Abstract
Following the discussion of electrochemical systems based on microorganisms (lecture no. 2), this lecture looks at bioelectrodes and biopiles built from enzymatic systems. This is not a new field, since a large number of biopiles already exist, such as glucose biopiles, which use enzymes to convert chemical energy (glucose) into electricity. What's new is the nature of the enzymes that can now be exploited, thanks to the growing mastery of the operating conditions of these often fragile enzymes, or the electrode materials (nanostructuring, protective polymers, etc.) on which these enzymes are deposited, or finally the methods for immobilizing the enzymes on the electrodes. A very good example, discussed in detail in this lecture to understand the technological difficulties of such devices, is the photoelectrochemical cell developed by E. Reisner in Cambridge. It consists of photosystem II (from plants) at the photoanode and a bacterial hydrogenase at the cathode. Thanks to the development of such a cell, an original "semi-biological" photosynthesis has been achieved, coupling biological elements of natural photosynthesis with synthetic electrode materials. Although performance is still lacking, particularly in terms of current density, this system operates with excellent yields.
