Thermodynamic properties of the novel photocatalyst BiSbO4 phase determined from 1.8 K to 1073 K

Growing interest in BiSbO4 application as the superior photocatalytic material leads to the problem of its thermodynamic stability. However, its thermodynamic properties have not been determined so far. In order to provide this data five experimental methods followed by critical data evaluation were used. BiSbO4 samples were obtained by the solid state synthesis. Low-temperature heat capacity data were obtained with physical property measurement system (PPMS) and standard entropy S0298.15 = 127.1 (±2.0) J/(mol·K) was derived. Next, using differential thermal analysis/differential scaning calorimetry method (DTA/DSC), high-temperature heat capacity of BiSbO4 phase has been measured and is given in the form of Maier-Kelley equation. Metal oxide equilibration established three phase equilibrium characterized by constant temperature and pO2. Finally, employment of the e.m.f. cell with the solid electrolyte gave Gibbs free energy change of the reaction Bi + O2+ 1/2Sb2O4 = BiSbO4. Then, the Third Law analysis provided the standard heat of formation of BiSbO4 from elements equal to ΔH0f,298.15 = −859.50 (±3.57) kJ/mole. This set of thermodynamic data allowed the calculation of the oxide Cp, heat content, S0T and μ0T, which are given in the range of temperature from 298.15 to 1100 K.