<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>