Hydrothermal synthesis of Fe[sbnd]Mn bimetallic nanocatalysts as high-efficiency cathode catalysts for microbial fuel cells

Abstract

High-efficiency cathode catalysts are essential for microbial fuel cell development since they are one of the key components in chemical energy conversion in organic compounds into electricity. Here, novel FeMn bimetallic nanocatalysts are designed and hydrothermally synthesized for microbial fuel cells. Fe:Mn (atom%) = 1:4, 1:2, 1:1, and α-MnO2 are applied in air-cathodes with Pt/C and activated carbon catalysts as benchmarks, and FeMn catalysts can enhance the performance. When Fe:Mn = 1:2, the FeMn2 achieves a maximum power density of 1940 ± 31 mW m−2 in microbial fuel cells and a current density of 19.4 A m−2 at −0.056 V in abiotic electrochemical tests, 24% and 37% higher than Pt/C respectively. Material characteristics are systematically analyzed since they are directly related to the catalytic performance. The high catalytic activity of FeMn2 proves to result from a combination of the weak MnO bonds, large quantity of defects, large specific surface area and high Mn(III):Mn(IV) ratio, according to the proposed possible mechanisms of FeMn catalysts to enhance the output. This work not only puts forwards an easy-to-accomplish method to design and prepare bimetallic nanocatalysts, but also provides a potential alternative to Pt/C in microbial fuel cells for sustainable energy generation.