Construction of Mn0.5Zn0.5Fe2O4 modified TiO2 nanotube array nanocomposite electrodes and their photoelectrocatalytic performance in the degradation of 2,4-DCP

Abstract

An ultrasound-assisted impregnation deposition technique was adopted to construct Mn_0.5Zn_0.5Fe₂O₄ nanoparticles on TiO₂ nanotube arrays (NTAs) which were prepared by electrochemical anodization in a hydrofluoric acid system. The Mn_0.5Zn_0.5Fe₂O₄ nanoparticles were found to successfully deposit on the surface of the highly oriented TiO₂ NTAs causing no damage to the ordered structure of the nanotubes. The as-prepared Mn_0.5Zn_0.5Fe₂O₄/TiO₂ NTAs exhibited much improved photoelectrochemical capability. Compared with pure TiO₂ NTAs, a more than 2.36-fold enhancement in photo-current density and a 2.17-fold enhancement in photo-conversion efficiency of the Mn_0.5Zn_0.5Fe₂O₄/TiO₂ NTAs were achieved. The photoelectrocatalytic (PEC) activities of Mn_0.5Zn_0.5Fe₂O₄/TiO₂ NTAs were evaluated by the degradation of toxic 2,4-dichlorophenol (2,4-DCP) in aqueous solution under simulated sun light irradiation. The experimental results indicated that the heterostructure photoelectrode showed much higher PEC activity than the pure TiO₂ NTAs for the degradation of 2.4-DCP under simulated sun light irradiation. In addition, electron spin resonance examination confirmed that the photogenerated active species (˙OH and ˙O₂⁻) were involved in the PEC degradation of 2,4-DCP. A mechanism accounting for the enhanced PEC activity of the Mn_0.5Zn_0.5Fe₂O₄/TiO₂ NTAs was proposed. The enhanced PEC activity of the nanocomposite electrode could be attributed to the synergistic effects between the lowered electron–hole recombination rate by the applied bias and the wider spectral response promoted by the Mn_0.5Zn_0.5Fe₂O₄ component.