High-performance gas-diffusion electrodes for H2O2 electrosynthesis

Abstract

The application of gas diffusion electrodes (GDE) modified with carbon black materials at high overpotentials leads to the substantial production of H2O2 via oxygen reduction reaction. The greatest challenge in this process lies in the reduction of the high overpotentials without affecting H2O2 selectivity. One way of circumventing this problem is through the modification of GDEs with coordination compounds. The present work investigates the modification of Printex L6 carbon (CPL6) with different amounts of porphyrin complexes containing the following metallic centers: Mn, Co, Ni, Cu and Zn. The application of 5.0 wt % Co-Porphyrin/CPL6 modifier yielded the best results, with high selectivity for H2O2 generation (90.2%) and marked improvement in catalytic activity (72.6%) compared to CPL6; these positive effects are attributed to the enhancement of both the interaction energy between Co and HOO* reaction intermediate and the effect of the conjugated π-electrons of the CPL6. The application of the modified GDE led to the electrogeneration of 340 mg L−1 of H2O2 with energy consumption of 86.6 kWh kg−1 and 92.1% improvement in efficiency compared to the unmodified GDE. Thus, the findings show that the 5.0 wt % Co-Porphyrin/CPL6 modifier is an excellent cathode for application in H2O2 generation and in electrochemical advanced oxidation processes.