Tandem system of dyes sensitized solar cell-photo electro chemical (DSSC-PEC) employing TiO2 nanotube/BiOBr as dark cathode for nitrogen fixation

Abstract

Up to now the Haber-Bosch process is a main choice for industry to produce ammonia from nitrogen gas. The process requires very high temperatures and pressures, and hydrogen source from fossil fuels, which produce very large CO2 gas emissions. Therefore we need other alternative process to synthesize ammonia, that can be operated at relatively low temperature and utilize environmentally friendly hydrogen source. In this study a tandem system between dyes sensitized solar cells (DSSC) and photoelectrochemical cell (PEC) has been developed. The DSSC cells were prepared using N719 dyes sensitized TiO2 photoanode. The PEC zone employed a composite of TiO2 nanotube-Bismuth Oxide Bromide (BiOBr), where the conversion of nitrogen into ammonia taken place, and its counter electrode was Ti3+-TiO2 where photocatalytic oxidation of water taken place to provide a source of protons. The DSSC zone of the developed DSSC-PEC tandem system showed solar cell efficiency up to 7.22%, while as a whole, the system provide photon to ammonia generation approximately 0.005%. The best ammonia amount that can be produced by proposed DSSC-PEC tandem system, by solely visible light energy source and water as proton, under current conditions is 4 × 10-2 μmol/hr.