Generation of faradaic photocurrents at the bacteriorhodopsin film electrodeposited on a platinum electrode

Bacteriorhodopsin (bR)-containing purple membranes (PMs) were electrodeposited on a platinum electrode to form an oriented PM film. In an aqueous solution of supporting electrolyte, illumination of the electrode with green light that excites bR caused cathodic photocurrent. The photocurrent was a steady-state faradaic current and occurred at electrode potentials close to EH2/H-2, suggesting that proton pumping through the PM film assists the proton reduction at the platinum cathode.