Biophotochemical cell (BPCC) to photodecompose biomass and bio-related compounds by UV irradiation with simultaneous electrical power generation

UV-light decomposition and simultaneous electrical power generation from urea, a urine model, with a biophotochemical cell (BPCC) comprising a nanoporous TiO2 photoanode and an O2-reducing cathode showed that urea can be photodecomposed to CO2 and N2 at the theoretical 1/1 molar ratio while donating electrical charges into the outer circuit at a high efficiency of more than 90%. Photodecomposition of ammonia, product from urine catalyzed by urease present abundant in nature, was also investigated by a thin layer cell to prove that urine can be photo (UV) decomposed and cleaned with simultaneous electrical power generation. The effect of air bubbling on the thin layer cell performance was studied by using a glycine aqueous solution. It was demonstrated that the I–V characteristics of a thin layer cell degraded rapidly without air bubbling, but are maintained nearly constant under air bubbling. It was demonstrated that the energy conversion efficiency from glycine to electrical power can reach 50%. In order to fabricate a submodule for the future module fabrication, thin layer cells with different sizes from 2 cm × 2 cm to 20 cm × 20 cm were fabricated, and the I–V characteristics of a glycine aqueous solution were investigated in these cells. It was found that enlargement of the cell is in principle no problem to obtain conversion efficiency similar to a small size cell. It was found that MnO2 is as efficient as a Pt- based catalyst for the O2-reducing cathode. It was shown that tris(2,2′-bipyridine)ruthenium(II) complex can in principle work as a sensitizer for a visible light-driven BPCC.