TY - JOUR
T1 - Semiconducting properties of ZnO/TiO2 composites by electrochemical measurements and their relationship with photocatalytic activity
AU - Ramírez-Ortega, David
AU - Meléndez, Angel M.
AU - Acevedo-Peña, Próspero
AU - González, Ignacio
AU - Arroyo, Rubén
N1 - Funding Information:
This research was partially supported by the Universidad Industrial de Santander (Project 5716: Fabricación y caracterización de nano-estructuras: primera parte). David A. Ramírez-Ortega gratefully acknowledges the support of a CONACYT scholarship CVU No. 329398.
PY - 2014/9/10
Y1 - 2014/9/10
N2 - ZnO core/TiO2 shell nanocomposite powders with different ZnO:TiO2 molar ratios (01:99, 03:97, 06:94, 12:88 and 20:80) were synthesized by sol-gel procedure, using ZnO rods and titanium(IV) alkoxide as precursors. This synthesis method allows obtaining core/shell systems comprising multiple cores. Morphology, crystalline phase, particle size, specific surface area, and optical band gap energy of as-prepared photocatalyst powders were determined by FE-SEM, HR-TEM coupled with energy-dispersive spectroscopy (EDS), XRD, nitrogen adsorption isotherms and diffuse reflectance UV-visible spectroscopy (DRS). The semiconducting properties of the composites were obtained in the dark by cyclic voltammetry (CV) and the Mott-Schottky analysis (capacitance measurements). The band edge energy levels of all samples were estimated through measurements of flat band potentials and forbidden band gaps. The photodegradation of 4-chlorophenol in aqueous solution using the nanocomposite powders showed the highest photocatalytic activity for 06 ZnO:94 TiO2 molar ratio. Correlations between the energetic positions of band edges, density of donors and the extent of 4-chlorophenol oxidation allowed explaining this high photocatalytic activity. The presence of surface states, due to grain boundary appearing at the ZnO/TiO2 interface, can affect the band bending by modifying the transport (and separation) of charge carriers, thereby changing the photocatalytic activity of the samples.
AB - ZnO core/TiO2 shell nanocomposite powders with different ZnO:TiO2 molar ratios (01:99, 03:97, 06:94, 12:88 and 20:80) were synthesized by sol-gel procedure, using ZnO rods and titanium(IV) alkoxide as precursors. This synthesis method allows obtaining core/shell systems comprising multiple cores. Morphology, crystalline phase, particle size, specific surface area, and optical band gap energy of as-prepared photocatalyst powders were determined by FE-SEM, HR-TEM coupled with energy-dispersive spectroscopy (EDS), XRD, nitrogen adsorption isotherms and diffuse reflectance UV-visible spectroscopy (DRS). The semiconducting properties of the composites were obtained in the dark by cyclic voltammetry (CV) and the Mott-Schottky analysis (capacitance measurements). The band edge energy levels of all samples were estimated through measurements of flat band potentials and forbidden band gaps. The photodegradation of 4-chlorophenol in aqueous solution using the nanocomposite powders showed the highest photocatalytic activity for 06 ZnO:94 TiO2 molar ratio. Correlations between the energetic positions of band edges, density of donors and the extent of 4-chlorophenol oxidation allowed explaining this high photocatalytic activity. The presence of surface states, due to grain boundary appearing at the ZnO/TiO2 interface, can affect the band bending by modifying the transport (and separation) of charge carriers, thereby changing the photocatalytic activity of the samples.
KW - Core/shell nanoparticles
KW - Electron traps
KW - Photocatalytic degradation
KW - Surface states
UR - http://www.scopus.com/inward/record.url?scp=84906951278&partnerID=8YFLogxK
U2 - 10.1016/j.electacta.2014.06.060
DO - 10.1016/j.electacta.2014.06.060
M3 - Artículo
SN - 0013-4686
VL - 140
SP - 541
EP - 549
JO - Electrochimica Acta
JF - Electrochimica Acta
ER -