In-situ microcalorimetry study on thermodynamic functions of Cu2 O nanocubes

Four different sizes of cuprous oxides (Cu 2 O) nanocubes in the range of 40–120 nm were synthesised by liquid phase reduction method. The morphology, size, and structure of synthesised Cu 2 O nanocubes were characterised by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. In-situ microcalorimetry was used to calculate the conventional and surface thermodynamic functions of Cu 2 O nanocubes by combining thermodynamic principles and transition state theory. The effect of particle size on conventional thermodynamic functions and surface thermodynamic functions were investigated and analysed, whose results were supported by the established thermodynamic models. Results showed that both the standard molar enthalpy of formation and the standard molar entropy of formation were increased with decreasing particle size, while the standard molar Gibbs energy of formation decreased. Also, the molar surface Gibbs energy, molar surface enthalpy, and molar surface entropy grew with the reduction of particle size, which correlated well with the models. Such a property is of scientific significance for enriching and developing disciplines such as surface physics and surface thermodynamics.