Synergistic effect of PDA and PVP on nanosized Pd doped graphite felt/Ni electrode for promoting the electrocatalytic degradation of 2,4- dichlorophenoxyacetic acid.

[Display omitted] • GF/Ni/PDA/Pd-PVP electrode showed excellent dechlorination efficiency for 2,4-D. • PDA and PVP doping on the electrode remarkably promoted the generation of H* ads. • Indirect reduction mechanism of 2,4-D via H ads * plays the dominant role. • The desorption energy of PA was enhanced on the GF/Ni/PDA/Pd-PVP electrode. Reducing the mass transfer barrier for the diffusion of water and pollutants to Pd sites is an important measure to achieve efficient degradation of chlorinated organic compounds. Herein, a simple electroless deposition method for preparing a superhydrophilic nanosized Pd-loaded graphite felt/Ni electrode with the aid of the dispersibility of polyvinylpyrrolidone (PVP) and adhesiveness of polydopamine (PDA) is proposed. The GF/Ni/PDA/Pd-PVP electrode exhibited high electrocatalytic activity toward 2,4-dichlorophenoxyacetic acid (2,4-D) under the optimized conditions, namely degradation and dechlorination efficiencies of 90.5% and 88.53%, respectively, corresponding to 39% higher than that on the GF/Ni/Pd electrode. Experimental results revealed that PDA and PVP doping enhanced the hydrophilicity of the electrode, promoted the dispersibility of Pd nanoparticles (NPs), and the formation of Pd (1 1 1) and Ni (1 1 1) crystal facets. Compared to the electron-deficient PVP, the appropriate electron-donating ability of PDA promoted the formation of a suitable ratio of electro-deficient and electron-rich Pd, thus enhancing the production of H ads * and C-Cl scission. Moreover, theoretical calculation indicated that the doping of PDA and PVP optimized the adsorption energies of 2,4-D, H ads *, and the main dechlorination product PA, which was obtained via 4-electron transfer via H ads *. Therefore, this study provides a simple and feasible way to fabricate an efficient cathode for 2,4-D dechlorination. [ABSTRACT FROM AUTHOR]