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 H 2 O 2 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 H 2 O 2 production with the doping level. In contrast, the H 2 O 2 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 O 2 and liquid electrolyte in the GDE for high-rate electrosynthesis of H 2 O 2 .