Scan-Rate-Induced Transition from Redox to Ion Current Rectification in Carbon Nanopipettes

The electrochemical performance of carbon nanopipettes results from the interplay between ion transport and electron transfer, two distinct charge-based processes governed by different mechanisms that offer complementary insights. We present a simple yet effective approach to decoupling these contributions via cyclic voltammetry. At scan rates below 0.1 V s^-1, the response is typically driven by redox reactions at the nanopipette surface, as indicated by the presence of redox peaks, whereas at scan rates above 0.5 V s^-1 up to 1 V s^-1, the response is dominated by ion transport. Thus, by adjusting the scan rate, it seems possible to transition between electron and iontronic signals. Importantly, this method enables the observation of ICR in the 0.5-1 V s^-1 range in asymmetric and charged nanofluidic devices, thereby achieving the transition from pure redox behavior to ICR. This tunable strategy opens the door to studying complex systems in nanoelectrochemistry and developing sensors that exploit both signals for different purposes within a single setup.