Electrochemical and theoretical investigation of the silver nanoparticles/TiO2 interface: the “silver-ion electrode”

A sandwich-like structure electrode of silver nanoparticles embedded in a titania (anatase polymorph) photoactive layer was prepared [1-2] and electrochemically characterized by cyclic voltammetry and electrochemical impedance spectroscopy. In comparison with literature data on bare silver nanoparticles-modified electrodes [3-5], the new device features a pronounced electrocatalytic effect on the silver oxidation peak (Fig. a) together with a great increase in the current intensity. Plane-wave DFT calculations, performed using the VASP code, described the composite junction as a distorted bulk Ag structure, commensurate with the periodicity of the (101) face of the I41/amd TiO2 polymorph. The silver atoms close to the semiconductor were found to gain a partially positive charge, quickly decreasing with the distance from the TiO2 surface. These joint theoretical and experimental evidences demonstrate that the device could be considered as a “positively charged silver nanoparticles-based electrode”, with positively ionized surface silver atoms protected by the titania layer, which holds a partial negative charge. This peculiar electrode structure shows interesting properties, among which self-cleaning ability, to be conveniently used for sensor applications. References [1] G. Soliveri, V. Pifferi, G. Panzarasa, S. Ardizzone, G. Cappelletti, D. Meroni, K. Sparnacci, L. Falciola, Analyst, 140, (2015), 1486 – 1494. [2] V. Pifferi, G. Soliveri, G. Panzarasa, S. Ardizzone, G. Cappelletti, D. Meroni, L. Falciola, RSC Advances, 5, (2015), 71210 – 71214. [3] O. S. Ivanova, F. P. Zamborini, J. Am. Chem. Soc., 132, (2010), 70–72. [4] G. Chang, J. Zhang, M. Oyama, K. Hirao, J. Phys. Chem. B, 109, (2005), 1204-1209. [5] S.E. Ward Jones, F.W. Campbell, R. Baron, L. Xiao, R.G. Compton, J. Phys. Chem. C, 112, (2008), 17820–17827. Acknowledgements This work has been supported by Fondazione Cariplo (Milano, Italy), grant no. 2014-1285. We acknowledge the CINECA and the Regione Lombardia award under the LISA initiative (grant SURGREEN) for the availability of high performance computing resources. We also thank the Chemistry Department for funding through the Development Plan of Athenaeum grant – line B1 (UNIAGI 17777).