The use of copper and cobalt phthalocyanines as electrocatalysts for the oxygen reduction reaction in acid medium

Abstract

Direct electrochemical generation of hydrogen peroxide in aqueous medium represents an attractive method for the production of the oxidizing agent. This paper describes the development of electrocatalysts comprising Printex L6 carbon black containing 0 to 10% (w/w) of copper or cobalt phthalocyanine (CuPc and CoPc, respectively) as modifier. Formation of H2O2 by the ORR in acidic medium was investigated by linear voltammetry using a rotating ring-disc electrode, whose glassy carbon disc contained a microporous layer of the catalyst. Incorporation of CuPc into Printex decreased the current efficiency for H2O2 formation [i(H2O2)%] from 75.4% for unmodified Printex to a minimum of 53.3% when 10% of the modifier was present. However, i(H2O2)% increased when CoPc was employed as modifier, and a maximum value of 92.3% was attained with Printex containing 1.0% CoPc. Moreover, a shift of +340mV (relative to unmodified Printex) was observed in the overpotential required for the generation of H2O2 when 10% of CoPc was present. SECM demonstrated that, at a potential of -0.2V, Printex with 10% CoPc produced larger amounts of H2O2 compared with unmodified Printex. It is concluded that the use of the CoPc modifier is promising for the electrogeneration of H2O2 on a large scale.