Search

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.

Hydrogen peroxide (H 2 O 2 ) is a commonly used oxidant with a wide variety of applications in, for example, organic synthesis and wastewater treatment. This paper describes the development of catalysts for the electrogeneration of H 2 O 2 in acidic medium using gas diffusion electrodes (GDE). Initial experiments were performed using rotating ring-disk electrodes modified with microporous layers of Printex 6L carbon containing various amounts of cobalt (II) phthalocyanine (CoPc) in order to evaluate catalytic activities. The results showed that the current efficiency for the formation of H 2 O 2 increased from 69.7% for Printex 6L carbon without catalyst to 81.5% when using Printex 6L carbon with CoPc, and this was accompanied by a decrease in the number of electrons involved in the oxygen reduction reaction from 2.6 to 2.3. Based on these findings, modified GDEs were constructed containing 3.0, 5.0 and 10.0% of CoPc on Printex 6L carbon. The concentration of H 2 O 2 that formed after 90 min electrolysis with the GDE modified with Printex 6L carbon alone was 176 mg L −1 , while the GDE with 5.0% CoPc on carbon produced 331 mg L −1 of H 2 O 2 , i.e. an increase in yield of 89.1% relative to Printex 6L carbon. Additionally, using GDE s modified with CoPc on carbon, the potential at which H 2 O 2 formation attained its maximum value shifted to less negative values in comparison with electrodes without catalyst. It is concluded that CoPc is an appropriate catalyst for efficient electrogeneration of H 2 O 2 .