Imaging of Anodic Electrocatalytic Reactions via Cathodic Electrochemiluminescence on Focused Ion Beam-Fabricated Closed Bipolar Nanoelectrode Arrays

Electrochemiluminescence (ECL) imaging through closed bipolar nanoelectrode arrays (BPnEAs) has emerged as a promising method for in situ label-free wide-field electrochemical imaging. In this study, a cathodic ECL system based on [Ru(bpz)₃²⁺]/S₂O₈^2- is combined with the BPnEAs fabricated on silicon nitride membrane windows through focused ion beam nanofabrication, enabling effective bipolar imaging of heterogeneous anodic electrocatalytic reactions. The shape, distribution, size, and material composition of individual electrodes within the array can be precisely controlled. The comparison of anodic and cathodic ECL on BPnEAs has been achieved, showing highly localized cathodic ECL emissions on the nanoelectrodes, which is ideal for high-resolution imaging. The heterogeneous patterned BPnEA of different materials can be further fabricated, demonstrating the ability to effectively distinguish various coupled oxidation reactions based on ECL luminescent potential and accurately assess the catalytic activity of heterogeneous anodic reactions. Through catalyst imaging examples, it was verified that each electrode in the array can independently and clearly perform reaction coupling and sensing. This cathodic ECL-BPnEA imaging system shows great potential as a high-resolution electrochemical imaging and parallel sensing device for anodic electrochemical reactions.