Surface Modification of Ni-Foam Electrodes via Acid Etching to Enhance Power-Generation Efficiency of Microbial Fuel Cells

Abstract

This study investigates the effect of acid etching on the power-generation efficiency of microbial fuel cells (MFCs) configured with Ni-foam electrodes. The performance of the MFCs improved after they were configured with an acid-etched Ni-foam electrode, specifically, the MFCs afforded by a 60 min acid-etched Ni-foam electrode exhibited a power density of 708.0 mWm⁻², as high as 3.8× that afforded by an unmodified electrode (187.3 mWm⁻²). This improvement results from the formation of hydrophilic functional groups and oxygen vacancies during the acid-etching treatment of the Ni-foam surface. The introduced hydrophilic functional groups and oxygen vacancies converted the hydrophobic Ni-foam electrode to superhydrophilic, thus facilitating the bacterial colonization and improving the electron transfer efficiency between the microorganisms and electrodes. Additionally, acid etching increased the electrode surface roughness, thus creating more contact areas for bacterial adhesion and further enhancing power generation. However, prolonged acid etching damaged the framework structure of the Ni-foam electrodes, thereby reducing the contact regions for bacterial adhesion and diminishing the power output. Acid etching remains a simple, rapid, and cost-effective method for improving the surface properties of Ni-foam electrodes and advancing the practical applications of MFCs.