Comprehensive review on 2.5D electrode architectures: Bridging the gap between 2D scalability and 3D performance for advanced applications

The escalating challenge of treating refractory organic pollutants in industrial wastewater demands high-performance, cost-effective electrochemical oxidation (EO) systems. Conventional 2-Dimension (2D) electrodes are limited by poor mass transport and restricted active surface area. 3-Dimension (3D) systems suffer from complex, non-scalable fabrication and elevated costs. This review focuses on the emerging 2.5-Dimension (2.5D) electrode architecture as a superior hybrid alternative. The 2.5D design strategically integrates a structurally simple planar Main Electrode (ME) with movable and magnetically recoverable Auxiliary Elements (AEs). This configuration successfully combines the scalability of 2D systems with the enhanced reaction kinetics associated with 3D structures. The unique geometry facilitates synergistic operating mechanisms, including intensified localized turbulence, optimized mass transport dynamics and enhanced hydroxyl radical generation through dynamic AE-ME electrochemical interactions. The principal results confirm significant advancements in system performance. 2.5D Electrodes document 30–50% gains in current efficiency and a substantial 40–70% reductions in specific energy consumption compared to traditional planar setups. The system also demonstrates high versatility in degrading recalcitrant contaminants (e.g., PFCs, pharmaceuticals), with magnetic AEs enabling high recovery rates (> 95%), promoting operational sustainability. This paper provides a critical analysis of the 2.5D electrode paradigm, comprehensively detailing the fundamental design principles, governing reaction mechanisms and current performance in diverse wastewater applications.