MOF assisted synthesis of a Ho2O3/CNT nanocomposite photocatalyst for organic pollutants degradation

In this work, a holmium oxide (Ho₂O₃/CNT) photocatalysts were successfully synthesized through a MOF assisted route for the first time. The effects of the morphology and purity on the photocatalytic behavior of the products, were investigated by determining various physicochemical properties. The Ho₂O₃/CNT nanocomposite was systematically analyzed by powder X-ray diffraction (P-XRD), transmission electron microscopy (TEM), ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy studies. The Ho₂O₃ derived from a MOF assisted synthetic route using Ho(NO₃)₃·5H₂O and terephthalic acid with a 1:1 M ratio at a temperature of 750 °C for 3 h prove the most advantageous, 98% degradation of 20 mg/L aqueous tetracycline pollutant was observed within 60 min. The elevated photocatalytic activity was mainly attributable to the unique synthetic route, improved crystallinity, wide UV-light absorption rate and excellent adsorption capabilities of CNT, as well as enhanced oxygen deficiency. The photocatalytic results confirm that the Ho₂O₃/CNT nanocomposite is an efficient photocatalyst for the degradation of toxic tetracycline pollutant and is thus suitable for use in environmental remediation.     

Preparation of graphene film decorated TiO2 nano-tube array photoelectrode and its enhanced visible light photocatalytic mechanism

Graphene film decorated TiO₂ nano-tube array (GF/TiO₂ NTA) photoelectrodes were prepared through anodization, followed by electrodeposition strategy. Morphologies and structures of the resulting GF/TiO₂ NTA samples were characterized by scanning electrons microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. In addition, the optical and photoelectrochemical properties were investigated through UV–visible light diffuse reflection spectroscopy, photocurrent response and Mott–Schottky analysis. Furthermore, the photodecomposition performances were investigated through yield of hydroxyl radicals and photocatalytic (PC) degradation of methyl blue (MB) under visible light irradiation. It was found that GF/TiO₂ NTA photoelectrode exhibited intense light absorption both in UV light and visible region, higher transient photoinduced current of 0.107 mA cm⁻² and charge carrier concentration of 0.84 × 10¹⁹ cm⁻³, as well as effective PC performance of 65.9% for the degradation of MB. Furthermore, contribution of several reactive species to the PC efficiency of GF/TiO₂ NTA photoelectrode was distinguished. Moreover, the enhanced visible light PC mechanism was proposed and confirmed in detail.     

Preparation and characterization of TiO2 photocatalysts by Fe doping together with Au deposition for the degradation of organic pollutants

Fe³⁺ doped TiO₂ deposited with Au (Au/Fe–TiO₂) was successfully prepared with an attempt to extend light absorption of TiO₂ into the visible region and reduce the rapid recombination of electrons and holes. The samples were characterized by X-ray diffraction (XRD), N₂ physical adsorption, Raman spectroscopy, atomic absorption flame emission spectroscopy (AAS), UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra. The photocatalytic activities of the samples were evaluated for the degradation of 2,4-chlorophenol in aqueous solutions under visible light (λ > 420 nm) and UV light irradiation. The results of XRD, XPS and high-resolution transmission electron microscopy (HRTEM) analysis indicated that Fe³⁺ substituted for Ti⁴⁺ in the lattice of TiO₂, Au existed as Au⁰ on the surface of the photocatalyst and the mean particle size of Au was 8 nm. Diffuse reflectance measurements showed an extension of light absorption into the visible region for Au/Fe–TiO₂, and PL analysis indicated that the electron–hole recombination rate has been effectively inhibited when Au deposited on the surface of Fe-doped TiO₂. Compared with Fe doped TiO₂ sample and Au deposited TiO₂ sample, the Au/Fe–TiO₂ photocatalyst exhibited excellent visible light and UV light activity and the synergistic effects of Fe³⁺ and Au was responsible for improving the photocatalytic activity.     

Optoelectronic properties of In-doped SnS thin films

Nanostructured un- and In-doped SnS thin films were deposited on fluorine-doped tin oxide (FTO) substrates via an electrochemical deposition technique. The deposited thin films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS), photoluminescence (PL) spectroscopy and UV–visible spectroscopy. The XRD patterns demonstrated that all deposited thin films are made of polycrystalline SnS particles. The AFM images illustrated a distinct change in the surface topography of the SnS thin films due to In-doping. The PL spectra showed two blue emission peaks and a green emission peak for all samples. Also, they highlighted a PL peak for the In-doped thin films. The incorporation of In-dopant leads to enhance in the optical absorption of SnS lattice. The optical energy band gap (E_g) of the deposited thin films was estimated using UV–vis spectroscopy, which indicated that In-doping decreases the E_g value of SnS thin films by creating defect levels. The photocurrent results demonstrated a higher photocurrent response and photocurrent amplitude for the In-doped SnS samples relative to the un-doped SnS thin film. The Mott–Schottky analysis revealed p-type conductivity for all samples. In addition, the carrier concentration of SnS was increased after In doping. The EIS spectra declared that In-doping improves the rate of charge transfer for SnS thin films. The charge transfer resistance of In-doped SnS decreased compared to the undoped SnS thin film. Finally, according to the J-V characteristics, the conversion efficiency of the In-doped SnS thin films was higher than that of the un-doped SnS sample. Therefore, the optical and electrical performance of SnS thin films were improved due to In-doping.     

Construction of CaTiO3 nanosheets with boron nitride quantum dots as effective photogenerated hole extractor for boosting photocatalytic performance under simulated sunlight

Herein, titanate-based perovskite CaTiO₃ nanosheets were successfully designed via boron nitride quantum dots (BNQDs) to fabricate CaTiO₃/BNQDs catalyst. The as-fabricated composite catalysts were analysed by transmission electron microscope (TEM), scanning electron microscopy coupled with energy dispersive spectrometry (SEM-EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), X-ray diffraction (XRD), UV–vis spectroscopy (UV-DRS), photoluminescence (PL) and electrochemical impedance spectroscopy (EIS) techniques. SEM-Mapping analysis showed that the boron and nitrogen elements dispersed well over the CaTiO₃ surface which was useful for building electronic channels for rapid transport of photo-induced charge pairs. TEM images verified the attachment of BNQDs around the surface of host CaTiO₃ forming intimate interface while the distribution of chemical states was observed by XPS analysis demonstrating strong coupling effect between BNQDs and CaTiO₃ through Ti–O–N and Ti–O–B bonds. Moreover, PL and light absorption properties enhanced with the quantum confinement effect of BNQDs. As expected, the photocatalytic degradation rate of CaTiO₃/BNQDs was increased to k_app = 0.015 min^{? 1} with optimum BNQDs loading, which was 2.31 times folder than that of bare CaTiO₃ (0.006 min^{? 1}). The enhanced photocatalytic efficiency was observed for CaTiO₃/BNQDs than pristine perovskite on account of formation of electron tapping sites, decreased band gap energy and hindered recombination rate. On the other hand, in the presence of H₂O₂, the degradation percentage increased from 88.5% to 92.1% at the end of 120 min of irradiation while 96.8% of TC was quickly degraded within 60 min after activating with peroxymonosulfate which created strong sulphate radicals. Radical trapping tests indicated that the photo-generated holes were the primary active species in the photocatalytic mechanism. Moreover, CaTiO₃/BNQDs catalyst showed excellent stability in recycling tests. Besides, the possible degradation mechanism was proposed. This study shed light on the significance of BNQDs in the enhancement of the photocatalytic activities of titanate-based perovskite for effective degradation of tetracycline antibiotic in contaminated water.     

Solvothermal synthesis and characterizations of graphene-ZnBi12O20 nanocomposites for visible-light driven photocatalytic applications

The Bismuth based Zinc metal oxide (ZnBi₁₂O₂₀) nanorods were synthesized via single step solvothermal approach. The characterization of synthesized hybridized structure was done by several analysis such as X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (UVvis–DRS), Fourier transform-infrared spectroscopy (FT–IR), Thermogravimetric analysis (TGA), Raman spectroscopy, Field-Emission scanning electron microscopy (FESEM), Energy dispersive analysis of X-rays (EDX), High-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy. The photocatalytic activity of ZnBi₁₂O₂₀ and an incorporation of varying weight percentages of GO (1–4 wt %) into ZnBi₁₂O₂₀ catalyst (GZBC) were analyzed under visible light irradiation by the degradation of an aqueous solution of Methylene blue (MB) and Methyl orange (MO) dye. Among various developed nanocomposites, 3 wt% GZBC reduced graphene oxide exfoliated nanocomposites has revealed the degradation efficiency as 96.04, 94.52% at 100 and 120 min for MB and MO respectively with enriched visible light absorption range. The photocatalytic property of 3 wt % reduced graphene oxide exhibits higher degradation behavior than that of other synthesized nano-composites.     

Visible light induced photocatalytic activity of MnO2/BiVO4 for the degradation of organic dye and tetracycline

In this work, α-MnO₂/BiVO₄ nanocomposites with varying MnO₂ contents (0–7 wt%) were successfully prepared via the simple chemical method. The structure, morphology, and optical properties of prepared nanocomposites were studied by various analytical techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible absorption spectroscopy, and photoluminescence (PL) spectroscopy. The photocatalytic efficiency of α-MnO₂/BiVO₄ nanocomposites was studied via decomposition of rhodamine B (RhB) and tetracycline (TC) under exposure to visible light (λ ≥ 420 nm). Due to good structure and composite advantages, 5%MnO₂/BiVO₄ (MnBV-5) photocatalyst exhibited superior RhB and TC degradation efficiency to all other samples. In addition, the MnBV-5 photocatalyst showed good stability, and no apparent reduction in photocatalysis efficiency was noted after five testing cycles. Therefore, the MnO₂/BiVO₄ nanocomposite demonstrated a good potential for photocatalytic decomposition of new water contaminants.     

Fabrication and photocatalytic performance of one-dimensional Ag3PO4 sensitized SrTiO3 nanowire

The 1D Ag₃PO₄ sensitized SrTiO₃ nanowires are prepared by simple route of electrospinning-in situ deposition technique. The results of the thermogravimetry (TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive Spectrometer (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV–Visible diffuse reflectance spectroscopy (UV–Vis) indicate that the Ag₃PO₄ nanoparticles has been deposited on the surface of the SrTiO₃ nanowires successfully. Experimental results showed that compared with pure SrTiO₃, the as-prepared 1D Ag₃PO₄ sensitized SrTiO₃ nanowires exhibit obvious enhancement of photocatalytic performance and stability. Especially, the Ag₃PO₄/SrTiO₃ (3AS sample) had a satisfactory photocatalytic activity for degrading methylene blue (MB) more than 98% under visible light irradiation. As to pure SrTiO₃ and Ag₃PO₄, only 9.8% and 49% of MB was decomposed after 35?min irradiation respectively. Furthermore, the mechanism of the enhancing photocatalytic activity could be ascribed to the nano-heterojunction of the Ag₃PO₄/SrTiO₃, the visible light response of the Ag₃PO₄, and the 1D structure of the nanowires.     

Magnetic Fe2O3/CNT nanocomposites: Characterization and photocatalytic application towards the degradation of Rose Bengal dye

In this work, hybrid nanocomposite materials for the wastewater treatment via photocatalysis have been developed by combining multi walled carbon nanotubes (MWCNT) and hematite (α-Fe₂O₃).A straightforward strategy via sonication method has been used to prepare theα-Fe₂O₃/CNT nanocomposites with varying CNT content (5%, 7.5%, and 10%)and characterized by X-ray Diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and UV–Vis. spectrophotometer. XPS spectra was used to identify the defects/oxygen vacancies in the α-Fe₂O₃ lattice. TEM revealed the well deposition of α-Fe₂O₃ nanoparticles on the CNT surface. α-Fe₂O₃/CNT 10% nanocomposites have higher photocatalytic activity with 87% degradation of Rose Bengal dye in 90 min. The increased photocatalytic activity can be attributed to the synergistic contribution of α-Fe₂O₃ and CNTs, which inhibits photo-generated charge carrier recombination and the formation of highly active radical species (OH^• radicals, and O₂^• radicals) on the surface of CNTs. This research may be useful not only for understanding the photocatalytic mechanism, but also for developing efficient photocatalysts for the organic pollutant degradation.     

Photocatalytic activity enhancement by composition control of mechano-thermally synthesized BiVO4-Cu2O nanocomposite

In this paper, BiVO₄-Cu₂O nanocomposites have been synthesized by a mechano-thermal method with a controlled composition of Bi₂O₃, V₂O₅ and Cu₂O contents. The effects of milling time, heat treatment temperature and composition on the structure and microstructure of the prepared samples were studied. The optical properties and photocatalytic performance of the samples under visible light irradiation were studied by Diffuse reflectance spectroscopy (DRS), photoluminescence (PL) and dye degradation. The BiVO₄ and Cu₂O contents in the nanocomposite were changed and the effects on the structural stability and photocatalytic performance were studied. X-ray diffraction (XRD) patterns showed that both BiVO₄ and Cu₂O contents were effective on the synthesis and stability of the monoclinic phase of BiVO₄. Field emission scanning electron microscopy (FESEM) micrographs indicated semi-spherical nanocomposite particles with an average particle size of 100 nm. The heterostructure at the interface between Cu₂O and BiVO₄ was shown by Transmission electron microscopy (TEM) and proved by X-ray photoelectron spectroscopy (XPS) spectra. DRS results indicated the minimum band gap energy of 2.12 eV for BiVO₄-10 wt% of Cu₂O with a 10 wt% excessive V₂O₅ content. The PL result has shown the lowest rate of the recombination of electron-holes for this sample. Also, the maximum degradation of 97% has been obtained for methylene blue (MB) by this sample after 240 min of being irradiated in visible light region. The photocatalytic mechanism was determined using scavengers. The kinetics of MB and methyl orange (MO) degradations was compared to study the effect of pH on the photocatalytic performance.     

Core–shell BaMoO4@SiO2 nanospheres: Preparation,characterization, and optical properties

Core–shell BaMoO₄@SiO₂ nanospheres were prepared in reverse microemulsions and exhibited enhanced photoluminescence (PL) intensity as compared to that of the uncoated BaMoO₄. Characterization was performed using transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), energy-dispersive X-ray spectroscopy (EDX), and X-ray powder diffraction (XRD). It was found that the silica shell could increase the PL intensity, but the shell is not the thicker the better. The PL emission can be decomposed into three individual Gaussian components: two UV emissions at 308 nm and 369 nm and a visible emission at 448 nm. Such short emission wavelengths can be attributed to quantum size effect of the small BaMoO₄ cores (～16 nm).     

Synthesis of zinc oxide and carbon nanotube composites by CVD method: photocatalytic studies

The present work describes the synthesis of multiwall carbon nanotubes (CNT), zinc oxide (ZnO) and their photocatalytic evolutions. Nickel doped fumed SiO₂ used as substrate for the synthesis of CNT by in chemical vapour deposition method. In-situ synthesis of ZnO:CNT composites was achieved in alkaline ethanolic medium with zinc chloride and CNT. The prepared composites were investigated by the Fourier Transform Infrared spectroscopy, confocal Raman spectroscopy, diffuse reflectance UV–visible spectrophotometer (DRS), X-ray diffraction, X-ray Photoelectron Spectroscopy (XPS), Brunaur–Emmett–Teller surface area and field emission scanning/transmission electron microscopy. The composites were employed in the degradation methylene blue and Reactive red-198 under visible light irradiation. The photocatalytic activity was determined by the spectrophotometric technique. The percentage of degradation was more for ZnO:CNT composites and shows higher capacitance, when compared to that of ZnO and CNTs. The recovered and reused catalysts catalytic activity was compared with that of fresh catalyst.     

Electrochemical energy storage applications of carbon nanotube supported heterogeneous metal sulfide electrodes

Electrochemical system centered on hierarchically carbon-based metal sulphide assemblies are of great fame for competent supercapacitors. Herein, the synthesis of a hierarchical CNT anchored MoS₂–Bi₂S₃ nanocomposite is reported. Attractively, a vertically grown Bi₂S₃ nanorods supported on MoS₂ nanosheets with carbon framework acts as a highly effective electrode in alkaline electrolyte. More interestingly, this hierarchical structure and synergetic upshot of CNT and composites provide excess coverage of active sites with improved conductivity and stability. Advancing from the physical and compositional properties of nanocomposites, the specific capacitance of MoS₂–Bi₂S₃@CNT composites is measured to be 1338 F/g at 10 mV/s, columbic efficiency of 99.5% over 10000 cycles and long-term stability (60% retention at 0.5 A g^?1 over 2000 cycles and 34.6% up to 10000 cycles). The success of this MoS₂–Bi₂S₃@CNT composite may be attributed to the structural advantages, admirable cyclic stability, and better capacitance retention for supercapacitor applications.     

Photocatalytic and antibacterial characteristics of decorated polyester textile with ceramic nanoparticles of cobalt ferrite

In this study, a multifunctional textile profiting from photocatalytic activity, magnetic, and antibacterial properties was generated through decorating polyester fabric with cobalt ferrite (CoFe₂O₄) nanoparticles using the co-precipitation technique. The X-ray diffraction (XRD) results supported the successful decoration of fabrics with CoFe₂O₄ magnetic nanoparticles. Field emission electron scanning microscopy (FESEM) images accompanied by energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) analyses demonstrated the morphology, dispersion, and chemical structure of particles on the surface. The mean particle size of cobalt ferrite was measured to be approximately 40 nm. Vibrating sample magnetometer (VSM) results confirmed the ferrimagnetic behavior of the decorated fabrics with saturation magnetization (M_s) and coercivity (H_c) of 1.8 emu/g and 1902 Oe, respectively. The UV–vis diffuse reflectance spectrum (DRS) and photoluminescence (PL) data indicated the appropriate performance under visible light irradiation and postponed electron-hole recombination of the decorated fabric, respectively. The maximum MB degradation efficiency of 97% after 180 min of visible light illumination was obtained. The active species trapping analyses indicated that hydroxyl radicals (^●OH) were the effective species in the photocatalytic degradation mechanism. The decorated sample with the best photocatalytic activity revealed more than 99% reduction in the number of colonies against gram-negative and gram-positive bacteria after 24 h contact time, which validated its excellent potential for antibacterial applications. Outstanding photocatalytic and antibacterial characteristics of the decorated textile with cobalt ferrite nanoparticles turn it into promising composite material for self-cleaning purposes.     

Synthesis and photocatalytic activity of BiFeO3 and Bi/BiFeO3 cubic microcrystals

BiFeO₃ and Bi/BiFeO₃ cubic microcrystals were synthesized in this work. The phase, microstructure, optical and photo electrochemical properties, as well as the photocatalytic activities in photocatalytic hydrogen generation were investigated. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results demonstrate the successful synthesis of BiFeO₃ and Bi/BiFeO₃. The scanning electron microscope (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray (EDX) results give the evidence of cubic morphology and the deposition of metal Bi on the surface of BiFeO₃. The absorption spectra show that Bi/BiFeO₃ has longer absorption edge and stronger absorption capability to visible light. The photocurrent curves, emission spectra, and electrochemical impedance spectroscopy (EIS) spectra demonstrate that Bi/BiFeO₃ has higher efficiency of electron-hole separation and charge transfer, as well as longer lifetime of the charge carriers. These benefit to the enhancement of activity in photocatalytic hydrogen generation.     

Enhanced structural,optical, and photocatalytic activity of novel Cd–Zn co-doped Mg0.25 Fe1.75O4 for degradation of RhB dye under visible light irradiation

Cd_xZn_1-xMg_0.25Fe_1.75O₄ (where x = 0.00, 0.25, 0.50, 0.75, 1.00) have been successfully produced by a facile hydrothermal technique for a thorough comparison of structural, optical, and photocatalytic properties (degradation of Rhodamine B -RhB dye under visible light irradiation). X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) confirmed the formation of cubic spinel structure for all of the samples. Fourier transform infrared (FTIR) spectroscopy verified the presence of metal-oxygen (M–O) bonding in the prepared samples with two frequency bands corresponding to phonon vibrational stretching in both the octahedral and tetrahedral lattice positions. UV–Visible Spectrophotometer and photoluminescence (PL) spectroscopy investigated the bandgap variation (2.7 eV-1.7 eV) and emission spectrum peaks appearing in the range of 405–471 nm region. The comparison in the photo-degradation of Rhodamine B (RhB) revealed the superior performance (98% degradation of RhB dye in 80 min having a K value of 0.04966 with excellent reusability) of Cd_0.50Zn_0.50Mg_0.25Fe_1.75O₄ sample having 50/50 dopant ratio of Cd and Zn in the parent Mg Ferrite, attributed to the lowest bandgap, longer lifetime of charge carriers, active octahedral lattice site, electron/hole pair recombination preventions, and the least value of ohmic impedance at higher frequency.     

Influence of CVD parameters on Co-TiO2/CNT properties: A route to enhance energy harvesting from sunlight

Carbon nanotubes (CNTs) have been employed to enhance the photoactivity of titanium dioxide (TiO₂). In this work, CNTs were deposited by chemical vapor deposition (CVD) onto the surface of anodized Co-TiO₂ nanotubes. The influence of CVD parameters (time and temperature) on the Co-TiO₂/CNT structure and properties was investigated. We studied three synthesis times (10, 20, and 30 min) and two synthesis temperatures (700 and 800°C). The samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and X-ray diffraction (XRD). The photocurrent performance of the electrodes was determined by linear voltammetry. The results showed the successful formation of Co-TiO₂/CNT hybrid structures. The shortest synthesis time produced higher quality CNTs. The samples synthesized at 700 and 800°C for 10 min exhibited a current density of 1.13 mA.cm⁻² and 7.84 mA.cm⁻², respectively, which is 9 and 65 times greater than the Co-TiO₂ sample. The synergistic effect of the CNT deposition and the crystalline phase composition significantly improved the photoresponse of TiO₂. The proper choice of synthesis parameters allowed the control of the sample structure, leading to the production of electrodes with better light-harvesting performance.     

The Heterojunction of Ni and Co9S8 was Synthesized and Anchored on Carbon Nanotubes to Improve the Performance of Water Electrolysis

Developing durable, low-cost water electrolysis catalysts plays a critical role in solving clean energy problems. Herein, we synthesized Ni/Co₉S₈@CNT micro flower comprising Ni/Co₉S₈ mesoporous nanosheets and carbon nanotubes (CNT). HRTEM images indicate that the Ni/Co₉S₈@CNT micro flower contains abundant Ni/Co₉S₈ heterojunctions. The band structure and coupling effect of the Ni/Co₉S₈ heterostructure optimizes the transfer of electrons, thus the synergistic hybrid effectively improves conductivity and electrocatalytic performance. Therefore, Ni/Co₉S₈@CNT shows good evolution reaction (OER) and hydrogen evolution reaction (HER) performance in an alkaline environment. Specifically, at a current density of 10 mA cm^?2, the overpotential of OER is 289 mV, and the overpotential of HER is 228 mV. The Tafel slope is 69 mV dec^?1. In addition, Ni/Co₉S₈@CNT in alkaline electrolyte only loses 10% of its activity after working for 10 h at a current density of 10 mA cm^?2. These results indicate that composite materials composed of transition metal sulfides and highly conductive carbon materials are a good choice for low-cost electrocatalysts.

Graphic abstract

Synthesize the heterojunction of metal Ni and Co9S8 and anchor it on the CNT to improve the performance of OER and HER.

     

Enhancement in the photocatalytic and optoelectronic properties of erbium oxide by adding zinc oxide and molybdenum

Rare earth metals like erbium oxide (Er₂O₃) show outstanding photocatalytic properties. However, its high recombination rate and low surface area limit its performance. Therefore, various metal oxide composites with Er₂O₃ have been reported to improve their photocatalytic and optoelectronic properties. In this study, a composite of Er₂O₃ and zinc oxide (ZnO) was synthesized using the sol-gel combustion method to enhance its surface area. Moreover, molybdenum (Mo) was loaded on the matrix to suppress the charge recombination. The detailed characterizations were conducted by employing X-ray Diffraction (XRD), Raman Spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), Brunauer–Emmett–Teller (BET) analysis, Photoluminescence (PL) spectroscopy and UV–Vis spectroscopy. BET analysis revealed the enhancement in surface area by adding ZnO and Mo (from S_BET = 29.07 m²/g to S_BET = 45.71 m²/g). Additionally, the loading of Mo enhanced the immobilization of carriers that facilitate the photooxidation process and suppressed the electron-holes recombination (from 800 counts to 100 counts) as confirmed by the PL spectroscopy. Photocatalytic studies were comparatively analyzed by degradation of textile dye named methylene blue (MB). The efficiency of Er₂O₃ improved by up to 80% by adding the ZnO and Mo. The composite of Er₂O₃ with ZnO and loading of Mo, not only improved the photocatalytic properties but also improved the electrical properties of the Er₂O₃ (σ = 4.4 × 10⁻⁴ Sm⁻¹ to σ = 5.1 × 10⁻⁴ Sm⁻¹) as confirmed by the Hall Effect. Due to enhancement in properties, the proposed material can be rendered as one of the most suitable candidates for optoelectronic applications.     

Controlled synthesis of various SrTiO3 morphologies and their effects on photoelectrochemical cathodic protection performance

As an n-type semiconductor with typical perovskite structure, SrTiO₃ has broad research prospects in photochemical cathodic protection because of its suitable energy band structure. However, there is a lack of research on the effect of SrTiO₃ micro morphology on Photoelectrochemical cathodic protection performance. In this paper, a series of SrTiO₃ samples with controllable morphology were designed and prepared by changing the ratio of alcohol to water in the solvent, including nanoparticles (NPs), nano ball (NBs), nano rod (NRs), coral stone-like microspheres (CSLMs) and flower-like microspheres (FLMs). The experimental results show that FLMs samples have better photochemical cathodic protection performance. Under the condition of on light, the photocurrent density of FLMs samples reaches 9.2 μA. The photocurrent density of NPs samples is only 2.5 μA. The former is about 3.6 times that of the latter. The open circuit potential of FLMs samples has shifted from ?0.18 V to ?0.42 V, with a negative shift of 240 mV, while CSLMs samples have only a negative shift of 180 mV. In contrast, FLMs samples have a more negative shift of 60 mV. After four light cycle experiments, the performance of FLMs samples is stable without obvious change.