Carbon dioxide-mediated decomposition of hydrogen peroxide in alkaline solutions

Abstract

Rapid hydrogen peroxide decomposition in aerated alkaline solutions is described, the maximum rate being attained at pH values between 11.5 and 11.7, where the peroxide (pK_a= 11.7) is ca. 50% unprotonated. The reaction proceeds with the release of protons and is strictly dependent upon the continuous presence of carbon dioxide, but not of carbonate anions, in the peroxide solutions. The following two-step mechanism is proposed: (1) formation of percarbonic acid (H₂CO₄) by condensation of CO₂ with the undissociated peroxide (H₂O₂) and (2) reduction of the acid by perhydroxyl anions (HO^–₂).