Application of the thermodynamic calculation of the Pt–Ni–Ru–(O2) system to the development of Pt-based catalyst

•The unreported phase diagram of Pt–Ru-Ni–O2 system has been calculated.•The stability area where low-Pt trimetallic catalysts can be formulated was determined.•Ru contributes to achieve fcc as unique phase during the combustion process.•This methodology will simplify the preparation of the catalysts reducing costs.

The research on new Pt-based compositions is generally expensive and implies important difficulties, especially concerning the high cost of the raw materials, the formation of secondary phases and the stability, in the experimental conditions, of the prepared alloys. Nevertheless, the importance of this material in the catalysis of many reactions claims for new research around this element and its compounds. In the present work CALPHAD methodology is implemented to study the phase composition of the, unreported, Pt–Ru–Ni system and its evolution with temperature and oxygen partial pressure. Ternary system Pt–Ru–Ni has been calculated from thermodynamic assessments of Pt–Ni, Pt–Ru and Ni–Ru binary systems using a symmetric extrapolation. Gibbs energies of the liquid, FCC and HCP phases have been described by a sub-regular solution model. The behaviour of modelled ternary solutions at different oxygen partial pressures has been also simulated by thermodynamic calculations, describing the gas as an ideal phase. In this work, the thermodynamic calculation is directly applied to the synthesis of Pt–Ru–Ni based materials by means of the combustion method. Comparison of the experimental results with the calculated data evidences the useful of the thermodynamic description of the system in the design and development of Pt–Ru–Ni materials.

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