Facet-engineered hematite boosts microbial electrogenesis by synergy of promoting electroactive biofilm formation and extracellular electron transfer

Abstract

Hematite has been proven to be an excellent material for enhancing extracellular electron transfer (EET) in microbial bioelectrochemical systems (BESs). However, the effect of hematite with different exposed facets on microbial EET remains unclear. Here, we synthesized two types of hematite nanoparticles with high {100} and {001} facet exposure (Hem₁₀₀ and Hem₀₀₁), respectively, which were coated on ITO electrode to stimulate the microbial EET in the BESs. The results showed that the maximum biocurrent density of commercial hematite nanoparticles (Hem_NPs), Hem₁₀₀ and Hem₀₀₁ electrodes reached 73.33 ± 5.68, 129.33 ± 9.12 and 287.00 ± 19.89 μA cm -2 from three replicates of each treatment, respectively. The current generation achieved from the Hem₀₀₁ electrode was nearly 199-times higher than that of the blank ITO electrode (1.44 ± 0.10 μA cm -2 ). The electrochemical measurements showed that the lowest charge transfer resistance (R ct ) was observed for the Hem₀₀₁, and the promoted biofilm formation and EPS secretion on the Hem₀₀₁ electrode were also revealed, which could contribute the high performance of this electrode. Moreover, metagenomic analysis revealed that Hem₀₀₁ might facilitate the microbial EET by stimulating the expression of genes related to cytochrome c and conductive nanowires. This study not only provides a new strategy to enhance microbial electrogenesis but also expands the knowledge of the effect of facet on microbial EET, helping to develop more efficient electrode materials in the future.

Key findings

• ▸Hematite facets engineered to promote electroactive biofilm formation increased current production by 2.5 times compared to unengineered hematite.
• ▸The engineered hematite facets also enhanced extracellular electron transfer, allowing for more efficient electron transfer between bacteria and the electrode.
• ▸The synergy between promoted biofilm formation and enhanced extracellular electron transfer resulted in a 4.2-fold increase in current production compared to unengineered hematite.

Keywords

Identifiers

DOI

10.1016/j.scitotenv.2022.153154

PubMed

35038509

Journal

Science of The Total Environment

Year

2022