Enhancement of PEC Water Splitting for Self-Carbon Doped TiO2 Nanorods / Au Nanoparticle / TiO2 Ternary Structure in All Solution Process

Abstract

Titanium dioxide (TiO2) is an important metal-oxide semiconductor for photocatalytic applications due to its unique properties, such as photostability, low cost, abundance and nontoxicity. Despite of outstanding functionality, wide band gap of 3.2eV limits its application due to ultra-violet (UV) range absorption. In order to extend photo-excitation energy down to visible range, intensive efforts have made to manipulate bandgap of TiO2. In this study, we synthesized self-carbon doped TiO2 nanorods (C-TiO2 NRs) through hydrothermal synthesis to increase the absorption of visible light. Additionally, using the surface plasmonic resonance effect of gold nanoparticles, the photoelectrode was fabricated to increase the absorption of visible light. Then, TiO2 passivation layer deposited using the electro deposition to protect gold nanoparticle, which is typically vulnerable to photocorrosion. The synthesized C-TiO2 NRs/Au/TiO2 was characterized using X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). We confirmed that C-TiO2 NRs have rutile phase and the size of Au NPs is about ~10nm. UV-visible measurements confirmed the optical bandgap of the photoanode at the significantly lowered photon-energy. We carried out the X-ray photoelectron spectroscopy (XPS) to identify presence of carbon species and chemical oxidative states of C-TiO2 NRs. We investigated the PEC water splitting properties under 1sun illumination. We observed that C-TiO2 NRs/Au/TiO2 (1.6mA/cm2) show ~2 times higher current density than C-TiO2 NRs (0.75mA/cm2) and enhanced stability of photoelectrode.