Electrochemical behavior of carbon paper on cerium methanesulfonate electrolytes for zinc-cerium flow battery

The voltammetric behavior of the Ce(III)/(IV) half-cell reaction in various electrolytes containing 0.6MCe was investigated on both pristine and metal-modified carbon paper (CP) electrodes at three different temperatures (25, 40 and 55 degrees C) in order to find the most favorable electrochemical conditions. The pristine CP displayed robust electrochemical performance for up to 200 repetitive CV cycles while the Pt loaded electrode's performance was stable for only 70 cycles, even though the latter exhibited a more reversible behavior, moving from a quasi-reversible to a reversible system (D-ox. = 4.0 x 10 (6)cm(2) s (1) and D-red. = 2.5 x 10 (6) cm(2) s (1)). The In and La metal modified electrodes did not show any improvement with regard to the kinetics or reversibility of the reaction. The addition of 1M H2SO4 to the base electrolyte enhanced the cerium reduction reaction by a factor of 3, (-7.2 x 10 (3)Acm (2)). The highest exchange current densities (j(o)) were achieved at 40 degrees C for the CP-Pt (1 x 10 (3) Acm (2)) attributable to the presence of the catalytic Pt. Elevated temperatures (40 and 55 degrees C) improved D and Delta E-p. while also the mass transport parameters a) dynamic viscosity (similar to 1.5mPa.s) and b) electrolytic conductivity (similar to 265mScm (1)) of the Ce (III)/(IV) half-cell reaction. Overall, pristine CP and to a lesser extent CP-Pt demonstrated good stability with prolonged cycling and kinetics comparable with the ones of Pt and Pt based electrodes. (C) 2014 Elsevier Ltd. All rights reserved.