Trial Fabrication of NADH-Dependent Enzymatic Ethanol Biofuel Cell Providing H2 Gas as well as Electricity

Abstract

Abstract The oxidative conversion of NADH to NAD+ is a key process for enzymatic biofuel cells to obtain high performance. To promote this conversion, we utilized a photogalvanic cell whose reactions involved the indirect oxidation of NADH mediated by photo-excited flavinmononucleotide (FMN) at the anode and electroreduction of H+ to produce H2 gas at the cathode. Based on the relationship between the passing charge and the concentration changes in NADH, NAD+, and FMN during the discharge, it was determined that the FMN-mediated oxidation of NADH quantitatively proceeded. The enzymatic biofuel cell was fabricated using this photogalvanic cell. By introducing both the ethanol biofuel and alcohol dehydrogenase (ADH) to the photogalvanic cell, the cell current continued to flow because NAD+ was converted to NADH by the biofuel and the enzyme. This cell provided not only electricity, but also H2 gas as a by-product. This is an advantageous feature, which typical enzymatic fuel cells do not possess.