Carbon supported PtPdCr ternary alloy nanoparticles with enhanced electrocatalytic activity and durability for methanol oxidation reaction

In this work, the trimetallic PtPdCr nanoparticles with low platinum loading (~5 wt%) supported on Vulcan carbon (PtPdCr/C) were synthesized through a facile two-step co-reduction method and showed superior methanol oxidation activity. The particle size distribution, morphology and elemental composition of the PtPdCr/C were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. The electrochemical performance for methanol oxidation of the PtPdCr/C was found to be higher with the mass activity of 969 mA·mg⁻¹_Pt compared to Pt/C (581 mA·mg⁻¹ _Pt) and PtRu/C (725 mA·mg⁻¹ _Pt). Moreover, the stability studies confirmed the enhanced durability of PtPdCr/C over Pt/C and PtRu/C catalysts after the accelerated durability test (ADT) and chronoamperometry (CA) analysis. The increased methanol oxidation activity and durability of the trimetallic PtPdCr/C in acid medium can be attributed to the change in binding energy of Pt and the induced synergistic effect from Pd and Cr atoms to Pt, which demonstrated a promising strategy for the preparation and utilization of ternary alloy catalysts towards methanol electrooxidation.     

TiC supported Pt-based nanoparticles: Facile sonochemical synthesis and electrocatalytic properties for methanol oxidation reaction

In this study, we synthesized Pt nanoparticles (NPs) with small amounts of Mn (≤11.4 at%) included, hence Pt(Mn) NPs, on titanium carbide (TiC) support (denoted as Pt(Mn)/TiC) in three different Pt loadings (16.0–33.2 wt%) and investigated their electrocatalytic performance for methanol oxidation reaction (MOR) in acidic media. The syntheses were achieved via one-pot sonochemical reactions of Pt(acac)₂ and Mn(acac)₂ (acac = acetylacetonate) in ethylene glycol in the presence of TiC particles and without any other additives. The Pt(Mn) NPs were uniform in size (4–6 nm) and were evenly deposited on the TiC surface. The electronic structure of Pt in Pt(Mn)/TiC samples, probed by X-ray photoelectron spectroscopy (XPS) and other techniques, is systematically changed with the Pt loading, by which enhanced electrocatalytic properties from pure Pt are expected. In addition, the TiC support contributes to enhancing the electrocatalytic properties of Pt(Mn) NPs through its high conductivity, chemical resistance to corrosion, and the TiO₂ formed on the surface which exerts the bifunctional mechanism to reduce the CO poisoning on Pt. The electrochemical performance of Pt(Mn)/TiC was investigated by the rotating disk electrode (RDE) technique. The specific and mass MOR currents are, respectively, 1.6–2.2 and 0.9–1.4 times higher in Pt(Mn)/TiC samples than in commercial Pt/C. All Pt(Mn)/TiC samples show 93–98% of the initial electrochemical surface areas after 3000 potential cycles, superior electrochemical stability to commercial Pt/C (86%).     

Bimetallic Pt3Mn nanowire network structures with enhanced electrocatalytic performance for methanol oxidation

Pt-based catalysts are still most attractive and could be the major driving force for facile electrochemical reactions in direct methanol fuel cells (DMFCs). In this work, a Pt₃Mn nanowire network structures (NWNs) catalyst was successfully synthesized by a soft template (CTAB) method. The morphology and elemental composition of the Pt₃Mn NWNs were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma-optical emission spectroscopy (ICP-OES). The electrocatalytic behavior of the synthesized Pt₃Mn NWNs catalyst towards methanol oxidation reaction (MOR) was studied by cyclic voltammetry (CV) and chronoamperometry (CA). The results reveal that the Pt₃Mn NWNs has superior MOR activity and durability compared to Pt NWNs and commercial Pt/C. The mass and specific activities of Pt₃Mn NWNs are 0.843 A mg⁻¹ and 1.8 mA cm⁻² respectively, which are twice that of commercial Pt/C. Additionally, the results of CA test indicate that the Pt₃Mn NWNs possesses better durability than Pt NWNs and commercial Pt/C catalysts in acidic media, which is expected to be a new alternative anode material in DMFCs.     

Pt modified TiO2 nanotubes electrode: Preparation and electrocatalytic application for methanol oxidation

Pt nanoparticles decorated TiO₂ nanotubes (Pt/TiO₂NTs) modified electrode has been successfully synthesized by depositing Pt in TiO₂NTs, which were prepared by anodization of the Ti foil. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and electrochemical methods were adopted to characterize their structures and properties. The Pt/TiO₂NTs electrode shows excellent electrocatalytic activity toward methanol oxidation reaction (MOR) in alkaline electrolyte without UV irradiation.     

Fabrication of a bimetallic Cu/Pt particle-modified carbon nanotube paste electrode and its use for the electrocatalytic oxidation of methanol

In this work, carbon nanotube paste electrode (CNTPE) was used as a substrate for deposition of bimetallic Cu/Pt particles. At first, a Cu film was prepared by electrochemical reduction of Cu ions onto the CNTPE in 0.1 M H₂SO₄ solution. Cu/Pt catalysts were prepared by partial galvanic replacement of Cu with Pt by simply immersion of the Cu-coated CNTPE in 2.0 mM H₂PtCl₆ solution. The nature and surface morphology of the bare CNTPE and fabricated Cu/Pt species were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. The Cu/Pt-modified CNTPE exhibits remarkable electrocatalytic activity towards methanol oxidation. It has been shown that carbon nanotubes improve the electrocatalytic activity of the catalysts towards oxidation. Then, the influence of various parameters such as Cu source concentration, electrodeposition time, replacement time, and methanol concentration on its oxidation as well as long-term stability of the modified electrode have been investigated by electrochemical methods.     

Facile synthesis of Pd-Ru-P ternary nanoparticle networks with enhanced electrocatalytic performance for methanol oxidation

Liquid fuel cells have attracted broad research interests for past several decades, especially for direct methanol fuel cells (DMFCs) because of their compact volume, environmentally benign and easy storage. Exploring cost-effective electrocatalysts toward methanol electrooxidation is meaningful for the development of (DMFCs). Herein, a series of PdRu/P network catalysts have been fabricated and modified via a facile and reproducible method taking benzyl alcohol, hydrazine hydrate as solvent and reducing agents, respectively. Profiting from the 3D network structure, the synergistic effect together with the increased electron mobility induced by the addition of nonmetal phosphorous (P). The PdRu/P catalysts display markedly improved efficient electrocatalytic activity with excellent current peak, more negative onset potential, as well as superior long-term stability compared to commercial Pd/C, PdRu and Pd/P prepared under the same condition. In this work, we highlight the effect of the incorporation of nonmetals P on the electrocatalytic performance of PdRu binary catalysts, which will contribute to broadening the application of nonmetal P or even for other nonmetals for electrooxidation. Our efforts will dedicate to accelerating the commercialization of efficient and stable anode catalysts in fuel cells by means of doping transition metals or nonmetals into Pd.     

Highly dispersed ultrafine Pt nanoparticles on nickel-cobalt layered double hydroxide nanoarray for enhanced electrocatalytic methanol oxidation

Highly dispersed ultrafine Pt nanoparticles (NPs) were loaded on a nickel-cobalt layered double hydroxide (NiCo-LDH) nanoarray that was grown on Ni foam (NF) via an in situ redox reaction without any external agent between Co²⁺ (Co(OH)₂) in NiCo-LDH and PtCl₆^2-. The obtained Pt/NiCoLDH/NF composite was used as a catalyst for methanol oxidation in alkaline media, showing much higher electrocatalytic activity and better anti-poisoning ability and stability for methanol oxidation than commercial Pt/C, mainly because of the uniform dispersion of ultrafine Pt NPs, the synergistic effect and stable support of NiCoLDH. The NiCoLDH nanoarray effectively increased the specific surface area and location sites for supporting Pt NPs and enhanced the catalytic performance and tolerance to intermediate species. This enhancement was probably due to the synergistic effect between Pt and the NiCo-LDH nanosheets, in which the LDH can provide adequate OH^?_ads species for accelerating the methanol oxidation reaction (MOR).     

Pt nanoparticles supported on WO3/C hybrid materials and their electrocatalytic activity for methanol electro-oxidation

A simple and novel method for the preparation of WO₃/C is presented. This method includes the adsorption and decomposition of phosphotungstic acid (PWA) on carbon. For the purpose of comparison, WO₃/C is also prepared by a conventional method using sodium tungstate as the precursor. These two WO₃/C species are denoted as WO₃/C-1 and WO₃/C-2, respectively. It is shown from transmission electron microscopy (TEM) that the WO₃ particles in WO₃/C-1 present a more even distribution and smaller particle size than those in WO₃/C-2. Pt particles dispersed on WO₃/C-1 display the characteristic diffraction peaks of Pt in the face-centered cubic phase. Cyclic voltammetry and chronoamperometry show that the Pt-WO₃/C-1 catalyst exhibits much better methanol oxidation activity than the Pt-WO₃/C-2 and Pt/C catalysts. This significant improvement in catalytic performance may be attributed to the hydrogen spillover effect and the uniform distribution of Pt and WO₃ particles.     

Coverage-dependent electro-catalytic activity of Pt sub-monolayer/Au bi-metallic catalyst toward methanol oxidation

The coverage-dependent catalytic properties of a Pt nanofilm formed on a Au substrate were investigated for the electro-oxidation of methanol. The coverage of Pt nanofilm was precisely fabricated by the formation of coverage-controlled under potential deposition of Cu adlayer and followed by the surface limited redox replacement reaction with different Pt complex ions. The STM images exhibit the formation of Pt nano-film on Au substrate with different coverage. It was clearly shown that the activity of Pt nanofilm deposited on Au substrate toward the methanol electro-oxidation was highly sensitive to its surface coverage. Pt–Au bimetallic catalyst was found to become active at the Pt surface coverage near 0.2 and reached its maximum around 0.6. The electro-catalytic activity as well as CO tolerance on Pt–Au bimetallic system was found higher than those on a Pt electrode.     

Enhanced electrocatalytic performance of Pt nanoparticles immobilized on novel electrospun PVA@Ni/NiO/Cu complex bio-nanofiber/chitosan based on Calotropis procera plant for methanol electro-oxidation

Bioinspired Ni/NiO nanocomposite was synthesized in the Calotropis procera wood and its size and structure were confirmed by transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). The green and environmental friendly approach was performed for the preparation of copper nanocomplex (CC) under ultrasonic irradiation. Polyvinyl alcohol (PVA) nano-biofibers containing Ni/NiO nanocomposite and copper nanocomplex were obtained by electrospinning method. This novel bio nanocomposite was characterized by field-emission scanning electron microscope (FESEM), TEM, and atomic force microscopy (AFM) for further investigation. Novel Pt/PVA@Ni/NiO/Cu nanocomplex/chitosan (Pt/PVA@NOCC/CH) was synthesized and its catalytic performance was studied towards methanol electro-oxidation. Pt/PVA@NOCC/CH catalyst exhibits enhanced electrocatalytic performance towards methanol oxidation (MO), compared to Pt/PVA/CH and Pt/PVA@NOCC with respect to its better stability, larger electrochemically active surface area, enhanced mass activity, and improved resistance to poisoning. By and large, Pt/PVA@NOCC/CH is known as a promising electrocatalyst for fuel cells.     

Facile one-pot hydrothermal synthesis of Pt nanoparticles and their electrocatalytic performance

Pt nanoparticles are synthesized by a facile one-pot hydrothermal synthesis using one kind triblock Pluronic copolymers as reducer and stabilizer for the first time. The size of the Pt nanoparticles can be controlled through simply varying the reaction conditions. The morphology and structure of the Pt nanoparticles were well characterized by different techniques. The electrocatalytic test indicated that the obtained Pt nanoparticles exhibit a better electrocatalytic performance for methanol oxidation in acidic media compared to the commercial Pt/C catalyst. The results of this paper provide a promising approach to prepare Pt-based nanocatalysts for direct alcohols fuel cells (DAFCs).     

CeO2 nanowires stretch-embedded in reduced graphite oxide nanocomposite support for Pt nanoparticles as potential electrocatalyst for methanol oxidation reaction

A novel hybrid composite RGO-CeO_{2 NWS} with the nanowire-sheet structure was synthesized by a facile hydrothermal process using ethanol/water as the solvent without any organic additives. The graphene oxide proceeds to reduce to graphene and chemical bonds form between graphene oxide and CeO_{2 NWS}. Pt-based catalysts with the RGO-CeO_{2 NWS} composite as the support were then prepared by a microwave-assisted polyol process. The resultant catalysts were characterized by X-ray diffraction, Raman spectroscopy, Scanning tunneling microscopy, X-ray photoelectron spectroscopy, High resolution transmission electron microscopy and electrochemical tests. The results show that the hybrid Pt/RGO₄-CeO_{2 NWS} exhibits the best catalytic activity and the increased catalytic efficiency of Pt in the hybrid catalysts is evidence that CeO_{2 NWS} are anchored onto the chemical defects in the wrinkles and edges of the graphene surface. This avoids the restacking of graphene oxide, thus hindering the Pt nanoparticles embedded in folding and increasing the exposed active sites. The changed valence state from Ce⁴⁺ to Ce³⁺ in CeO_{2 NWS} will introduce oxygen vacancies and thus promote the tolerance of intermediate species in methanol oxidation.     

Temperature dependence on methanol oxidation and product formation on Pt and Pd modified Pt electrodes in alkaline medium

The effect of temperature on the catalytic oxidation of methanol on electrodeposited platinum and platinum-palladium alloy were carried out for a temperature range of 293-353 K. The morphology of the catalyst surface was studied using scanning electron microscopy, where as the structure and bulk composition of the Pt-Pd/C catalyst were determined by X-ray diffraction and energy dispersive X-ray spectroscopy. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy were used to investigate the electrochemical parameters related to electro-oxidation of methanol under the influence of temperature. Apparent activation energies of the oxidation reactions on Pt/C and Pt-Pd/C were determined at different potentials within the same temperature range. A pronounced influence of temperature towards methanol oxidation was observed on the Pt-Pd/C catalyst as compared to Pt alone. The incorporation of Pd into Pt decreases the charge transfer resistance and activation energy of the methanol oxidation substantially which ensures greater tolerance of this catalyst towards methanolic residues. Quantitative analysis of the oxidation reaction product by ion chromatography further substantiates the much better performance of the Pt-Pd electrode than Pt alone for electrocatalytic oxidation of methanol in alkaline medium.     

ZnO/Polytyramine nanocomposite film: Facile electrosynthesis and high performance electrocatalytic activity toward methanol oxidation

In the present study, the methanol oxidation reaction was investigated on a nickel ion incorporated to the zinc oxide-sodium dodecyl sulfate-polytyramine (ZnO-SDS-Pty) nanocomposite film by cyclic voltammetry and chronoamperometry. ZnO-SDS-Pty nanocomposite was prepared by using the repeated potential cyclic voltammetry in a solution containing ZnO nanoparticles and tyramine in an acidic solution of SDS by cycling the potential. The electrochemical oxidation of methanol was investigated by a stable redox behavior of the Ni(III)/Ni(II) couple at the potential of 0.4 V, after the immersion of the modified electrode (ZnO-SDS-Pty/G) in an alkaline media (i.e. NaOH 0.1 molL^?1) of nickel chloride solution. The electrochemical characterization of the modified electrode exhibited that the ZnO-SDS-Pty nanocomposite, electrodeposited on the electrode surface, improved the catalytic efficiency of the dispersed nickel ions toward methanol oxidation. The catalytic rate constant and diffusion coefficient of the methanol oxidation reaction were calculated by chronoamperometry. The Ni-ZnO-SDS-Pty nanocomposite displayed a highly stable response during the oxidation of methanol, proving to be a suitable electrode material in methanol fuel cells.     

Facile fabrication and electrocatalytic activity of Pt0.9Pd0.1 alloy film catalysts

A nano-thickness porous Pt_0.9Pd_0.1 alloy film with a greatly enhanced surface area were firstly synthesized at a glassy carbon electrode (GCE) using a facile cyclic voltammetry (CV) method. The atomic ratio of the alloy can be controlled by controlling the composition of the electrodeposition solution. We found that small amount of alloying Pd is an excellent catalytically enhancing agent for the Pt catalyst, and 10% Pd is the optimal. The structures of the Pt_0.9Pd_0.1 alloy film were characterized by FE-SEM, XPS, XRD and electrochemical techniques. It was found that the Pt_0.9Pd_0.1 film was in nanoporous structure and consisted of crystallites of 10.1 nm on average, leading to the modified electrode (Pt_0.9Pd_0.1/GCE) has an effective surface area as large as 790 times that of a corresponding bare Pt disk electrode. The Pt_0.9Pd_0.1/GCE exhibited significantly higher stability and catalytic activity for both of the methanol electro-oxidation reaction (MOR) and the oxygen electro-reduction reaction (ORR) than the correspondingly electrodeposited Pt modified GCE. The advantage can be attributed to the CV-prepared nano-porous structure on the electrode surface. This method and the prepared electrode can be expected to have promising applications in biosensors and fuel cells, etc.     

Construction of carboxyl functional groups and their enhancement effect for methanol electrocatalytic oxidation reaction

In this paper, we investigated the effect of ozone oxidation on properties of commercial carbon black supported platinum (Pt) nanoparticles for the methanol electro-oxidation reaction. The results indicated that the oxygenated functional groups could be introduced on the carbon black evenly with the increase of processing time. Apparently, mainly introduced oxygenated functional group is carboxyl. Platinum nanoparticles could be uniformly immobilized on the surfaces of carbon black treated with ozone, which has significant high electro-catalytic activity and stability for methanol electrooxidation. This phenomenon is attributed to the fact that oxygen-containing groups (mainly for carboxyl functional groups) produced by ozone oxidation are good for improving the dispersion and strengthening the interaction between support and platinum nanoparticles. The ozone oxidation conditions had significant effects on the defects properties of carbon black which showed a positive correlation between the defect levels and methanol electro-oxidation performances. This paper also fully demonstrated the positive relationship between carboxyl functional groups and the performance of methanol electrocatalytic oxidation.     

Well dispersed Pt nanoparticles on commercial carbon black oxidized by ozone possess significantly high electro-catalytic activity for methanol oxidation

In this paper, the electro-catalytic methanol oxidation on the commercial carbon black treated with ozone at different temperatures to support platinum (Pt) nanoparticles was investigated. The necessary techniques like transmission electron microscopy (TEM), Raman spectroscopy, nitrogen adsorption-desorption techniques, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) have been used to discovery the composition, morphology and structure of the catalysts. The electro-catalytic methanol oxidation activity and durability of the catalysts was estimated by the cyclic voltammetry and chronoamperometric techniques. The results indicated that the platinum nanoparticles with average sizes of 2.04 nm can be uniformly dispersed on the surfaces of carbon black oxidized by ozone at 140 °C. In the meanwhile it has significantly high electro-catalytic activity for methanol oxidation. This phenomenon is attributed to the fact that ozone oxidation increase the content of oxygen-containing groups on the carbon black, which is helpful for improving the dispersion and decreasing the size of platinum nanoparticles. Oxygen-containing groups play a critical role in enhancing the performance of methanol electro-oxidation.     

Crystalline nickel boride nanoparticle agglomerates for enhanced electrocatalytic methanol oxidation

In this paper, crystalline Ni₃B nanoparticle agglomerates have been successfully prepared via dry-powder annealing of the solution-produced amorphous nickel boride. The electron microscopy (EM) images indicate that the Ni₃B nanomaterial is composed of numerous nano-sized particles with a diameter ranging from 100 to 200 nm. The electrocatalytic characteristics of nickel boride in an alkaline medium were observed by cyclic voltammetry (CV) and chronoamperomerty (CA). Compared to the amorphous nickel boride/Ni foam (ANB/NF), the crystalline Ni₃B/Ni foam (CNB/NF) electrode exhibits a higher catalytic performance with low initial oxidation potential of 0.35 V and a high anodic oxidation current density of 62 A g⁻¹ at 0.55 V in a 6 M KOH solution with 0.5 M methanol. And the CNB/NF electrode shows good long-term cycling stability and the catalytic current of methanol retains 87% of the initial value after 1000 time cycles. The CNB/NF electrode should be a promising candidate for alkaline direct methanol fuel cells (DMFCs).     

Preparation of Pt/NiO-C electrocatalyst and heat-treatment effect on its electrocatalytic performance for methanol oxidation

Pt catalyst supported on Vulcan XC-72R containing 5 wt% NiO (Pt/NiO–C) showed larger electrochemical active surface area and higher electrochemical activity for methanol oxidation than Pt catalyst supported on Vulcan XC-72R using polyol method without NiO addition. Prepared Pt/NiO–C electrocatalyst was heat-treated at four temperatures (200, 400, 600, and 800 °C) in flowing N₂. X-ray diffraction and temperature-programmed desorption results indicated that NiO was reduced to Ni in inert N₂ during heat-treatments at temperatures above or equal to 400 °C, while oxygen from NiO reacted with carbon support due to the catalytic effect of Pt. The reduced Ni formed an alloy with Pt, which, according to the X-ray photoelectron spectroscopy data, resulted in a shift to a lower binding energy of Pt 4f electrons. The Pt/NiO–C electrocatalyst heat-treated at 400 °C showed the best activity in methanol oxidation due to the change in Pt electronic structure by Ni and the minimal aggregation of Pt particles.     

Enhanced electro-oxidation of methanol at nanoparticle-based Ru/Pt bimetallic catalyst: Impact of GC substrate pretreatment

This study addresses the facile preparation of electro-active Ru–Pt binary nanocatalyst layer electrodeposited onto glassy carbon (GC) electrodes for efficient methanol electrooxidation reaction (MOR). Unmodified GC and GC electrodes modified with Nafion (Naf/GC) and zeolite (Naf-Zeo/GC) are used as substrates for the electrodeposition of the Ru–Pt binary catalyst. Morphological, compositional, crystallographic and electrochemical characterizations were disclosed using scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX) unit, XRD, and cyclic voltammetry (CV), respectively. The electrocatalytic activity of the various modified GC electrodes towards MOR depends markedly on the structure of the catalyst layer and the pretreatment of the underlying GC substrate as well. The highest catalytic activity was obtained at Ru–Pt/Naf-Zeo/GC electrode as demonstrated in highest peak current and favorable negative shift of the onset potential of MOR. The underlying zeolite increases the tolerance of the Ru–Pt catalyst layer against CO poisoning possibly by facilitating its oxidative removal and thus retrieval of Pt active sites.