Single-atom Pd loaded on nitrogen-doped carbon as a bifunctional catalyst for the electrochemical degradation of 2,4-dichlorophenol

Abstract

A nitrogen-doped carbon-anchored single atom Pd (SA-Pd/NC) electrocatalyst was prepared by pyrolysis of Pd-doped zeolite imidazolite framework (ZIF) precursors. The SA-Pd/NC catalyst was characterized by high-resolution transmission electron microscopy, aberration-corrected high-angle annular dark field scanning transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectrometry and applied in the degradation of 2,4-dichlorophenol (2,4-DCP). We demonstrate that the SA-Pd/NC catalyst has dual functions, with both electrocatalytic hydrodechlorination (ECH) activity and in situ heterogeneous electro-Fenton (hetero-EF) activity even at low current density. The ECH process was the main pathway of 2,4-DCP degradation without oxygen aeration. Under aerobic conditions, hetero-EF coupling with ECH occurred simultaneously on the SA-Pd/NC cathode, i.e., the dechlorination product phenol was oxidatively degraded with the reactive oxygen species produced on the electrode. The degradation rate of 2,4-DCP and TOC removal rate reached 95.1% and 37.6%, respectively, with a current density of 2.5 mA cm−2 and an initial pH of 3.0. This work provides the design of bifunctional single-atom catalysts for 2,4-DCP degradation, including dechlorination and mineralization.