Co²⁺ ion-doped MnO₂ electrode for microfluidic H₂O₂ biosensors: formation, characterization, and catalytic...

H₂O₂ serves as a vital signalling molecule within biological systems and presents potential as a disease biomarker. Consequently, the development of sensitive and accurate sensors for its measurement within microfluidic systems is of significant importance. This article focuses on the development of a working electrode for an electrochemical microfluidic system designed for the quantitative determination of hydrogen peroxide. Here, we show that a MnO₂-based catalytic material can be improved by adding Co²⁺ ions. By changing the Co²⁺ concentration, an electrode material with improved catalytic performance was formed. The results of amperometric measurements of catalytic activity show a substantial increase in sensitivity and an expanded range of H₂O₂ concentrations that can be quantified using the new electrode. The characteristics of the MnO₂-modified Co²⁺ electrode were thoroughly examined by SEM, XPS. The combination of previously accumulated material and new data offers insights into the underlying reasons for the high catalytic activity of MnO₂, supported by quantum-chemical calculations. This research lays the groundwork for a method utilizing MnO₂ as a working electrode for detecting the concentration of H₂O₂ within a microfluidic cell. During experiments, a stop-flow protocol is employed, enabling data collection from coulometric measurements of the electrochemical processes occurring on the electrode within a limited measurement timeframe.