Surface sensitization of g-C3N4/TiO2via Pd/Rb2O co-catalysts: accelerating water splitting reaction for green fuel production in the absence of organic sacrificial agents

Abstract

Global warming and the energy crisis due to the fast consumption of fossil fuels obligate researchers to develop renewable clean energy sources. In this work, we have designed an effective catalyst (Pd–Rb₂O@g-C₃N₄/TiO₂). The photocatalysts were prepared via a chemical reduction method followed by hydrothermal treatment. The morphology and optical characteristics of catalysts were demonstrated by the following analytical techniques: XRD, Raman, FT-IR, UV-vis/DRS, PL and SEM. The surface properties, particle sizes, and chemical composition were examined via AFM, BET, and XPS techniques. Hydrogen generation experiments were conducted at GC-TCD, and the prepared photocatalysts were evaluated for comparative hydrogen generation activities under sunlight. The Pd metal present over g-C₃N₄/TiO₂ enhances charge separation and photocatalytic performances. Rb₂O consumed holes, alleviated the Fermi energy level of the semiconductor in the photoreaction, and resulted in higher electron transport to the metal active sites (Pd co-catalysts). Rb species after consuming holes were again deposited on the surface of the semiconductor. The results reveal that the higher H₂ production activities were attributed to the origination of the type II heterojunction between g-C₃N₄/TiO₂ and the formation of a Schottky barrier between the semiconductor and Pd. However, Pd–Rb₂O@g-C₃N₄/TiO₂ was found to be the most active photocatalyst, delivering 19.7 mmol g⁻¹ h⁻¹ of hydrogen.