An electrode with intimate and well‐aligned ZnFe2O4/TiO2 composite nanotube arrays is prepared via electrochemical anodization of pure titanium foil in fluorine‐containing ethylene glycol, followed by a novel cathodic electrodeposition method. The deposition of ZnFe2O4 is promoted in the self‐aligned, vertically oriented TiO2 nanotube arrays but minimized at the tube entrances. Thus, pore clogging is prevented. Environmental scanning electron microscopy, energy‐dispersive X‐ray spectra, high‐resolution transmission electron microscopy, X‐ray diffraction patterns, and X‐ray photoelectron spectroscopy indicate that the as‐prepared samples are highly ordered and vertically aligned TiO2 nanotube arrays with ZnFe2O4 nanoparticles loading. The TiO2 nanotubes are anatase with the preferential orientation of <101> plane. Enhanced absorption in both UV and visible light regions is observed for the composite nanotube arrays. The current–voltage curve of ZnFe2O4‐loaded TiO2 nanotube arrays reveals a rectifying behavior. The enhanced separation of photoinduced electrons and holes is demonstrated by surface photovoltage and photocurrent measurements. Meanwhile, the photoelectrochemical investigations verify that the ZnFe2O4/TiO2 composite nanotube array modified electrode has a more effective photoconversion capability than the aligned TiO2 nanotube arrays alone. In addition, the photoelectrocatalytic ability of the novel electrode is found enhanced in the degradation of 4‐chlorophenol.
A ternary Ag/AgBr/TiO(2) nanotube array electrode with enhanced visible-light activity was synthesized by a two-step approach including electrochemical process of anodization and an in situ photoassisted deposition strategy. The dramatically enhanced photoelectrocatalytic activity of the composite electrode was evaluated via the inactivation of Escherichia coli under visible light irradiation (λ>420 nm), whose performance of complete sterilization was much superior to other reference photocatalysts. PL, ESR, and radicals trapping studies revealed hydroxyl radicals were involved as the main active oxygen species in the photoelectrocatalytic reaction. The process of the damage of the cell wall and the cell membrane was directly observed by ESEM, TEM, and FTIR, as well as further confirmed by determination of potassium ion leakage from the killed bacteria. The present results pointed to oxidative attack from the exterior to the interior of the Escherichia coli by OH(•), O(2)(•-), holes and Br(0), causing the cell to die as the primary mechanism of photoelectrocatalytic inactivation.
In an effort to develop nanostructured
photocatalysts to achieve
high performance in heterogeneous photocatalysis, a novel composite
V2O5/BiVO4/TiO2 photocatalyst
was successfully synthesized by using a sequentially hydrothermal
and adhering method. The structural and optical properties of the
as-prepared samples were comparatively characterized. The formed ternary
nanojunctions were composed of TiO2 nanobelts and V2O5/BiVO4 nanorods which were self-assembled
by smaller V2O5 and BiVO4 nanoparticles.
Compared to pure TiO2 nanobelts and V2O5/BiVO4 nanorods, the V2O5/BiVO4/TiO2 composite exhibited higher photocatalytic
activity in decomposition of gaseous toluene under visible light irradiation
(λ > 400 nm). Electron spin resonance examination confirmed
that the photoinduced active species (•OH and O2
•–) were involved in the photocatalytic
degradation of toluene. A detailed mechanism accounting for the enhanced
photocatalytic activity of the V2O5/BiVO4/TiO2 nanocomposite was proposed in terms of the
energy band structures of the components. The rationally designed
ternary nanojunctions could effectively enhance the photocatalytic
performance by increasing photoinduced charge carriers through the
charges separation across their multiple interfaces.
Single atom catalysts (SACs) are considered as the emerging catalysts for boosting electricity‐driven CO2 reduction reaction (CRR) and hydrogen evolution reaction (HER). To replace the rare and expensive noble metal electrocatalysts, developing nonprecious metal SACs (NPMSACs) with superior electrocatalytic activity and stability is of paramount importance for achieving high efficiency in CRR and HER. Herein, a brief overview of recent achievements in the carbon‐rich NPMSACs for both CRR and HER is provided. The synthesis strategies and corresponding electrocatalytic performances of various carbon‐rich NPMSACs are discussed in the order of various metals (Ni, Co, Fe, Zn, and Sn for CRR, as well as Ni, Co, Fe, Mo, and W for HER), with a special attention paid to understand the structure–activity relationships. Finally, the remaining challenges and future perspectives for enhancing CRR and HER performance of NPMSACs are outlined.
This work aims at the exploration of nanostructured ferroelectric-material-modified semiconductor electrodes for enhanced photo-induced activity. A well-aligned BiFeO3/TiO2-nanotubes (NTs) array with visible-light activity was successfully synthesized on a titanium sheet by combining anodization and an ultrasonic-immersion method followed by annealing. The structural and optical properties of the TiO2-NTs and the composite BiFeO3/TiO2-NTs were comparatively characterized. The composite BiFeO3/TiO2-NTs grown on a Ti sheet and used as an electrode exhibited a stronger absorption in the visible region and a much higher photoconversion efficiency than the pure TiO2-NTs/Ti electrode. Electrochemical impedance investigation attested to a significant improvement of the interfacial electron-transfer kinetics with enhanced separation of electron-hole pairs. The as-prepared composite electrode showed a high efficiency for photoelectrocatalytic degradation towards rhodamine B under visible-light irradiation (λ > 400 nm). The enhanced photoelectrocatalytic activity of the composite electrode could be attributed to the synergistic effect between the lowered electron-hole recombination rate by the applied bias and the wider spectral response promoted by the BiFeO3 component.
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