Pd/γ-MnO₂/Ni foam cathode for efficient electrocatalytic hydrodechlorination of chlorophenols in aqueous solution and...

Electrocatalytic dehalogenation has emerged as a sustainable technology for environmental remediation. However, efficient electrocatalysts are still lacking, especially for wastewater treatment. In this study, a Pd/γ-MnO₂/Ni foam composite electrode was designed. The introduction of hexagonal flake-like γ-MnO₂ successfully prevented Pd aggregation and optimized electrode structure. Compared to previously reported electrodes, Pd/γ-MnO₂/Ni foam composite electrode had lower Pd loading and higher dehalogenation efficiency and current efficiency. In 2-chlorophenol (2-CP) solution and dye wastewater, over 99 % dehalogenation efficiencies were achieved within 120 min (10 mA), without adjusting the pH value. Computational results suggested that γ-MnO₂ can promote the adsorption of H₂O, which is the key rate-limiting step for 2-CP hydrodechlorination. In addition, γ-MnO₂ facilitated water dissociation and served as an intermediary for transferring atomic hydrogen (H*) from Pd to Ni foam. This hydrogen spillover mechanism extended the reactive area of electrode, hindered H₂ evolution and enhanced the dehalogenation efficiency. It was found that Pd/γ-MnO₂/Ni foam electrode showed excellent dehalogenation performance under both acidic and neutral conditions, and exhibited good resistance to the coexisting ions (such as Cl^-, NO₃^- and HCO₃^-). Hence, the Pd/γ-MnO₂/Ni foam electrode demonstrates strong potential for the treatment of high-salinity wastewater. The high dehalogenation efficiency and long service life of Pd/γ-MnO₂/Ni foam electrode in dye wastewater confirmed its feasibility and applicability. This study explored the synthesis and interfacial mechanism of electrodes, paving the way for efficient remediation of halogenated organic pollutants in wastewater.