Redox Cycling in Two-Polarized Electrode Sensors: Diagnostic Insights Guided by Theory.

Abstract

Two-polarized electrode (2PE) electrochemical configurations are adopted in miniaturized and disposable sensors, reducing instrumentation complexity and avoiding practical complications associated with reference electrodes. Redox-cycling strategies have been proposed for signal amplification by preconverting the target species to complete a reversible redox couple, thereby enabling sustained interconversion between the two polarized electrodes. In these configurations, rational device design and quantitative interpretation of the measured response require explicit consideration of the mutual coupling between the two interfacial processes. This work develops a theoretical framework for redox cycling in two-electrode, single-potentiostat configurations, describing the full current-potential-time response under chronoamperometric and cyclic voltammetric conditions. Closed-form expressions are obtained for the current, interfacial concentrations and local potentials at each electrode. Working curves map the signal enhancement and defining features of chronoamperometric and voltammetric responses across the steady-state, transient redox-cycling and semi-infinite diffusion regimes, thereby providing practical diagnostic criteria for the design, characterization and interpretation of 2PE devices. The theory and signal-analysis protocols are validated experimentally, obtaining good agreement between simulated and measured responses.