Improving photoelectrochemical performance of transferred TiO2 nanotubes onto FTO substrate with Mo2C and NiS as Co-catalyst

The photoelectrochemical (PEC) performance of titanium dioxide nanotube (TiO2 NT) photoelectrodes for sustainable hydrogen production has garnered significant research interest. Despite the advantages of TiO2 NT fabricated via anodization of titanium metal, such as their well-ordered vertical structure, challenges persist including the thick oxide barrier layer, limited optical transparancy, and the wide energy band gap (similar to 3.0 eV), which constrain their practical efficiency in PEC applications. This study addresses these limitations by introducing a novel approch to transfer TiO2 NT onto a fluorine-doped tin oxide (FTO) substrate. TiO2 NTs were synthesized with varying anodization times and steps to achieve optimal free-standing structures. To further enhance PEC performance, co-catalyst including molybdenum carbide (Mo2C) and nickel sulfide (NiS) were incorporated using immersion and successive ionic layer adsorption reaction (SILAR) methods, respectively. Comprehensive characterization using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) provided insights into the crystal phase, morphological structure, band gap, and elemental composition of the photoelectrodes. Photoelectrochemical and photostability evaluations were conducted through linear scan voltammetry (LSV) and chronoamperometry under dark and light conditions. Results indicate that transferring TiO2 NTs onto FTO significantly enhanced photocurrent density, achieving a 2.5-fold increase at 0.7 V versus a TiO2 NT/Ti substrate. The incorporating of co-catalysts Mo2C, NiS and the combined NiS/Mo2C further enhanced the photocurrent density to 2.20, 3.00 and 8.00 mA cm(-2) respectively, with a remarkable 31-fold enhancement compared to the TiO2 NT/Ti substrate. This findings underscore the potential of the TiO2 NT/FTO photoelectrode with optimized co-catalyst integration for advanced photoelectrochemical applications.