Ag grid induced photocurrent enhancement in WO_3 photoanodes and their scale-up performance toward photoelectrochemical H2 generation

摘要

The hydrogen generation from photoelectrochemical (PEC) water splitting under visible light was investigated using large area tungsten oxide (WO_3) photoanodes. The photo-anodes for PEC hydrogen generation were prepared by screen printing WO_3 films having typical active areas of 0.36, 4.8 and 130 cm2 onto the conducting fluorine-doped tin oxide (FTO) substrates with and without embedded inter-connected Ag grid lines. TiO_2 based dye-sensitized solar cell was also fabricated to provide the required external bias to the photoanodes for water splitting. The structural and morphological properties of the WO_3 films were studied before scaling up the area of photoanodes. The screen printed WO_3 film sintered at 500 ℃ for 30 min crystallized in a monoclinic crystal structure, which is the most useful phase for water splitting. Such WO_3 film revealed nanocrystalline and porous morphology with grain size of ~ 70-90 nm. WO_3 photoanode coated on Ag grid embedded FTO substrate exhibited almost two-fold degree of photocurrent density enhancement than that on bare FTO substrate under 1 SUN illumination in 0.5 M H_2SO_4 electrolyte. With such enhancement, the calculated solar-to-hydrogen conversion efficiencies under 1 SUN were 3.24% and ~2% at 1.23 V for small (0.36 cm2) and large (4.8 cm2) area WO_3 photoanodes, respectively. The rate of hydrogen generation for large area photoanode (130.56 cm2) was 3 mL/min.