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

• Incorporation of CoPc modifier reached H2O2 formation higher than 90%.
• CuPc modifier decreased H2O2 formation to a minimum of 53.3%.
• 10% CoPc catalyst promoted + 340 mV overpotencial shift required to H2O2 electrogeneration.
• SECM confirmed incorporation of CoPc increased the H2O2 electrogeneration.

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 +340 mV (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 -0.2 V, 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.