A novel Pd loaded Ti electrode was prepared with a carbon nanotubes and polypyrrole interlayer modification, referred to as a Pd/CNTs–PPy/Ti electrode. Pretreated CNTs were deposited on the substrate uniformly by electrophoretic deposition technique. Modification by the CNTs–PPy interlayer made the Pd particles smaller and well-distributed. Pulsed-current electrodeposition technique led to more compact Pd particles. The hydrogen adsorption current value increased 55.3% and the electrochemical active surface area (EASA) increased 58.7% compared to the electrode without modification. The prepared Pd/CNTs–PPy/Ti electrode was employed in dechlorination of 2,3-dichlorophenol (2,3-DCP) in aqueous solution. The potential impact factors on the electrocatalytic dechlorination were studied, including dechlorination current, initial pH value of catholyte, reaction temperature and common ions in aqueous solution. Complete dechlorination could be achieved within 70 min under the selected conditions i.e., current of 5 mA, and an initial pH of 2.5 at ambient temperature. The common ions in aqueous solution, such as NO3−, CO32−, HCO3−, Mg2+, K+ and Ca2+, had no obvious effect on the electrocatalytic dechlorination within the scope of this investigation. The prepared Pd/CNTs–PPy/Ti electrode exhibited promising dechlorination potential with higher electrochemical activity.

Palladium/carbon nanotubes-nafion film-modified titanium mesh electrode (Pd/CNTs-nafion film/Ti electrode) was prepared and used for catalytic dechlorination of 2,3,5-trichlorophenol (2,3,5-TCP). The influences of factors, such as Pd2+ concentration, plating solution pH, and electrodeposition time and current, on the preparation of the electrode were studied by cyclic voltammetry (CV) to establish the optimal electrode preparation conditions. Additionally, the CV results highlighted that the addition of the CNTs-nafion film could enhance the electrochemical performance of the electrode. The Pd/CNTs-nafion film/Ti electrode was characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and inductively coupled plasma-atomic emission spectrometry (ICP-AES). The electrode exhibited good stability and high catalytic dechlorination capacity on 2,3,5-TCP―100 mg L−1 2,3,5-TCP was completely dechlorinated within 100 min at a dechlorination current of 5 mA and an initial solution pH of 2.3. High-performance liquid chromatography (HPLC) was used to detect the chlorinated phenolic intermediates, and the results revealed that the final products were mainly phenol. The kinetics studies revealed that the dechlorination of 2,3,5-TCP followed two-stage mixed order kinetics, and a possible degradation pathway for 2,3,5-TCP was proposed.

•Ce-doped MWCNTs electrode was successfully synthesized via electrodeposition.•Microstructure of the electrode surface changed by deposition of CeO2.•The ceftazidime degradation on the modified MWCNTs electrode was irreversible.•The removal efficiency of ceftazidime was close to 100% after 60 min electrolysis.•The possible mechanism of ceftazidime degradation on the electrode was elucidated.A modified multiwalled carbon nanotubes (MWCNTs) electrode doped with a rare earth metal, cerium, was prepared by electrodeposition. Scanning electron microscopy showed that cerium doping altered the microstructure and crystal orientation of the electrode surface, and the resulting electrode displayed a uniform and compact morphology. X-ray diffraction and X-ray photoelectron spectroscopy confirmed the successful deposition of CeO2 on the MWCNTs substrate. Cyclic voltammetry indicated that ceftazidime degradation on the modified MWCNTs electrode was irreversible. The Tafel curve showed that the modified electrode had a relatively high positive corrosion potential and a relatively low corrosion current density, indicating that the modified electrode could sustain a certain degree of corrosion. The degradation effects of the modified MWCNTs electrode on ceftazidime were evaluated systematically under different current densities, initial pH, supporting electrolyte concentration, electrode spacing, and initial ceftazidime concentration. The results suggested that the removal efficiency of ceftazidime with an initial concentration of 1 mg L−1 was approximately 100% after 60 min electrolysis in a 1 g L−1 Na2SO4 supporting electrolyte solution with a current density of 3 mA cm−2 and an electrode spacing of 1 cm. The possible mechanism of ceftazidime degradation was monitored by liquid chromatography-mass spectrometry.

Polymeric pyrrole-sodium lauryl sulfonate (PPy-SLS) composite film was applied to the preparation of palladium/foam-nickel (Pd/foam-Ni) electrode. The prepared Pd/PPy-SLS/foam-Ni electrode was characterized by cyclic voltammetry (CV), scanning electron microscope (SEM), X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and X-ray photoelectron spectroscopy (XPS). The addition of SLS improved the polymerization of pyrrole to form PPy-SLS film, which was conducive to prepare small Pd microparticles and led to the lower Pd loading, 0.85 mg cm−2. The composite electrode was used for electrochemically reductive dechlorination of 2,4-dichlorophenol (2,4-DCP) in aqueous solution. The influences of dechlorination current and initial pH value on the conversion efficiency and current the efficiency of 2,4-DCP dechlorination were studied. Complete dechlorination could be achieved on the Pd/PPy-SLS/foam-Ni electrode at ambient temperature under the condition of dechlorination current of 5 mA and initial pH value of 2.5 within 50 min. The electrode exhibits promising potential for dechlorination with high catalytic activity, good stability and low cost.

•Bimetallic Pd–Ni loaded Ti electrodes were prepared by electrodeposition method assisted with surfactant.•Pd–Ni(CTAB)/Ti electrode with high electro-catalytic hydrodechlorination potential was applied to PCP dechlorination.•Complete removal of PCP at ambient temperature was achieved.•Dechlorination of PCP followed pseudo first order reaction and apparent activation energy was 16.7 kJ mol−1.Palladium–nickel (Pd–Ni) bimetallic electrodes were prepared by electrodeposition method assisted with surfactants of cetyl trimethyl ammonium bromide (CTAB), sodium lauryl sulfonate (SLS) or sodium dodecyl sulfate (SDS). The prepared Pd–Ni electrodes were characterized in terms of cyclic voltammetry (CV), scanning electron microscope (SEM), X-ray diffraction (XRD), and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The electrode prepared with CTAB assistance, Pd–Ni(CTAB)/Ti, with higher electrochemical activity, was applied to the dechlorination of pentachlorophenol (PCP) in aqueous solution. The influences of dechlorination current and initial pH value on the PCP removal were studied. Complete removal could be achieved at ambient temperature under the conditions of constant current of 3 mA and initial pH value of 2.1 on the Pd–Ni(CTAB)/Ti electrode within 90 min. Moreover, decay kinetics and apparent activation energy of PCP dechlorination were investigated.Graphical abstract

Hydrodehalogenation (HDH) of 2,4-dichlorophenol (2,4-DCP) on a palladium–nickel (Pd–Ni) bimetallic electrode was investigated in this paper. The Pd–Ni bimetallic electrode was prepared on meshed titanium (Ti) substrate by electrochemical deposition with assistance of sodium dodecyl benzene sulfonate (SDBS). Cyclic voltammetry (CV) results revealed that the hydrogen adsorption peak current value of electrode became larger when SDBS was added in electrode preparation process. The structure and composition of the electrode were characterized by scanning electron microscopy (SEM), inductively coupled plasma-atomic emission spectrometry (ICP-AES) and X-ray diffraction (XRD). Dechlorination experiment was conducted on the Pd–Ni(SDBS)/Ti electrode in the presence of 100 mg L−1 (0.61 mmol L−1) 2,4-DCP. The removal efficiency of 2,4-DCP reached 100% with dechlorination current of 5 mA within 70 min in aqueous solution, meanwhile the current efficiency was 33.9%. The Pd–Ni(SDBS)/Ti electrode exhibits a good application prospect for electrocatalytic degradation of 2,4-DCP.Highlights► Electrocatalytic hydrogenolysis process was applied to hydrodehalogenation. ► The hydrogen adsorption capability increased with the addition of SDBS. ► The addition of SDBS could prevent Pd–Ni particles from aggregating. ► Complete dechlorination of 2,4-DCP in aqueous solution was achieved.

The electrochemically reductive dechlorination of 2,4-dichlorophenol (2,4-DCP) in aqueous solution on palladium/polymeric pyrrole–sodium dodecyl sulfonate film/meshed titanium electrode (Pd/PPy–SLS/Ti electrode) was investigated in this paper. The Pd/PPy–SLS/Ti electrode was prepared by electrodesposition and characterized in terms of surface morphology (SEM), structural feature (XRD), specific surface area (BET) and Pd loading level (ICP-AES). Effects of the dechlorination current and the initial pH value of the solution on the removal efficiency and the current efficiency were studied in the 2,4-DCP dechlorination process on Pd/PPy–SLS/Ti electrode. Effective removal of 2,4-DCP was achieved with removal efficiency of 100% and current efficiency of 33.9% in the presence of 100 mg L−1 2,4-DCP under the conditions of initial pH of 2.36, dechlorination current of 5 mA and dechlorination time of 70 min. The intermediate products were 2-chlorophenol (2-CP) and 4-chlorophenol (4-CP). The final products were mainly phenol. Its further reduction product cyclohexanone was also detected. The stability of the electrode was good that the dechlorination efficiency was maintained at 100% after having been reused 8 times. The stable electrode demonstrated a promising application prospect in dechlorination process with high effectiveness and low cost.Graphical abstractHighlights► Effective dechlorination of 2,4-DCP on surfactant-assisted Pd loaded electrode. ► PPy–SLS composite film led to high catalytic activity and low Pd content. ► Removal efficiency kept 100% after 8 times dechlorination on the stable electrode. ► Dechlorination obeys first order reaction with activation energy of 22.61 kJ mol−1. ► Management of the final solution at neutral benefits the subsequent treatment.

Electrochemical dechlorination of chloroform in neutral aqueous solution was investigated using palladium-loaded electrodes at ambient temperature. Palladium/foam-nickel (Pd/foam-Ni) and palladium/polymeric pyrrole film/foam-nickel (Pd/PPy/foam-Ni) composite electrodes which provided catalytic surface for reductive dechlorination of chloroform in aqueous solution were prepared using an electrodepositing method. Scanning electron microscope (SEM) micrographs showed that polymeric pyrrole film modified the electrode-surface characteristics and resulted in the uniform dispersion of needle-shaped palladium particles on foam-Ni supporting electrode. The experimental results of dechlorination indicated that the removal efficiency of chloroform and current efficiency in neutral aqueous solution on Pd/PPy/foam-Ni electrode could be up to 36.8% and 33.0% at dechlorination current of 0.1 mA and dechlorination time of 180 min, which is much higher than that of Pd/foam-Ni electrode.