Electrical and electrochemical characterization of proton transfer at the interface between chitosan and PdHx†
In bioelectronic medicine and electroceuticals, electronic devices that conduct electrons are used to monitor and control ion-based biochemical reactions in order to detect and treat medical conditions. Advancing these devices will require a thorough understanding of the electrochemical pathways that transduce electronic currents into the ionic currents that interact with the natural system. Here, we analyze the tranduction of electronic current into a protonic current (H+) using Pd/PdHx contacts and a model proton conductor, chitosan. Linear sweep voltammetry and electrochemical impedance spectroscopy data indicate that, for Pd, limited proton injection occurs at the interface aided by water oxidation. For PdHx, H desorption and electrochemical oxidation to H+ lead to sustainable proton injection and transfer to the chitosan protonic conductor. We have developed electroanalytical expressions and predictive digital simulations that match the experimental results. This work confirms that PdHx contacts integrated in DC devices, in parallel with electrochemical impedance spectroscopy, comprise a suitable means for measuring H+ currents and interrogating the proton conductivity in biomaterials.