Mimicking the Microbial Oxidation of Elemental Sulfur with a Biphasic Electrochemical Cell

Abstract

<p>The lack of an artificial system that mimics elemental sulfur (S<sub>8</sub>) oxidation by microorganisms inhibits a deep mechanistic understanding of the sulfur cycle in the biosphere and the metabolism of sulfur-oxidizing microorganisms. In this article, we present a biphasic system that mimics biochemical sulfur oxidation under ambient conditions using a liquid|liquid (L|L) electrochemical cell and gold nanoparticles (AuNPs) as an interfacial catalyst. The interface between two solvents of very different polarity is an ideal environment to oxidise S<sub>8</sub>, overcoming the <a>incompatible solubilities </a>of the hydrophobic reactants (O<sub>2</sub> and S<sub>8</sub>) and hydrophilic products (H<sup>+</sup>, SO<sub>3</sub><sup>2–</sup>, SO<sub>4</sub><sup>2–</sup>, <i>etc.</i>). The interfacial AuNPs provide a catalytic surface onto which O<sub>2</sub> and S<sub>8</sub> can adsorb. Control over the driving force for the reaction is provided by polarizing the L|L interface externally and tuning the Fermi level of the interfacial AuNPs by the adsorption of aqueous anions.</p>