Abstract:

To investigate the kinetic behaviors of nanoparticle heterogeneous reactions, we introduced a liquidphase reduction method to control the synthesis of cubic cuprous oxide with a particle size of 55 nm. Based on the differences between nano-Cu₂O and bulk Cu₂O, in-situ microcalorimetry was used to acquire fine thermodynamic information of Cu₂O systems in HNO₃. The reaction kinetic parameters of Cu₂O were calculated by a combination of thermodynamic principles and kinetic transition state theory, whose results are discussed and verified with the kinetic models of a cube that has been built. The results demonstrate that unlike the higher reaction rate constant than bulk Cu₂O, nano-Cu₂O shows lower kinetic parameters, including apparent activation energy, pre-exponential factor, activation enthalpy, activation entropy and activation Gibbs free energy. Both the reaction rate constant and activation Gibbs free energy increase with increasing temperature. The kinetic models show that the main factors affecting the reaction kinetic parameters are as follows:(i) the partial molar surface enthalpy affects the apparent activation energy; (ii) the partial molar surface entropy affects the preexponential factor; and (iii) the partial molar surface Gibbs free energy affects the reaction rate constant. We also provide a universal theoretical model and experimental method for gaining and analyzing kinetic parameters of nanomaterial heterogeneous reactions.

Key words: In-situ microcalorimetry, Reaction kinetics, Kinetic model, Nanomaterial, Cubic cuprous oxide