Electrocatalytic hydrodechlorination of chlorophenols enhanced by hydrogen spillover on Pd-HxWO3 catalysts

Electrocatalytic hydrodechlorination (EHDC) is a promising approach for decomposing chlorinated organic compounds in water treatment. However, the efficiency of EHDC is constrained by kinetic mismatch between C−Cl bond cleavage and atomic hydrogen (H*) utilization. Herein, we develop a heterostructured Pd-H x WO 3 electrocatalyst with Pd nanoparticles (Pd NPs) anchored on H x WO 3 substrate, which can efficiently decompose 2,4-dichlorophenol (2,4-DCP) by taking advantage of the hydrogen spillover effect. Specifically, the resulting Pd-H x WO 3 electrocatalyst exhibits superior dechlorination rate constant ( k  = 1.142 h −1 ) and Faradic efficiency (FE = 10.1 %) than monometallic Pd ( k  = 0.3600 h −1 , FE = 3.74 %) and bare H x WO 3 ( k  = 0.1167 h −1 , FE = 2.11 %), along with exceptional pH adaptability and stability. Electron spin resonance (ESR) and electrochemical and kinetic isotope effect (KIE) measurements indicate that the transport of the H* from H x WO 3 to Pd NPs is the key to enhanced EHDC performance. Theoretical studies reveal that the Volmer step of water dissociation to produce H* is more favorable due to lower transition state (TS) energy (0.344 eV) on H x WO 3 than that on Pd (TS = 0.532 eV). Furthermore, the interfacial electron redistribution in Pd-H x WO 3 lowers the thermodynamic (Δ G = 0.207 eV) and kinetic (Δ G = 0.239 eV) barriers for H* transfer from the internal site of H x WO 3 to interfacial Pd sites, thereby facilitating the proton-coupled electron transfer (PCET)-mediated EHDC on Pd site. This work provides a new proof-in-concept demonstration for designing hydrogen spillover-integrated electrocatalysts to enhance H* generation-transfer-utilization in EHDC for water decontamination.