Unveiling the Electrochemical Kinetics of an FeWO4-NiFeOOH Anode: Electrolyte Effects on Energy Conversion

This study aims to determine the electrochemical performance of FeWO4 (Fe), NiFeOOH (Ni), and FeWO4/NiFeOOH (FeNi) electrodes in 0.1 M Na2SO4 and 0.1 M NaOH electrolytes, highlighting the impact of SO42− and OH− ions. Nyquist analysis demonstrated that the FeWO4/NiFeOOH electrode had the lowest charge transfer resistance, indicating superior charge transport and capacitive performance over the individual electrodes. In Na2SO4, SO42− ions stabilized double-layer capacitance and enhance ionic mobility. Conversely, in NaOH, highly conductive and mobile OH− ions significantly improved charge transfer and diffusion, making NaOH more effective for electrochemical applications. Tafel analysis revealed better charge transfer kinetics and greater energy efficiency in NaOH, with the composite electrode excelling in both electrolytes. Linear voltammetry showed a synergistic interaction between FeWO4 and NiFeOOH, achieving a photocurrent density of 6.70 mA·cm−2 in NaOH under illumination, an 830.56% increase over Na2SO4. Additionally, the FeWO4/NiFeOOH composite electrode exhibited longer electron lifetimes in NaOH than in Na2SO4, attributed to the smaller ionic radius and higher diffusion coefficient of OH− ions. Pulsed photocurrent analysis revealed notable improvements in photocurrent generation and stability in NaOH. These findings indicate that the FeWO4/NiFeOOH composite is a highly efficient and stable material for advanced energy technologies, with NaOH providing optimal performance conditions.