Ag grid induced photocurrent enhancement in WO3 photoanodes and their scale-up performance toward photoelectrochemical H2 generation

The hydrogen generation from photoelectrochemical (PEC) water splitting under visible light was investigated using large area tungsten oxide (WO3) photoanodes. The photoanodes for PEC hydrogen generation were prepared by screen printing WO3 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. TiO2 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 WO3 films were studied before scaling up the area of photoanodes. The screen printed WO3 film sintered at 500 °C for 30 min crystallized in a monoclinic crystal structure, which is the most useful phase for water splitting. Such WO3 film revealed nanocrystalline and porous morphology with grain size of ∼70–90 nm. WO3 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 H2SO4 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 WO3 photoanodes, respectively. The rate of hydrogen generation for large area photoanode (130.56 cm2) was 3 mL/min.