Photoelectrochemical reaction of biomass-related compounds in a biophotochemical cell comprising a nanoporous TiO2 film photoanode and an O2-reducing cathode

Photoelectrochemical decomposition of bio-related compounds such as ammonia, formic acid, urea, alcohol, and glycine by a biophotochemical cell (BPCC) comprising a nanoporous TiO2 film photoanode and an O2-reducing cathode generating simultaneously electrical power was investigated. The bio-related compounds studied were all photodecomposed by the present BPCC when they were either liquid or soluble in water. It was shown that ethanol exhibits similar characteristics both under 1 atm O2 and air as studied by cyclic voltammograms. Although the present BPCC utilizes only UV light, a solar simulator at AM 1.5G and 100 mW cm−2 light intensity gave also moderate photocurrent–photovoltage (J–V) characteristics with about 2/5 of the short circuit photocurrent (J sc) values (J sc) of that under a Xe lamp irradiation at the intensity of 503 mW cm−2. It was demonstrated that varieties of bio-related compounds can be used as a direct fuel simultaneously for photodecomposition and electrical power generation. The charge transport processes in the BPCC operation were analyzed using glycine by an alternating current impedance spectroscopy, showing that the charge transfer reactions on the photoanode and the cathode surfaces compose the major resistance for the cell performance.