Rational Design and Structural Regulation of Robust Catalysts for Electrocatalytic Hydrodechlorination: From Nanostructures to Single Atoms

Abstract

As a class of persistent pollutants that are easily bioaccumulatable and highly biotoxic, chlorinated organic pollutants exist in the environment and pose a substantial threat to ecological safety. The electrocatalytic hydrodechlorination (EHDC) technology shows the advantages of high efficiency, simple operation, mild reaction conditions, and no secondary pollution and thus promises a good application prospect in the treatment of chlorinecontaining pollutants. Pd-based catalysts are considered the most efficient catalysts for electroreductive dechlorination thus far, yet the reserves of Pd are scarce, and the price is often prohibitively high. The development of noble metal catalysts with high atom utilization and non-noble metal catalysts for EHDC has become a hot research topic, but relevant reviews are still lacking. In this paper, the research progress on EHDC catalysts during recent years is reviewed and the influence of catalyst microstructure regulation on the EHDC performance is discussed in detail. The regulation strategies including the regulation mechanisms of electronic effect, support effect, size effect, and coordination effect for enhancing the EHDC performance of catalysts at different scales (from nanostructures to single atoms) are summarized and proposed, which could provide guidance for the development of efficient EHDC catalysts from the atomic scale. At the end of this review, the application prospects and challenges for EHDC catalysts are also discussed.

Efficient Palladium Catalysts: Application and Challenges of Electrocatalytic Hydrodechlorination Technology in Wastewater Treatment

“…[31] The single-atom Pd catalyst facilitated the Volmer reaction and produced more H* favorable for dechlorination [32] In single-atom catalysts, the metal catalysts were not aggregated because the individual metals were anchored by heteroatoms. [33] The metal single-atom catalysts prepared in this way were able to achieve 100 % utilization. [34] This minimized the use of the noble metal Pd and thus reduced costs significantly.…”

Enhanced Mineralization of Organic Pollutants through Atomic Hydrogen-Mediated Alternative Transformation Pathways

“…In recent years, hydroxyl radical ( · OH)-mediated anodic oxidation technology has emerged as a promising approach for removing diverse organic contaminants from wastewater. Its advantages over established wastewater treatment technologies lie in its ability to produce · OH in situ through modular cell construction, which reacts nonselectively with various contaminants, such as phenol, aniline, organosulfur compounds, and deprotonated amines. − However, the efficiency of · OH-mediated oxidation process may diminish when treating organics with electron-withdrawing groups, including olefins, unactivated hydrocarbons, and halogenated organic compounds. , The oxidation of these antioxidant pollutants requires a higher potential than the redox potential of · OH at E ° = 2.73 V vs SHE, thus necessitating extended treatment duration and increased electrical consumption for their mineralization. − For example, carbon–halogen bonds of halogenated contaminants generally remain intact during · OH-oxidation due to the high dissociation energy of 222–456 kJ/mol. ,− Consequently, low removal efficiencies for compounds like 4-chloroaniline were observed in a dual photoelectrode photoelectrochemical system . Additionally, insufficient 4-nitrophenol removal of 51% and total organic carbon (TOC) of 20% after 300 min anodic oxidation treatment were observed .…”

Phosphorus-Coordinated Pd@MXene Electrocatalyst for Efficient Electrocatalytic Hydrodechlorination of Diclofenac

“…One promising alternative is electrocatalytic hydrodechlorination (EHDC), which offers several advantages, including modularity, the absence of additional chemical requirements, and ease of operation . The key to achieving a high dechlorination efficiency lies in the development of suitable electrocatalysts.…”