Effect of particle size and morphology on surface thermodynamics and photocatalytic thermodynamics of nano-Cu2O

In-situ microcalorimetry was used to obtain the molar surface Gibbs energy, molar surface enthalpy and molar surface entropy of Cu 2 O nanoparticles, and their influences of particle size and morphology were investigated. The activity and mechanism of photocatalytic degradation of methyl orange were discussed with a correlation between the Cu 2 O surface energy. Results indicated that the surface thermodynamic functions increased with the decrease of the particle size. The Cu 2 O surface energy was of the following order: spherical   >   octahedral   >   tremella-like with corresponding values of 9.826, 8.438 and 6.901   kJ   mol −1 , respectively. The order of catalytic activity was tremella-like   >   particle spherical   >   octahedral with a corresponding degradation rate of 94.79, 70.10 and 68.19%, respectively. The photocatalytic activity was significantly related to surface energy. Interestingly, we found that nano-Cu 2 O with low surface energy exhibited a high photocatalytic activity. This study provided a new understanding of the surface-activity relationship between nanomaterial surface energy and catalytic properties.