Enhancing Electrocatalytic Hydrodechlorination through Interfacial Microenvironment Modulation

Electrochemical reduction (ER) is a promising approach to safely remove pollutants. However, sluggish reaction kinetics and significant side reactions considerably limit the applicability of this green process. Herein, we uncovered the previously ignored role of interfacial hydrophilicity in determining the ER performance through electron microscopy observations, contact angle (CA) analysis, and electrochemical measurements. A Pd/C electrocatalyst forms dense nanopores on the electrode surface, rendering it highly hydrophobic and achieving a CA of up to 145 degrees. This imposes a large mass-transfer barrier for the diffusion of water and pollutants into Pd sites. Moreover, the release of H2 is suppressed, which changes the solid-liquid (Pd-polluted water) interface into a solid-gas (H2)-liquid interface. This further slows down mass transfer and the decontamination process. This dilemma can be easily alleviated by adding hydrophilic polymers like polyethylene glycol to increase hydrophilicity and improve mass transfer. By this way, the activity and Faraday efficiency of Pd/C in the electrochemical hydrodehalogenation of 2,4-dichlorophenol could be increased by 4-5 times. Moreover, this interfacial microenvironment modulation strategy is parallel to other approaches, such as Pd structural engineering, and therefore these strategies can be combined to further increase the electrochemical decontamination performance of electrocatalysts.

Automated summary

Electrochemical reduction (ER) is a promising method for pollutant removal, but its application is limited by slow reaction kinetics and side reactions. In this study, the role of interfacial hydrophilicity in determining ER performance was investigated. It was found that a hydrophobic Pd/C electrocatalyst hindered the diffusion of water and pollutants, leading to decreased mass transfer and decontamination efficiency. However, this dilemma could be overcome by increasing hydrophilicity with hydrophilic polymers, resulting in a significant improvement in the activity and efficiency of the electrocatalyst.