Pd/TiC/Ti electrode with enhanced atomic H* generation, atomic H* adsorption and 2,4-DCBA adsorption for facilitating electrocatalytic hydrodechlorination

Electrocatalytic hydrodechlorination (ECH) has been proposed as a potential technology for the effective degradation of organochlorine contaminants. In this study, a nanoscale Pd/TiC catalyst with low resistance was dip-coated onto Ti, aiming to fabricate a stable Pd/TiC/Ti electrode with enhanced ECH reactivity for efficient dechlorination. Electrochemical techniques indicated that the Pd/TiC/Ti electrode had a larger electrochemically active surface area and more rapid interfacial charge transfer than the conventional Pd/C/Ti electrode. In a batch experiment, the dechlorination rate for ECH of 2,4-dichlorobenzoic acid (2,4-DCBA, a model pollutant) by Pd/TiC/Ti was 1.3-14.5 times higher than those by Pd/C/Ti, Pd/MWCNTs/Ti, and Pd/MoS2/Ti, respectively. Scavenger experiments, ESR spin-trapping spectroscopy, and cyclic voltammetry clarified the intensified atomic H* generation by Pd/TiC/Ti. DFT calculations revealed that Pd/TiC/Ti had stronger binding ability with atomic H* (E-ads: -2.89 eV vs. -2.44 eV) and 2,4-DCBA (E-ads: -3.62 eV vs. -2.15 eV), respectively, when compared with Pd/C/Ti. As a result, enhanced generation of atomic H*, together with strengthened adsorption of atomic H* and 2,4-DCBA, would contribute to a faster ECH reaction. The Pd/TiC/Ti electrode retained its reactivity after 10 successive batch experiments (80 h), and showed high tolerance to the constituents in actual water matrices including lake water and river water. This study proposed a promising ECH electrode for the treatment of chlorinated organics in water matrices.