Turning Electrode Orientation into a Design Parameter: Gravity‐Driven Convection for Coupling Electrochemical and Enzymatic Reactions

Electrochemical systems are often limited by the mass transport of reactants to the electrode and products away from the electrode. Convective transport arising from gravity acting on reaction‐induced density gradients is frequently overlooked. Recent studies have shown that partial electrode fouling can enhance this form of convection, thereby increasing reaction rates. Using electrochemiluminescence (ECL) microscopy in both aqueous and organic electrolytes, we investigate how electrode fouling and orientation relative to gravity can serve as design parameters to couple electrochemical reactions with immobilized enzymatic processes. We first examine how fouling‐induced convection depends on electrolyte composition and cell orientation. We then demonstrate that electrodes partially fouled with non‐conductive agar domains containing immobilized enzymes enable controlled coupling between electrochemical reactions at clean electrode regions and subsequent chemical reactions occuring on insulating islands. Horseradish peroxidase (HRP) immobilized in agar on glassy carbon electrodes creates conductor–insulator–electrolyte boundaries that stabilize enzymatic activity. Applying density gradient‐driven convection enhances phenol degradation, yielding ~30% conversion after 30 min of electrolysis. These results establish electrode heterogeneity and cell orientation as powerful design parameters for enhancing electrochemically coupled chemical processes.