Modified stainless steel for high performance and stable anode in microbial fuel cells

Graphical abstract: A high performance and stable anode was prepared for microbial fuel cells by surface modification of stainless steel mesh including steps of acid etching, binder-free carbon black (CB) coating and the low-temperature heat treatment below 400 °C. The modified anode could deliver a stable and high current density of 1.91 mA cm⁻². - Highlights: • A high-performance anode for MFC is prepared by surface modification of SSM. • The modified SSM could generate a high current density of up to 1.91 mA cm⁻². • The formation of Fe₃O₄ layer enhanced the interaction between the CB and SSM. • The modified SSM was stable under the potential of +0.2 V (vs. Ag/AgCl). • The modified SSM was an ideal anode for upscaling applications of MFCs. - Abstract: The surface modification of the stainless steel mesh (SSM) was conducted by acid etching, binder-free carbon black (CB) coating and the low-temperature heat treatment below 400 °C to improve the microbial bioelectrocatalytic activity for use as high-performance anode in microbial fuel cells. The modified SSM, such as SSM/CB-400, could generate a high current density of up to 1.91 mA cm⁻², which was nearly three orders of magnitude higher than the untreated SSM electrode (0.0025 mA cm⁻²). Moreover, it was stable and recovered the equal current density after removal of the formed biofilms. Surface characterization results demonstrate that the performance improvement was attributed to the CB/Fe₃O₄ composite layer formed onto the surface of the SSM, which protected the biofilms from being poisoned by the Cr component in the SSM and ensured a rapid electron transfer from biofilms to the SSM surface. The CB/Fe₃O₄ composite layer showed excellent corrosion-resistant under the oxidizing potential of + 0.2 V (vs. Ag/AgCl). Rising the heating temperature to 500 °C, the SSM-500 and SSM/CB-500 electrodes suffered from corrosion due to the formation of α-Fe₂O₃ crystals.