Interplay of Active Sites and Microenvironment in High-Rate Electrosynthesis of H2O2 on Doped Carbon

Heteroatom doping is widely used in the design of electrocatalysts as it can tune the electronic structure and create more active sites. However, it may simultaneously alter the wetting properties of the catalyst microenvironment, which plays a critical role in gas-involving reactions. Here, we report an interplay between the active sites and the microenvironment in the electrosynthesis of H2O2 via two-electron oxygen reduction on doped carbon. For both oxygen-doped and fluorine-doped carbon, rotating ring-disk electrode (RRDE) measurements indicated a monotonic increase of the intrinsic activity for H2O2 production with the doping level. In contrast, the H2O2 production rate in a gas-diffusion-electrode (GDE) flow cell reached the highest value on a moderately doped carbon catalyst but declined on catalysts with further increased doping. In both cases, the doping created more active sites in carbon but also changed its wetting characteristics. Only a microenvironment with moderate hydrophilicity or hydrophobicity could enable an optimal balance between gaseous O2 and liquid electrolyte in the GDE for high-rate electrosynthesis of H2O2.

Automated summary

Heteroatom doping is widely used in electrocatalyst design to improve performance, but it can also affect the wetting properties of the catalyst microenvironment. This study investigates the interplay between active sites and microenvironment in the electrochemical synthesis of H2O2 on doped carbon. The results show that while doping increases the intrinsic activity for H2O2 production, the optimal production rate is achieved with a moderately doped carbon catalyst due to changes in wetting characteristics.