Hongye Bai

Fabrication of TiO2–BiOCl double-layer nanostructure arrays for photoelectrochemical water splitting

A novel TiO2–BiOCl double-layer nanostructure array (rutile nanowires@anatase/BiOCl nanosheets) was successfully designed and prepared. The obtained samples were systematically characterized by scanning electron microscopy, X-Ray diffraction, the UV–Vis diffuse reflectance spectra, Raman spectroscopy, photocurrent versus potential (I–V) curves, and the incident photon to current efficiency (IPCE) curves. According to the photoelectrochemical data, the introduction of the BiOCl nanosheet on the TiO2 nanowire film could markedly enhance the photocurrent and IPCE value, due to the formation of TiO2/BiOCl heterostructures on the FTO substrate. Furthermore, the sample exhibits the best photoelectrochemical performance when the depositing cycle of BiOCl is 60 times.

An in situ photoelectroreduction approach to fabricate Bi/BiOCl heterostructure photocathodes: understanding the role of Bi metal for solar water splitting

This paper presents for the first time a novel method of depositing plasmonic Bi nanoparticles on BiOCl nanosheets (Bi/BiOCl) via insitu photoelectroreduction, and Bi/BiOCl as the photocathode enabled solar water splitting in a TiO2–Bi/BiOCl photoelectrochemical (PEC) system. It is one of the challenges to understand the relationship between the PEC performance and the composite ratio of Bi/BiOCl, and the density functional theory calculation results show that charges obviously transfer from the Bi cluster to the BiOCl (001) surface. The structure of Bi/BiOCl photocathode has been successfully optimized, according to the current–potential curves and charge injection efficiency. The highly enhanced PEC activity could be attributed to the dual roles of Bi nanoparticles in enhancing the charge transfer and surface plasmon resonance (SPR) effect. More importantly, the optimal Bi/BiOCl photocathode achieved a solar hydrogen evolution rate of 2.4 µmol h−1 under full spectrum illumination (100 mW cm−2).

Semiconductors with NIR driven upconversion performance for photocatalysis and photoelectrochemical water splitting

Infrared light (IR) occupies about 50% of solar irradiation, therefore, how to effectively utilize IR light is one of the main issues at present. Two major strategies which have been pursued for the development and utilization of near infrared (NIR) light in the field of photocatalysis and photoelectrochemical (PEC) water splitting are reviewed in this highlight. The main text is divided into two parts: the first is the modification of semiconductors with upconversion lanthanide (Ln) compounds; the other is the modification of semiconductors with upconversion carbon quantum dots (CQDs).

Fabrication of MgFe2O4/MoS2 Heterostructure Nanowires for Photoelectrochemical Catalysis

A novel one-dimensional MgFe2O4/MoS2 heterostructure has been successfully designed and fabricated. The bare MgFe2O4 was obtained as uniform nanowires through electrospinning, and MoS2 thin film appeared on the surface of MgFe2O4 after further chemical vapor deposition. The structure of the MgFe2O4/MoS2 heterostructure was systematic investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectrometry (XPS), and Raman spectra. According to electrochemical impedance spectroscopy (EIS) results, the MgFe2O4/MoS2 heterostructure showed a lower charge-transfer resistance compared with bare MgFe2O4, which indicated that the MoS2 played an important role in the enhancement of electron/hole mobility. MgFe2O4/MoS2 heterostructure can efficiently degrade tetracycline (TC), since the superoxide free-radical can be produced by sample under illumination due to the active species trapping and electron spin resonance (ESR) measurement, and the optimal photoelectrochemical degradation rate of TC can be achieved up to 92% (radiation intensity: 47 mW/cm(2), 2 h). Taking account of its unique semiconductor band gap structure, MgFe2O4/MoS2 can also be used as an photoelectrochemical anode for hydrogen production by water splitting, and the hydrogen production rate of MgFe2O4/MoS2 was 5.8 mmol/h·m(2) (radiation intensity: 47 mW/cm(2)), which is about 1.7 times that of MgFe2O4.

Fabrication of Au@CdS/RGO/TiO2 heterostructure for photoelectrochemical hydrogen production

This study reports a novel Au@CdS/RGO/TiO2 heterostructure as a photoelectrode for photoelectrochemical (PEC) hydrogen generation via water splitting. The unique heterostructures of the Au@CdS/RGO/TiO2 photoelectrode were confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Au@CdS nanoparticles with a core–shell structure were introduced into the TiO2 photoelectrode for the first time, and the Au@CdS nanoparticles could endow the TiO2 photoelectrode with both visible light response ability and the plasmonic property. Moreover, the RGO thin film sandwiched between TiO2 nanorod and Au@CdS core–shell nanoparticles played an important role in the fast transport of photogenerated charges, due to its excellent electrical conductivity. Clear enhancements of photocurrent and monochromatic incident photon-to-photocurrent efficiency were observed, resulting from the synergistic effect between Au@CdS core–shell nanoparticles and the RGO thin film. More importantly, Au@CdS/RGO/TiO2 photoelectrode achieved a considerable hydrogen evolution rate (4.821 mmol h−1 m−2) under full spectrum illumination (47 mW cm−2).

Titanium dioxide macroporous materials doped with iron: synthesis and photo-catalytic properties

A series of iron doped three-dimensional (3D) ordered macroporous TiO2 hybrid materials (Fe–Ti–Oxide-M) have been successfully prepared by using polymethylmethacrylate nanospheres (PMMAs) as templates. The crystal structure of Fe–Ti–Oxide-M (50%) could be assigned to the Fe3Ti3O10 phase by XRD characterization. Synthetic samples were also studied by TEM and UV-vis absorption spectra in detail. All obtained samples possessed 3D ordered macroporous structures, and the absorption spectra of Fe–Ti–Oxide-M gradually extended to the visible light region with increased doping quantities of Fe. Furthermore, the photo-catalytic degradation of tetracycline (TC) was investigated, and the observed photo-catalytic performances of Fe–Ti–Oxide-M (1%, 2%, 5%, 10%, 20%, and 50%) were associated with their composition, which further indicates that the introduction of Fe has a remarkable influence on the photo-activity of 3D ordered macroporous TiO2 materials.

Hydrothermal synthesis of Fe2O3/ZnO heterojunction photoanode for photoelectrochemical water splitting

We report a photoanode based on Fe2O3/zinc oxide (ZnO) heterojunction synthesized by hydrothermal method for photoelectrochemical (PEC) water splitting. The forming heterojunction is systemically characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results from the I–V characteristic curve and conversation efficiency of Fe2O3/ZnO heterojunction reveal that the forming heterojunction would be a benefit for electron transferring from conduction band of ZnO to that of Fe2O3. However, the quantity of ZnO film has an effect on the photocurrent density, the suitable of which has shown enhanced PEC performance.

Rod-in-tube nanostructure of MgFe2O4: electrospinning synthesis and photocatalytic activities of tetracycline

Magnesium ferrite (MgFe2O4) nanofibers were synthesized by direct annealing of electrospun precursor fibers using an appropriate heat treatment process. The crystal structure, morphology and surface area of the as-synthesized MgFe2O4 nanofibers were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, respectively. The optical properties of the as-synthesized products were studied through ultraviolet-visible and photoluminescence spectroscopy. Due to its potential application in photocatalysis, the photocatalytic degradation of tetracycline (TC) was conducted, and the result indicated that MgFe2O4 showed a better photocatalytic degradation ratio (1.5 times and 2 times) of TC than the others under visible-light irradiation, which may be due to the unique rod-in-tube structure, and larger specific area and the larger specific surface area could absorb more catalyst and provide more active sites.

Controllable TiO2 heterostructure with carbon hybrid materials for enhanced photoelectrochemical performance

In TiO2 both advantages (stability and low cost) and disadvantages (large bandgap) coexist, so how to optimize a bare TiO2 electrode is a continuous hot topic for the construction of suitable photoelectrochemical (PEC) devices based on TiO2 for water splitting. This paper reports a facile and simple fabrication of a TiO2/RGO/C3N4 photoelectrode for PEC splitting of water. Its heterostructure configuration has been characterized and confirmed by XRD, Raman spectroscopy, XPS, TEM and STEM. The introduction of both RGO and C3N4 film onto the surface of TiO2 is mainly due to the fact that C3N4 has a strong photoelectric ability to respond to visible light and RGO plays an important role in the fast transfer of photogenerated charges across interfaces. Photocurrent and monochromatic incident photon-to-photocurrent efficiency (IPCE) of the titled heterostructure have been obviously improved, and the IPCE value (0.5 V vs. AgCl/Ag) of TiO2/RGO/C3N4 was estimated to be up to 28% at a wavelength of 400 nm.

Fabrication of stable photoanode built from ZnO nanosheets in situ decorated with carbon film

In this work, we successfully fabricated a novel stable photoanode, which was built from ZnO nanosheets in situ decorated with carbon film (ZnO/carbon). The thin carbon film, as a passivation layer, can not only improve the photoelectrochemical (PEC) performance, but also significantly depress the photocorrosion of ZnO. Compared with bare ZnO photoanode, the photocurrent density of ZnO/carbon has been increased nearly five times, and its IPCE value can be up to 27% (0.5V versus Ag/AgCl). Moreover, the XRD, SEM and TEM data further demonstrate the crystal and microscopic structure of ZnO/carbon in detail.