Deposition Of ZnO Research Articles

Formation of zinc tetraammine difluoride and dinitrate and conversion to zinc oxide and zinc hydroxyfluoride under ambient conditions

The zinc tetraammine complexes [Zn(NH3]4]F2 (ZAF) and [Zn(NH3]4](NO3)2 (ZAN) have been isolated from methanolic ammonia and characterized by single crystal X-ray diffraction and Raman spectroscopy. As determined from Raman data, the tetrahedral structure of the zinc tetraammine cation complex is sustained in solutions that contain high concentrations of ammonia. Dilution of ZAF or ZAN solutions in bulk water results in the deposition of ZnO as determined by X-ray powder diffraction (XRD). Lower dilution, as when aqueous ZAF is applied to wet surfaces, results in Zn(OH)F deposition as identified by XRD. These mineral products are readily obtained from zinc tetraammine solutions under ambient conditions and lend themselves to biomedical and materials applications.

Ionic liquid-functionalized ZnO nanomaterial: Multifunctional additives enhancing tribological performance and corrosion resistance in ester oil

A multifunctional nanomaterial (ZnO-IL), comprising zinc oxide modified with corrosion-resistant ionic liquid groups, was designed and synthesized. It was used as an additive in bis(2-ethylhexyl) sebacate (DIOS) to evaluate its tribological and corrosion resistance properties, and compared with the commercial additive sulfurized isobutylene (SIB). ZnO-IL exhibited good solubility and thermal stability in DIOS. Lubricants containing ZnO-IL showed excellent anti-wear performance under various loads and temperatures. Its deposition on metal surfaces and the synergistic action of benzotriazole groups in the anions effectively prevented corrosion on the surfaces of metal friction pairs, thereby addressing the challenge of friction pair corrosion caused by the hydrolysis of ester-based oils. The ZnO-IL nanomaterial rapidly formed an organic-inorganic multilayer adsorption film on metal surfaces through electrostatic interactions. During friction, a boundary lubrication film composed of ZnO deposition and friction chemical reaction films was formed, thereby avoiding direct metal contact, reducing contact pressure, and exhibiting outstanding friction reduction and anti-wear properties.

Atomic Layer Deposition of Nickel Using Ni(dmamb)2 and ZnO Adhesion Layer Without Plasma

In this study, a novel deposition technique that utilizes diethylzinc (C4H10ZnO) with H2O to form a ZnO adhesion layer was proposed. This technique was followed by the deposition of vaporized nickel(II) 1-dimethylamino-2-methyl-2-butoxide (Ni(dmamb)2) and H2 gas to facilitate the deposit of uniform layers of nickel on the ZnO adhesion layer using atomic layer deposition. Deposition temperatures ranged from 220 to 300 °C. Thickness, composition, and crystallographic structure results were analyzed using spectroscopic ellipsometry, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), respectively. An average growth rate of approximately 0.0105 angstroms per cycle at 260 °C was observed via ellipsometry. Uniform deposition of ZnO with less than 1% of Ni was displayed by utilizing the elemental analysis function via SEM, thereby providing high-quality images. XPS revealed ionizations consistent with nickel and ZnO through the kinetic and binding energies of each detected electron. XRD provided supplemental information regarding the validity of ZnO by exhibiting crystalline attributes, revealing the presence of its hexagonal wurtzite structure.

Electroless ZnO Deposition on Mg-Al Alloy for Improved Corrosion Resistance to Marine Environments

Electroless ZnO (≈900 nm) was deposited on the surface of an Mg-Al alloy (AM60) to reduce its degradation in the marine environment. Uncoated and coated ZnO samples were exposed to an SME simulated marine solution for up to 30 days. The AFM and optical images revealed that the corrosion attack on the ZnO-AM60 surface was reduced due to an increase in the surface hydrophobicity of the ZnO coating (contact angle of ≈91.6°). The change in pH to more alkaline values over time was less pronounced for ZnO-AM60 (by ≈13%), whereas the release of Mg2+ ions was reduced by 34 times, attributed to the decrease in active sites on the Mg-matrix provided by the electroless ZnO coating. The OCP (free corrosion potential) of ZnO-AM60 shifted towards less negative values of ≈100 mV, indicating that electroless ZnO may serve as a good barrier for AM60 in a marine environment. The calculated polarization resistance (Rp), based on EIS data, was ≈3 times greater for ZnO-AM60 than that of the uncoated substrate.

Stearic Acid Modified Nano-ZnO Superhydrophobic Coating for Steel Mesh

Abstract To mitigate the detrimental effects of water on metal textiles, hydrophobic modification of such materials has garnered significant attention. However, traditional approaches often rely on complex procedures or costly materials, limiting their widespread application. Herein, we present a facile method for fabricating a superhydrophobic coating on steel mesh, and characterize the properties of the modified material. Initially, the surface of the dry steel mesh is uniformly coated with nano-ZnO crystals using a liquid deposition technique at room temperature. Subsequently, stearic acid is employed to hydrophobically modify the ZnO crystals, yielding a ZnO-based superhydrophobic coating. The influence of ZnO concentration and deposition duration on the surface crystal structure, hydrophobicity, and abrasion resistance is investigated. X-ray diffraction (XRD) analysis is performed to study the surface groups before and after hydrophobic modification, while static contact angle measurements are used to assess the hydrophobic properties of the coated surface. Remarkably, even after abrasion with 1000-mesh sandpaper, the superhydrophobic properties of the steel mesh with an optimized ZnO concentration decrease by only 4%. This simple, cost-effective, and highly efficient preparation method holds promising potential for applications in related fields.

Innovative Photocatalyst Design: Advancing ZnO/MIL‐100(Fe) through Atomic Layer Deposition in Hydrogen Evolution

This study investigates the integration of ZnO nanoparticles into the MIL‐100(Fe) framework using atomic layer deposition (ALD) at atmospheric pressure, varying ALD cycles from 0.5 to 2. The goal is to enhance the photocatalytic efficiency of MIL‐100(Fe) in water splitting under ultraviolet light. Among the composites, the ZnO/MIL‐100(Fe) synthesized with a 1‐cycle ALD process stands out, demonstrating superior hydrogen evolution rates (8465 μmol·g⁻¹·h⁻¹) and improved durability, surpassing the base MIL‐100(Fe) in repeated PWS trials. Comprehensive characterization using various analytical techniques, including BET analysis, DRS, EDS, SEM, TEM, XRD, FT‐IR, Raman, and PL, sheds light on the structural, chemical, and optical properties of the MIL‐100(Fe)/ZnO materials, confirming successful ZnO deposition within the MIL‐100(Fe) structure. Furthermore, the enhancement in photocatalytic activity is associated with increased absorption intensity and reduced trap sites, implying improved charge carrier dynamics and separation. The inclusion of ZnO not only reduced the bandgap of composites, but also influences the photoluminescence characteristics significantly, leading to a reduction in non‐radiative recombination and enhancing the availability of photogenerated electrons for photocatalytic reactions. Specifically, the increased photoluminescence intensity observed with ZnO/MIL‐100(Fe) composites indicates a higher defect density, which corresponds to more active sites for photocatalysis.

Optimized electrophoretic zinc oxide coating on SS316L with enhanced hardness and scratch resistance

The major issues in electrophoretic deposition of ZnO coating on SS316L are lack of adhesive strength, control of electrophoretic mobility, and the presence of cracks in the coating. The novelty of the present study is mainly focused on optimizing the electrophoretic deposition parameters by varying the concentration of the ZnO NPs (1.0 g/L and 1.5 g/L) and the applied voltages (30 V and 40 V) to minimize these coating defects. The impact of nanoparticle concentrations and applied voltages on the morphology, roughness, phase composition, functional groups, hardness, surface energy, and scratch resistance of ZnO coatings was analyzed. Various deposition conditions produced different crystal sizes ranging from 16 to 24 nm. Among the deposition conditions, the ZnO-3 coating demonstrated an increased crystal size with decreased microstrain. However, a higher applied voltage of 40 V in the ZnO-3 coating significantly increased the electrophoretic mobility of the NPs, leading to the agglomeration of the NPs and the formation of larger crystals. Furthermore, morphological analysis confirmed uniform distribution and higher deposition rates in the ZnO-2 coating. The ZnO-2 coating deposited at a concentration of ZnO NPs (1.5 g/L) and a lower applied voltage (30 V), exhibited higher coating hardness (216 HV), lower surface roughness (0.207 µm), low surface energy, and better adhesive strength than the other three ZnO coatings. Thus, the optimized electrophoretic coating of ZnO-2 on SS316L emerged as a solution to reduce the cracks, improve the adhesion with better control over electrophoretic mobility.

Sputter deposition of ZnO–AlN pseudo-binary amorphous alloys with tunable band gaps in the deep ultraviolet region

ZnO–AlN pseudo-binary amorphous alloys (a-ZAON hereinafter) with tunable band gaps in the deep ultraviolet (DUV) region have been synthesized using magnetron sputtering. The miscibility gap between ZnO and AlN has been overcome using room-temperature sputtering deposition, leveraging the rapid quenching abilities of sputtered particles to fabricate metastable but single-phase alloys. X-ray diffraction patterns and optical transmittance spectra revealed that the synthesized films with chemical composition ratios of [Zn]/([Zn] + [Al]) = 0.24–0.79 likely manifested as single-phase of a-ZAON films. Despite their amorphous structures, these films presented direct band gaps of 3.4–5.8 eV and thus high optical absorption coefficients (105 cm−1). Notably, the observed values adhered to Vegard’s law for crystalline ZnO–AlN systems, implying that the a-ZAON films were solid solution alloys with atomic-level mixing. Furthermore, atomic force microscopy analyses revealed smooth film surfaces with root-mean-square roughness of 0.8–0.9 nm. Overall, the wide-ranging band gap tunability, high absorption coefficients, amorphous structures, surface smoothness, and low synthesis temperatures of a-ZAON films position them as promising materials for use in DUV optoelectronic devices and power devices fabricated using large-scale glass and flexible substrates.

Optimizing the photocatalytic properties of macroporous geopolymer foam: Influence of SILAR-technique synthesis conditions

Macroporous cross-linked materials such as 3D honeycomb foams are used as substrates for heterogeneous photocatalysis. They offer a number of interesting properties. They are highly open-porosity substrates, guaranteeing optimum mass and radiation transfer, making them ideal for photo-conversion applications such as photo-oxidation or photo-reduction, which take place in photo-reactors for pollutant degradation or solar fuel production. Many cross-linked supports such as polymeric and metallic foams studied in the literature have revealed photocatalytic capacities similar to those obtained for the catalyst nanoparticle suspensions used as a reference. To reduce the production costs of this type of material, geopolymers, widely used in civil engineering, offer a wide range of properties suitable for shaping cellular foams. In addition to their low cost and mechanical properties, it is also possible to impart porous properties and modulate their characteristics according to the synthesis operating conditions so as to elaborate macroporous cellular foams. In this study, we propose to investigate the photocatalytic properties of honeycomb geopolymer foams coated with a catalyst: ZnO. To achieve ZnO deposition, the SILAR technique was applied by modifying the key synthesis operating conditions, i.e. precursor concentration and the number of quenching cycles applied. The results obtained make it possible to define the optimum operating conditions (pH, temperature) and, above all, the number of cycles and precursor concentration required to obtain the best photocatalytic efficiency. These innovative and promising materials, little studied in the literature, are prime candidates for solar photo-conversion applications.

A novel Cu-doped ZnO confined structure: Precisely preparation, and sensitization mechanism for ppb-level H2S gas detection

It is still highly desired and challengeable to design H2S sensor with high selectivity and sensitivity due to its toxicity and new application in biomarkers like monitoring halitosis. Here, we reported a novel confined structure as highly sensitive and selective H2S gas sensor. The sensing material was prepared with a HKUST-1 templated method by atomic layer deposition (ALD) ZnO decorated on HKUST-1 and calcination. The gas sensor exhibits a high gas sensitivity (Ra/Rg = 2.67 @ 2 ppm) with excellent selectivity to H2S. Furthermore, the obtained sensor shows ppb-level detection ability (Ra/Rg = 1.13 @ 0.1 ppm). Apart from releasing electrons by the oxidization of H2S on oxygen vacancies with adsorbed oxygen species O2− on ZnO surface (Langmuir-Hinshelwood mechanism), the Cu was proved to be the active sites, and would react with surficial S species. The suggestion was confirmed by operando XAS (X-ray adsorption spectrum) measurements combined with DFT calculations (Mars-van Krevelen mechanism). This work provides valuable insights for developing efficient sensing materials and understanding the sensing mechanism.

Low‐Temperature Dual‐Material Area‐Selective Deposition: Molybdenum Hexafluoride‐Mediated SiO2 Fluorination/Passivation for Self‐Aligned Molybdenum/Metal Oxide Nanoribbons

AbstractArea‐selective deposition (ASD) is a forefront nanopatterning technique gaining substantial attention in the semiconductor industry. While current research primarily addresses single‐material ASD, exploring multi‐material ASD is essential for mitigating complexity in advanced nanopatterning. This study describes molybdenum hexafluoride (MoF6)‐mediated fluorination/passivation of the hydroxylated SiO2 (SiO2‒OH) at 250 °C as a new method to pacify nucleation during subsequent ZnO and TiO2 atomic layer deposition (ALD). In contrast, Al2O3 ALD is not passivated on the fluorinated SiO2 (SiO2‒F). The study further shows that Mo ALD using MoF6 and silane (1 wt% SiH4 in Ar) selectively proceeds on hydrogen‐terminated Si (Si‒H), whereas SiO2‒OH becomes fluorine‐passivated without observable Mo deposition. This enables subsequent ZnO and TiO2 ASD on Mo versus SiO2‒F, as confirmed by X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and scanning transmission electron microscopy (STEM). Proposed growth and inhibition mechanisms highlight the importance of the metal oxide precursor in achieving selectivity. Taken together, self‐aligned Mo/ZnO and Mo/TiO2 nanoribbons are demonstrated on coplanar nanoscale Si‒H/SiO2‒OH patterns by sequentially integrating two individual ASD processes: 1) Mo ASD on Si‒H versus SiO2‒OH; and 2) ZnO or TiO2 ASD on Mo versus SiO2‒F. This work highlights the potential for this approach in new ASD systems.

Nanoarchitectonics of Nanocellulose Filament Electrodes by Femtosecond Pulse Laser Deposition of ZnO and In Situ Conjugation of Conductive Polymers.

Electroactive filament electrodes were synthesized by wet-spinning of cellulose nanofibrils (CNF) followed by femtosecond pulse laser deposition of ZnO (CNF@ZnO). A layer of conducting conjugated polymers was further adsorbed by in situ polymerization of either pyrrole or aniline, yielding systems optimized for electron conduction. The resultant hybrid filaments were thoroughly characterized by imaging, spectroscopy, electrochemical impedance, and small- and wide-angle X-ray scattering. For the filaments using polyaniline, the measured conductivity was a result of the synergy between the inorganic and organic layers, while the contribution was additive in the case of the systems containing polypyrrole. This observation is rationalized by the occurrence of charge transfer between ZnO and polyaniline but not that with polypyrrole. The introduced conductive hybrid filaments displayed a performance that competes with that of metallic counterparts, offering great promise for next-generation filament electrodes based on renewable nanocellulose.

Linearization and characterization of the Wemple – DiDomenico model of ZnO/Ni/ZnO tri-layer thin films prepared by ALD and DC magnetron sputtering

Our present work is devoted to analyzing the influence of Ni on the optical properties of ZnO thin films deposited on glass and Si (100) substrates, with the use of ALD for ZnO deposition and DC magnetron sputtering for Ni interlayer deposition. The compositions as well as the crystalline structure of various multilayer thicknesses of Ni (10, 30, 50, and 70 nm), that sandwiched between ZnO Films (70 nm), before being optically characterized, were carried out by the X-ray diffraction (XRD). Based on the XRD results, the crystallite size was increased with the increase of the Ni interlayer concentration. Additionally, the material densities for both ZnO and Ni show the expected close-to-bulk values in all formations, where the large cavities between atoms, on the films make the dislocation density become smaller and the surface roughness values decrease as well, with the increase of Ni interlayer concentration. Different optical properties were observed for different Ni content. The optical absorption coefficient (α), refractive index (n), and extinction coefficient (k) have been deduced from the transmission T(λ) and absorption measurements A(λ). The optical energy gap Egoptare estimated from Tauc΄s extrapolation procedure and the Kubelka-Munk approach. The static refractive index (no), the oscillator energy (Eo), and the dispersion energy (Ed) are calculated using the Wemple-DiDomenico (WDD) theoretical model. Analysis of third-order nonlinear optical properties in crystalline ZnO/Ni/ZnO are being detailed. These promising results imply that the high-quality films produced by ALD, show how the insertion of Ni could enhance the quality of the optical properties of ZnO films.

Performance Comparison of Si and GaAs Solar Cell due to Deposition of ZnO and SiO2 Antireflection Coating Layer

Performance Comparison of Si and GaAs Solar Cell due to Deposition of ZnO and SiO2 Antireflection Coating Layer

Efficient degradation of naproxen in wastewater using Ag-deposited ZnO nanoparticles anchored on a house-of-cards-like MFI-type zeolite: Preparation and physicochemical evaluations of the photocatalyst

We utilized Pr6-diquat-5 as an organic structure-directing agent (OSDA) to synthesize hierarchically intergrown ZSM-5 (HI-ZSM-5) as a catalytic support. ZnO particles were deposited onto HI-ZSM-5 via precipitation to remediate naproxen (NPX) in wastewater, while Ag was photo-deposited onto ZnO to prevent electron-hole pair recombination. XRD analysis revealed crystalline structures and particle sizes influenced by synthesis temperatures, and FT-IR confirmed ZnO and Ag deposition onto HI-ZSM-5 surfaces. Based on N2 adsorption-desorption isotherms, all samples exhibited Type I and IV isotherms with H4-type hysteresis loops, indicating the presence of both micro- and mesopores within HI-ZSM-5. XPS analysis confirmed the presence of peaks indicating Zn in ZnO and metallic Ag interacting with ZnO. TEM analysis identified aggregated Ag/ZnO nanoparticles in the photocatalysts, while EDX confirmed uniform element distribution. FE-SEM images revealed a uniform distribution of ZnO and Ag on HI-ZSM-5 with “house-of-cards” morphologies. PL analysis indicated reduced electron-hole recombination and an extended lifespan. NPX photodegradation experimental results showed that the reaction rate constant of the 3 %AZ composite was 2.8 times higher than that of ZnO/HI-ZSM-5 (0.0163 vs. 0.059 min−1, respectively). Evaluation of influential operating parameters demonstrated 90.8 % elimination of NPX under optimum conditions: a catalyst dosage of 1.5 g L−1 at pH 5 within 120 min. The impact of common anions on NPX decontamination and the catalyst's capability for COD and TOC removal (up to 62.6 and 53.4 %, respectively) was also discussed. The 3 %AZ optimum catalyst could be recycled for 5 cycles with remarkable reusability, maintaining 80.1 % removal efficiency after five regeneration cycles.

Advanced Photodegradation of Azo Dye Methyl Orange Using H2O2-Activated Fe3O4@SiO2@ZnO Composite under UV Treatment.

The Fe3O4@SiO2@ZnO composite was synthesized via the simultaneous deposition of SiO2 and ZnO onto pre-prepared Fe3O4 nanoparticles. Physicochemical methods (TEM, EDXS, XRD, SEM, FTIR, PL, zeta potential measurements, and low-temperature nitrogen adsorption/desorption) revealed that the simultaneous deposition onto magnetite surfaces, up to 18 nm in size, results in the formation of an amorphous shell composed of a mixture of zinc and silicon oxides. This composite underwent modification to form Fe3O4@SiO2@ZnO*, achieved by activation with H2O2. The modified composite retained its structural integrity, but its surface groups underwent significant changes, exhibiting pronounced catalytic activity in the photodegradation of methyl orange under UV irradiation. It was capable of degrading 96% of this azo dye in 240 min, compared to the initial Fe3O4@SiO2@ZnO composite, which could remove only 11% under identical conditions. Fe3O4@SiO2@ZnO* demonstrated robust stability after three cycles of use in dye photodegradation. Furthermore, Fe3O4@SiO2@ZnO* exhibited decreased PL intensity, indicating an enhanced efficiency in electron-hole pair separation and a reduced recombination rate in the modified composite. The activation process diminishes the electron-hole (e-)/(h+) recombination and generates the potent oxidizing species, hydroxyl radicals (OH˙), on the photocatalyst surface, thereby playing a crucial role in the enhanced photodegradation efficiency of methyl orange with Fe3O4@SiO2@ZnO*.

Flower-like ZnO modified TiO2@Ti3C2Tx composite for efficient adsorption of malachite green and oil-water separation

The intensification of industrial production has led to a sharp increase in the discharge of toxic organic chemicals and wastewater from printing and dyeing industry. In this study, flower-like ZnO modified TiO2@Ti3C2Tx composites (ZnO/TiO2@Ti3C2Tx) were prepared by in-situ oxidation solvothermal method from zinc nitrate hexahydrate and tetramethylammonium hydroxide intercalated Ti3C2Tx. During the solvothermal processes, sodium hydroxide acted as an etchant to further exfoliated the accordion-like Ti3C2Tx into single or few-layer; and at the same time, TiO2 was formed in-situ on the surface of Ti3C2Tx with simultaneous deposition of flower-like ZnO. The layer structural Ti3C2Tx facilitates the loading and dispersion of ZnO and TiO2 on its surface. After the in-situ oxidation by solvothermal method, TiO2 was evenly distributed on the surface of Ti3C2Tx, adjusting the functional groups on the surface of the ZnO/TiO2@Ti3C2Tx composite, and improving its adsorption performance. ZnO/TiO2@Ti3C2Tx can be used as an efficient adsorbent for malachite green with a high maximum adsorption capacity of 1232.7 mg g−1, which is higher than that of TiO2@Ti3C2Tx (628.57 mg g−1). Moreover, a superhydrophilic and underwater superoleophobic ZnO/TiO2@Ti3C2Tx@PU sponge was prepared by loading ZnO/TiO2@Ti3C2Tx onto polyurethane (PU) sponge. The introduction of ZnO enhances the surface roughness of the ZnO/TiO2@Ti3C2Tx@PU sponge, which can effectively separate six oil-water mixtures, and has a high separation flux of 171784 L m−2 h−1 and separation efficiency of 99.6% for cyclohexane-water mixture.

Surface functionalization of 3D printed poly-ε-caprolactone by ultrashort laser mirostructuring and ZnO nanolayer deposition

Due to its mechanical properties and good biocompatibility, polycaprolactone (PCL) is a promising material for bone tissue regeneration. However, a major limitation to its use remains the lack of inherent antimicrobial properties and its susceptibility to bacterial colonisation and biofilm formation. A potent strategy for overcoming such issues is surface functionalisation at micro and nano level, which can have a great impact on cell-surface interaction without affecting the integrity of the material. This study presents a novel methodology for surface modification of polymers combining ultrashort laser microstructuring and atomic layer deposition of ZnO. For this purpose, the surface of 3D printed PCL scaffolds was treated with a femtosecond laser (λ=800 nm; τ=75 fs) in order to develop parallel microchannels onto which ZnO nanolayers were further deposited. The presence of ZnO on the laser structured and unstructured scaffolds was detected by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX). Both methods confirmed the successful layering as EDX further highlighted a trend that ZnO built up substantially more at the bottom of the microchannels rather than at the top of them. The obtained results would allow proceeding to the next step of the study – investigating the antimicrobial effect of the developed interfaces.

Enhanced photoelectrochemical water splitting using carbon cloth functionalized with ZnO nanostructures via polydopamine assisted electroless deposition.

ZnO nanorods (ZnO-nr) have been widely studied as a promising nanomaterial for photoelectrochemical water splitting. However, almost all prior studies employed planar electrodes. Here, we investigated the performance of ZnO nanorods on a fibrous carbon cloth (CC) electrode, which offers a larger surface area for functionalization of photocatalysts. ZnO nanorods and Ni nanofilm were deposited on carbon cloth substrates for investigation as the photoanode and cathode of a photoelectrochemical water splitting setup, respectively. The use of polydopamine in the electroless deposition of ZnO ensured a uniform distribution of nanorods that were strongly adherent to the microfiber surface of the carbon cloth. Compared to ZnO nanorods grown on planar ITO/glass substrates, the CC-based ZnO photoanodes exhibited smaller onset potentials (1.1 VRHEvs. 1.8 VRHE), ∼40× larger dark faradaic currents at 1.23 VRHE and 5.5×-9× improvement in photoconversion efficiencies. Ni/CC cathodes were also found to exhibit a lower overpotential@10 mA cm-2 than Ni/Cu by 90 mV. The photocurrent obtained from the ZnO-nr/CC anode was highly stable across an hour and the peak current decreased by only 5% across 5 cycles of illumination, compared to 72% for the planar ZnO-nr/ITO anode. However, the response of the CC-based setups to changes in the illumination conditions was slower, taking hundreds of seconds to reach peak photocurrent, compared to tens of seconds for the planar electrodes. Using cyclic voltammetry, the double-layer capacitance of the electrodes was measured, and it was shown that the increased efficiency of the ZnO-nr/CC anode was due to a 2 order of magnitude increase in electrochemically active sites provided by the copious microfiber surface of the carbon cloth.

Improved flux and anti-fouling performance of a photocatalytic ZnO membrane on porous stainless steel substrate for microalgae harvesting

Photocatalytic self-cleansing ZnO membranes were developed and used for pre-concentrating microalgae solution prior to harvesting. The inorganic membranes were fabricated via two different methods: (i) direct deposition of ZnO onto a porous stainless steel substrate and (ii) post-growth oxidation of a deposited metallic Zn layer. Systematic surface characterisation revealed a thin layer of homogeneous, crystalline ZnO on the porous membrane. Direct ZnO deposition resulted in a thicker layer with higher UV light absorption capability compared with the post-growth oxidization method. The ZnO coating made the membrane surface highly hydrophilic, resulting in two-fold increase in water permeance compared to the base stainless steel substrate. The high hydrophilicity of the ZnO-coated membrane also led to an increase in the permeate flux of the microalgae solution by up to 100%, making it suitable for microalgae pre-concentration. Upon UV light irradiation, the ZnO membrane demonstrated self-cleansing capability due to the photocatalytic activity of the ZnO coating layer. After 30 min of UV irradiation, the ZnO membrane could achieve 60% permeance recovery after complete fouling. No recovery was observed with the base stainless steel membrane, which was used as the control.