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Behavior of Pt/C catalysts obtained by the platinum deposition on standard and nitrogen-doped carbon supports with different microstructure has been studied in the oxygen electroreduction reaction in an acidic electrolyte. The catalysts based on the modified supports are characterized by a uniform spatial distribution of small-sized (1.5–2 nm) Pt nanoparticles over the surface of the supports, which results in high values of the electrochemically active surface area (110–130 m2 g− 1 (Pt)). The use of various stress testing protocols has shown that the Pt/C material based on the N-doped KetjenBlack EC DJ-600 possesses the highest mass activity and durability, which noticeably exceed the corresponding characteristics of the commercial HiSPEC3000 catalyst.

Platinum–carbon catalysts are widely used in the manufacturing of proton-exchange membrane fuel cells. Increasing Pt/C activity and stability is an urgent task and the optimization of their structure seems to be one of the possible solutions. In the present paper, Pt/C electrocatalysts containing small (2–2.6 nm) nanoparticles (NPs) of a similar size, uniformly distributed over the surface of a carbon support, were obtained by the original method of liquid-phase synthesis. A comparative study of the structural characteristics, catalytic activity in the oxygen electroreduction reaction (ORR), and durability of the synthesized catalysts, as well as their commercial analogs, was carried out. It was shown that the uniformity of the structural and morphological characteristics of Pt/C catalysts makes it possible to reduce the negative effect of the small size of NPs on their stability. As a result, the obtained catalysts were significantly superior to their commercial analogs regarding ORR activity, but not inferior to them in terms of stability.

The effect of the SnO2 nanoparticles content on the structure and electrochemical behavior of Pt/(SnO2/C) catalysts containing about 20 wt% Pt was studied. In this case, SnO2/C nanostructured materials were obtained by tin electrodeposition on the carbon particles in suspension. It was found that the optimal combination of stability and activity in the oxygen electroreduction reaction is demonstrated by materials containing 25–30% wt. SnO2. A comparative assessment of the durability and activity of Pt/(SnO2/C) catalysts and a commercial Pt/C catalyst with 20% Pt-loading has been carried out.

Electrocatalysts based on Pt-M bimetallic nanoparticles deposited on carbon supports have already been used in commercially available Proton Exchanged Membrane Fuel Cells (PEM FC). Nevertheless, production and practical use of such materials faces with the problems caused by the need to combine high specific activity in current-forming reactions and their durability, with the stability of the element's composition during the operation of PEM FC. The suggested stepwise approach to the PtCu/C materials synthesis in the liquid phase is based on the initial deposition of platinum nuclei and their subsequent growth due to the joint or sequential deposition of copper and platinum from the solutions of their precursors. The PtCu/C catalysts, obtained in this way, demonstrated not only higher activity in oxygen reduction reaction compared to the commercial Pt/C catalyst, but also a significantly higher corrosion-morphological stability.

The development of energy systems based on high specific power hydrogen–air fuel cells using domestic nanostructured materials and technologies is an urgent task. The technologies used for manufacturing proton-exchange membrane fuel cells (PEM FC) by the Russian company BMPower using Pt/C-electrocatalysts of the PM series produced by another Russian company, Prometheus R&D, are presented. It has been shown that, in terms of their functional characteristics, catalysts of the PM series are superior to imported analogues. The use of the PM40 catalyst, as well as other innovative solutions in the field of nanotechnology (nanostructured coatings of bipolar plates, formation of an ionomer on the catalytic layer) makes it possible to achieve a specific power of more than 1 kW/kg in the PEM FC power module with air cooling.

One of important problems associated with the use of Pt/C electrocatalysts in low-temperature fuel cells is their degradation due to oxidation of the carbon support. The use of noncarbon supports resistant to oxidation, for example, oxides of certain metals in the highest degree of oxidation is a promising direction. TiO2 with the high specific surface area (104 m2/g) is synthesized and used in fabrication of supported platinum catalysts. For Pt/TiO2 and carbon-containing composite Pt/TiO2+C, the electrochemically active surface area of platinum and the their activity in oxygen electroreduction reaction are estimated. The assessed stability of synthesized materials far exceeds the stability of commercial Pt/C catalysts.

New nanostructured Pt/(SnO2/C)-electrocatalyst (20 wt % Pt) is synthesized via platinum chemical deposited onto composite SnO2/C-support microparticles (4 wt % Sn). The composite support was prepared beforehand using unique method of the tin electrochemical deposition onto disperse carbon black particles. It was shown by X-ray diffraction and transmission electron microscopy that the platinum and tin oxide nanoparticles distributed over the carbon surface are sized 2.4 and 2.9 nm, respectively. Electrochemical measurements showed the obtained catalyst to approach the commercial Pt/C HiSPEC 3000 catalyst (20 wt % Pt) with respect to its mass-activity in the oxygen electroreduction reaction and to be superior thereto as for the electrochemically active surface area, stability in stress test, and activity in methanol electrooxidation reaction. The peculiarities in electrochemical behavior of the synthesized Pt/(SnO2/C)-electrocatalyst can be explained by the SnO2 nanoparticle effect on the platinum nanoparticle nucleation/growth, as well as presence of Pt–SnO2–C triple junction nanostructure at the surface. The Pt/SnO2 contact provides stable platinum-to-support adhesion and asserts bifunctional catalysis mechanism of the methanol electrooxidation. And the Pt/C junctions provide for electron supplying/retraction to or from the platinum nanoparticles.

Materials containing from 3.1 to 7.7 wt % of cobalt were obtained by electrodeposition of cobalt on Vulcan XC72 carbon powder in suspension. The composition and average diameter of CoO crystallites formed as result of cobalt oxidation in the process of filtering and drying materials, depending on the electrolysis conditions and electrolyte composition, were studied using thermogravimetry and XRD. It is shown that the maximum amount of cobalt can be deposited from electrolytes containing, along with cobalt sulfate, additives of copper and nickel sulfates. Calculations by the Scherrer equation showed that an increase in the CoO content leads to a decrease in the diameter of crystallites, the size of which is in the nano-range. The analysis of X-ray and electrochemical studies indicates the formation, in the course of the borohydride’s synthesis, of combined catalysts containing nanoparticles of the Pt3Co solid solution. The best PtCo/C material demonstrated significant improvement in ORR activity and superior stability compared to commercial Pt/C catalyst of the same platinum loading.

Durability is one of the most important characteristics of electrocatalysts used in low-temperature fuel cells with a proton exchange membrane. The degradation degree of deposited electrocatalysts containing platinum and platinum-copper nanoparticles with Pt-loading of about 20% by weight was assessed by voltammetric stress-testing, which corresponded to different mechanisms of degradation. The differences in the Pt Cu nanoparticles architecture, caused by the peculiarities in their synthesis, affect the catalysts stability and their composition change due to the stress tests. It has been shown that at the close values of Pt-loading and electrochemically active surface area (ESA), the bimetallic catalysts on the Vulcan XC72 carbon carrier demonstrate significantly higher stability compared to commercial Pt/C catalysts. In this case, the “gradient” catalyst obtained by successive multi-stage copper and platinum deposition showed the highest residual activity in ORR, as well as resistance to stress testing and to the copper selective dissolution.

Stability is one of the most important characteristics of electrocatalysts used in low-temperature fuel cells with a proton exchange membrane. The corrosion-morphological stability of supported electrocatalysts containing platinum and platinum-copper nanoparticles with ~20 wt % Pt was evaluated under the conditions of voltammetry stress testing corresponding to different degradation mechanisms. The effect of the difference in the architecture of Pt–Cu nanoparticles on the stability of catalysts and changes in their composition as a result of stress tests were studied. At close values of the electrochemically active surface area (ECAS), the carbon-supported bimetallic catalysts demonstrated significantly higher stability compared to the commercial Pt/C catalysts. The Pt(Cu)/C catalyst obtained by sequential deposition of copper and platinum showed the highest resistance to the degradation and selective dissolution of copper during the testing.

Supported PtCu/C electrocatalysts containing core–shell bimetallic PtCu nanoparticles were synthesized by sequential chemical reduction of Cu2+ and Pt(IV) in a carbon suspension, prepared on the basis of ethylene glycol–water solvent, and then treated at different temperatures in the range from 250 to 350 °C. The structural characterization of “as-prepared” PtCu nanoparticles and of those obtained after the thermal treatments was performed by transmission electron microscopy, X-ray diffraction, and Pt L3- and Cu K-edge extended X-ray absorption fine structure spectroscopy. The atomic cluster models of PtCu nanoparticles before and after the thermal treatment, reflecting the character of the components’ distribution, were generated. The electrochemical performance of the obtained PtCu/C electrocatalysts in oxygen reduction reaction was studied by cycling and linear voltammetry.

A number of new platinum-based catalysts with Pt loading from 15.2% to 17.3% was obtained by wet chemical synthesis. Ethylene glycol, formaldehyde, and formic acid were used as reducing agents. The synthesis was performed both at ambient conditions and when the solution was saturated with carbon monoxide. It was shown that the catalysts obtained in the CO environment possess a larger electrochemical active surface area (EСSA), 140–146 m2 g−1 (Pt), compared to the analogues that have been made at ambient conditions, 72–120 m2 g−1(Pt). This could be explained by a smaller platinum NPs average size as well as a very narrow distribution of their size. In contrast to the materials synthesized at ambient conditions, the ECSA values of the catalysts, obtained in the CO-saturated media, in fact, do not depend on the type of reducing agent and the synthesis conditions. Such catalysts demonstrate the best mass-activity in ORR, which is higher than that of the commercial Pt/C catalyst HiSPEC 3000 (20% of Pt loading) and the analogues obtained at ambient conditions. Distinctive features of the nanoparticles nucleation/growth and their structure were determined and studied when formic acid was applied as a reducing agent. Absorption processes of the CO molecules on the surface of platinum nuclei are a plausible explanation for the CO influence on nucleation/growth and, therefore, on the microstructure and EСSA, as well as other functional characteristics of Pt/C-catalysts.

The structure characteristics and the electrochemical behavior of Pt(Cu)/C electrocatalysts synthesized by consecutive deposition of copper and platinum on carbon-support microparticles is studied. The stability and catalytic activity of Pt(Cu)/C materials in reactions of oxygen electroreduction and methanol electrooxidation are assessed and compared with analogous characteristics of a commercial Pt/C material. It is shown that combining the method of galvanic displacement of Cu by Pt with the additional chemical deposition of Pt favors optimization of the structure and functional characteristics of Pt(Cu)/C electrocatalysts. The effect of thermal treatment on the characteristics and properties of electrocatalysts is studied and the optimal conditions of such pretreatment are revealed.

The architecture of bimetallic nanoparticles has strong influence on durability and activity of PtM/C electrocatalysts in the oxygen electroreduction (ORR) and the methanol electrooxidation reactions (MOR). In the present study the Pt0.8(Cu)/C electrocatalyst was obtained by the methods of successive multistage reduction of platinum and copper from the solutions of their precursors while platinum concentration in the matrix solution was increasing step by step. The composition, structural characteristics and electrochemical behavior of this material were compared with the Pt1.0Cu/C catalyst based on the nanoparticles of a solid solution, which was obtained by the combined single-step chemical reduction of precursors, as well as with a commercial Pt/C sample with the same Pt-loading (20% by weight). The catalyst based on the Pt–Cu gradient nanoparticles demonstrated the highest corrosion-morphological stability in the stress-test, as well as the highest activity in ORR and MOR in the HClO4 solutions. Both of the studied bimetallic catalysts lose a significant amount of copper during the standardizing cycling and the stress-test. In the stabilized composition of the “gradient catalyst” the residual copper content, however, is considerably higher than that of the catalyst with the solid solution nanoparticles. The positive features of the electrochemical behavior of Pt0.8(Cu)/C catalyst arise apparently due to the faster formation of a durable protective layer of platinum on the surface of nanoparticles in the process of functioning, compared to the analogue based on the nanoparticles of the solid solution. High stability and activity of Pt0.8(Cu)/C compared to the Pt/C analogue are associated with the larger size of the nanoparticles and the promoting influence of residual copper on the catalytical activity of platinum.

The need to reduce platinum content in PEMFC catalyst layers has sparked a new wave of interest in ways to control the microstructure of Pt/C catalysts, which must combine high platinum surface area and activity. A comparative study of platinum nanoparticle nucleation/growth under a liquid-phase synthesis of Pt/C materials, with formaldehyde and formic acid being used as reducing agents, has been carried out. Analysis of the color change in the reaction medium and the in situ spectral-kinetic studies performed with absorption spectroscopy, were used as methods to study the reactions kinetics. The effect of the synthesis temperature on the features of the Pt(IV) reduction stages, nucleation/growth of Pt(0) nanoparticles, as well as on the size of the resulting Pt nanoparticles were studied. The role of the ethylene glycol and its derivatives, formed in the reaction medium at high pH, in the processes of Pt(IV) reduction and in the Pt(0) nanoparticles formation, is shown. The positive effect of the dispersed carbon support on the morphological characteristics of the resulting Pt/C catalysts is demonstrated, with carbon being introduced into the reaction medium in the initial stage of the synthesis. The roles of homogeneous and heterogeneous phase formation in the synthesis of Pt nanoparticles and Pt/C materials in the liquid phase are estimated.

A comparative study of the nucleation/growth processes of the platinum nanoparticles has been carried out with and without ultraviolet (UV) radiation. Platinum‑carbon catalysts containing 20%wt Pt with the average crystallite size ranges from 1.3 to 3.6 nm obtained by the liquid phase synthesis, using various reducing agents. It is shown, that for materials obtained under UV irradiation action the electrochemically active surface area increases up to 80% in comparison with the analogs. Improvement in the functional characteristics of the catalysts is due to narrowing in the size distribution of Pt nanoparticles and an increase in the uniformity of their spatial distribution. The synthesized catalysts demonstrated mass activity in ORR, which significantly exceeded the commercial analog activity. The approaches to the production of nanomaterials shown in the article are of great applied importance, since they can be used for gram-level syntheses.

PtCu/C electrocatalysts with bimetallic PtCu nanoparticles were synthesized by successive chemical reduction of Cu2+ and Pt(IV) in a carbon suspension prepared based on an aqueous ethylene glycol solution. The atomic structure of as-prepared PtCu nanoparticles and nanoparticles subjected to thermal treatment at 350°C was examined using PtL 3 and CuK EXAFS spectra, transmission electron microscopy (TEM), and X-ray powder diffraction (XRD). The results of joint analysis of TEM microphotographs, XRD profiles, and EXAFS spectra suggest that the synthesized electrocatalysts contain PtCu nanoparticles with a Cu core–Pt shell structure and copper oxides Cu2O and CuO. Thermal treatment of electrocatalysts at 350°C results in partial reduction of copper oxides and fusion of bimetallic nanoparticles with the formation of both homogeneous and ordered PtCu solid solutions.

The influence of the atmosphere composition (CO, Ar, air), in which wet synthesis of Pt/C electrocatalyst was carried out, on the structural and morphological characteristics, and electrochemical behavior of electrocatalysts have been studied. For comparison, commercial Pt/C electrocatalysts with the same platinum loading were also studied. It has been shown that the adsorption of CO molecules on the surface of the growing platinum nuclei leads to the decrease in the average size of the nanoparticles and the narrowing of the size distribution in the Pt/C. Homemade electrocatalysts, with the values of electrochemically active surface area being from 94 to 139 m2 g−1 (Pt), prove to be in no way inferior to their commercial counterparts in oxygen reduction reaction mass activity. Durability of the homemade Pt/C samples in accelerated stress tests exceeds durability of the commercial ones.

In this paper we report the results obtained by a comparative study of catalytic activity of bimetallic (Ru–Rh, Ni–Cu) catalysts synthesized on a surface of different carbon supports: detonation nanodiamonds (DND), infrared pyrolyzed polyacrylonitrile, carbon black Vulcan-XC-72, in steam reforming of methanol (MSR) for hydrogen production. All obtained catalysts were characterized by N 2 physisorption, SEM, TEM, FTIR spectroscopy, X-ray diffraction. It was shown, that activity of catalysts and products distribution depends on metal type, support material and the specific surface area. Support effect was investigated for Ru–Rh system. DND showed the best properties as a catalyst support. Ru–Rh system is more active than Cu–Ni as it is shown on the example of DND supported catalysts. Comparative study between conventional (CR) and membrane (MR) reactors was carried out. MR represented a flow system with a plane Pd-containing membrane. The effect of different catalysts on the MR performances as well as a general comparison of the experimental results was considered. Obtained results demonstrate the ability of the membrane to increase the reaction conversion. The hydrogen stream produced from the MR is ultra pure: especially, it is CO-free and thus suitable to be directly fed to a polymer electrolyte membrane fuel cell.

Deposited electrocatalysts with different distributions of components in PtCu bimetallic nanoparticles involved in their composition were synthesized by simultaneous and sequential reduction of Cu(2+) and Pt(IV) in a carbon suspension. The dependence of the atomic structure of PtCu nanoparticles on the synthesis conditions and the degree of influence of post-treatment was established from analysis of the changes in Fourier transforms of the experimental Pt and Cu EXAFS spectra, as well as the structural parameters obtained by their fitting before and after the treatment of the materials in an acid solution. A technique was proposed for visualizing the atomic structure of synthesized bimetallic nanoparticles. This technique made it possible to determine the character of the distribution of the components over the nanoparticle volume in accordance with the component composition and local atomic structure parameters determined from EXAFS spectroscopy and to obtain the visualization of the distribution of the components in PtCu nanoparticles synthesized by the aforementioned methods.

Carbon supported Pt–Cu and Pt–Co electrocatalysts with increased platinum content on the surface layer of nanoparticles were synthesized by different chemical methods. The compositions, microstructures and electrochemical behaviors of these electrocatalysts were studied using the X-ray diffraction, thermogravimetry, X-ray fluorescence analysis, TEM and cyclic voltammetry. During stability tests (1000 voltammetric cycles in HClO4 solution) the values of electrochemically active surface area (ESA) for Pt–Cu/C catalysts reduced by 34%. Commercial Pt/C catalyst HiSPEC 3000 decreased ESA value by 70% (from 102 to 30 m2g−1 (Pt)) in the similar tests. High stability of the prepared Pt–Cu/C catalysts combined with the high ESA values and ORR activity may be due to the fact that despite a comparatively large size of nanoparticles most of them have a core-shell or hollow (nanoporous) structure. The obtained result demonstrates a great potential for using bimetallic catalyst systems with an uneven surface distribution of metals in nanoparticles as electrocatalysts in low temperature fuel cells and show the way for combining high activity and durability of electrocatalysts.

Carbon supported Pt–Cu electrocatalyst with increased platinum content in the surface layer of nanoparticles was synthesized by a sequential chemical reduction of Cu (II) and Pt (IV) compounds from their solutions. A subsequent thermo-treatment and the combination of thermo- and corrosion treatment of the catalyst resulted in a slight increase in an average crystallite size, but had not an essential negative impact on the electrochemically active surface area (ESA) value. During stability tests (1000 voltammetric cycles), the values of ESA for pristine and post-treated Pt–Cu/C catalysts decreased by 15–20% from 61–65 to 56 m2g−1 (Pt). In similar tests of commercial Pt/C catalyst TEC10v30e an ESA value decreased by 56% from 80 to 36 m2g−1 (Pt). High stability of the prepared Pt–Cu/C catalysts in combination with high ESA values and oxygen reduction reaction activity may be since, despite the comparatively large size of nanoparticles, the majority of them have a core-shell or hollow structure. The obtained result demonstrates the prospect of using bimetallic catalyst systems with an uneven surface distribution of metals in nanoparticles as electrocatalyst in low temperature fuel cells and shows a way of combining high activity and durability of the electrocatalyst.

The sequential chemical reduction of metals (copper or silver) and platinum was used to prepare M@Pt/C electrocatalysts that contain a high content of platinum on the surface of bimetallic nanoparticles. The compositions, microstructures and electrochemical behaviors of these electrocatalysts were studied using X-ray diffraction, thermogravimetry, X-ray fluorescence analysis, TEM and cyclic voltammetry. Depending on the composition and mode of synthesis, the obtained electrocatalysts have electrochemically active surface areas ranging from 35 to 61 m2 g−1 (Pt). The presence of nanoparticles with a core-shell structure was directly confirmed for Cu0.9Pt0.1@Pt/C sample. Copper-containing electrocatalysts exhibited better stability during voltammetric cycling compared to a similar composition of commercial Pt/C electrocatalyst and Ag0.9Pt0.1@Pt/C systems, but one of Ag0.9Pt0.1@Pt/C electrocatalysts has shown the highest specific activity in ORR.

Pt/C catalysts containing 10 to 20 wt % Pt have been prepared by chemical reduction of platinum from Pt(IV) solutions. The use of an intermediate hydroxide support (Fe(OH)2 or SiO2 · nH2O) in Pt/C synthesis has been shown to have a significant effect on the weight percentage, crystallite size, and electrochemically active surface area of Pt. We have established how the composition of the liquid-phase synthesis atmosphere (air, Ar, or CO) influences the structural characteristics of the Pt/C materials. The electrochemically active surface area of Pt in the synthesized catalysts ranges from 32 to 152 m2/g Pt.

Nanostructured Pt/C electrocatalysts containing about 20 wt % Pt have been produced by chemical reduction in Pt(IV) solutions. The nature of the reductant (sodium borohydride, ethylene glycol, formaldehyde, or formic acid) and the associated changes in synthesis conditions have a significant effect on the structural characteristics of the materials obtained. In particular, the average size of Pt nanoparticles (crystallites) ranges from 1.8 to 5.5 nm. The largest electrochemically active surface area of the Pt in the catalysts obtained in this study (128 m2/g Pt) considerably exceeds that of E-TEK, a commercially available Pt/C catalyst similar in composition ( 110 m2/g Pt).

The article discusses a wide range of issues related to the relationship between the composition and fine structure (architecture) of bimetallic nanoparticles and electrochemical performance of Pt-M/C (M = Cu, Co, Ni) electrocatalysts. Among these questions are: evolution of nanoparticles during thermo-treatment, catalytic activity in the oxygen reduction and methanol electro-oxidation reactions, corrosion-morphological stability of the catalysts, selective dissolution of alloying component.

The aim of this work was to investigate the morphology, average size, and the electrochemical behavior of platinum nanoparticles electrodeposited from water and mixed water–ethylene glycol solutions of the electrolyte of H2PtCl6 and H2SO4 at a rotating disk electrode coated with Vulcan XC-72 carbon powder. Cyclic voltammetry and linear sweep voltammetry were used to determine the electrochemically active surface area (ESA) and oxygen reduction reaction (ORR) activity of the prepared Pt/C materials, respectively. XRD and scanning electron microscopy were used to study the influence of the electrodeposition methods applied on the morphology of platinum particles deposited in water and mixed water–ethylene glycol solutions. The average size of Pt crystallites was in the range of ca. 6–10 nm, and the average size of deposited Pt particles was in the range of ca. 30–150 nm. It was found that the presence of ethylene glycol in the electrolyte solution increased the overpotential of electrodeposition and it also strongly affected the morphology of Pt deposits when constant current electrodeposition was employed. Moreover, it was shown that pulse current electrodeposition is a more effective method compared to constant current electrodeposition method for the preparation of the Pt/Vulcan electrode with high ESA of Pt and enhanced catalytic activity toward ORR. The results obtained concerning the morphology and the spatial distribution of platinum particles electrodeposited on the surface of carbon support at different conditions demonstrate new possibilities to improve synthesis of Pt/C by electrodeposition methods.

Nanocatalysts PtAg/C with different distributions of components in bimetallic PtAg nanoparticles were synthesized by the methods of simultaneous and sequential reduction of Ag+ and Pt(IV) in carbon suspension, prepared on the basis of ethylene glycol–water solvent. The characterization of atomic structure of as prepared PtAg nanoparticles and PtAg nanoparticles obtained after acid treatment at 90 °C was performed by Pt L3-edge extended X-ray absorption fine structure (EXAFS) using the technique for determining local structure parameters of the absorbing Pt atoms, which have the nearest surrounding consisting of Pt and Ag atoms. This technique enabled stable and unambiguous values of parameters for the local structure of Pt atoms in PtAg nanoparticles to be obtained under severe correlations between some of these parameters. The effects of averaging over the sizes and compositions of PtAg nanoparticles on the obtained values of structural parameters were studied by the method of cluster simulations. Analys...

High-temperature oxidation processes of carbon microparticles Vulcan XC72 coated with platinum nanoparticles (Pt/C) were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The presence of different specific temperature ranges in the oxidation of carbon support was shown to be due to both the peculiarities of granulometric composition of carbon black microparticles, different size, and uneven spatial distribution of platinum nanoparticles in the pores and on the surface of the carbon support. The correlation between the length of a section in the thermograms and the fraction of carbon microparticles poorly coated with platinum can be used to analyze the uniformity of Pt nanoparticle spatial distribution in the metal–carbon catalysts and therefore to select electrocatalysts with optimal microstructure. This analysis is expected to be effectively utilized in order to assess the uniformity of platinum distribution on carbon microparticles and also to provide additional in...

The microstructures of Pt/C and PtM/C (M = Ni, Cu, or Ag) electrocatalysts were studied using X-ray diffraction and transmission electron microscopy (TEM). The electrochemically active surface areas of the prepared materials were estimated by cyclic voltammetry in 1 M H2SO4. The materials, with metal contents ranging from 30 to 35 wt.%, were synthesized by chemically reducing the metal precursors in water–ethylene glycol solutions. The actual composition of the bimetallic nanoparticles corresponds to a theoretical (1:1) composition for the PtAg/C catalysts, whereas in the PtNi/C and PtCu/C materials, a portion of the alloying component exists in an oxide form. Decreasing the average metallic crystallite sizes from 3.5 to 1.6 nm does not increase the electrochemically active surface area. This apparent contradiction is because a majority of the PtNi and PtCu nanoparticles consist of 2–4 disordered crystallites. In addition, a portion of the PtNi or PtCu nanoparticle surface is covered by nickel or copper oxides, respectively. PtAg nanoparticles, which have a smaller size relative to other bimetallic particles according to the TEM data, are characterized by an intense platinum surface segregation. The agglomeration processes are lowest for the PtAg nanoparticles.

The results of the study of microstructural parameters and the data on the electrochemically active surface area of Pt/C and Pt50M50/C (M = Ni, Cu, Ag) catalysts in 1 M H2SO4 solutions are compared. The metal-carbon nanomaterials were prepared by the method of chemical reduction of metals from the organoaqueous solutions of their compounds. The loading of metal component in them was 30–33 wt %. It is found that actual composition of metal component in the synthesized binary systems fits best the theoretically expected one (1: 1) for the PtAg/C catalyst whereas in the PtNi/C and PtCu/C systems, a considerable fraction of alloying component is present in the form of the corresponding oxides. A decrease in the average size of crystallites of metal component from 3.8 to 1.6 nm in the series of studied materials PtAg/C > Pt/C ≥ PtCu/C s> PtNi/C does not correspond to the character of the variation of electrochemically active surface area of the catalysts: PtNi/C ≈ PtCu/C < Pt/C ≪ PtAg/C increasing from 16–20 to 62–69 m2/g(Pt). The contradiction can be caused by the preferential segregation of platinum on the surface of nanoparticles of PtAg alloy, a higher degree of agglomeration of smaller nanoparticles, and, in the case of PtNi/C and PtCu/C materials, also by the insulation of a fraction of nanoparticle surface area by the corresponding oxides.

Nanostructured Pt x Ni / C and Pt x Co / C catalysts ( 1 ≤ x ≤ 3 ) containing from 27 to 40 wt % of metal with the average size of metal (alloy) particles from 2.6 to 4.7 nm are obtained using the methods of liquid- phase synthesis. Addition of a doping component is found to yield a decrease in the average nanoparticle sizes and an improved activity of materials in oxygen electroreduction reactions. The obtained catalysts are charac- terized by high specific activity as compared to commercial Pt/C materials. The stability of electrocatalysts to selective dissolution of the doping component is evaluated.

Pt 3 Co/C electrocatalysts produced by the wet synthesis method out of water-ethylene glycol solu- tions of Pt and Co precursors were investigated by X-ray diffraction in conjunction with electrochemical mea- surements. It was shown that varying the binary solvent composition is an effective way to regulate the nano- particle and grain size distribution. It was found that the unit cell parameter of the Pt 3 Co/C electrocatalysts decreases nonlinearly as the particle sizes dwindle. The activity of the made-up Pt 3 Co/C catalysts for the ORR in H 2 SO 4 solution enhances as the particle size, unit cell parameter, and dispersion of the grain size distribution decrease. All the samples studied show higher catalytic activities than the commercial Pt/C materials.

A comparative study of alloy formation processes that occur during the electrochemical intercalation of lithium from lithium chloride solutions in dimethylformamide into intermetallic compounds of magnesium with zinc (MgZn2, Mg2Zn3) and the corresponding individual metals is studied by chronopotentiometric and voltammetric methods. Lithium-containing phases are formed in all samples studied; moreover, for MgZn2 and Mg2Zn3 electrodes, the phases formed are preferentially in the Li-Zn system. The largest number of lithium-containing phases is formed in zinc. It is shown that the electrochemical behavior of intermetallic electrodes is associated with their nature, where a single alloy component plays the key role, namely, zinc for MgZn2 and magnesium for Mg2Zn3. The cathodic intercalation of lithium into MgZn2 is characterized by anomalously low polarizability as compared with the other electrodes. The lithium extraction coefficient K ex Li increases from the first to the tenth cycle for all electrode studied. The highest K ex Li are typical of Zn and the lowest are typical of Mg2Zn3.

Development of optimal methods for the synthesis and for the control of multi-level microstructure of Pt/C materials is essential for the preparation of electrocatalysts , which have high activity and durability. Nucleation/growth of metallic nanoparticles could take place in the liquid phase, on the surface and in the pores of the carbon microparticles during the process of chemical reduction of Pt precursor in a liquid phase. These processes are sensitive to the composition of the medium, temperature, pH, mass transfer conditions, and other factors. On the one hand, that creates more opportunities to search the optimal conditions of synthesis. On the other hand, it makes difficult to control the reproducibility of the composition/structure of Pt/C . Pt/C materials with metal fraction from 10 to 20 wt% were obtained in this work. An average size of Pt crystallites was from 1.0 to 5.5 nm, depending on the method and conditions of synthesis. Electrochemically active surface area of catalysts measured by hydrogen electrodesorption method, was from 32 to 152 m2/gPt.

Nanocatalysts PtCu/C with different distribution of components in bimetallic PtCu nanoparticles (NPs) were synthesized by simultaneous and sequential deposition of Cu and Pt on carbon support. Electrochemical stability of the obtained samples PtCu/C was studied using the cyclic voltammetry. Characterization of atomic structure of as prepared PtCu NPs and obtained after acid treatment was performed by Pt L 3- and Cu K-edge EXAFS using the technique for determining local structure parameters of the absorbing atom under strong correlations among them. EXAFS derived parameters were used for generation of structural models of PtCu NPs by the method of cluster simulations. Within this approach, the models of atomic structure of PtCu NPs obtained by the two methods of synthesis, before and after post treatment and after two months from their preparation were revealed.