Influences of nano-effect on electrochemical thermodynamics of metal nanoparticles electrodes

Abstract

Nano-effect contributes significantly to changing the electrochemical thermodynamics of metal nanoparticles electrodes compared to conventional macroelectrodes. However, the influencing mechanisms and regularities of nano-effect on the electrochemical thermodynamics were still relatively poorly understood. In this paper, the influencing mechanisms and regularities of nano-effect were discussed basing on the theoretical relations of electrochemical thermodynamics for metal nanoparticles electrodes. In experiment, nano-Ag electrodes with different average radii were taken as a system, liquid phase reduction method was applied to prepare nano-Ag with different particle sizes, the standard electrode potential and its temperature coefficient, as well as the electrochemical thermodynamic quantities of the electrode reaction were determined at different temperatures. Both theoretical and experimental results indicate that the electrochemical thermodynamic quantities of metal nanoparticles electrodes highly depend on the particle size. As the particle size decreases, the standard electrode potential and the standard equilibrium constant decrease, while the temperature coefficient of standard electrode potential, the molar reaction Gibbs energy, enthalpy, entropy and reversible heat increase. These effects can be ascribed to nano-effect, and nano-effect includes interfacial area effect and interfacial tension effect. When the radius exceeds 10 nm, interfacial area effect plays a role, so there is a linear relationship between these electrochemical thermodynamic quantities and the reciprocal of particle size, respectively. While as the radius is less than 10 nm, interfacial area effect and interfacial tension effect work together, the relations of these electrochemical thermodynamic quantities with the reciprocal of particle size deviate the linear relations. Besides, for nano-Ag, the influences of interfacial area effect and interfacial tension effect are almost equal for particles of 1.5 nm in radius. And it can be predicted that interfacial tension effect would play a role with the continued decrease of particle size. This research can provide important guidances and references for the preparations and applications of metal nanoparticles electrodes.