Bio-inspired Porous Composite Electrode for Enhanced Mass Transfer and Electrochemical Water Purification by Modifying Local Flow Pattern

Porous electrodes offer a new opportunity for flow-through electrochemical water purification, but their irregular porous-structure makes the local flow pattern and mass transfer performance inhomogeneous, unpredictable, and uncontrollable. In this study, a bio-inspired design is reported for porous electrode by learning the micro-scale architectures of the wings of butterfly and owl based on analogy between heterogeneous mass transfer and sound absorption. Results demonstrate that combining gyroid and perforated plate can produce strong periodic vortex and inertial flow in interpenetrating channels even at laminar flow region. This enables homogeneous, predictable and controllable flow patterns and enhanced mass transfer, which can be explained by uniformity analysis and physical field synergy. Based on experimental tests on Cu electrode fabricated by selective laser melting, the composite gyroid electrode generates the limiting current density of 83% higher than random porous-structured electrode, accounting for nitrate removal as high as 95% by electrochemical denitrification. This study represents a paradigm shift to advance design for porous architectures by learning experiences of hydrodynamic behaviors from nature. In this way, it is feasible to enhance mass transfer by modifying local flow patterns on pore scale, which may have broader implications that extend to other heterogeneous reaction systems.