A novel hierarchical porous 2.5D electrode system with molecular sieve based particles: Towards efficient electrochemical oxidation of various pollutants by a single-pass process

In electrochemical oxidation (EO) wastewater treatment, the more recent 2.5D electrode system relying on appropriate amount of physically fixed micro/nano-scale particles on the main electrode surface offers several key advantages over conventional 2D/3D electrode system, such as prominent versatility and recyclability. However, the full potential of the 2.5D electrode system has not been released so far due to the insufficient utilization of the massive inner active sites. To overcome this challenge, in this study, a novel 2.5D electrode flow-through reactor coupling system (2.5D-FT system) was developed, which featured by a hierarchical porous electrode architecture (novel Sb-SnO₂ coated molecular sieve particles loaded on porous RuO₂-TiO₂ or Sb-SnO₂ main electrode) and a staggered-flow-enhanced mass-transfer paradigm, allowing pollutants to fully contact the numerous inner active sites. Results show that the molecular sieve based particles greatly increases the active sites and reduces the electrode impedance. Various model pollutants including acidic red G, bisphenol A, tetracycline, and ciprofloxacin could be degraded more efficiently (e.g., up to 100 % removal) by a single-pass EO process. The enhancement of radical pathway (•OH, •O₂^-) and non-radical pathway (¹O₂), as well as the direct electron transfer (DET) process originating from the hybrid composition and unique structure of the novel 2.5D-FT system, is confirmed by quenching experiment results and multiphysics simulation results. In addition, results of anti-inference and durability tests, energy consumption evaluation, real wastewater treatment and toxicity assessment demonstrate the competitive practicability of the novel 2.5D-FT system.