Cathodic deposition and characterization of tin oxide coatings on graphite for electrochemical supercapacitors

Amorphous tin oxide (SnOx) was cathodically deposited onto graphite electrode in a bath containing 0.1 M stannous chloride (SnCl2), 0.5 M sodium nitrate (NaNO3), and 0.4 M nitric acid (HNO3) in an aqueous solution of 50% (v/v) ethanol. The SnOx coatings grown on graphite were characterized as typical capacitive behaviors by cyclic voltammetry (CV), chronopotentiometric (CP) in 0.5 M KCl. Specific capacitance (in millifarad per square centimeter, C-a)changes linearly with the deposition charge up to 4.5 C cm(-2), and a maximum of as high as 355 mF cm(-2) was obtained with the SnOx coating grown at around 5 C cm(-2). For the SnOx coating deposited at 0.2 C cm(-2), a maximum specific capacitance (in farad per gram, C.) of 298 and 125 F g(-1) was achieved from CVs at a scan rate of 10, and 200 mV s(-1), respectively. The value of C,, significantly gets lower from 265 to around 95 F g(-1) when the deposition charge increases from 0.2 to around 6.0 C cm(-2). The long cycle-life and stability of the SnOx coatings on graphite via the presented cathodic deposition were also demonstrated. (c) 2007 Elsevier B.V. All rights reserved.