Electrocatalytic dehalogenation of aqueous pollutants by dealloyed nanoporous Pd/Ti cathode

Abstract

In this study, commercial Ti-0.15Pd alloy could be activated by selective dissolution of Ti using simple HF treatment, to catalyze electrochemical dehalogenation of aqueous pollutants. The surface of dealloyed cathodes was characterized with a Pd-enriched nano-porous structure, as confirmed by scanning electron microscopy, glow discharge spectroscopy and transmission electron microscopy with energy-dispersive X-ray spectroscopy. With respect to the surface loading of Pd and 2-chlorophenol (2-CP) hydrodechlorination rate, the [HF] and exposure time were optimized to be 0.5 M and 5 min, respectively. 2-CP removal was maximized at the lowest values of current density (2.5 mA/cm2) and pH (1.8). The activation energy and energy consumption for 2-CP dechlorination were estimated to be 30.7 kJ/mol and 47 kW h/kg for the nanoporous Pd/Ti cathode. Scavenging experiments for the electron (e−) and hydrogen radical (H·) confirmed that adsorbed H· was the active mediator responsible for the dechlorination, which was active for reductive removal of other brominated and iodinated organic compounds. Owing to an accumulation of reaction products inside the pores, periodic regeneration of the catalytic electrodes was necessary, with a proper cycle to minimize the loss of precious Pd component.