Porphyrin-sensitized nanoparticulate TiO ₂ as the photoanode of a hybrid photoelectrochemical biofuel cell

Porphyrin-sensitized nanoparticulate TiO ₂ on conducting glass has been investigated as a photoanode material for a new cell that converts light energy into electricity. The cell is a hybrid of a dye-sensitized nanoparticulate semiconductor photoelectrochemical solar cell, and a biofuel cell that oxidizes glucose. Porphyrin molecules excited by light inject electrons into the photoanode, from where they enter the external circuit. The resulting porphyrin radical cations are reduced by NADH in aqueous buffer, ultimately regenerating the photoanode and producing NAD ⁺. Glucose dehydrogenase oxidizes glucose, and in the process recycles NAD ⁺ back to NADH. The photoanode is coupled with a suitable cathode to make a functioning cell (Hg/Hg ₂SO ₄ was employed for evaluation purposes). The cell produces 1.1V at open circuit and has a fill factor of 0.61. These values are both significantly higher than those for a previously reported cell of a similar type based on an SnO ₂ electrode.