Sustainable electrochemical production of H₂O₂ on carbon blacks: Structural properties as key drivers

The electrochemical production of H₂O₂ via the two-electron oxygen reduction reaction (2e⁻ORR) has emerged as a sustainable alternative to the traditional anthraquinone process, which involves hazardous solvents and generates significant waste. Carbon blacks are extensively utilized as benchmark electrocatalysts for H₂O₂ production, with performance often attributed to electrical conductivity, composition, or hydrophobicity. However, the role of key parameters such as structural properties and surface area remains underexplored. To clarify this, we have analyzed four commercial carbon blacks commonly reported in the literature (Vulcan XC-72, Printex XE2, Superior Graphite and Prolabo) as benchmark electrocatalysts for the electrogeneration of H₂O₂. Results indicate that electrocatalytic activity in H₂O₂ accumulation assays of carbon blacks can be rationalized through a comprehensive characterization of their structural properties, with a minor impact of conductivity and composition (for un-functionalized carbon blacks with a high carbon content). Our results also highlight the need to complement the characterization of the electrocatalytic activity in rotating ring-disk electrodes -a common screening practice- with H₂O₂ accumulation tests to account for the impact of parasitic reactions in the long-term productivity and selectivity. This study contributes to the rational design of sustainable carbon-based electrocatalysts for H₂O₂ production, advancing green and efficient electrochemical processes.