Biogenic Realgar As4S4 Molecular Cluster Formed by One-pot Microbial-driven Process as a Li-ion Storage Material

Abstract

Eco‐efficient biogenic strategies for the removal of toxic elements result in the formation of unique nano/microstructured materials with dual functionalities for energy conversion and storage. In one pot under aqueous conditions, the bacterium Shewanella sp. strain HN‐41 precipitates nanostructured arsenic sulfides (realgar, As4S4) and its reduced graphene oxide nanocomposites. Considering the unique structural characteristics of the freestanding molecular‐cage‐like single clusters, the biogenic realgar structure is utilized as an independent anode unit since each cluster integrates four faceted five‐membered As4S4 rings, providing a short diffusion length into each cluster and facile chemical binding onto the sulfur atoms with lone pairs of electrons. Here, the role of the biogenic realgar structure in the reversible uptake and release of Li ions into and from the molecular‐cage‐like single clusters is investigated. Using in situ As K‐edge X‐ray absorption fine structure analyses, the Li‐ion uptake ability of realgar As4S4 (As4S4↔Li20As4S4) is achieved through a two‐step mechanism: (1) molecular clustering to form Li8As4S4 (≈500 mA h g−1) and (2) alloying to form Li12As4 only in the interior of the single clusters (≈750 mA h g−1). Thus, the bacteria‐driven biological synthesis under mild conditions can provide an alternative synthetic strategy and promotes easy scale‐up for nanostructured materials.