Au-based electrochemically etched cavity microelectrodes as optimal tool for quantitative analyses of finely dispersed electrode materials

The cavity microelectrode (C-ME) is an innovative tool for the study of finely dispersed electrode materials to be adopted in several electrochemical systems. Beside the different advantages of C-MEs, there is the possibility to carry out a rapid screening of the electrochemical behaviour of different materials thanks of the possibility of a quick and reliable electrode preparation [1,2]. In addition, the precise knowledge of the cavity volume (and thus of the amount of loaded powder) implies that any analysis carried out by a C-ME can be considered as quantitative [3]. This in turn leads to a optimal use of the C-ME as a tool for accurate evaluation of the relevant physico-chemical “specific” quantities of the powder under investigation, i.e. normalized by the amount of sample. In turn, this allows the rapid and quantitative screening of different electrocatalytic powder materials and to extract their intrinsic (“per site”) activities. The use of gold as the cavity current collector allows to obtain a regular cylindrical recess, whose volume is easily determined with good accuracy and precision. In particular different preparation methods were examined and that allow to obtain a very regular cylinder-shaped C-MEs was individuate. The features of Au/C-MEs is well demonstrated by the good linear correlation between the cavity volume (determined by electrochemical methods) and the quantity of charge related to the amount of electroactive powder inserted into the cavities. To further prove the point, we adopted two different test systems: Pt on carbon and an IrO2-based material. Finally, we proved the adequacy of Au/C-MEs in determining the electrocatalytic activity of Ag particles as electrocatalysts for the hydrodehalogenation of trichloromethane and the specific conductivity of different mixed oxide materials. Acknowledgements: Financial supports from the Italian Ministry of Education, University and Research (PRIN 2008N7CYL5), Fondazione Cariplo (2010-0506) and Università degli Studi di Milano (PUR 2009 Funds) are gratefully acknowledged. C.L. is grateful to the University of Milan for a post-doc fellowship. The contribution of Chiara Marchiori to the electrochemical experimental tests is also acknowledged. [1] A. Minguzzi, C. Locatelli, G. Cappelletti, M. Scavini, A. Vertova, P. Ghigna, S. Rondinini, J. Phys Chem 2012, 116, 6497. [2] A. Minguzzi, C. Locatelli, G. Cappelletti, C.L. Bianchi, A. Vertova, S. Ardizzone, S. Rondinini, J. Mater. Chem. 2012, 22, 8896. [3] C. Locatelli, A. Minguzzi, A. Vertova, C. Paola, S. Rondinini, Anal. Chem. 2011, 83, 2819.