Shengsen Zhang

Enhanced photocatalytic H2 evolution over noble-metal-free NiS cocatalyst modified CdS nanorods/g-C3N4 heterojunctions

In this report, CdS nanorods/g-C3N4 heterojunctions loaded with a noble-metal-free NiS cocatalyst were for the first time fabricated by an in situ hydrothermal method. The as-synthesized heterostructured photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy, UV-visible spectroscopy, nitrogen absorption, photoluminescence (PL) spectra, transient photocurrent responses and electrochemical impedance spectroscopy (EIS) measurements. Their photocatalytic activity for hydrogen production was evaluated using an aqueous solution containing triethanolamine under visible light (λ ≥ 420 nm). The results clearly demonstrated that the ternary hybridization of the NiS cocatalyst, 1D CdS nanorods and 2D g-C3N4 nanosheets is a promising strategy to achieve highly efficient visible-light-driven photocatalytic H2 evolution. Among all the photocatalysts employed, the ternary hybrid g-C3N4–CdS–9% NiS composite materials show the best photocatalytic performance with a H2-production rate of 2563 μmol h−1 g−1, which is 1582 times higher than that of the pristine g-C3N4. The enhanced photocatalytic activity was ascribed to the combined effects of NiS cocatalyst loading and the formation of the intimate nanoheterojunctions between 1D CdS nanorods and 2D g-C3N4 nanosheets, which were favorable for promoting charge transfer, improving the separation efficiency of photoinduced electron–hole pairs from the bulk to the interfaces and accelerating the surface H2-evolution kinetics. This work would not only provide a promising photocatalyst candidate for applications in visible-light H2 generation, but also offer a new insight into the construction of highly efficient and stable g-C3N4-based hybrid semiconductor nanocomposites for diverse photocatalytic applications.

Earth-abundant NiS co-catalyst modified metal-free mpg-C3N4/CNT nanocomposites for highly efficient visible-light photocatalytic H2 evolution.

In the present work, the earth-abundant NiS co-catalyst modified mesoporous graphite-like C3N4 (mpg-C3N4)/CNT nanocomposites were prepared via a two-step strategy: the sol-gel method and the direct precipitation process. The mpg-C3N4/CNT/NiS composite photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis absorption spectroscopy, photoluminescence spectroscopy (PL), photoelectrochemical (PEC) and electrochemical impedance spectra (EIS) experiments. The photocatalytic H2-production activity over the composite catalysts was also evaluated by using an aqueous solution containing triethanolamine under visible light (λ≥ 420 nm). The results showed that the loading of earth-abundant NiS co-catalysts onto metal-free mpg-C3N4/CNT nanocomposites can remarkably enhance their photocatalytic H2-production activity. The optimal loading amount of NiS on metal-free mpg-C3N4/CNT nanocomposites was about 1 wt%. The as-obtained mpg-C3N4/CNT/1% NiS ternary composite photocatalyst exhibits the best H2-evolution activity with the highest rate of about 521 μmol g(-1) h(-1) under visible light (λ≥ 420 nm), which is almost 148 times that of a pure mpg-C3N4/CNT sample. The enhanced photocatalytic activity can be mainly attributed to the synergistic effect of effectively promoted separation of photo-generated electron-hole pairs and enhanced H2-evolution kinetics. The co-loading of nanocarbon materials and earth-abundant co-catalysts onto metal-free mpg-C3N4 photocatalysts offers great potential for practical applications in photocatalytic H2 evolution under visible light illumination.

Metal-free carbon nanotube–SiC nanowire heterostructures with enhanced photocatalytic H2 evolution under visible light irradiation

In this report, metal-free multi-walled carbon nanotube (MWCNT)–SiC nanowire 1D–1D nanoheterostructures were successfully synthesized by an in situ chemical reaction between MWCNTs and silicon powder. A vapor–liquid–solid (VLS) mechanism was found to be responsible for in situ growth of SiC nanowires along MWCNTs. The structure, morphology and composition of the as-obtained MWCNT–SiC 1D–1D samples were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA) and UV-vis absorption spectroscopy. The H2 evolution photoactivities of the resultant MWCNT–SiC nanoheterostructures under visible light irradiation were also investigated. Results showed that the metal-free MWCNT–SiC 1D–1D nanoheterostructures exhibited the highest H2 evolution rate among all samples, up to 108 μmol g−1 h−1, which was 3.1 times higher than that of pure SiC without MWCNTs. It suggests that the H2 evolution activity enhancement of the MWCNT–SiC 1D–1D nanocomposites under visible light irradiation is mainly attributed to the synergistic effects of enhanced separation efficiency of photogenerated hole–electron pairs at the MWCNT–SiC interfaces, improved crystallinity, unique 1D–1D nanoheterostructures and increased visible light absorption. The present work not only gives new insights into the underlying photocatalysis mechanism of the metal-free MWCNT–SiC 1D–1D nanoheterostructures but also provides a versatile strategy to design 1D–1D nanocomposite photocatalysts, with great potential applications in photocatalytic H2 generation or environmental pollutant degradation.

Ultra-thin SiC layer covered graphene nanosheets as advanced photocatalysts for hydrogen evolution

Herein, for the first time, ultra-thin SiC nanoparticles or ultra-thin layer covered graphene nanosheets were successfully prepared via using a facile in situ vapor–solid reaction. The samples were characterized by X-ray diffraction, UV-visible spectroscopy, photoluminescence spectra analysis, Raman spectra, transient photocurrent responses and transmission electron microscopy. The photocatalytic activities were also evaluated by H2 evolution from pure water or water containing Na2S as an electron donor. The resulting SiC–graphene hybrids show enhanced photocatalytic H2-evolution activities in the presence of an electron donor. Especially, the graphene nanosheet and SiC nanocrystal hybrids show the highest photocatalytic activity in H2 production under visible light, which is about 10 times higher than that of the SiC nanocrystals. The enhanced activities of the SiC–graphene hybrids can be attributed to their 2D nanosheet structures, large surface area, enhanced visible-light absorption and rapid interfacial charge transfer from SiC to graphene. Our results can provide an effective approach to synthesize graphene-based heterogeneous nanocomposites for a wide variety of potential applications in solar energy conversion and storage, separation, and purification processes.

Application of carbon fibers to flexible, miniaturized wire/fiber-shaped energy conversion and storage devices

Carbon fibers (CFs) and CF-reinforced composites have been widely used as high performance structural materials in various military and civilian fields for decades. Owing to the rapid advances and boom in flexible/wearable electronics, CF materials endowed with excellent material properties have received great attention for building lightweight, cost-efficient and miniaturized flexible/wearable energy devices. Herein, a detailed overview of recent progress in wire/fiber-shaped flexible power devices made from micro-CFs is given for the first time. With an emphasis on electrode materials and architecture designs, CF-based wire/fiber energy devices including fiber nanogenerators, wire/fiber solar cells, wire-type batteries, fiber supercapacitors and integrated/hybrid fiber devices are discussed. Aiming to motivate more exciting applications, research directions and perspectives, efficient flexible wire-type CF energy devices are proposed.

A co-immobilized mediator and microorganism mediated method combined pretreatment by TiO2 nanotubes used for BOD measurement

In this paper, we proposed a method by using co-immobilized Escherichia coli (E. coli) as a biocatalyst and neutral red (NR) as an artificial electronic acceptor to modify glassy carbon electrode (GCE) for biochemical oxygen demand (BOD) measurement. Two different modification approaches of GCE were utilized and compared. In one approach, NR was electropolymerized on the surface of GCE, and E. coli cells were mixed with grafting copolymer PVA-g-PVP (briefly gPVP) and covered on NR polymer film to obtain a (gPVP/E. coli)/PNR/GCE. In the second approach, both NR and E. coli cells were mixed with the copolymer gPVP and modified GCE, after drying, which was electrochemically treated similar as above for obtaining a (gPVP/E. coli/NR)p/GCE. Based on the electrochemical evaluation, the performance of the latter was better, which may be caused by that the NR deposited on the surface of E. coli resulting in a good electron transport and permeability of cells membrane. To develop the results obtained at (gPVP/E. coli/NR)p/GCE further, the pretreatment by TiO(2) nanotubes arrays (TNTs) was employed, and different effects on samples of GGA, OECD, urea and real wastewater were evaluated. These results suggest that the present method holds a potential application for rapid BOD biosensor.

在FTO导电玻璃上电化学沉积高效可见光光电化学分解水Cu 2 O/g-C 3 N 4 异质结膜

Abstract An immobilized Cu2O/g-C3N4 heterojunction film was successfully made on an FTO substrate by electrophoretic deposition of g-C3N4 on a Cu2O thin film. The photoelectrochemical (PEC) performance for water splitting by the Cu2O/g-C3N4 film was better than pure g-C3N4 and pure Cu2O film. Under –0.4 V external bias and visible light irradiation, the photocurrent density and PEC hydrogen evolution efficiency of the optimized Cu2O/g-C3N4 film was –1.38 mA/cm2 and 0.48 mL h−1 cm−2, respectively. The enhanced PEC performance of Cu2O/g-C3N4 was attributed to the synergistic effect of light coupling and a matching energy band structure between g-C3N4 and Cu2O as well as the external bias.

Visible light photoelectrochemical properties of a hydrogenated TiO2 nanorod film and its application in the detection of chemical oxygen demand

A series of TiO2 nanorod array electrodes with different lengths have been successfully fabricated by a controlled hydrothermal method for photoelectrochemical (PEC) application. In order to enhance the conductivity of the TiO2 nanorods and enable the PEC activity under visible light irradiation, the TiO2 nanorod samples have been further hydrogenated. The influence of the length of the hydrogenated TiO2 nanorod arrays (H-TNRs) on their visible-light-driven photoelectrocatalytic activity was investigated. With increasing the length of the H-TNRs to about 3.0 μm, the activity was close to the maximum. Subsequently, the H-TNRs photoanode was fitted into a thin-layer photoelectrochemical cell for mineralization of organic compounds. The visible light PEC performance was enhanced so much that chemical oxygen demand (COD) detection was achieved under visible light as the light source for the first time. The excellent relationship between the photoelectrochemical COD and conventional COD values within the range of 0–288 mg L−1 suggests that the simple visible light driven PEC method is a promising alternative to the conventional COD method.

Facile synthesis of self-assembled mesoporous CuO nanospheres and hollow Cu2O microspheres with excellent adsorption performance

Self-assembled mesoporous CuO nanospheres (CuO NSs) and hollow Cu2O microspheres (Cu2O MSs) were synthesized by a facile ethylene glycol–water solvothermal method without any surfactants. The formation and evolution of copper oxides were investigated by controlling the synthesis conditions. The as-prepared CuxO materials showed an excellent adsorption capability for the quick removal of Acid Orange 7 (AO7) dye in water.

Electrospray synthesis of nano-Si encapsulated in graphite/carbon microplates as robust anodes for high performance lithium-ion batteries

Developing efficient Si-based anode materials for new-generation lithium-ion batteries (LIBs) has drawn extensive attention. Here, an electrosprayed Si/graphite/carbon (Si/G/C) composite is explored as a prominent anode material for LIBs. The designed Si/G/C composite possesses a reasonable structure with nano-Si encapsulated in the conductive graphite flake/amorphous carbon framework. The Si/G/C composite achieves superior reversible Li+ storage capability, showing a considerable discharge capacity of 832 mA h g−1 at 200 mA g−1. Moreover, it realizes an encouraging capacity of ca. 400 mA h g−1 under a high current density of 500 mA g−1 after 200 cycles. The excellent capacity and rate performance can be attributed to the structural benefits of the Si/G/C composite: (i) the highly conductive graphite flakes serve as good dispersive scaffolds and electronic conductors, allowing for fast charge transfer and favorable ion diffusion; (ii) the amorphous carbon layer acts as a protective coating to bind/fix nano-Si onto graphite and reduce the formation of unstable solid electrolyte interphase (SEI) film; and (iii) both the layered graphite and amorphous carbon layer introduce adequate buffer space or voids to alleviate the volume changes of Si during the Li+ insertion/extraction cycles. This high-capacitive and robust Si/graphite-based hybrid is attractive as an alternative anode material for practical rechargeable LIBs.