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

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.