A simulation-based analysis of optical read-out for electrochemical reactions using composite vortex beams

Abstract

We propose an optical read-out method for extracting faradaic current in electrochemical (EC) reactions and analyze its performance using opto-EC simulations. Our approach utilizes structured electrodes to generate composite optical vortex (COV) beams upon optical illumination. Through opto-EC simulations, we demonstrate that the EC reaction of 10 mM potassium ferricyanide induces a refractive index (RI) change, $$\Delta$$ Δ RI, of approximately $$10^{-4}$$ 10 - 4 RI units, leading to the rotation of the COV beam’s intensity profile with a peak rotation of $$40^{\circ }$$ 40 ∘ . This rotation’s magnitude is proportional to $$\Delta$$ Δ RI, while the rate correlates with the faradaic current ($$I_f$$ I f ) density responsible for $$\Delta$$ Δ RI. As the opto-EC information is from bulk $$\Delta$$ Δ RI, it remains unaffected by interfering non-faradaic components at the interface and is advantageous for studying intermediate species and bulk homogeneous reactions. Furthermore, as rotation depends on $$I_f$$ I f density rather than $$I_f$$ I f itself, this method proves beneficial in low $$I_f$$ I f scenarios, such as when employing micro-electrodes to decrease solution resistance or obtain localized EC data. Even in low $$I_f$$ I f density scenarios, like monitoring slow EC reactions, our method enables signal amplification by accumulating rotation over time. This interdisciplinary approach holds promise for advancing EC research and addressing critical challenges across various fields, including energy storage, corrosion protection, environmental remediation, and biomedical sciences.