Synthesis of Truncated‐Octahedral Pt–Pd Nanocrystals Supported on Carbon Black as a Highly Efficient Catalyst for Methanol Oxidation

A novel PtPd/C nanocrystals catalyst with truncated‐octahedral structure has been successfully prepared by ethylene glycol reduction to induce anisotropic growth in an isotropic medium by adding a small amount of Fe³⁺ species. Its structure, composition, and morphology are characterized by X‐ray diffraction, transmission electron microscopy, and scanning transmission electron microscopy‐energy dispersive spectroscopy elemental maps, respectively. The electrochemical measurements demonstrate that the highly dispersed and uniform PtPd/C nanocrystals have excellent poisoning tolerance, significantly higher electrocatalytic activity and durability for the methanol oxidation, as compared to solid solution PtPd/C and Pt/C catalysts. This may be ascribed to the stepped atoms and dangling bonds, which served as active sites for breaking chemical bonds during oxidation–reduction reaction; the high density of preferred crystal planes of (111) facets greatly enhanced the oxidation of poisonous residues during reaction.     

Matrix Material Study for in situ Grown Pt Nanowire Electrocatalyst Layer in Proton Exchange Membrane Fuel Cells (PEMFCs)

The cathode electrocatalyst layers were prepared by in situ growing Pt nanowires (Pt‐NWs) in two kinds of matrixes with various Pt loadings for proton exchange membrane fuel cells (PEMFCs). Commercial carbon powder and 20 wt.% Pt/C electrocatalyst were used as the matrix material for the comparison. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), polarization curves tests, and electrochemical impedance spectroscopy (EIS) were carried out to examine the effects of the matrix materials on the Pt‐NW growing and the electrode performance. The optimum Pt‐NW loadings of 0.30 mg cm⁻² in the carbon matrix (CM) and 0.20 mg cm⁻² for the Pt/C matrix (PM) were obtained. The results indicated that the Pt‐NWs grown in the CM had a better crystalline, longer size length and better catalyst activity than those in the PM. The mechanism of the matrix affection is further discussed in this paper.     

The Promoting Effect of Europium on PtSn/C Catalyst for Ethanol Oxidation

Well‐dispersed PtSnEu/C and PtSn/C catalysts were prepared by the impregnation–reduction method using formic acid as a reductant and characterised by X‐ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersion X‐ray spectroscopy (EDX) and X‐ray photoelectron spectroscopy (XPS). The synthesised catalysts with different atomic ratios of Pt/Sn/Eu have the Pt face centered cubic (fcc) structure and their particle sizes are 3–4 nm. The PtSnEu/C catalyst is composed of many Pt (0), SnO₂, Eu(OH)₃, a small amount of Pt(II) and partly alloyed PtSn, but no metallic Eu. The electrochemical measurements indicate that in comparison with Pt₃Sn₁/C catalyst, the Pt₃Sn₁Eu₁/C catalyst for ethanol oxidation has more negative onset potential, smaller apparent activation energy and lower electrochemical impedance so that it exhibits very high catalytic activity. Its peak current density increases by 135% and 40%, compared with Pt₃Sn₁/C and Pt₁Ru₁/C (JM) catalysts, respectively. This is because the Eu(OH)₃ formed by adding Eu to PtSn/C catalyst can provide the OH group which is in favour of the removal of adsorbed intermediates and ethanol oxidation.     

Study of Methanol‐tolerant Oxygen Reduction Reaction at Pt–Bi/C Bimetallic Nanostructured Catalysts

The nanostructured platinum–bismuth catalysts supported on carbon (Pt₃Bi/C, PtBi/C and PtBi₃/C) were synthesised by reducing the aqueous metal ions using sodium borohydride (NaBH₄) in presence of a microemulsion. The amount of metal loading on carbon support was found to be 10 wt.‐%. The catalyst materials were characterised by X‐ray diffraction (XRD), X‐ray fluorescence (XRF), transmission electron microscope (TEM) and electroanalytical techniques. The Pt₃Bi/C, PtBi/C and PtBi₃/C catalysts showed higher methanol tolerance, catalytic activity for oxygen reduction reaction (ORR) than Pt/C of same metal loading. The electrochemical stability of these nano‐sized catalyst materials for methanol tolerance was investigated by repetitive cycling in the potential range of –250 to 150 mV_MSE. Bi presents an interesting system to have a control over the activity of the surface for MOR and ORR. All Pt–Bi/C catalysts exhibited higher mass activities for oxygen reduction (1–1.5 times) than Pt/C. It was found that PtBi/C catalyst exhibits better methanol‐tolerance than the other catalysts.     

Methanol‐Tolerant Heterogeneous PdCo@PdPt/C Electrocatalyst for the Oxygen Reduction Reaction

We have prepared carbon‐supported nanoparticles with the heterogeneous structure of a PdPt shell on a PdCo core which are effective for the oxygen reduction reaction (ORR) in the presence of methanol. The preparation was based on the galvanic replacement reaction between PdCo/C nanoparticles and PtCl₄^2–, a method of general utility which can be extended to the preparation of other core‐shell electrocatalysts. The heterogeneous PdCo‐core and PtPd‐shell architecture was confirmed by multiple techniques including high resolution transmission electron microscopy, energy dispersive X‐ray spectroscopy, powder X‐ray diffraction and X‐ray photoelectron spectroscopy. The activity of the PdCo@PdPt/C catalyst in ORR was evaluated in acidic solutions both with and without methanol (0.1 M). The results showed four to sixfold increases in activity over a standard Pt/C catalyst with no apparent loss of catalyst stability. It is inferred that the strain effect from the lattice mismatch between the shell and core components is the major contributor for the enhancement of ORR activity and selectivity.     

Synthesis of Pd/C Catalyst by Modified Polyol Process for Formic Acid Electrooxidation

Pd catalyst supported on Vulcan XC‐72 carbon black was prepared by a modified polyol process. Its performance was compared with that of Pd/C catalyst prepared by impregnation reduction method by using NaBH₄ as a reducing agent for formic acid electrooxidation. Their physical characterisations were tested by means of energy dispersive analysis of X‐ray, X‐ray diffraction and transmission electron micrographs. Their activities were presented by cyclic voltammetry and chronoamperometry. The results show that the particle sizes of Pd/C catalysts prepared by modified polyol process and impregnation reduction method are 3.9 and 7.9 nm, respectively. The size dispersion of the former is narrower and more homogeneous than that of the latter. However, both of Pd/C catalysts display the characteristic diffraction peaks of a Pd face‐centred cubic (f.c.c.) crystal structure. The results of electrochemical measurements present that the Pd/C catalyst prepared by modified polyol process has the higher electrocatalytic activity and stability for formic acid electrooxidation in comparison to the Pd/C one by impregnation reduction method due to the particle size effect, and its peak current density of CV and the current of chronoamperometric curve at 1,000 s reach 33.2 and 11.2 mA cm^–2, respectively.     

Investigations of Compositions and Performance of PtRuMo/C Ternary Catalysts for Methanol Electrooxidation

PtRuMo/C catalyst was prepared by impregnation reduction method and characterised. Comparison is made between a home‐made PtRu/C prepared by similar method and Pt/C (E‐Tek Co., Pt/C‐ET) catalysts. One glassy carbon disc electrode for ternary alloy catalyst was used to evaluate the catalytic performances by cyclic voltammetric, chronoamperometric, amperometric i–t curves, and electrochemical impedance spectra (EIS). The electrochemical measurement results indicated that the performance of PtRuMo/C with a molar ratio of 6:3:1 was the highest among 15 Pt_xRu_yMo_10–x–y/C catalysts with different molar ratios. The composition, particle size, lattice parameter and morphology of the PtRuMo(6:3:1)/C catalyst were determined by means of X‐ray energy dispersive analysis, X‐ray diffraction (XRD) and transmission electron micrographs (TEM). The result of XRD analysis exhibits that PtRuMo(6:3:1)/C has the fcc structure with the smaller lattice parameter than the home‐made PtRu/C and Pt/C‐ET. Its typical particle sizes is only about 5 nm. With respect to the catalytic activity and stability, the PtRuMo(6:3:1)/C catalyst is superior to PtRu/C despite their comparable active areas. Though the electrochemically active surface area of Pt/C‐ET is the biggest, its performance is the lowest. EIS results also indicate that the reaction resistances for methanol electrooxidation on the PtRuMo(6:3:1)/C catalyst are smaller than those of PtRu/C at different polarisation potentials.     

Graphene and Functionalized Graphene Supported Platinum Catalyst for PEMFC

The graphene was synthesized by chemical oxidation followed by thermal exfoliation of natural graphite. The functionalized graphene (FG) was prepared by chemical treatment of the synthesized graphene. The as‐synthesized graphene and FG were characterized and used as Pt support materials. The 20 wt.% Pt/G and 20 wt.% Pt/FG catalysts were prepared by precipitation method. The prepared catalysts were characterized for particle size using X‐ray diffraction, surface morphology, electrochemical performance, and stability using cyclic voltammetry. The electrochemical surface area of the FG supported platinum catalyst was found to be more than 45% as compared to the commercial carbon supported platinum catalyst. The stability of the developed catalyst (Pt/G and Pt/FG) was significantly higher than the commercial Pt/C. The membrane electrode assembly was developed using the catalysts and tested in a PEMFC. The maximum power densities of the fuel cell were found to be 314, 426, and 455 mW cm^–2 using Pt/C, Pt/G, and Pt/FG, respectively.     

Facile Preparation of an Excellent Pt/RuO2‐MnO2/CNTs Nanocatalyst for Anodes of Direct Methanol Fuel Cells

RuO₂‐MnO₂ complex supported by multi‐wall carbon nanotubes (CNTs) was firstly synthesised by the oxidation–reduction precipitation of RuCl₃ and KMnO₄ in one step. Then Pt was loaded onto the obtained RuO₂‐MnO₂/CNTs to fabricate a novel anodic catalyst Pt/RuO₂‐MnO₂/CNTs for direct methanol fuel cells (DMFCs). The catalyst was characterised by transmission electron microscopy (TEM), X‐ray diffraction (XRD), temperature programmed reduction (TPR), X‐ray photoelectron spectroscopy (XPS) and BET specific surface areas (BET). Pt nanoparticles were found uniformly dispersed on the surface of CNTs, with the average diameter of about 2.0 nm. The activities of methanol and CO electrocatalytic oxidation were analysed, and the reaction mechanism of methanol electro‐oxidation on Pt/RuO₂‐MnO₂/CNTs catalyst was discussed. The MnO₂ in the catalysts improves the proton conductivity and electrochemical active surface area (EAS) for the catalysts. RuO₂ improves the CO oxidation activity and Pt dispersion. CNTs provide effectively electron channels. Thus, the Pt/RuO₂‐MnO₂/CNTs catalyst has high utilisation of the noble metal Pt, high CO oxidation ability and excellent methanol electro‐oxidation activity, being an outstanding anode catalyst for DMFC.     

Enhanced Electrocatalysis for Methanol Oxidation on Ordered {[PdPW11O39]5–/Pt/PAMAM}n Multilayer Composites

The {[PdPW₁₁O₃₉]^5–/Pt/PAMAM}_n multilayer composites constructed from G4.0 Amino‐terminated poly (amidoamine) dendrimer (PAMAM), Pt and Keggin‐type palladium(II)‐substituted polyoxometalates anion ([PdPW₁₁O₃₉]^5–) were prepared via layer by layer electro‐depositing technique. The X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD), and field emission scanning electron microscope (FE‐SEM) characterization indicate that the Pt nanoparticles have been anchored on the as‐prepared nanocomposites. And the morphologies of Pt nanoparticles are influenced by deposition potential, the number of layers of {[PdPW₁₁O₃₉]^5–/Pt/PAMAM}_n multilayer nanocomposites, and the existence of PAMAM. The electrocatalytic properties and stability of {[PdPW₁₁O₃₉]^5–/Pt/PAMAM}_n multilayer nanocomposites were investigated by cyclic voltammetry. Experimental investigation results reveal that PAMAM is a good support for Pt nanoparticle growth due to its interior cavity structure and high stability. [PdPW₁₁O₃₉]^5– play an important role to prevent intermediate product (mainly as CO) in the methanol oxidation from poisoning the as‐prepared catalyst. The {[PdPW₁₁O₃₉]^5–/Pt/PAMAM}₃/GC shows better electrocatalytic properties, stability, and CO tolerance ability than Pt/GC and {Pt/PAMAM}₃/GC fabricated by similar electrodeposition processes.     

Pd‐W Alloy Electrocatalysts and Their Catalytic Property for Oxygen Reduction

In order to design Pt‐free efficient cathode catalyst and promote the commercialization of fuel cells, different atomic ratio of carbon‐supported Pd‐W alloy catalysts were developed for oxygen reduction reaction (ORR). X‐ray diffraction (XRD) results show the Pd‐W alloys have the similar lattice characteristics to pure Pd. Transmission electron microscopy (TEM) and energy‐dispersive X‐ray spectroscopy (EDS) results show that the Pd‐W alloys disperse on the surface of carbon support uniformly. The results of the electrochemical tests show that the Pd₁₉W/C has two‐fold mass activity over Pd/C, which is hopeful for the application as low‐cost cathode catalyst.     

Controllable‐Nitrogen Doped Carbon Layer Surrounding Carbon Nanotubes as Novel Carbon Support for Oxygen Reduction Reaction

Novel nitrogen‐doped carbon layer surrounding carbon nanotubes composite (NC‐CNT) (N/C ratio 3.3–14.3 wt.%) as catalyst support has been prepared using aniline as a dispersant to carbon nanotubes (CNTs) and as a source for both carbon and nitrogen coated on the surface of the CNTs, where the amount of doped nitrogen is controllable. The NC‐CNT so obtained were characterized with scanning electron microscopy (SEM), Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS), and nitrogen adsorption and desorption isotherms. A uniform dispersion of Pt nanoparticles (ca. 1.5–2.0 nm) was then anchored on the surface of NC‐CNT by using aromatic amine as a stabilizer. For these Pt/NC‐CNTs, cyclic voltammogram measurements show a high electrochemical activity surface area (up to 103.7 m² g^–1) compared to the commercial E‐TEK catalyst (55.3 m² g^–1). In single cell test, Pt/NC‐CNT catalyst has greatly enhanced catalytic activity toward the oxygen reduction reaction, resulting in an enhancement of ca. 37% in mass activity compared with that of E‐TEK.     

Evaluation of the Performance of Carbon Supported Pt–Ru–Ni–P as Anode Catalyst for Methanol Electrooxidation

This research is aimed to improve the activity and stability of ternary alloy Pt–Ru–Ni/C catalyst. A novel anodic catalyst for direct methanol fuel cell (DMFC), carbon supported Pt–Ru–Ni–P nanoparticles, has been prepared by chemical reduction method by using NaH₂PO₂ as a reducing agent. One glassy carbon disc working electrode is used to test the catalytic performances of the homemade catalysts by cyclic voltammetric (CV), chronoamperometric (CA) and amperometric i–t measurements in a solution of 0.5 mol L^–1 H₂SO₄ and 0.5 mol L^–1 CH₃OH. The compositions, particle sizes and morphology of home‐made catalysts are evaluated by means of energy dispersive analysis of X‐ray (EDAX), X‐ray diffraction (XRD) and transmission electron micrographs (TEM), respectively. TEM images show that Pt–Ru–Ni–P nanoparticles have an even size distribution with an average diameter of less than 2 nm. The results of CV, CA and i–t curves indicate that the Pt–Ru–Ni–P/C catalyst shows significantly higher activity and stability for methanol electrooxidation due to the presence of non‐metal phosphorus in comparison to Pt–Ru–Ni/C one. All experimental results indicate that the addition of non‐metallic phosphorus into the Pt–Ru–Ni/C catalyst has definite value of research and practical application for enhancing the performance of DMFC.     

High Performance Carbon‐Supported Core@Shell PdSn@Pt Electrocatalysts for Oxygen Reduction Reaction

In this report, a low‐cost and high performance PdSn@Pt/C catalyst with core–shell structure is prepared by two‐stage route. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) examinations show that the composite catalyst particles distribution is quite homogeneous and has a high surface area and the PdSn@Pt/C catalyst has an average diameter of ca. 5.6 nm. The oxygen reduction reaction (ORR) activity of PdSn@Pt/C was higher than commercial Pt/C catalyst. Catalytic activity is studied by cyclic voltammetry. High electrocatalytic activities could be attributed to the synergistic effect between Pt and PdSn.     

Stability of Pt–Co/C and Pt–Pd/C based oxygen reduction reaction electrocatalysts prepared at a low temperature by a combined impregnation and seeding process in PEM fuel cells

The stability of Pt–Co/C and Pt–Pd/C electrocatalysts relative to that of a commercial Pt/C catalyst was measured in terms of the loss of the electrochemical surface area (ESA). The electrocatalytic activity was investigated in an acidic solution (0.3 M H₂SO₄) and in a single PEM fuel cell under H₂/O₂ conditions. In the acidic solution, the ESA of the catalyst decreased as the number of repeated potential cycles increased, which is likely to be due to dissolution of the different metals contained within the catalyst structure. In the fuel cell environment, the deterioration of the cell performance increased as the number of repeated potential cycles increased. Thus, the loss of cell performance may be related to the loss of the ESA. In addition, the loss of the catalyst’s ESA affected the cell performance at low-, medium-, and high- current densities, indicating a loss of either the activation potential or an ohmic loss. Among the three electrocatalysts evaluated, the Pt–Co/C based one exhibited the highest electrocatalytic activity in both the acidic solution and in the fuel cell environment.     

A Wasted Material,Duck Blood,as a Precursor of Non‐Precious Catalyst for the Oxygen Reduction Reaction

Searching for non‐precious electrocatalysts with high performance to replace the expensive Pt‐based electrocatalysts for oxygen reduction reaction (ORR) is a key issue in the industrial‐scale application of fuel cells. In this study, we have reported the synthesis of an iron doped N‐containing carbon materials, derived from duck blood, a wasted material in the duck meat production, as a novel and cost‐effective catalyst in ORR. The as‐prepared electrocatalysts were characterized by means of powder X‐ray diffraction, scanning electron microscopy, Raman spectroscopy and X‐ray photoelectron spectrometer. In 0.1 mol L⁻¹ KOH solution, the ORR onset potential and the half‐wave potential for the iron doped N‐containing carbon materials are 33 mV and –120 mV respectively, which are close to those of commercial Pt/C (20 wt%). In addition, the iron doped N‐containing carbon materials exhibit excellent tolerance to methanol crossover, which makes it a promising electrocatalyst for ORR in fuel cell.     

Electrochemical Deposition of Highly Dispersed Palladium Nanoparticles on Nafion‐Graphene Film in Presence of Ferrous Ions for Ethanol Electrooxidation

An efficient method was developed to produce highly dispersed Pd nano particles (NPs), supported on Nafion‐graphene film by electrochemical deposition at constant potential in presence of ferrous ions. The Fe²⁺ ions govern the size, shape and morphology of Pd NPs. The as‐prepared catalyst was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X‐ray diffraction (XRD). It was obeserved from TEM that the mean diameter of electrodeposited Pd NPs was 6.4 ± 1.3 nm with narrow diameter range from 4 to 10 nm. The electrocatalytic performance of the Pd NPs deposited on Nafion‐graphene (Nf‐G) catalyst was studied by cyclic voltametry (CV) and chronoamperometric measurements. The highly dispersed Pd NPs on Nf‐G film were obtained in presence of Fe²⁺ ions. This alters electrochemical active surface area and hence catalytic activity of Pd NPs. The prepared Pd/Nf‐G catalyst exhibit highest tolerance to the intermediate poisoning species (ratio I_f/I_b = 2.2). The as‐obtained catalyst shows an efficient electrocatalytic activity and good stability for ethanol oxidation in alkaline medium.     

ZrC–C and ZrO2–C as Novel Supports of Pd Catalysts for Formic Acid Electrooxidation

The Pd/ZrC–C and Pd/ZrO₂–C catalysts with zirconium compounds ZrC or ZrO₂ and carbon hybrids as novel supports for direct formic acid fuel cell (DFAFC) have been synthesized by microwave‐assisted polyol process. The Pd/ZrC–C and Pd/ZrO₂–C catalysts have been characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), energy dispersive analysis of X‐ray (EDAX), transmission electron microscopy (TEM), and electrochemical measurements. The physical characteristics present that the zirconium compounds ZrC and ZrO₂ may promote the dispersion of Pd nanoparticles. The results of electrochemical tests show that the activity and stability of Pd/ZrC–C and Pd/ZrO₂–C catalysts show higher than that of Pd/C catalyst for formic acid electrooxidation due to anti‐corrosion property of zirconium compounds ZrC, ZrO₂, and metal–support interaction between Pd nanoparticles and ZrC, ZrO₂. The Pd/ZrC–C catalyst displays the best performance among the three catalysts. The peak current density of formic acid electrooxidation on Pd/ZrC–C electrode is nearly 1.63 times of that on Pd/C. The optimal mass ratio of ZrC to XC‐72 carbon is 1:1 in Pd/ZrC–C catalyst with narrower particle size distribution and better dispersion on surface of the mixture support, which exhibits the best activity and stability for formic acid electrooxidation among all the samples.     

Functionalized-carbon nanotube supported electrocatalysts and buckypaper-based biocathodes for glucose fuel cell applications

The preparation and testing for electrocatalytic activity of functionalized carbon nanotube (f-CNT) supported Pt and Au–Pt nanoparticles (NPs), and bilirubin oxidase (BOD), are reported. These materials were utilized as oxygen reduction reaction (ORR) cathode electrocatalysts in a phosphate buffer solution (0.2 M, pH 7.4) at 25 °C, in the absence and presence of glucose. Carbon monoxide (CO) stripping voltammetry was applied to determine the electrochemically active surface area (ESA). The ORR performance of the Pt/f-CNTs catalyst was high (specific activity of 80.9 μA cm_Pt⁻² at 0.8 V vs. RHE) with an open circuit potential within ca. 10 mV of that delivered by state-of-the-art carbon supported platinum catalyst and exhibited better glucose tolerance. The f-CNT support favors a higher electrocatalytic activity of BOD for the ORR than a commercially available carbon black (Vulcan XC-72R). These results demonstrate that f-CNTs are a promising electrocatalyst supporting substrate for biofuel cell applications.     

Ultrahigh Durable PtPd/C Nanowire Networks Catalyst Synthesized by Modified Phase Transfer Method for Methanol Oxidation

A novel PtPd/C nanowire catalyst with interconnected network and fewer great grain boundaries has been successfully prepared by templateless and modified phase‐transfer method using cetyltrimethylammonium bromide as a capping in ethylene glycol solution by microwave‐assisted process. Its structure, composition, and morphology are characterized by X‐ray diffraction, energy dispersive analysis of X‐ray, and transmission electron microscopy, respectively. The electrochemical measurements demonstrate that the highly dispersed and uniform PtPd/C nanowire networks catalyst has a significantly higher electrocatalytic activity and durability for the methanol oxidation as compared to solid solution PtPd/C. The greatly improved durability of PtPd/C nanowire networks catalyst is mainly a consequence of the unique interconnected network structure with fewer grain boundaries, which provide more facile pathway for the electron transfer, and inhibit the particle growth and agglomeration, as well as prevent the particles embedded in the microporous of carbon support to enhance the Pt utilization.