A number of redox enzymes function as excellent electrocatalysts when attached to electrodes or conductor/semi-conductor surfaces. A particular focus of this review is on hydrogenases, enzymes which use a di-iron or nickel-iron center to interconvert 2H+ and H2 at extremely high turnover frequencies, although the concepts we highlight apply to a wider range of redox enzymes. Taking hydrogenases as our main case study, we examine how a detailed electrochemical understanding of the electrocatalytic behaviour of an enzyme can inform the development of devices in which the enzyme exchanges electrons directly with a range of inorganic materials, including graphite electrodes and particles, semi-conductor electrodes and quantum dots. We review recent developments in composite enzyme-inorganic catalysts, some of the biological and materials challenges in building devices based on enzymes, and the future opportunities for devices based on biological catalysts, including fuel cells, light-driven fuel production and coupled catalysis for chemical synthesis.
electrocatalysis; bioelectrochemistry; hydrogenase; enzyme fuel cell; hydrogen production
