High Activity For Methanol Electrooxidation Research Articles

Cation modulation in dual-phase nickel sulfide nanospheres by pulsed laser irradiation for overall water splitting and methanol oxidation reaction

The development of a non-precious and highly active multifunctional electrocatalyst is essential for obtaining efficient electrochemical energy storage and conversion devices. Nickel derivate occupies the most important place when it comes to the transition metal-based electrocatalyst. In this study, we used a simple and extremely effective controllable pulsed laser irradiation (PLI) technique to fabricate dual-phase nickel sulfide, and we studied cation modulation using Co and Cu atoms. The multifunctional activity was witnessed by the performances of oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and methanol oxidation reaction (MOR) measured in an alkaline medium. The cation adjustment resulted in the improvement of the catalytic performance of HER and OER during Cu and Co substitution, respectively. For the Co-Ni-S sample in OER, we achieved an overpotential of 368 mV at 10 mA/cm2 in OER. The higher ECSA Cu-Ni-S sample improved HER activity at a lower overpotential of 271 mV at 10 mA/cm2 and a lower Tafel slope of 98 mV/dec. The excellent bifunctional activity enhanced overall water splitting with a lower voltage of 1.88 V to achieve a geometrical current density of 10 mA/cm2, with high durability. Meanwhile, the high selectivity of Cu resulted in a very high methanol electrooxidation activity with a current density as high as 55.4 mA/cm2. The detailed electrochemical studies were presented with their supporting physiochemical analysis. This report shows the efficiency and simplicity of fabricating transition metal derivatives and cation modulation using superficial laser methods.

Synthesis of PtCuFe alloy nanoframes with high-index facets for efficient electro-oxidation of liquid fuels

By controlling the structure, surface and composition of Pt-based ternary alloy nanocrystals, the electro-catalytic performances of Pt-based catalysts can be improved effectively. In this paper, a one-pot method for synthesis of PtCuFe nanoframes (PtCuFe NFs) with tunable structure and defect density is reported. By controlling the heating mode and the type of ligand, then changing the nucleation/growth kinetics, two types of PtCuFe NFs were obtained. These types of catalysts exhibited excellent electro-catalytic performance for methanol electrooxidation (MOR) and formic acid electrooxidation (FAOR). Specifically, the dendritic nanoframes (d-NFs) showed high electro-catalytic activity for MOR and FAOR, which were 8.34 times and 3.68 times higher than commercial Pt/C, respectively. The stability was also greatly improved. The excellent electrocatalytic activity of PtCuFe NFs is attributed to the defect sites of high-index facets and open framework structures. This strategy provides a new idea for improving the electrocatalytic performance of Pt-based catalysts.

Pd/C Catalyst with High Activity for Methanol Electrooxidation

Pd/C Catalyst with High Activity for Methanol Electrooxidation

Synthesis of Pt-Co micro/nanoporous array with high activity for methanol electrooxidation

Pt-Co micro/nanoporous array was fabricated by electrochemical deposition with the aid of a colloidal monolayer as a template. Morphology observation revealed that the prepared Pt-Co array was composed of ordered, hexagonal and spherical hollow holes with uniform nanogaps on the inner pore walls. The average Co content in the array was about 20 at%. The electrochemical measurements showed that the Pt-Co porous array exhibited high catalytic activity and stability for methanol electrooxidation in alkaline medium, which made it more attractive for fuel cell applications.

Methanol oxidation reaction on core-shell structured Ruthenium-Palladium nanoparticles: Relationship between structure and electrochemical behavior

In this work the relationship between structural composition and electrochemical characteristics of Palladium(Pd)-Ruthenium(Ru) nanoparticles during alkaline methanol oxidation reaction is investigated. The comparative study of a standard alloyed and a precisely Ru-core-Pd-shell structured catalyst allows for a distinct investigation of the electronic effect and the bifunctional mechanism. Core-shell catalysts benefit from a strong electronic effect and an efficient Pd utilization. It is found that core-shell nanoparticles are highly active towards methanol oxidation reaction for potentials ≥0.6 V, whereas alloyed catalysts show higher current outputs in the lower potential range. However, differential electrochemical mass spectrometry (DEMS) experiments reveal that the methanol oxidation reaction on core-shell structured catalysts proceeds via the incomplete oxidation pathway yielding formaldehyde, formic acid or methyl formate. Contrary, the alloyed catalyst benefits from the Ru atoms at its surface. Those are found to be responsible for high methanol oxidation activity at lower potentials as well as for complete oxidation of CH3OH to CO2 via the bifunctional mechanism. Based on these findings a new Ru-core-Pd-shell-Ru-terrace catalyst was synthesized, which combines the advantages of the core-shell structure and the alloy. This novel catalyst shows high methanol electrooxidation activity as well as excellent selectivity for the complete oxidation pathway.

Pt nanoparticles supported on Co embedded coal-based carbon nanofiber for enhanced electrocatalytic activity towards methanol electro-oxidation

Abstract A Co embedded coal-based carbon nanofiber (Co-coal-CF) was proposed as a promising support of the Pt nanocatalyst for the methanol oxidation reaction. The nanofiber support was fabricated by electrospinning of polyacrylonitrile, oxidized coal and cobalt acetate, followed by carbonization process. And then the Pt nanoparticles were deposited on Co-coal-CF to fabricate the supported electrocatalyst. Cyclic voltammetry and chronoamperometry revealed a significantly high methanol electrooxidation activity and stability for the Pt/Co-coal-CF compared to that of the Pt nanoparticles deposited on carbon nanofiber (CF), coal-based carbon nanofiber (coal-CF) and Co embedded carbon nanofiber (Co-CF), respectively.

3D Hierarchical Pt-Nitrogen-Doped-Graphene-Carbonized Commercially Available Sponge as a Superior Electrocatalyst for Low-Temperature Fuel Cells.

Three-dimensional hierarchical nitrogen-doped graphene (3D-NG) frameworks were successfully fabricated through a feasible solution dip-coating method with commercially available sponges as the initial backbone. A spongy template can help hinder the graphene plates restacking in the period of the annealing process. The Pt/3D-NG catalyst was synthesized employing a polyol reduction process. The resultant Pt/3D-NG exhibits 2.3 times higher activity for methanol electro-oxidation along with the improvement in stability as compared with Pt/G owing to their favorable features including large specific surface area, high pore volume, high N doping level, and the homogeneous dispersion of Pt nanoparticles. Besides, Pt/3D-NG also presents high oxygen reduction reaction (ORR) performance in acid media when compared with Pt/3D-G and Pt/G. This work raises a valid solution for the fabrication of 3D functional freestanding graphene-based composites for a variety of applications in fuel cell catalysis, energy storage, and conversion.

Multiwall-carbon nanotube modified by N-doped carbon quantum dots as Pt catalyst support for methanol electrooxidation

The modification of N-doped carbon quantum dots (NCQDs) is an innovative approach to change the properties of multiwall-carbon nanotube (MWCNT). Here we report a facile hydrothermal treatment to synthesize NCQDs-MWCNT support, which acts as an improved catalyst support of Pt-based anode catalyst for direct methanol fuel cells. The structural properties of homemade catalysts are characterized by X-ray diffraction, Energy dispersive analysis of X-ray, transmission electron microscopy and X-ray photoelectron spectroscopy. The results indicate that Pt nanoparticles are well dispersed onto NCQDs-MWCNT and have a synergetic interaction with NCQDs. The results of electrochemical measurements reveal that Pt/NCQDs-MWCNT catalyst exhibits 1.3 times higher activity for methanol electrooxidation than that of Pt/MWCNT. The enhanced performance of Pt/NCQDs-MWCNT is attributed to the fact that NCQDs improve the dispersion of MWCNT and more uniform Pt nanoparticles are stabilized on NCQDs-MWCNT. NCQDs play a critical role in electrocatalytic performance for methanol electrooxidation.

Facile one-pot synthesis of Pt/graphene-TiO2 hybrid catalyst with enhanced methanol electrooxidation performance

Pt/graphene-TiO2 hybrid catalysts have been synthesized by a facile one-pot solvothermal method. The Structural properties of obtained Pt/graphene-TiO2 catalysts are characterized by X-ray diffraction (XRD), Energy dispersive analysis of X-ray (EDAX) and transmission electron microscopy (TEM).Interesting, TEM presents Pt nanoparticles seem preferentially to locate between TiO2 and graphene, forming the unique triple junctions structure. The electrochemical experimental results indicate that Pt/graphene-TiO2 catalyst exhibits 1.46 times higher activity for methanol electrooxidation than that of Pt/graphene and its stability is improved by 15% as compared with Pt/graphene. Moreover, performance of Pt/graphene-TiO2 hybrid catalyst is evaluated by the Single Fuel Cell Tests for the first time. Single fuel cell tests show the maximum power density of the direct methanol fuel cell using Pt/graphene-TiO2 as the anode catalyst is increased by 55% compared with that using Pt/graphene catalyst at the same operating conditions. The significantly enhanced electrochemical performance can be ascribed to (1) the synergetic effect between Pt, graphene and TiO2; (2) strong metal-support interaction (SMSI) between Pt nanoparticles and TiO2. These findings suggest their great potential applications in fuel cells.

A newly-designed sandwich-structured graphene–Pt–graphene catalyst with improved electrocatalytic performance for fuel cells

A novel sandwich-structured G–P–G catalyst prepared by a simple, facile synthesis method exhibits 1.27 times higher activity for methanol electro-oxidation than that of Pt/graphene and the stability is improved by 70% as compared with Pt/graphene.

One-pot synthesis of a three-dimensional graphene aerogel supported Pt catalyst for methanol electrooxidation

A Pt/graphene aerogel hybrid catalyst synthesized via a facile one-pot solvothermal method exhibits 2.86 times higher activity for methanol electrooxidation than that of Pt/graphene and the stability is improved by 10% as compared with Pt/graphene.

Application of Carbon Supported Ptcore–Aushell Nanoparticles in Methanol Electrooxidation

Pt/C catalyst (carbon supported Pt nanoparticles) is synthesized through a microwave-assisted polyol process. Moreover, it is further employed as the starting material to prepare the Pt@Au/C catalyst (carbon supported Ptcore–Aushell nanoparticles) by a heteroepitaxial growth method using glucose as a reducing agent. The research results indicate that the slow reduction of the Au precursor caused by glucose successfully induces the Au atoms to grow around the Pt nanoparticles in the Pt/C catalyst to form the Au shell, whose structure transforms gradually from the Pt to Au fcc structure during the course of its growth. Moreover, the Au shell of the Ptcore–Aushell nanoparticles retains the Pt fcc structure when the theoretical atomic ratio between Au and Pt atoms (RAu/Pt) in the catalyst is less than 0.2. Furthermore, the Au shell with the Pt fcc structure in the Pt@Au/C catalysts (RAu/Pt ≤ 0.2) simultaneously bestows on the catalysts high methanol electrooxidation activity, excellent CO tolerance, and satisfactory performance for CO electrooxidation.

Pt–rGO–TiO2 nanocomposite by UV-photoreduction method as promising electrocatalyst for methanol oxidation

Pt/TiO2-decorated reduced graphene oxide composite as catalyst for methanol electro-oxidation with three phase junction structure has been synthesized by UV-photoreduction (denoted as p-Pt/rGO@TiO2). The obtained p-Pt/rGO@TiO2 has been detailedly characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and chronoamperometry (CA). XRD and TEM characterizations indicate that photoreduction is favorable to anchoring Pt nanoparticles (NPs) (ca. 2.2 nm) at the interface between TiO2 and reduced graphene oxide (rGO), and forming the Pt, TiO2 and rGO three phase junction structure. P-Pt/rGO@TiO2 exhibits a higher activity for methanol electro-oxidation than m-Pt/rGO and m-Pt/rGO@TiO2 (prepared by microwave-assisted polyol process). Lifetime tests demonstrate that the electrochemical durability of p-Pt/rGO@TiO2 is improved by a factor of 2 or more as compared with m-Pt/rGO and m-Pt/rGO@TiO2. XPS characterizations of p-Pt/rGO@TiO2 reveal stronger interaction between Pt and support hybrid compared with m-Pt/rGO@TiO2, which facilitates poisoning species removal and prevents Pt nanoparticles from migrating/agglomerating on or detaching from carbon support. This provides a facile and promising strategy to improve both the activity and durability of electrocatalysts for DMFCs.

Synthesis of Ultrafine Mesoporous Tungsten Carbide by High-energy Ball Milling and Its Electrocatalytic Activity for Methanol Oxidation

Ultrafine mesoporous tungsten carbide (WC) was prepared from as-synthesized mesoporous WC using high-energy ball milling treatment. X-ray diffraction (XRD), scanning electron microscopy (SEM), and nitrogen adsorption-desorption techniques were used to characterize the samples. Brunauer-Emmett-Teller (BET) surface areas of WC samples increased with the increasing ball milling time and kept constant at 10–11 m2·g−1 for over 9 h. The electrocatalytic properties of methanol electro-oxidation at WC powder microelectrodes were investigated by cyclic voltammetry, chronoamperometry, and quasi-steady-state polarization techniques. The results reveal that ball-milled WC exhibits higher activity for methanol electro-oxidation than as-synthesized mesoporous WC. The suitability of ball-milled WC for methanol electro-oxidation is better than platinum (Pt) micro-disk, although the current peak is not as high as the Pt micro-disk. Moreover, increasing the methanol concentration and reaction temperature promotes methanol electro-oxidation on ultrafine mesoporous WC.

Synthesis and Characterization of PtRe Alloy Nanoparticles as Electrocatalysts for Methanol Oxidation

We report a new synthesis of PtRe alloy nanoparticles (NPs) and their electrocatalytic activity for methanol oxidation. PtRe alloy NPs with controlled composition were prepared by a capping agents-based colloidal method. In the synthesis, trioctylamine was used as high-boiling solvent, and oleylamine/oleic acid were employed as capping agents to control the particle size and dispersion. The PtRe NPs were fully characterized by TEM, EDX, XRD and XPS. The as-prepared PtRe NPs had a narrow size distribution, and displayed a good dispersion in hydrocarbon solvents. Carbon-supported PtRe catalysts were prepared by physical deposition of as-prepared particles on carbon powder, followed by the catalytic activation at 400 degrees C in Ar/H2. Electrochemical studies showed the PtRe catalysts had high activity for methanol electrooxidation.

High activity PtRu/C catalysts synthesized by a modified impregnation method for methanol electro-oxidation

A modified impregnation method was used to prepare highly dispersive carbon-supported PtRu catalyst (PtRu/C). Two modifications to the conventional impregnation method were performed: one was to precipitate the precursors ((NH 4) 2PtCl 6 and Ru(OH) 3) on the carbon support before metal reduction; the other was to add a buffer into the synthetic solution to stabilize the pH. The prepared catalyst showed a much higher activity for methanol electro-oxidation than a catalyst prepared by the conventional impregnation method, even higher than that of current commercially available, state-of-the-art catalysts. The morphology of the prepared catalyst was characterized using TEM and XRD measurements to determine particle sizes, alloying degree, and lattice parameters. Electrochemical methods were also used to ascertain the electrochemical active surface area and the specific activity of the catalyst. Based on XPS measurements, the high activity of this catalyst was found to originate from both metallic Ru (Ru 0) and hydrous ruthenium oxides (RuO x H y ) species on the catalyst surface. However, RuO x H y was found to be more active than metallic Ru. In addition, the anhydrous ruthenium oxide (RuO 2) species on the catalyst surface was found to be less active.

Highly active PtRuFe/C catalyst for methanol electro-oxidation

High methanol electro-oxidation activity was obtained on novel PtRuFe/C (2:1:1 at.%) catalyst. Mass and specific activities were 5.67 A g −1 catal. and 177 mA m −2 for the PtRuFe/C catalyst while those of the commercial PtRu/C catalyst were 2.28 A g −1 catal. and 87.7 mA m −2, respectively. CO stripping results showed that on-set voltage for CO electro-oxidation was lowered by incorporation of Fe. XRD and XPS results revealed that Fe 2O 3 was formed instead of Fe(0), which resulted in large electron deficiency in Pt and easy CO electro-oxidation. The electron deficiency of Pt was proved by XPS results of Pt4f peaks, which moved to higher binding energies in PtRuFe/C than PtRu/C.

Synthesis of PtRu/carbon nanotube composites in supercritical fluid and their application as an electrocatalyst for direct methanol fuel cells

PtRu nanoparticles were decorated on multi-walled carbon nanotubes (MWCNTs) using H2PtCl6 and RuCl3 as precursors with the aid of supercritical CO2, and the resulting composites were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy. TEM observation showed that nanoparticles of size about 5nm were distributed evenly on the MWCNTs, and XRD analysis showed that the particles had a face-centered cubic crystal structure. The loading content of the nanoparticles on the MWCNTs could be adjusted by manipulating the relative ratio of the precursor to MWCNTs. The as-prepared PtRu/MWCNT composites exhibited high activity for methanol electro-oxidation.

Microwave polyol synthesis of Pt/C catalysts with size-controlled Pt particles for methanol electrocatalytic oxidation

Pt/C catalysts with different mean size of Pt particles were prepared by a microwave-assisted polyol process and characterized by TEM and XRD. The effects of the synthesis solution pH on Pt particles size and distribution, and their activity for methanol electrooxidation were investigated. Pt nanoparticles were small and uniform with mean size of 2.7 nm under the pH of 9.5. Pt/C catalyst showed high activity for methanol electrooxidation.

Effective preparation of carbon nanotube-supported Pt–Ru electrocatalysts

Carbon nanotube (CNT)-supported electrocatalysts, such as Pt/CNT and Pt–Ru/CNT, have been intensely studied recently for membrane fuel cell applications. These novel electrocatalysts were generally prepared by chemical reduction deposition using ethylene glycol (EG) as a reducing agent. However, due to different metal deposition conditions, CNT-supported binary and multi-component electrocatalysts cannot be prepared using EG alone with satisfactory results. In this study, an effective method for preparation of CNT-supported Pt–Ru alloy electrocatalysts has been developed. Suitable amounts of sodium hydrogen sulfite (NaHSO 3) and calcium hydroxide aqueous solutions were employed as additives to EG forming a modified reducing agent. This new approach was based on the use of more suitable Pt–Ru deposition environments created by the modified EG near the isoelectric point (IEP) on the acid-oxidized CNT surfaces. It gave rise to enhanced formation of Pt–Ru/CNT with high metal deposition efficiency, excellent nanoparticle morphology and desired electrocatalyst composition. In addition, the prepared Pt–Ru/CNT exhibited high methanol electrooxidation activity in 0.5 M H 2SO 4 aqueous solution better than that of a carbon black-supported commercial product. Overall, preparation of Pt–Ru/CNT using the modified EG resulted in much better electrocatalyst formations than those prepared using a variety of common reducing agents.