One-Pot Facile Synthesis of ZrO2-CdWO4: A Novel Nanocomposite for Hydrogen Production via Photocatalytic Water Splitting

Abstract

ZrO2-based nanocomposites are highly versatile materials with huge potential for photocatalysis. In this study, ZrO2-CdWO4 nanocomposites (NC) were prepared via the green route using aqueous Brassica rapa leaf extract, and its photocatalytic water-splitting application was evaluated. Brassica rapa leaf extract acts as a reducing agent and abundant phytochemicals are adsorbed onto the nanoparticle surfaces, improving the properties of ZrO2-CdWO4 nanocomposites. As-prepared samples were characterized by using various spectroscopic and microscopic techniques. The energy of the direct band gap (Eg) of ZrO2-CdWO4 was determined as 2.66 eV. FTIR analysis revealed the various functional groups present in the prepared material. XRD analysis showed that the average crystallite size of ZrO2 and CdWO4 in ZrO2-CdWO4 was approximately 8 nm and 26 nm, respectively. SEM and TEM images suggested ZrO2 deposition over CdWO4 nanorods, which increases the roughness of the surface. The prepared sample was also suggested to be porous. BET surface area, pore volume, and half pore width of ZrO2-CdWO4 were estimated to be 19.6 m2/g. 0.0254 cc/g, and 9.457 Å, respectively. PL analysis suggested the conjugation between the ZrO2 and CdWO4 by lowering the PL graph on ZrO2 deposition over CdWO4. The valence and conduction band edge positions were also determined for ZrO2-CdWO4. These band positions suggested the formation of a type I heterojunction between ZrO2 and CdWO4. ZrO2-CdWO4 was used as a photocatalyst for hydrogen production via water splitting. Water-splitting results confirmed the ability of the ZrO2-CdWO4 system for enhanced hydrogen production. The effect of various parameters such as photocatalyst amount, reaction time, temperature, water pH, and concentration of sacrificial agent was also optimized. The results suggested that 250 mg of ZrO2-CdWO4 could produce 1574 µmol/g after 5 h at 27 °C, pH 7, using 30 vol. % of methanol. ZrO2-CdWO4 was reused for up to seven cycles with a high hydrogen production efficiency. This may prove to be useful research on the use of heterojunction materials for photocatalytic hydrogen production.