A comparative analysis of the photoelectrochemical performance of g-C3N4/TiO2 nanotube composites

Sunlight driven photoelectrochemical (PEC) water splitting has garnered excessive attention as an eco-friendly technique to produce renewable hydrogen. Designing TiO₂ based composites have evolved as an efficient strategy to extend the photoactivity of TiO₂, inhibit their charge recombination and increase their stability. Owing to its well-matched energy bands, graphitic carbon nitride (g-C₃N₄) has emerged as an effective counterpart of TiO₂. The present work reports the synthesis of gC₃N₄/ TiO₂ composites from a three-step process where bulk g-C₃N₄ was electrodeposited on separated TiO₂ nanotubes from a constantly rotating organic suspension at a voltage of about ~ 90 V for desired time. To explore the role of crystalline TiO₂ nanotubes on the composite formation, g-C₃N₄ was similarly electrodeposited on amorphous separated nanotubes etched from Ti Foil to obtain g-C₃N₄/amorphous TiO₂ nanotube which was then annealed at 450°C for 3 h. UV-Vis, FTIR, Raman and PL spectra was recorded for virgin TiO₂ nanotube and g-C₃N₄/ TiO₂ nanotube composites formed under varying deposition conditions to investigate their optoelectronic properties comparatively. The photoresponse of the samples was evaluated from photoelectrochemical measurements. All the composites demonstrated good photoactivity and enhanced photoelectrochemical response going upto an order increase than bare TiO₂. The microstructural study revealed the effect of crystalline TiO₂ nanotubes on the composite formation. TiO₂ nanotube arrays provide a direct pathway for electron transfer and the ease of access of its inner and outer surfaces aid in light scattering more efficiently. Incorporating bulk g-C₃N₄ is appealing as a simple process that decreases the complexity and promotes increased light harvesting.