Decoupling the Roles of Oxygen-Containing Functional Groups and Aromatic Carbon Clusters in the Reduction of Halogenated Contaminants on Carbon-Based Cathodes.

While carbon-based cathodes are widely used to mediate the electrochemical reduction of contaminants, the structural properties governing their rapid electron transfer remain poorly understood. Here, we decouple the roles of bulk conductivity and surface reactivity by quantifying the size of aromatic clusters and oxygen functional groups (OFGs) in biomass-derived cathodes. We demonstrate fundamental governing principles using tetrabromobenzene as the probe pollutant. We find that while increasing pyrolysis temperature drives the growth of aromatic clusters and increases dehalogenation performance (e.g., plateauing at 850 °C with a cluster size of ∼14 aromatic rings), these conductive networks are inert in the absence of OFGs. Introducing OFGs onto these clusters increases electron transfer efficiency by 50-85%, whereas selectively reducing these groups decreases activity by up to 75%. The optimized cathodes exhibit capacities that surpass those of commercial activated carbon and rival those of carbon black, providing a rational blueprint for designing high-efficiency carbon electrodes and enabling improved performance across a range of applications.