The open circuit potential of hydrogen peroxide at noble and glassy carbon electrodes in acidic and basic electrolytes

The open circuit potentials (OCPs) of H2O2 at Pt, Pd. Au, and glassy carbon electrodes are measured in H2SO4 and NaOH electrolyte solutions. Effects of concentration of H+, OH- and H2O2 as well as temperature on the OCP of H2O2 are investigated. The OCP of H2O2 is much lower than its theoretical reduction potential in both acidic and basic medium. The OCP is actually a mixed potential of H2O2 electroreduction and electrooxidation simultaneously occurring at electrode surfaces and it is more close to the equilibrium potential of H2O2 electrooxidation rather than electroreduction. The OCP of H2O2 is around 0.77-0.80 V at [H+] = (H2O2] = 1.0 mol dm(-3) in H2SO4 solution and is about 0-0.06 V at [OH-] = [H2O2] = 1.0 mol dm(-3) in NaOH at 298 K on Pt, Pd, Au and GC electrodes. The OCP of H2O2 is independent of H2O2 concentration within the range of 0.01 to 1.0 mol dm(-3). It increases approximately linearly with the logarithm of H+ concentration from 0.02 to 2.0 mol dm(-3), decreases with the logarithm of OH- concentration from 0.01 to 1.0 mol dm(-3) and decreases with increase of temperature from 278 K to 333 K. The linear equations were presented and discussed. (C) 2011 Elsevier B.V. All rights reserved.