Effects of N2 plasma modification on the surface properties and electrochemical performance of Ni foam electrodes for double-chamber microbial fuel cells

Abstract

This study assessed the feasibility of using a plasma-modified Ni foam as an anode to improve the electrochemical performance of double-chamber microbial fuel cells (MFCs). Scanning electron microscopy results showed that Ni foam exhibited an open cellular structure and rough surface morphology, providing a large contact area between bacteria and anodes in the MFCs. N₂ plasma modification did not influence the surface morphology of the Ni foam, whereas the hydrophobic surfaces of the Ni foam became highly hydrophilic. X-ray photoelectron spectrometer results revealed that Ni–N and NH₃ functional groups, formed on the surface of the Ni foam during the N₂ plasma modification, were responsible for its highly hydrophilic surface. Electrochemical measurements demonstrated that the highest power density of the MFC configured with an unmodified Ni foam anode electrode (166.9 mW m⁻²) was much higher than those of the MFCs configured with dense Ni rod (5.1 mW m⁻²) or graphite rod (29.5 mW m⁻²) anodes because Ni foam combined the advantages of an open cellular structure and good electrical conductivity. The highest power density of MFC configured with Ni foam was further improved to 247.1 mW m⁻² after 60 min N₂ plasma treatment owing to the high hydrophilicity of the N₂ plasma-modified Ni foam electrodes, which facilitated bacteria adhesion and biofilm formation.