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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.

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.

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 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.

Composite metal-carbon electrocatalysts PtCu/C containing core-shell bimetallic PtCu nanoparticles were synthesized by sequential chemical reduction of Cu (II) and Pt (IV) in carbon suspension, prepared on the basis of ethylene glycol–water solvent. The characterization of “as prepared” and obtained after the acid treatment PtCu nanoparticles was performed by TEM, XRD, Pt L 3 - and Cu K -edge extended X-ray absorption fine structures (EXAFS). The technique and computational code were proposed for visualization of components distribution over the volume of cluster, which represents the mean bimetallic nanoparticle, according to the values of structural parameters derived from EXAFS. By this technique, the cluster models of PtCu nanoparticles before and after acid treatment, reflecting the character of components’ distribution, were generated. The study of electrochemical performances of the obtained PtCu/C electrocatalyst revealed the similar oxygen reduction reaction (ORR) activity and increased durability compared to commercial Pt/C electrocatalyst E-TEK 20.

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.

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.

For the purpose of reducing the cost and improving the performance of the proton exchange membrane fuel cell (PEMFC), some low-Pt or non-Pt catalysts have been studied in recent years. PtCo/C electrocatalysts are synthesized by a two-step reduction approach followed by the heat treatment. PtCo metal particles are uniformly dispersed on the surface of XC-72 carbon support, with a uniform particle size distribution. The PtCo/C catalyst after 400 degrees C heat treatment has the best electrochemical performance among the as-prepared catalysts, even superior to the commercial Pt/C catalyst. In the durability test, PtCo/C-400 also shows excellent stability with only 6.9% decline of electrochemical surface area (ECSA) after 1000 cyclic voltammetry (CV) cycles. In-situ X-ray absorption near edge structure (XANES) technique is conducted to explore the nanostructure change of Pt during the PEMFC operation. For PtCo/C catalyst, with the fuel cell operation potential decreasing from open circuit voltage (OCV) to 0.3 V, the Pt L-3 white line intensity decreases continuously, indicating the decline of Pt 5d-vacancy due to the adsorption of oxygenated species. (C) 2015 Elsevier B.V. All rights reserved.

Pt 3 Co/C electrocatalysts prepared by wet synthesis method from water–ethylene glycol solutions of Pt and Co precursors were investigated by X-ray diffraction in conjunction with electrochemical measurements. It was shown that varying the binary solvent composition is an effective means of control over the average nanoparticle size and the grain size distribution. It was found that unit cell parameter of the Pt 3 Co/C electrocatalysts decreases nonlinearly with decreasing particle size. The activity of the prepared Pt 3 Co/C catalysts for the oxygen reduction reaction (ORR) in H 2 SO 4 solution enhances with decrease in the particle size, the unit cell parameter, and the dispersion of the grain size distribution. All samples studied show higher catalytic activities in comparison with the commercial Pt/C materials.