Electrolyte Optimization of a Dual Compartment Hydrogen Peroxide Fuel Cell with Prussian Blue and Tantalum Electrodes

Hydrogen peroxide fuel cells have emerged as a promising class of electrochemical energy conversion device owing to the dual redox character of H2O2, its liquid-phase storage, and its ability to operate in air-free environments. In this work, a dual-compartment direct H2O2 fuel cell using a Prussian Blue cathode and a tantalum anode, separated by a Nafion 115 proton exchange membrane, was systematically characterized and optimized with respect to electrolyte pH and ionic composition. The influence of pH on OCV was investigated independently in each compartment across the range of pH 2 to 12. In the tantalum compartment, OCV increased non-linearly with pH from 573 mV to 808 mV, driven by the enhanced electrochemical reactivity of the system under alkaline conditions. In the Prussian Blue compartment, OCV decreased from 676 mV to 199 mV with increasing pH, reflecting the instability of the material in alkaline conditions. The effect of the electrolyte ionic composition on average current density was subsequently investigated by varying the concentrations of NaCl and Dy(NO3)3. Increasing NaCl from 0 to 2.5 M produced an increase in current density from 0.414 mA/cm2 to 0.973 mA/cm2, consistent with ohmic resistance reduction through improved ionic conductivity. The addition of Dy(NO3)3 produced a positive response with an optimal concentration of 0.05 M, at which current density reached 1.08 mA/cm2, before declining sharply. Under the fully optimized conditions, pH 12 in the tantalum compartment, pH 2 in the Prussian Blue compartment, 0.3 M H2O2, 2.0 M NaCl, and 0.05 M Dy(NO3)3, the cell produced an OCV of 724 mV and a peak power density of 0.283 mW/cm2 at a current density of 0.8 mA/cm2. These results demonstrate that meaningful electrochemical performance can be achieved in a dual-compartment H2O2 fuel cell without the use of precious metal catalysts and highlight electrolyte engineering as an effective strategy for improving cell output in this class of device.