Impact of carbon nanotubes concentrations on the performance of carbon nanotubes/zinc oxide nanocomposite for photoelectrochemical water splitting

Under the influence of visible light, the photoelectrochemical (PEC) method of water splitting offers a green method for producing sustainable hydrogen. In this work, several volume ratios of carbon nanotubes (CNTs) were incorporated in the zinc oxide (ZnO) matrix to prepare ZnO/CNTs nanocomposites on a glass substrate as photo-electrodes for hydrogen production. These electrodes were synthesized via the spray pyrolysis technique and chem-ical vapor deposition. Various approaches were used to analyze the chemical composition, crystal structure, morphology, and optical properties of pure ZnO and ZnO/CNTs nanocomposites. The structural properties showed that crystallite size is decreased from 44.2 nm to 36.8 nm, and the optical shows that the energy bandgap (Eg) en-hanced from 3.07 to 2.87 eV for pure ZnO and the optimum sample of ZnO/7 mL CNTs nanocomposite, respec-tively. The maximum photocurrent density (Jph) was found for the 7 mL CNTs among the produced ZnO/X CNTs nanostructures. The value of Jph for ZnO/7 mL CNTs (200.7 & mu;A/cm2) is around 33 times greater compared with pure ZnO (6.96 & mu;A/cm2). At 490 nm, the incident photon-to-current efficiency (IPCE) of ZnO/7 mL CNTs is roughly 9.85 %. The ZnO/CNTs photoelectrode showed a hydrogen evolution rate of 4.34 mmole/h.cm2. The im-proved photoelectrode additionally exhibits strong chemical stability and a lengthy lifetime under visible light without photo-corrosion. Finally, the electrochemical impedance spectroscopy and the PEC water-splitting mech-anism for ZnO/CNTs were discussed. This study presents a simple method that enables the fabrication of inexpen-sive and efficient ZnO/CNTs photoelectrode for renewable energy applications.