Zinc Oxide Precursor Research Articles

Boosting highly transparent and conducting indium zinc oxide thin films through solution combustion synthesis: influence of rapid thermal annealing

IZO thin films with In:Zn ratio of 7:3 and 3:7 were prepared by solution combustion synthesis of metal oxide nitrates and influence of post-deposition rapid thermal annealing (RTA) was studied. Individual 0.5 M indium and zinc oxide precursor solutions were mixed in 7:3 and 3:7 compositions. XRD analysis showed IZO 7:3 composition has only cubic bixbyite In2O3 structure while IZO 3:7 composition showed both hexagonal wurtzite ZnO and cubic bixbyite In2O3 phases. SEM and AFM analysis showed low roughness for IZO 7:3, rms < 2 nm whereas for IZO 3:7 composition surface roughness was >22 nm due to phase segregation. UV/ViS/NIR analysis showed transparency range desirable of transparent conductors for both compositions. Post-deposition RTA treatment resulted in high conductivity single phase IZO 7:3 films. Segregation of phases enhanced carrier scattering resulting in decreased mobility for IZO 3:7 films. Best performing IZO films demonstrated low resistivity 7.66 × 10−3 Ohm cm and high carrier concentration 5.09 × 1019/cm3 after 10 min RTA at 600 °C. These results demonstrate combustion synthesis and RTA are successful for development of films with enhanced conductivity and transparency through low cost vacuum-free synthesis reducing indium content for applications in photovoltaic devices, flat panel displays and transparent electronics.

Synthesis and Characterization of ZnO-decorated GO Nanocomposite Material with Different ZnO Loading through Sol-gel Method

This work aimed is to synthesis a well dispersed zinc oxide (ZnO) nanoparticles (NPs) decorated on graphene oxide (GO) nanosheet with a practical way by using sol-gel technique. Zinc acetate dehydrate (Zn(CH3COO) 2·2H2O) was used as precursor of ZnO and absolute ethanol as solvent. 1 weight percent (wt%), 5 wt%, 10 wt%, and 20 wt% of ZnO was decorated on GO nanosheet. A series of analysis was carried out to characterize the synthesized ZnO-decorated GO nanocomposite material. The results of XRD analysis show some long area of peak at 25° to 80° allocate for ZnO in the ZnO-decorated GO nanocomposite material. By performing zeta potential analysis, the findings show that there was increment of negative surface charge on ZnO-decorated GO nanocomposite material. The experiment result also found that the hydrodynamic particle size of ZnO-decorated GO nanocomposite material become larger when high ZnO loaded. FESEM micrographs demonstrated that spherical-shaped of ZnO NPs appeared on the GO nanosheet with further proved by EDX where the content of ZnO-decorated GO nanocomposite material was composed by 71.3 wt% of C, 17 wt% of O, and additional element of 11.7 wt% of Zn. Thus, it can summarize that the synthesized ZnO-decorated GO nanocomposite material was high in purity. The findings in this study proved that ZnO NPs loading in ZnO-decorated GO nanocomposite material were successfully synthesized by sol-gel method. A ZnO-decorated GO nanocomposite material with layering ZnO NPs on GO nanosheet was produced.

Manufacturing of a hierarchical carbon foam with tailored catalytically Me/MexOy particles

Carbon foams are characterised by their high specific surface areas (SSAs) in combination with ultra-low densities. Due to these unique properties, carbon foams are particularly suitable for applications such as catalysts, where high surface area is essential. Metals or metal oxides are added to the carbon structure to increase the catalytically effectiveness. In this study, we present a new and efficient manufacturing method, with the potential for a large-scale production resulting in a 3D hierarchical carbon foam with incorporated catalytically metal or metal oxides. The manufacturing starts with the preparation of a ceramic zinc oxide (ZnO) precursor powder containing catalytically active materials (Me/MexOy), uniaxial pressing and sintering yielding to templates. The replication of the template morphology into a hollow carbon structure in the chemical vapour deposition (CVD) process, in which the catalytic materials remain in the carbon foam. Furthermore, the morphology of these structures and the grain size distribution are investigated using scanning electron (SEM) and transmission electron microscopy (TEM). The final amount of catalytically particles is analysed by thermal gravimetric analysis (TGA). Finally, the SSA of the synthesised carbon-based catalysts is measured by Brunauer-Emmett-Teller (BET) method.

Low-temperature solution-processed zinc oxide field effect transistor by blending zinc hydroxide and zinc oxide nanoparticle in aqueous solutions

We present a novel methods of fabricating low-temperature (180 °C), solution-processed zinc oxide (ZnO) transistors using a ZnO precursor that is blended with zinc hydroxide [Zn(OH)2] and zinc oxide hydrate (ZnO ∙ H2O) in an ammonium solution. By using the proposed method, we successfully improved the electrical performance of the transistor in terms of the mobility (μ), on/off current ratio (Ion/Ioff), sub-threshold swing (SS), and operational stability. Our new approach to forming a ZnO film was systematically compared with previously proposed methods. An atomic forced microscopic (AFM) image and an X-ray photoelectron spectroscopy (XPS) analysis showed that our method increases the ZnO crystallite size with less OH− impurities. Thus, we attribute the improved electrical performance to the better ZnO film formation using the blending methods.

Enhancement of Inverted Polymer Solar Cells Performances Using Cetyltrimethylammonium-Bromide Modified ZnO.

In this study, the performance and stability of inverted bulk heterojunction (BHJ) polymer solar cells (PSCs) is enhanced by doping zinc oxide (ZnO) with 0–6 wt % cetyltrimethylammonium bromide (CTAB) in the sol-gel ZnO precursor solution. The power conversion efficiency (PCE) of the optimized 3 wt % CTAB-doped ZnO PSCs was increased by 9.07%, compared to a PCE of 7.31% for the pristine ZnO device. The 0–6 wt % CTAB-doped ZnO surface roughness was reduced from 2.6 to 1 nm and the number of surface defects decreased. The X-ray photoelectron spectroscopy binding energies of Zn 2p3/2 (1021.92 eV) and 2p1/2 (1044.99 eV) shifted to 1022.83 and 1045.88 eV, respectively, which is related to strong chemical bonding via bromide ions (Br−) that occupy oxygen vacancies in the ZnO lattice, improving the PCE of PSCs. The concentration of CTAB in ZnO significantly affected the work function of PSC devices; however, excessive CTAB increased the work function of the ZnO layer, resulting from the aggregation of CTAB molecules. In addition, after a 120-hour stability test in the atmosphere with 40% relative humidity, the inverted device based on CTAB-doped ZnO retained 92% of its original PCE and that based on pristine ZnO retained 68% of its original PCE. The obtained results demonstrate that the addition of CTAB into ZnO can dramatically influence the optical, electrical, and morphological properties of ZnO, enhancing the performance and stability of BHJ PSCs.

Production and Characterization of Superhydrophobic and Antibacterial Coated Fabrics Utilizing ZnO Nanocatalyst

Dirt and microorganisms are the major problems in textiles which can generate unpleasant odor during their growth. Here, zinc oxide (ZnO) nanoparticles prepared by sol-gel method were loaded on the cotton fabrics using spin coating technique to enhance their antimicrobial properties and water repellency. The effects of ZnO precursor concentration, precursor solution pH, number of coating runs, and Mg doping percent on the structures, morphologies, and water contact angles (WCA) of the ZnO-coated fabrics were addressed. At 0.5 M concentration and pH7, more homogeneous and smaller ZnO nanoparticles were grown along the preferred (0 0 2) direction and uniformly distributed on the fabric with a crystallite size 17.98 nm and dislocation density 3.09 × 10−3 dislocation/nm2. The substitution of Zn2+ with Mg2+ ions slightly shifted the (002) peak position to a higher angle. Also, the zeta potential and particle size distribution were measured for ZnO nanoparticle suspension. A superhydrophobic WCA = 154° was measured for the fabric that coated at 0.5 M precursor solution, pH 7, 20 runs and 0% Mg doping. Moreover, the antibacterial activities of the ZnO-coated fabric were investigated against some gram-positive and gram-negative bacteria such as Salmonella typhimurium, Klebsiella pneumonia, Escherichia coli, and Bacillus subtilis.

Nanoscale Ferromagnetic Cobalt‐Doped ZnO Structures Formed by Deep‐UV Direct‐Patterning

AbstractCobalt (II) acetate is mixed with zinc methacrylate (ZnMAA) to form a photopatternable Co‐doped zinc oxide precursor. By using deep‐UV (DUV) interference lithography, Co‐doped ZnMAA precursor can be patterned as negative tone resist and transformed into ferromagnetic Co:ZnO films after thermal treatment. Moreover, Co:ZnO patterns as small as 300 nm line‐width can be easily obtained. To have an in‐depth understanding to the effect of DUV‐patterning process as well as thermal annealing on Co:ZnO films derived from Co‐doped ZnMAA precursor, optical, magnetic, and electrical characterizations are performed on Co:ZnO films prepared in different conditions. For the Co:ZnO film prepared without DUV‐patterning, large zero‐field‐cooling (ZFC)–field‐cooling (FC) irreversibility appears in superconducting quantum interference device measurements after vacuum annealing, indicating that Co clusters have formed inside the film. On the other hand, no ZFC–FC bifurcation can be observed for the DUV‐patterned Co:ZnO film after the vacuum annealing, suggesting that the uniformity of Co ion distribution inside ZnO lattice is improved by DUV‐patterning.

Synthesis and Physico-Chemical Properties of Zinc Layered Hydroxide-3-4-Dichlorohenoxy Acetic Acid (ZLH34D) Nanocomposite

A herbicide, 3,4-Dichlorophenoxy acetic acid (34D) was successfully intercalated into the zinc layered hydroxide (ZLH) by direct reaction with zinc oxide (ZnO) to form a new organic-inorganic zinc layered hydroxide-3,4-Dichlorophenoxy acetate (Z34D) under an aqueous environment. The pH of the solution was adjusted to 7.5 using 2 M sodium hydroxide (NaOH). The pure phase and well-ordered was synthesized at 0.3 M Z34D. PXRD patterns show well-ordered nanohybrid material with basal spacing at 26.1 Å. The percentage loading of 34D in the Z34D is 57.5 % (w/w) calculated based on the percentage of carbon in the sample. FESEM shows the ZnO precursor has very fine granular structure and transformed into agglomerate structure when the nanohybrid are formed. This work shows that the nanohybrid of Z34D can be synthesized using simple, direct-reaction method.

Quantum Dots-Facilitated Printing of ZnO Nanostructure Photodetectors with Improved Performance.

A nanocomposite ink composed of zinc oxide precursor (ZnOPr) and crystalline ZnO quantum dots (ZnOPrQDs) has been explored for printing high-performance ultraviolet (UV) photodetectors. The performance of the devices has been compared with their counterparts' printed from ZnOPr ink without ZnO QDs. Remarkably, higher UV photoresponsivity of 383.6 A/W and the on/off ratio of 2470 are observed in the former, which are significantly better than 14.7 A/W and 949 in the latter. The improved performance is attributed to the increased viscosity in the nanocomposite ink to enable a nanoporous structure with improved crystallinity and surface-to-volume ratio. This is key to enhanced surface electron-depletion effect for higher UV responsivity and on/off ratio. In addition, the QD-assisted printing provides a simple and robust method for printing high-performance optoelectronics and sensors.

Synthesis and Physico-Chemical Properties of Zinc Layered Hydroxide-4-Chloro-2-Methylphenoxy Acetic Acid (ZMCPA) Nanocomposite

Hybrid nanocomposite zinc layered hydroxide-4-chloro-2-methylphenoxyacetic acid (ZMCPA) was successfully synthesized via direct reaction of 4-chloro-2-methylphenoxy acetic acid (MCPA) with zinc oxide (ZnO) under an aqueous environment. The pure phase and well-ordered ZMCPA was obtained when ZMCPA was synthesized at 0.3 M MCPA. The resulting nanocomposite, ZMCPA was characterized by powder X-ray diffraction (PXRD), fourier transform infrared(FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), thermogravimetric and differential thermogravimetric analyses (TGA/DTG) and CHNS Analyzer. Basal spacing showed that the gallery height of zinc layered hydroxide (ZLH) expanded from 11.Å to 24.1 Å, indicating that the MCPA anions were successfully intercalated into the interlayer space of ZLH. The FTIR spectrum of the ZMCPA shows it resembles the spectra of ZnO and MCPA that confirms the intercalation of MCPA between the ZLH sheets. FESEM shows the ZnO precursor has granular structure and transformed into a flake–like structure when the nanohybrid is formed. Percentage loading of MCPA interleaved in the nanohybrid is 50.2%.

Surface modification of line-patterned electron transfer layer for enhancing the performance of organic solar cells

In this study, we fabricated inverted organic solar cells (i-OSCs) using line-patterned interlayer for electron extraction. The short circuit current density (JSC) of line-patterned interlayer device increased drastically, while the fill factor (FF) decreased rather than flat-type interlayer device. So, an additional flat-type Zinc oxide (ZnO) layer with 1% vol. ethylene glycol (EG) added as an additive between the line-patterned ZnO layer and the ITO electrode was fabricated. The addition of EG in ZnO precursor has reported that the oxygen molecules in EG passivate the surface defects of ZnO and alters its electron affinity of ZnO. As a result, the power conversion efficiency (PCE) of the line-patterned devices introduced an additional flat-type ZnO layer and a ZnO precursor with 1% vol. EG was enhanced from 6.5% to 7.6%.

Nanocomposite of ZnO with montmorillonite for removal of lead and copper ions from aqueous solutions

Abstract The clay minerals montmorillonite (MMT) was combined with ZnO to form efficient nanocomposite which was used as an adsorbent. Zinc oxide nanoparticles (ZnO-NP) were successfully incorporated into the layers of montmorillonite by green simple heat method using zinc nitrate and sodium alginate as zinc oxide precursor and stabilizer respectively. The XRD and FESEM measurements revealed the presence of ZnO nanoparticles with hexagonal wurtzite structure in the ZnO/MMT nanocomposites. The role of the ZnO in enhancing the adsorption efficiency of the ZnO/MMT nanocomposite for the removal of copper and lead ions from aqueous solutions was investigated. The effects of different parameters such as contact time, dosage, initial concentration, and pH were investigated. Kinetics of adsorption were studied using pseudo-first-order and pseudo-second order. The efficiency of the nanocomposites was studied by Langmuir and Freundlich isotherms. The material showed high efficiency in a wide pH range, for the adsorption of Pb and Cu ions. Kinetic studies showed that the adsorption followed the pseudo-second-order and equilibrium best described by Langmuir isotherm. The regeneration results show that the nanocomposites can be utilized for at least three times because of its stability and durability. Thus, it can serve as a promising adsorbent for the removal of copper and lead ions from aqueous solutions.

A Novel Synthesis of Zinc Borates from a Zinc Oxide Precursor via Ultrasonic Irradiation.

In this study, zinc borate hydrate (Zn3B6O12 · 3.5H2O) was synthesized from zinc oxide (ZnO) and boric acid (H3BO3) via a novel method of ultrasonic irradiation. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR) and Raman spectroscopy were used to characterize the synthesized products. Scanning electron microscopy (SEM) was used to determine the effects of reaction time and reaction temperature on the morphology of the products. Thermal dehydration kinetics were studied using thermal gravimetry and differential thermal gravimetry analysis (TG/DTA). The Doyle and Kissinger non-isothermal kinetic methods were used to analyse the TG/DTA data. The XRD results confirmed the successful synthesis of Zn3B6O12 · 3.5H2O at a range of reaction temperatures and times. Additionally, FT-IR and Raman analysis of the products identified peaks specific to zinc borate. Using the methods of Doyle and Kissinger, the activation energies of thermal dehydration of zinc borate were found to be 341.61 kJ/mol and 390.17 kJ/mol, respectively.

Low Temperature Reaction of Molecular Zinc Oxide Precursors in Ionic Liquids Leading to Ionogel Nanoparticles with Shape Anisotropy

The majority of particle synthesis methods are based on nucleation and growth processes in solvents. Whereas the role of capping agents has been investigated extensively regarding control particle size and shape, the unique role of the solvent is understood to a much lesser extent. Compared to other polar solvents, e.g. water, ionic liquids (ILs) are unique because their properties can be fine‐tuned precisely by appropriate choice and modification of cation and anion. This makes ILs also interesting for particle synthesis. We present the generation of zinc oxide (ZnO) in imidazolium ILs starting from molecular precursors. A hydrolytic, sol‐gel based synthesis route is suitable to achieve nanocrystalline ZnO. We find by in‐situ synchrotron wide angle X‐ray diffraction that in ILs an unusual ZnO phase with α‐boron nitride structure acts as an intermediate prior to crystallization of the thermodynamically stable Wurtzite. This special mechanism leads to organic‐inorganic hybrid IL/ZnO nanoparticles with plate‐like morphology. Because of the large content of IL embedded in the ZnO matrix the novel particles gain ionogel properties, e.g. ion conductivity probed by impedance spectroscopy.

Electrophoretic deposition of silica and its composite coatings on Ti-6Al-4V, and its in vitro corrosion behaviour for biomedical applications

Novel bioceramics have an intriguing role in implants and prostheses as surface protecting agents. These bioceramics have promising features such as biocompatible, bioactive, and corrosion-resistant natures. Among bioceramics, silica glass and its composite unravel its better desirability against corrosion and wear with interfacial bone bonding capability in physiological systems by nucleating calcium phosphates over the surface, thereby enhancing the osteoinductive property. In the current study, SiO2 and ZnO were obtained by processing silica and zinc oxide precursors at low temperature using low thermal volatilization sol-gel method. SiO2, ZnO, and its composite powders were characterized by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), and scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDAX). Electrophoretic deposition (EPD) was used for coating on Ti-6Al-4V for improved coating characteristics. In addition, the effect of additives such as iodine and Polyvinylpyrrolidone (PVP) on coating limits was also optimized. Thin-film XRD, Optical Microscopy, SEM-EDAX, Raman spectroscopy, and the scratch resistance test characterized the coating. Tafel polarization and electrochemical impedance spectroscopy (EIS) studies were also carried out to assess corrosion resistance behaviour of the coating. The results showed that the composite coating has greater corrosion resistance than uncoated Ti-6Al-4V. Furthermore, improved mechanical property with better scratch resistance was also observed. These observations showed that composite coating could be useful in biomedical applications.

Preparation of Flower-Like ZnO Nanoparticles by High-Gravity Assisted Ammonia Decomposition Method and Their Photoluminescence Properties

Zinc oxide (ZnO) nanoparticles with tunable particle size and photoluminescence (PL) properties were successfully prepared by a facile ammonia decomposition method in a rotating packed bed (RPB) reactor. The zinc-ammonia complex, generated from chemical process of zinc mineral, reacted with steam to precipitate the precursor of ZnO. It was found that both the particle size of ZnO and the precipitation rates of Zn strongly depended on the steam flow rate, high-gravity level, calcination temperature. The flower-like ZnO with primary particle size of ~45 nm had improved PL performance, which further confirmed the intensification of RPB reactor. Moreover, the results showed that the precipitation rate of Zn could reach up to 98% under the optimized conditions. It was believed that RPB reactors with well mass transfer and mixing performances, short preparation time and low energy consumption would be a promising device for the continuous preparation of nano-ZnO materials.

A New Precursor Route to Semiconducting Zinc Oxide

We demonstrate a new precursor route toward solution-processed films of the II–VI semiconductor zinc oxide (ZnO). Spray pyrolysis of aqueous solutions of the zinc salt zinc chloride (ZnCl2) onto a substrate heated to at least 250 °C gives films that are insoluble in water, display an absorption edge at 365 nm, and when electrically gated display thin film transistor characteristics similar to ZnO films derived via the established zinc acetate (ZnAc) precursor route; we, therefore, identify it as ZnO. Control experiments attempting spray pyrolysis of aqueous zinc sulfate solutions, and delayed pyrolysis of cold-sprayed and dried ZnCl2 films, do not lead to semiconducting films. Formation of ZnO from an aqueous Zinc salt requires the simultaneous presence of zinc ions, chloride ions, and water, at the time of pyrolysis. We, therefore, suggest that the actual ZnO precursor is the ZnCl x H2O(4– x ) species that forms when ZnCl2 dissolves in water [The Journal of Chemical Physics 39, 3436 (1963)]. The reported process is easy to upscale for large area ZnO coatings, e.g., on window panes for thermal control, as no organic solvent vapors are released.

Preparation of ZnO hybrid nanoparticles by ATRP

Zinc oxide (ZnO) is a wide bandgap semiconductor material that has attracted widespread interest as particle filler in polymer nanocomposite materials. However, its applications have been hindered by the limited dispersibility and surface-modification techniques. Herein, three distinct approaches for the synthesis of polymer-tethered ZnO hybrid materials are compared in terms of uniformity and yield of the particle-brush product: “grafting-from”, “grafting-onto”, and “grafted-copolymer template” methods. In the “grafting-from” method, pristine ZnO nanoparticles (NP) were first functionalized with atom transfer radical polymerization (ATRP) initiators followed by grafting-from process to form poly(methyl methacrylate) (PMMA) or poly(styrene-co-acrylonitrile) (PSAN) tethered polymer chains. In the “grafting-onto” method, PMMA-b-PAA (poly[acrylic acid]) and PSAN-b-PAA diblock copolymers were prepared and attached onto the surface of ZnO NPs using sonication bath. For the “grafted-copolymer template” method, PSAN-b-PtBA-Br (poly[tert-butyl acrylate]-Br) macroinitiators were crosslinked with divinylbenzene (DVB) to form PSAN-b-PtBA-PDVB core-shell star polymers. After hydrolysis to form PSAN-b-PAA-PDVB star polymers, the functional stars were used as polymer templates for the synthesis of ZnO NPs within the PAA-core of the stars. Core-shell molecular bottlebrushes with PAA-b-PS block-copolymer side chains were also used as anisotropic analogues of star template to prepared worm-like ZnO particles. Several ZnO precursors, zinc nitrite, zinc 2-ethylhexanoate, and zinc acetate were evaluated as precursors of ZnO. Conditions were identified that enable the synthesis of polymer-tethered ZnO with excellent size uniformity and dispersion characteristics using the star-template method.

Photoelectrochemical Water Splitting By Using a Porous ZnRh2O4 Photocathode Under Visible Light Irradiation and Significant Effect of Necking Treatment

Photoelectrochemical (PEC) water splitting utilizing semiconductor electrodes has attracted considerable attention as a potential means of converting solar energy into chemical energy in the form of usable hydrogen, which is a clean and renewable energy. To date, there have been many studies on the oxide-based photoanodes such as WO3,Fe2O3,and BiVO4,but there have been few reports on the oxide-based photocathodes. Examples of the latter include Cu2O, Rh-doped SrTiO3, and CaFe2O4 photocathodes, which are p−type oxide semiconductors with visible light responses. We have successfully developed a porous ZnRh2O4 electrode by an electrophoretic deposition method on a fluorine−doped tin oxide (FTO) substrate. In addition, we have investigated the PEC water splitting performance in a three−electrode configuration using a silver−silver chloride (Ag/AgCl) reference electrode and a Pt coil counter electrode under visible light irradiation (λ>420 nm). The electrolyte was 0.1 M Na2SO4 solution (pH 6). The electrolyte was stirred and purged with Ar gas for 30 min before measurement. The ZnRh2O4 electrode exhibited a cathodic photocurrent in response to irradiation of visible light, indicating that ZnRh2O4 is a p−type oxide semiconductor. The cathodic photocurrent of ZnRh2O4 was increased with an increase in the applied potential, and its photocurrent density reached –110 mA/cm2 at 0 V vs. RHE. The onset potential of ZnRh2O4 was ca. +1.20 V vs. RHE, which compares favorably with any p−type semiconductor oxide such as Cu2O (ca. +0.55 V vs. RHE), CaFe2O4 (+1.24 V vs. RHE), and CuBi2O4 (+1.05~1.1 V vs. RHE). For further improvement of the photocurrent, we attempted to do necking treatment over the ZnRh2O4 electrode by using a zinc oxide (ZnO) precursor solution. Since p−n heterojunction diodes composed of p–type ZnRh2O4 and n–type ZnO have been reported, the following two significant effects was anticipated by ZnO necking treatment: (1) bridging ZnRh2O4 particles with ZnO for smooth carrier conduction, and (2) a depletion layer formed at the ZnRh2O4/ZnO p–n junction could also assist in extracting photo–generated electrons from ZnRh2O4. Actually, the photocurrent of ZnO–treated ZnRh2O4 photocathode was enhanced to ca. two−fold higher than that of the bare electrode. The incident photon to charge carrier efficiencies of the ZnRh2O4 and ZnO–treated ZnRh2O4 photocathodes were calculated to be ca. 8% and ca. 13% at 400 nm, respectively, at 0 V vs. RHE in aqueous Na2SO4 solution. Evolved H2 gas was detected by an on−line gas chromatograph (GC) with a thermal conductivity detector (Agilent Technology Co. MicroGC) equipped with MS−5A column. The hydrogen evolution from ZnRh2O4 and ZnO–treated ZnRh2O4 photocathodes was confirmed with the faradaic efficiency of ca. 77% and ca. 85%, respectively. We will describe the PEC performance of ZnRh2O4 and ZnO–treated ZnRh2O4 photocathodes in poster session, and discuss the mechanism of photocurrent improvement by ZnO necking treatment.

ENHANCED ACTIVITY OF C3N4 WITH ADDITION OF ZnO FOR PHOTOCATALYTIC REMOVAL OF PHENOL UNDER VISIBLE LIGHT

Phenol is a stable and hazardous compoundthat is commonly found as an industrial effluent 1. Phenol can be treated by photocatalysis using ZnO as a photocatalyst'' 3. Unfortunately, the use of zinc oxide (ZnO) in photocatalysis is limited due to the photocorrosion effect and poor response to the visible light, Various methods have been reported to improve the performance of ZnO,such as the use of carbon nitride (C3N4) to suppress the photocorrosion and improve the absorption in the visible light regions. It was reported that the ZnO-C3N4could be prepared by mixing the powder ZnO with C3N4that was dispersed in methanol, followed by drying process under nitrogen atmospheres. In the present study, a series of ZnO-C3N4was prepared bya simplermethod, which was impregnationof zinc oxide precursor on the C3N4, followed by calcination process. The effect of zinc to carbon ratio (Zn/C) on the properties and photocatalytic activity was examined.XRD patterns of the samples revealed that as the Zn/C ratio increased, the intensity of diffraction peaks for ZnO also increased but the intensity for C3N4 decreased. All the prepared composite materials have an extended absorption band in the visible light region due to the presence of C3N4, as supported by DR-UV Vis spectra. The prepared ZnO-C3N4 composites were further investigated in the photocatalytic removal of phenol under visible light irradiation for 5 hours. All ZnO-C3N4 samples showed higher activity than the bare ZnO (Figure 1). The ZnO-C3N4 with Zn/C ratio of 1 mol% showed the highest photocatalytic activity for removal of phenol among all the samples. The high activity observed on the ZnO-C3N4 would be due to the role of C3N4 to suppress electron-hole recombination and extend the absorption ofZnO in the visible light region.