Influence of particle size on electrochemical thermodynamics of Nano-Au electrodes: Mechanism, factors, range and degree

There is a significant effect of particle size on electrochemical thermodynamics of nano-metal electrodes, it is still unclear, however, the mechanism, factors, range and degree of the effect. Herein, in theory, we derived the relations of the electrochemical thermodynamic quantities and the size of nanoparticles which constituted the nano-metal electrodes, discussed the mechanism and the influencing factors. Experimentally, nano-Au with different radii (0.9-37.4 nm) made as nano electrodes to research the size dependence of electrochemical thermodynamic quantities. Combining the results of theory and experiments, discussed the influencing regularities, range and degree. The regularities obtained from these experiments are consistent with the theoretical relations. The research results show that particle size has pronounced effect on electrochemical thermodynamic quantities. Both the Eo and the lnKo decrease with the particle size decreasing, while other electrochemical thermodynamic quantities increase. These effects should be attributed to partial molar surface area, surface tension and its temperature coefficient. Thereinto, partial molar surface area and surface tension are the major influencing factors for Eo, Ko, ΔrGm and ΔrHm, partial molar surface area and temperature coefficient of surface tension are for (∂E/∂T)p, ΔrSm and Qr,m. For Au nanoparticles, as the radius exceeds 10 nm, the major factor is partial molar surface area, there exist linear relationships between the electrochemical thermodynamic quantities and reciprocal of radius. However, as the radius is less than 10 nm, the effects of surface tension and its temperature coefficient gradually hold the main positon with the radii decreasing, respectively; as well as there are no linear relationships. Our research offer significant fundamental insight on the size-dependent electrochemical thermodynamics, and can greatly impact future exploration and application of nano-metal electrodes.