Tandem system of dyes sensitizer solar cell and photo electro-chemical (DSSC-PEC): Investigation of TiO2-nanotube/BiOBr as photoanode for water splitting

The utilization of renewable energy sources is a solution to replace and reduce the excessive use of fossil fuels. The production of hydrogen (H2) is a good choice for utilizing renewable energy sources because of the future potential for the global energy market. The most abundant and exploitable energy source is solar energy conversion to produce hydrogen through water splitting. This study reports a tandem Dye-Sensitized Solar Cells - Photo Electrochemical (DSSC-PEC) system for hydrogen production. In the DSSC cells, the N719 dye was used to sensitize TiO2-nanotubes (TNT/N719) as photoanode and Pt/FTO as the cathode. Whereas, in the PEC cell, photoanode, where water will be oxidized to proton and molecular oxygen, was developed using TiO2-nanotubes/Bismuth Oxybromide (TNT/BiOBr) synthesized by the SILAR (Successive Ionic Layer Adsorption and Reaction) method with various concentrations of equimolar bismuth and bromide ions as the precursors (10 mM, 20 mM, and 30 mM). On the other hand, the cathode of PEC was TiO2-nanotube enriched Ti3+(TNT/Ti3+), which was prepared by electrochemical reduction of TiO2 nanotube, where H+ to hydrogen conversion will take place. The results showed that the TNT/BiOBr PEC system for the three concentration variations had formed BiOBr on TiO2-nanotubes, the bandgap energy was 2.89 eV; 2.80 eV; and 3.02 eV with a current density of 0.256 mA/cm2; 0.254 mA/cm2; and 0.252 mA/cm2. The efficiency of the DSSC system is 1.596%, and the efficiency of the DSSC-PEC solar to hydrogen (STH) system is 0.0025%. Although the efficiency is still low at present, the proposed device provides a basis for solar to hydrogen-producing devices.