carbon nanotube (CNT), ceria oxide (CeO2), and metal (i.e., Pt and/or Pd), using the reduction method for preparation. The characterization of the prepared catalysts was determined by transmission electron microscopy (TEM), X-ray diffraction, and Raman spectroscopy. The electrocatalytic performance of the prepared catalysts was examined by electrochemical measurements, e.g., cyclic voltammetry, chronoamperometry and CO stripping voltammetry. Among the catalysts, the obtained 1Pt1Pd − CeO2/CNT electrocatalyst provides a high electrochemical surface area, as well as high oxidation activity and durability for the oxidation of methanol, ethanol, and formic acid. The enhancement of the catalytic activity is attributed to changes in the surface electronic structures of Pt, Pd, and CeO2 on the CNT surface that incrementally effect the active sites for oxidation. A required catalytic performance for these oxidations were observed with small-size and high-dispersion of the metal i.e.1Pt1Pd (3.34 nm) on the CeO2/CNT support nanocomposite. The results also show substantial improvement in the kinetics for oxidations and mass transfer efficiency owing to the catalyst structure. Therefore, the prepared catalysts have promising potential for application in low-temperature fuel cells.

In this work, the preparation, characterization, and electrocatalytic analysis of the catalysts on various carbon substrates for direct alcohol fuel cells were studied. Selected carbons were modified with/without polydopamine (labelled as PDA-C and C) and further metal electrodeposited incorporated onto the glassy carbon (labelled as 5Pt1Pd/PDA-C and 5Pt1Pd/C). Four various carbon materials were used e.g. graphite (G), carbon nanotube (CNT), graphene (GP) and graphene oxide (GO) and the carbons were modified with PDA denoted as PDA-G, PDA-CNT, PDA-GP and PDA-GO, respectively. The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) experimental observation showed narrow size distribution of metal anchored on the PDA-C and C materials. Chemical compositions and oxidation states of the catalysts were determined by X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX). The catalytic performances for small organic electro-oxidation (e.g. methanol and ethanol) were measured by cyclic voltammetry (CV). Among different PDA-C and C catalysts, monometallic Pt showed less activity than the bimetallic catalysts. Among catalysts with PDA, the 5Pt1Pd/PDA-GO catalyst facilitated methanol and ethanol oxidations with high oxidation currents and If/Ib value and stability with low potentials while among catalysts without PDA, the 5Pt1Pd/CNT provides highest activity and stability. It was found that the catalysts with PDA provided high activity and stability than the catalysts without PDA. The improved catalytic performance of the prepared catalysts could be related to the higher active surface area from polymer modification and bimetallic catalyst system in the catalyst composites.

Home-made graphene oxide (GO) with a high surface area was functionalized by polydopamine (PDA) and was labeled PDA-GO, while GO without PDA was labeled as GO. With different compositions of metals (Pt and/or Pd), the electrodeposition of the metals onto the prepared GO and PDA-GO supports was prepared for the anode electrocatalyst. The electrocatalytic activities of the electrocatalysts (xPtPd/GO and xPtPd/PDA-GO, where x = 1–5) were studied in the oxidation of alcohols (e.g., methanol and ethanol). Morphologies obtained from transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) images showed that the as-prepared GO and PDA-GO supports can accommodate electrodeposited metals loaded on the topmost layer of the support surfaces, although the size of nanoparticles is somewhat different. The electrochemical results indicated that the xPtPd/PDA-GO catalysts offered outstanding oxidation efficiencies. The prepared 5PtPd/PDA-GO catalyst provided enhanced activity and long-time stability in the oxidation reactions. The GO surface modified by the polymer and the other electrodeposited metal catalysts provided a larger number of available active sites, as the PDA offered a greater electric connection between the metal catalysts and the GO support during alcohol oxidation.

The synthesized nickel (Ni) nanoparticles are attached on mixed carbon support multi-walled carbon nanotubes (CNT) and carbon black (CB) as a composite support before loading with Pt nanoparticles, and various carbon compositions of Pt/xCNT-Ni-yCB catalyst materials (x and y = 1–2) were prepared. The as-prepared catalysts were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and their electro-characteristics, activity and stability were determined via electrochemical measurements. The results demonstrate that Pt/1CNT-Ni-2CB shows higher catalytic activity, electron transfer and stability than other catalysts (e.g., Pt/1CNT-Ni-1CB and Pt/2CNT-Ni-1CB) and commercial Pt/C towards oxidizing methanol and formic acid. The architecture of the mixed CNT and CB carbon structure induces unique structural and functional properties of those catalyst components and remarkably enhances electrochemical activation and catalytic performance. Thereby, demonstrating a synergistic effect between these components, which is also discussed in this article.

Preparation, characterization, and electrocatalytic study of the electrodeposited Pt and Pd (e.g., Pt and PtPd) catalysts on titanium dioxide (TiO2) modified reduced graphene oxide (rGO) support for formic acid oxidation were performed. The catalyst composites are labeled as xPt/rGO-TiO2, xPtyPd/rGO-TiO2, and yPd/rGO-TiO2 where x and y are cycle numbers of metal electrodeposition (x and y = 2–6). The characterizations of the catalysts were performed by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Small and dispersed metal nanoparticles are obtained on rGO-TiO2. The catalytic performances for formic acid oxidation were measured by cyclic voltammetry (CV) and chronoamperometry (CA). The electrocatalytic results reveal that the bimetallic 4Pt2Pd/rGO-TiO2 catalyst facilitates formic acid oxidations at the lowest potentials and generates the highest oxidation currents and also improves the highest CO oxidation compared to the monometallic 6Pt/rGO-TiO2 catalyst. According to the experimental data, the Pd and TiO2 enhance the electrocatalytic activity of the catalysts towards the formic acid oxidation; the improved catalytic performance of the prepared catalysts strongly relates to the high electrochemically active surface area (ECSA) investigated.

The objective of our work is to improve low-temperature fuel cell catalysts by increasing the surface area to augment the efficiency of catalytic reactions. Reduced graphene oxide (rGO) supports were prepared by adding N-containing derivatives of polydopamine (PDA) and loading of Pt and Pt-based metal alloy nanoparticles were accomplished for catalyst preparation. To study the effects of surface modification on catalyst activity, the GO surfaces modified by addition of PDA (PDA-rGO) were richer in oxygen- and nitrogen-containing functional groups, which reduced the number of graphene defects. Reduction of metals (M = Pt, Pd, PtxPdy where x and y = 1–3) by NaBH4 produced M/GO (metal on GO) and M/PDA-rGO (metal on PDA-rGO) catalysts. Examination of morphology and chemical composition confirmed that the existence of particle size on M/PDA-rGO catalysts was smaller than that on M/GO catalysts in agreement with calculated electrochemically active surface areas (ECSA). Electrochemical analysis was conducted to evaluate the catalyst activity and stability. The prepared catalysts had significantly greater surface areas as a result of association between the metal nanoparticles and the oxygen and nitrogen functional groups on the rGO supports. The catalysts also exhibited lower onset potentials and greater current intensities, If/Ib values, and long-term stabilities for methanol and ethanol oxidation compared with those of commercial PtRu/C. Moreover, the diameter of the Nyquist plot of the catalysts on PDA-rGO were smaller than that of the catalysts M/GO. The results suggest that variation of the PtxPdy atomic ratio on carbon nanocomposites is an encouraging means of enhancing electrocatalytic performance in direct alcohol fuel cell applications.