Jinzhao Huang

Morphology-modulation of SnO2 Hierarchical Architectures by Zn Doping for Glycol Gas Sensing and Photocatalytic Applications.

The morphology of SnO2 nanospheres was transformed into ultrathin nanosheets assembled architectures after Zn doping by one-step hydrothermal route. The as-prepared samples were characterized in detail by various analytical techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and nitrogen adsorption-desorption technique. The Zn-doped SnO2 nanostructures proved to be the efficient gas sensing materials for a series of flammable and explosive gases detection, and photocatalysts for the degradation of methyl orange (MO) under UV irradiation. It was observed that both of the undoped and Zn-doped SnO2 after calcination exhibited tremendous gas sensing performance toward glycol. The response (S = Ra/Rg) of Zn-doped SnO2 can reach to 90 when the glycol concentration is 100 ppm, which is about 2 times and 3 times higher than that of undoped SnO2 sensor with and without calcinations, respectively. The result of photocatalytic activities demonstrated that MO dye was almost completely degraded (~92%) by Zn-doped SnO2 in 150 min, which is higher than that of others (MO without photocatalyst was 23%, undoped SnO2 without and with calcination were 55% and 75%, respectively).

One-pot Synthesis of CdS Irregular Nanospheres Hybridized with Oxygen-Incorporated Defect-Rich MoS2 Ultrathin Nanosheets for Efficient Photocatalytic Hydrogen Evolution

Robust and highly active photocatalysts, CdS@MoS2, for hydrogen evolution were successfully fabricated by one-step growth of oxygen-incorporated defect-rich MoS2 ultrathin nanosheets on the surfaces of CdS with irregular fissures. Under optimized experimental conditions, the CdS@MoS2 displayed a quantum yield of ∼24.2% at 420 nm and the maximum H2 generation rate of ∼17203.7 umol/g/h using Na2S-Na2SO3 as sacrificial agents (λ ≥ 420 nm), which is ∼47.3 and 14.7 times higher than CdS (∼363.8 μmol/g/h) and 3 wt % Pt/CdS (∼1173.2 μmol/g/h), respectively, and far exceeds all previous hydrogen evolution reaction photocatalysts with MoS2 as co-catalysts using Na2S-Na2SO3 as sacrificial agents. Large volumes of hydrogen bubbles were generated within only 2 s as the photocatalysis started, as demonstrated by the photocatalytic video. The high hydrogen evolution activity is attributed to several merits: (1) the intimate heterojunctions formed between the MoS2 and CdS can effectively enhance the charge transfer ability and retard the recombination of electron-hole pairs; and (2) the defects in the MoS2 provide additional active S atoms on the exposed edge sites, and the incorporation of O reduces the energy barrier for H2 evolution and increases the electric conductivity of the MoS2. Considering its low cost and high efficiency, this highly efficient hybrid photocatalysts would have great potential in energy-generation and environment-restoration fields.

Controlled assembly of Bi2S3 architectures as Schottky diode, supercapacitor electrodes and highly efficient photocatalysts

Bismuth sulfide (Bi2S3) microflowers have been successfully fabricated through a one-pot hydrothermal method. The structures and morphologies of the as-obtained products are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and Raman spectroscopy. The experimental results show that Bi2S3 microflowers are composed of many microrods with lengths of 18–20 μm. Metal/semiconductor/metal (MSM) sandwich structures are fabricated, and the current–voltage (I–V) characteristics exhibit a clear back-to-back Schottky-diode behavior. The galvanostatic charge–discharge performance illustrates that the prepared Bi2S3 microflowers exhibit good performance for discharge efficiency at current densities from 1 mA cm−2 to 10 mA cm−2. Furthermore, the as-synthesized Bi2S3 microflowers are also used as the efficient UV-light photocatalysts for the photocatalytic degradation of methylene orange (MO) under light illumination, which shows almost complete degradation (∼95%) of MO dye.

Surface/Interfacial Structure and Chemistry of High-Energy Nickel-Rich Layered Oxide Cathodes: Advances and Perspectives

The urgent prerequisites of high energy-density and superior electrochemical properties have been the main inspiration for the advancement of cathode materials in lithium-ion batteries (LIBs) in the last two decades. Nickel-rich layered transition-metal oxides with large reversible capacity as well as high operating voltage are considered as the most promising candidate for next-generation LIBs. Nonetheless, the poor long-term cycle-life and inferior thermal stability have limited their broadly practical applications. In the research of LIBs, it is observed that surface/interfacial structure and chemistry play significant roles in the performance of cathode cycling. This is due to the fact that they are basically responsible for the reversibility of Li+ intercalation/deintercalation chemistries while dictating the kinetics of the general cell reactions. In this Review, the surface/interfacial structure and chemistry of nickel-rich layered cathodes involving structural defects, redox mechanisms, structural evolutions, side-reactions among others are initially demonstrated. Recent advancements in stabilizing the surface/interfacial structure and chemistry of nickel-rich cathodes by surface modification, core-shell/concentration-gradient structure, foreign-ion substitution, hybrid surface, and electrolyte additive are presented. Then lastly, the remaining challenges such as the fundamental studies and commercialized applications, as well as the future research directions are discussed.

NiCo2O4-Based Supercapacitor Nanomaterials

In recent years, the research on supercapacitors has ushered in an explosive growth, which mainly focuses on seeking nano-/micro-materials with high energy and power densities. Herein, this review will be arranged from three aspects. We will summarize the controllable architectures of spinel NiCo2O4 fabricated by various approaches. Then, we introduce their performances as supercapacitors due to their excellent electrochemical performance, including superior electronic conductivity and electrochemical activity, together with the low cost and environmental friendliness. Finally, the review will be concluded with the perspectives on the future development of spinel NiCo2O4 utilized as the supercapacitor electrodes.

Low-temperature solution synthesis of CuO/Cu2O nanostructures for enhanced photocatalytic activity with added H2O2: synergistic effect and mechanism insight

CuxO (CuO, CuO/Cu2O, and Cu2O) nanostructures have been controllably synthesized through a facile low-temperature solution method. The morphologies and compositions of CuxO nanostructures were well controlled by tuning the reductant amount of hydroxylamine hydrochloride, which experienced the transformation of nanosheets to octahedrons as well as the phase change of CuO to Cu2O. The as-grown samples showed photodegradation selectivity to MO (maximum photocatalytic efficiency of 52% for methyl orange (MO) and 16% for rhodamine B (RhB) after 180 min photodegradation) and different photocatalytic activities in the absence or presence of H2O2 (62% without H2O2 and 82% with H2O2). The morphological transformations of as-grown samples were observed after the photocatalytic measurement in the presence of H2O2. The structural and morphological features after photodegradation were studied by XPS, SEM, and TEM investigations, revealing the possible mechanism of the as-prepared samples whereby the photodegradation of organic dyes occurred on the surface with respect to the adsorption ability, structure, and morphology of CuxO. In addition, H2O2 played an important role in the photodegradation of organic dyes.

Rare earth ion doped phosphors for dye-sensitized solar cells applications

Dye-sensitized solar cells (DSSCs) have attracted extensive attention as one of the promising alternatives to silicon solar cells. However, DSSCs have a maximum absorption in the visible light of solar spectrum, which confines their power conversion efficiency. Lots of research efforts have been focused on extending light absorption to enhance the conversion efficiency. Rare earth ion doped up/down conversion materials is an available approach to compensate for the non-absorbable wavelength region of DSSCs via converting ultraviolet and near-infrared radiation to visible emission. In addition to the light-harvesting enhancement, light-scattering effect and recombination loss can also be achieved in DSSCs by utilizing upconversion (UC) or downconversion (DC) materials. Moreover, the introduction of UC or DC facilitates to improve the stability of solar cells. In this review paper, the performance of dye-sensitized solar cells based on up or down conversion materials will be introduced.

Fabrication and properties of ZnO/GaN heterostructure nanocolumnar thin film on Si (111) substrate

Zinc oxide thin films have been obtained on bare and GaN buffer layer decorated Si (111) substrates by pulsed laser deposition (PLD), respectively. GaN buffer layer was achieved by a two-step method. The structure, surface morphology, composition, and optical properties of these thin films were investigated by X-ray diffraction, field emission scanning electron microscopy, infrared absorption spectra, and photoluminiscence (PL) spectra, respectively. Scanning electron microscopy images indicate that the flower-like grains were presented on the surface of ZnO thin films grown on GaN/Si (111) substrate, while the ZnO thin films grown on Si (111) substrate show the morphology of inclination column. PL spectrum reveals that the ultraviolet emission efficiency of ZnO thin film on GaN buffer layer is high, and the defect emission of ZnO thin film derived from Zni and Vo is low. The results demonstrate that the existence of GaN buffer layer can greatly improve the ZnO thin film on the Si (111) substrate by PLD techniques.

One-pot hydrothermal synthesis of CdS decorated CuS microflower-like structures for enhanced photocatalytic properties

CdS decorated CuS structures have been controllably synthesized through a one-pot hydrothermal method. The morphologies and compositions of the as-prepared samples could be concurrently well controlled by simply tuning the amount of CdCl2 and thiourea. Using this strategy, the morphology of the products experienced from messy to flower-like morphologies with multiple porous densities, together with the phase evolution from pure CuS to the CdS/CuS composites. Serving as a photocatalyst, the samples synthesized with the addition of 1 mmol cadmium chloride and 3 mmol thiourea during synthetic process, showed the best photocatalytic activity, which could reach a maximum photocatalytic efficiency of 93% for methyl orange (MO) photodegradation after 150 min. The possible mechanism for the high photocatalytic efficiency of the sample was proposed by investigating the composition, surface area, structure, and morphology before and after photocatalytic reaction.

One-Step Solvothermal Method to Prepare Ag/Cu2O Composite With Enhanced Photocatalytic Properties.

Ag/Cu2O microstructures with diverse morphologies have been successfully synthesized with different initial reagents of silver nitrate (AgNO3) by a facile one-step solvothermal method. Their structural and morphological characteristics were carefully investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and the experimental results showed that the morphologies transformed from microcubes for pure Cu2O to microspheres with rough surfaces for Ag/Cu2O. The photocatalytic activities were evaluated by measuring the degradation of methyl orange (MO) aqueous solution under visible light irradiation. The photocatalytic efficiencies of MO firstly increased to a maximum and then decreased with the increased amount of AgNO3. The experimental results revealed that the photocatalytic activities were significantly influenced by the amount of AgNO3 during the preparation process. The possible reasons for the enhanced photocatalytic activities of the as-prepared Ag/Cu2O composites were discussed.