Theoretical and experimental study on the size- and morphology-dependent electrochemical thermodynamics of nano-silver electrode

Nanometer-sized electrodes differ greatly from the corresponding bulk electrodes in electrochemical thermodynamics, which is determined by the size and morphology of nanoparticles that constructing the electrodes. However, the influence of size and morphology on the electrochemical thermodynamics remains vague. Herein, the relations of the electrode potential; the temperature coefficient of electrode potential; and the equilibrium constant, thermodynamic properties, and reversible heat of reaction of nanoelectrodes to size and morphology of nanoparticles were systematically deduced. Experimentally, different sizes of nano-silver with morphologies of sphere, wire, and cube were prepared, characterized, and made into nanoelectrodes. And then, the size and morphology-dependent electrochemical thermodynamics of the nanoelectrodes were obtained. Experimental results agree with the theoretical predictions, indicating that with the decrease of particle size, the electrode potential and the reaction equilibrium constant decrease, but the temperature coefficient, the thermodynamic properties, and reversible heat of reaction increase. Furthermore, linear dependences of these electrochemical properties on inverse particle size were confirmed within the experimental size range. At the same equivalent size, the order of size of the electrode potential is E (wire) > E (sphere) > E (cube), while the temperature coefficient and the thermodynamic properties of reaction are opposite. These findings provide important guidance and basis for the design and preparation of highly sensitive electrochemical sensors and chemical cells with high electromotive force and large capacity, and for the electrochemical catalysis and electrochemical corrosion protection.