Ultralow-Loading Pd Nanoparticles on Co ₃ O ₄ Nanoarrays as Highly Active Electrodes for Efficient Electrochemical Dechlorination

Electrocatalytic hydrogenation dechlorination (EHDC) has emerged as a promising and environmentally benign strategy for the degradation of chlorinated phenols (CPs), owing to its green process characteristics and the absence of hazardous byproducts. Achieving high EHDC efficiency necessitates both a highly active electrocatalyst and optimized reaction conditions. In this work, we fabricated a Pd/Co 3 O 4 electrode, comprising ultralow-loading Pd nanoparticles (0.011 mg Pd cm –2 ) supported on a Co 3 O 4 nanoarray grown on carbon fiber paper (CFP), for EHDC applications. The well-defined array structure facilitates uniform potential and current density distribution while also expanding the number of electroactive sites. Electrochemical and theoretical analyses reveal that abundant oxygen vacancies (OVs) in Co 3 O 4 induce a spatial charge redistribution in the Pd/Co 3 O 4 heterostructure, thereby strengthening the metal-support interaction (SMSI). This optimization of geometric and electronic properties significantly enhances both hydrogen evolution capability and EHDC performance. Under optimized operational parameters, including pH, substrate concentration, and applied potential, the Pd/Co 3 O 4 /CFP electrode achieves nearly complete degradation (close to 100%) of 10 mg·L –1 4-chlorophenol (4-CP) within 180 min at a cathodic potential of −0.8 V vs Ag/AgCl, with phenol (P) as the main product. The mass activity (MA) for 4-CP dechlorination reaches 1.0289 min –1 mg –1 . Density functional theory (DFT) calculations further illustrate that the underlying oxygen vacancy rich Co 3 O 4 modulates the electronic structure of Pd, boosting hydrogenation capacity and EHDC efficiency. These findings underscore the great potential of the Pd/Co 3 O 4 /CFP electrode as an efficient and practical electrocatalyst for EHDC processes.