Bioelectrocatalysis is the acceleration of electrochemical reactions at an electrode by biological catalysts, principally redox enzymes, which lower the activation energy of electron-transfer reactions while performing the conversion at mild conditions and with high specificity ^[1]. In bioelectrocatalysis, a redox enzyme immobilized at or near an electrode catalyzes the oxidation or reduction of a substrate by exchanging electrons with the electrode either directly, through intimate electrical contact between the enzyme's active site and the conductive surface, or indirectly, through a redox mediator that shuttles electrons between the enzyme and the electrode ^[2]. The field is defined by the coupling of biological catalysis—exploiting the selective active sites of enzymes—to an electrode, so that a biochemical reaction is coupled to the flow of electric current and the electrode acts as the terminal electron donor or acceptor ^[1]. Bioelectrocatalysis is distinguished from conventional electrocatalysis, in which inorganic catalysts drive electron transfer, by the use of biological macromolecules as the catalytic species and by the dependence of the reaction on enzyme structure and on the electrical communication between the enzyme and the electrode ^[2]. Its defining feature is the biological mediation of electrode electron transfer ^[3].