Photoelectrochemical(PEC) water splitting has gained great attention as a route for future hydrogen production owing to its sustainable and cost-effective properties. However, since PEC water splitting has limitations on efficiency and stability, research on materials, structures and catalysts are in progress to solve those problems. In our experiments, the nano-pattern structure is created using direct-printing to increase the photoanode efficiency.

In this study, enlarged surface area is accomplished by micropillar structured FTO and Fe₂O₃ nanorods. We fabricated micropillar structure via direct printing method. The direct-printing method has advantages in not only simple process but also low price to form micro-nano size structures. To obtain micropillar structure, spin coating of hydrogen silsesquioxane(HSQ) was performed on micropillar patterned polydimethylsiloxane(PDMS) mold. Then, we applied glass substrate and pressure on it. Detachment of PDMS mold is followed by deposition of FTO layer. Hydrothermally synthesized Fe₂O₃ nanorods are formed on micropillar structured FTO and Co-Pi catalyst was electrodeposited on Fe₂O₃ nanorods to enhance surface water oxidation.

Due to micropillar pattern, optical absorption of patterned Fe₂O₃ photoanode is higher than that of flat Fe₂O₃ photoanode in the whole range of optical wavelength. Also micropillar patterned Fe₂O₃ sample showed 2.6 times higher photocurrent at 1.23 V_RHE than flat Fe₂O₃ sample. These results were confirmed that micropillar structure increased the surface area and light scattering effect. Furthermore, applying Co-Pi catalyst increased photocurrent at 1.23 V_RHE for 2.0 times higher owing to the enhancement of surface water oxidation. As a result, photocurrent of the micropillar patterned, decorated with Co-Pi sample shows 1.51 mA/cm², and that of flat, non-decorated sample shows 0.29 mA/cm² at 1.23 V_RHE.