Electrocatalysis by H2–O2 membrane-free fuel cell enzymes in aqueous microenvironments confined by an ionic liquid

Abstract

An O₂-tolerant [NiFe] hydrogenase and a blue Cu oxidase exhibit excellent catalytic electrochemistry under almost dry conditions – inspiring the concept of a new type of miniature fuel cell able to provide a potential difference close to one volt. Each enzyme is immobilized on a carbon electrode that contacts an aqueous microvolume (1 μL) surrounded by an immiscible, aprotic ionic liquid. Separately, the enzymes display excellent electrocatalytic activity: brought together at a synaptic junction, an anode and cathode modified with each enzyme constitute a membrane-less fuel cell that produces over 0.8 V when equilibrated with a 96% H₂–4% O₂ mixture. The results show there is considerable scope for using ionic liquids to miniaturize selective enzyme fuel cells.