Simple Co-precipitation Method Research Articles

Ultrafast Room‐Temperature Synthesis of Yb3+/Er3+ Codoped K3ZrF7 Nanocrystals for Thermal Enhancement of Upconversion

AbstractLanthanide (Ln3+)‐doped upconversion nanocrystals (NCs) have attracted great attention due to their outstanding luminescent performance and wide applications in various fields. However, the preparation of most Ln3+‐doped NCs requires rigorous conditions such as high reaction temperature, long reaction time, strict anhydrous and oxygen‐free environment, and tedious post‐treatment process. Herein, sub‐100 nm Yb3+/Er3+ codoped K3ZrF7 octahedral NCs are prepared by an extremely simple coprecipitation method (10 s only at room temperature). The resulting NCs show excellent upconversion luminescence (UCL), significantly superior to both their conventional high‐temperature‐synthesized counterparts and the room‐temperature‐synthesized NaBiF4:Yb/Er controls. More importantly, abnormal thermally enhanced UCL over a temperature range from room temperature to 473 K is found in these K3ZrF7:Yb/Er NCs, making them promising candidates for ratiometric thermometry applications. By employing the luminescence intensity ratio between two non‐thermally coupled energy levels of Er3+, namely 4F9/2 and 2H11/2, these NCs display an extraordinarily high absolute sensitivity of 443.2% K−1 and a comparatively large relative sensitivity of 1.55% K−1 at room temperature. These results reveal that K3ZrF7:Yb/Er NCs can not only be facilely prepared via an ultrafast room‐temperature synthesis, but also hold great potential in various areas such as optical temperature sensing and biological applications.

A simple method of fabrication hybrid electrodes for supercapacitors

The increasing need for electrode materials exhibiting improved performance to meet the requirements of supercapacitors is on the rise. Hybrid electrodes, which combine reduced graphene oxide (rGO) with transition metal-based oxides, have emerged as promising materials due to their impressive specific capacitance and cost-effectiveness, attributed to their synergistic properties. In the present study, a binder-free CoOrGO composite electrode was synthesized using a facile, fast, and simple one-step co-precipitation method. This was done to improve both capacity and stability for supercapacitor applications. The composite materials underwent comprehensive characterization utilizing various surface analytical techniques, including X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), field-emission scanning electron microscopy (FE-SEM), fourier-transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) analysis. Electrochemical measurements of the CoOrGO composite revealed at current density of 2 A cm− 2 a specific capacitance of 132.3 mF cm− 2, with an impressive 95.91% retention of capacitance after 7000 cycles. The results from electrochemical impedance spectroscopy (EIS) highlighted a meager low relaxation time constant of 0.53 s for the composite films. The reason behind this can be linked to the synergistic interactions, and minimal charge transfer resistance exhibited by the porous electrode without binders. Based on the obtained results, this work introduces a flexible methodology for crafting advanced energy storage systems. This demonstrates the potential for designing high-efficiency supercapacitors that are suitable for a broad range of large-scale applications.

Facile synthesis of CuCo2O4@CdS nanoheterostructure for asymmetric supercapacitor

The abundant active sites, high theoretical capacitance, and cost-effective synthesis of transition metal oxides@sulfides (TMOs@TMSs) have made them a highly desirable choice as active electrode materials for supercapacitors. This study demonstrated the successful fabrication of a CuCo2O4@CdS nanoheterostructure electrode using a simple and economical co-precipitation method The morphology, physicochemical properties, and electrochemical behavior of this electrode were subsequently studied. The synthesized CuCo2O4@CdS nanoheterostructure was characterized using Infrared Fourier-transform spectroscopy, X-ray diffraction, Raman spectroscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, High-resolution transmission electron microscopy, N2 adsorption/desorption isotherms and atomic force microscopy. The electrochemical performance was studied using cyclic voltammetry, impedance spectroscopy, and galvanostatic charge-discharge (GCD) measurements with a 6 Molar KOH aqueous electrolytic solution. Results from powder X-ray diffraction pattern and energy dispersive X-ray revealed the formation of CuCo2O4@CdS nanoheterostructure. Furthermore, SEM images showed the formation of more spherical structures in nanoheterostructure. The results of optical measurements of thin films were analyzed, which showed an increase in the energy gap (Eg) of CuCo2O4 nanoparticles when combined with cadmium sulfide (CdS). Additionally, the intensity of photoluminescence of the CuCo2O4@CdS nanoheterostructure was lower compared to the pure nanoparticles. Moreover, the newly synthesized CuCo2O4@CdS nanoheterostructure showed a specific capacitance of 257.5 F g−1 at a current density of 0.5 A g−1 via a three-electrode galvanostatic charge-discharge system, respectively. In the asymmetric device, the supercapacitor yielded an optimum energy density and power density of 19.6 Wh kg−1 and 700 W kg−1 at 1 A g−1 current density, respectively. Although the capacitance retention was maintained at nearly 85.2 % after 4000 cycles at a current density of 3 A g−1.

Surface hydroxyls of spinel oxides: A double-edged sword in the peroxymonosulfate activation process

The sulfate-based advanced oxidation process (SR-AOP) mediated by spinel oxides has shown great potential in pollutant degradation. However, the role of surface hydroxyls in the reaction process remains unclear, especially in real environments containing salts. Here, we investigated the role of surface hydroxyls of spinel oxides in activating peroxymonosulfate (PMS). By adjusting the intrinsic composition of the metal elements, we synthesized a CoFeMnO4 spinel with high surface hydroxyls using a simple and scalable co-precipitation method. CoFeMnO4 demonstrated unparalleled activation performance and a unique non-radical activation pathway (dominated by high-valence metal-oxo species and singlet oxygen), achieving 100 % sulfamethoxazole degradation within 4 min with a low concentration of PMS. Surface hydroxyls of CoFeMnO4 played a crucial role in the activation process, serving as adsorption sites for PMS and facilitating its activation. Interestingly, we discovered that several common anions (Cl−, HCO3−, SO42− and NO3−) could undergo ligand exchange with surface hydroxyls of CoFeMnO4, occupying some of sites intended for PMS adsorption, which significantly inhibited the PMS decomposition on the catalyst surface. Further, it was finally discovered that the inhibition of the reaction system by these anions was primarily due to their competition for surface hydroxyls, rather than the commonly believed the consumption of reactive oxygen species by anions. Given the inevitable presence of various anions in real water bodies, this finding highlights the dual nature of surface hydroxyls as active sites in SR-AOPs: While they aid in activation process, the competition from anions for them would diminish the overall system performance.

Facet engineering in Au nanoparticles buried in Cu2O nanocubes for enhanced catalytic degradation of rhodamine B and larvicidal application

Water systems around the world are significantly impacted by organic pollutants from industrial activities. In this study, we report a novel and promising approach utilizing a cost-effective and simple chemical co-precipitation method for the synthesis of Cu2O@Au nanocubes. The characterization of these nanocubes was conducted using various advanced techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL). These analyses revealed the formation of crystalline nanocube-structured catalyst, confirming their purity, chemical state, and electronic structure. The synthesized Cu2O@Au nanocubes, particularly with 5 % Au over Cu2O, showed the highest catalytic efficiency in degrading Rhodamine B (RhB), achieving about 99.6 % degradation in 7 min. The deposition of Au significantly enhanced the electron mobility, thereby increasing the catalytic efficiency of the catalyst. GC/MS analysis performed to identify the intermediates formed and a possible degradation pathway of RhB was proposed. In addition, the toxicity of intermediates also evaluated by ECOSAR software. Reusability tests were conducted to assess the consistency and practical application of Cu2O@Au-5 % nanocubes. The results indicated high stability and sustained catalytic performance over multiple cycles. Additionally, the multifunctional properties of the synthesized material were validated through larvicidal activity tests, demonstrating its potential for broader environmental applications. Overall, Cu2O@Au-5 % presents a highly efficient and versatile catalyst for environmental remediation and other practical applications, demonstrating significant potential for large-scale use. These findings underscore the promise of Cu2O@Au as a multifunctional catalyst, capable of delivering substantial advancements in both environmental and public health domains.

3D-micro-flower like [formula omitted] nanoplate solid solution: A facile and rapid room-temperature synthesis with excellent photocatalytic decomposition of antibiotics in water

This research addresses the environmental threat posed by residual antibiotics in water and explores the potential of the photocatalytic process as an eco-friendly solution for antibiotic wastewater treatment. Here in, a series of BiOBr1−xClx nanoplate solid solutions with varied Br:Cl molar ratios were synthesized through a simple co-precipitation method. These solid solutions exhibited superior visible-light-driven photocatalytic activity compared to pristine BiOCl and BiOBr. Notably, the BiOBr0.25Cl0.75 sample demonstrated exceptional performance, achieving 89 % and 99 % degradation efficiency for ciprofloxacin (CIP) and tetracycline hydrochloride (TCH), respectively, within 20 min under optimum conditions. The outstanding performance is attributed to factors such as a large specific surface area, suitable morphology and band gap, effective separation of photo-generated electron-hole pairs, and the presence of meso-size pores in the structure. Thermodynamic studies confirmed the exothermic and spontaneous nature of the photocatalytic reactions. The proposed degradation pathway of CIP and TCH, along with the photocatalytic mechanism, is elucidated. The solid solution, BiOBr1−xClx, exhibits facile recyclability, robust stability, and excellent adaptability to actual aquatic environments, establishing its potential as a promising eco-friendly photocatalyst for antibiotic pollution control.

A Minimalist Iron Oxide Nanoprobe for the High-Resolution Depiction of Stroke by Susceptibility-Weighted Imaging.

The precise mapping of collateral circulation and ischemic penumbra is crucial for diagnosing and treating acute ischemic stroke (AIS). Unfortunately, there exists a significant shortage of high-sensitivity and high-resolution in vivo imaging techniques to fulfill this requirement. Herein, a contrast enhanced susceptibility-weighted imaging (CE-SWI) using the minimalist dextran-modified Fe3O4 nanoparticles (Fe3O4@Dextran NPs) are introduced for the highly sensitive and high-resolution AIS depiction under 9.4 T for the first time. The Fe3O4@Dextran NPs are synthesized via a simple one-pot coprecipitation method using commercial reagents under room temperature. It shows merits of small size (hydrodynamic size 25.8nm), good solubility, high transverse relaxivity (r2) of 51.3 mM-1s-1 at 9.4 T, and superior biocompatibility. The Fe3O4@Dextran NPs-enhanced SWI can highlight the cerebral vessels readily with significantly improved contrast and ultrahigh resolution of 0.1mm under 9.4 T MR scanner, enabling the clear spatial identification of collateral circulation in the middle cerebral artery occlusion (MCAO) rat model. Furthermore, Fe3O4@Dextran NPs-enhanced SWI facilitates the precise depiction of ischemia core, collaterals, and ischemic penumbra post AIS through matching analysis with other multimodal MR sequences. The proposed Fe3O4@Dextran NPs-enhanced SWI offers a high-sensitivity and high-resolution imaging tool for individualized characterization and personally precise theranostics of stroke patients.

Persistent luminescence nanomaterials with up-/down-conversion modes for power battery temperature measurement

With the development of new energy vehicles, the safety concern of power batteries has become urgent, making the exploitation of new temperature sensors for the batteries important. In this paper, persistent luminescence nanoparticles (PLNPs) of Bi1.91Ga4O9: 0.04 Er3+, 0.05 Eu3+ with up- and down-conversion luminescence were prepared by a simple and low-cost co-precipitation method. Single rare earth element doping of Er3+ achieves up-conversion luminescence at 526nm/550nm under 980nm excitation. After co-doping with rare earth element Eu3+, it can realize the down-conversion luminescence at 590nm/614nm under 254nm excitation. They showed obvious temperature dependence at 293 K-503 K and 423 K-573 K, respectively. The corresponding maximum relative sensitivities are 0.98% K-1 and 0.55% K-1. Interestingly, all temperature ranges cover the spontaneous ignition point of the power battery at 473K. Thus, the PLNPs-based sensor was successfully validated for monitoring overheating and spontaneous combustion of power battery with the dual-channel temperature measurement modes. The two kinds of temperatures were verified with each other for the improved sensitivity and accuracy, so they were used to accurately measure the temperature of the power battery in real time for early warning and the improved safety. Thus, we provided a new application scenarios of PLNPs in the field of temperature sensing for monitoring the temperature of battery.

Hybrid Pd0.1Cu0.9Co2O4 nano-flakes: a novel, efficient and reusable catalyst for the one-pot heck and Suzuki couplings with simultaneous transesterification reactions under microwave irradiation.

We report the fabrication of a novel spinel-type Pd₀.₁Cu₀.₉Co₂O₄ nano-flake material designed for Mizoroki-Heck and Suzuki coupling-cum-transesterification reactions. The Pd₀.₁Cu₀.₉Co₂O₄ material was synthesized using a simple co-precipitation method, and its crystalline phase and morphology were characterized through powder XRD, UV-Vis, FESEM, and EDX studies. This material demonstrated excellent catalytic activity in Mizoroki-Heck and Suzuki cross-coupling reactions, performed in the presence of a mild base (K₂CO₃), ethanol as the solvent, and microwave irradiation under ligand-free conditions. Notably, the Heck coupling of acrylic esters proceeded concurrently with transesterification using various alcohols as solvents. The catalyst exhibited remarkable stability under reaction conditions and could be recycled and reused up to ten times while maintaining its catalytic integrity.

Valence switching of bismuth in ferricyanide as cathode materials for sodium-ion batteries

Sodium-ion batteries (SIBs) are considered potential alternatives to lithium-ion batteries, and the key to their widespread use lies in finding efficient and cost-effective cathode materials. Ferricyanides have emerged as promising candidates for SIBs cathodes due to their low cost and open channel structure allowing for favorable ion and electron transport. However, traditional ferricyanides such as Prussian blue (PB) and its analogs (PBAs) have a limited two-electron transfer capacity, which hampers their practical application. Bi-based ferricyanide materials with multiple valence states, low toxicity and abundant resources are attractive for electrochemical reactions and enable multiple electron transfers to develop high-capacity cathode materials. In this study, we synthesized a rod-like BiHCF·4H2O sample using a simple coprecipitation method. After dehydration, the rod-like BiHCF compounds with a robust framework and reduced lattice water defects demonstrated good electrochemical performance in SIBs. The rod-like BiHCF electrode exhibited a specific capacity of 221 mAh g−1 at 20 mA g−1 based on a three-electron transfer of Bi3+/Bi0. A full SIBs composed of a BiHCF cathode and Bi anode demonstrated acceptable performance, indicating potential for practical applications. This work provides valuable insights into the development of redox-active site substitution strategies for high performance positive electrode materials in SIBs.

Mn doping and ZnS nanoparticles modification on Bi2MoO6 to achieve an highly-efficient photocatalyst for TC degradation

Environmental pollution presents significant challenges to both human production and daily life. Photocatalytic technology offers a promising solution for environmental remediation, and Bi2MoO6 is widely recognized as an excellent visible light photocatalyst for the degradation of organic pollutants. Nevertheless, the high recombination rate of photogenerated charge carriers in Bi2MoO6 limits the number of charge carriers available for photocatalytic reactions, resulting in reduced photocatalytic efficiency. To overcome this limitation, we designed and synthesized a composite photocatalyst (30% ZnS/Mn0.08-Bi2MoO6). Mn-doped Bi2MoO6 nanosheets (Mn-Bi2MoO6) were prepared through a simple coprecipitation method, and ZnS nanoparticles were introduced to modify the surface, forming a ZnS/Mn-Bi2MoO6 composite photocatalyst. Experimental results demonstrated that the photocatalytic degradation rate of tetracycline using the 30% ZnS/Mn0.08-Bi2MoO6 composite increased 11.1 times and 3.7 times compared with pure Bi2MoO6 and ZnS, respectively. The formation of ZnS/Mn-Bi2MoO6 heterojunction was confirmed through XRD, XPS, SEM, and TEM analyses. Furthermore, photoelectrochemical measurements, including photocurrent, EIS, and PL, indicated that Mn doping and the ZnS nanoparticle modification significantly improved the separation and transfer efficiency of photogenerated charge carriers. DFT calculations and experimental results revealed the photocatalytic mechanism of the 30% ZnS/Mn0.08-Bi2MoO6 composite. This study provides valuable theoretical and technical insights into photocatalyst modification.

The facile preparation of polydopamine-modified sepiolite and its adsorption properties and microscopic mechanism for cadmium ion

Natural sepiolite (SEP) has the characteristics of cation exchange, abundant reserves, low cost, and environmental friendliness, but its adsorption capacity for heavy metal pollutants is limited. Because polydopamine (PDA) molecules contain rich functional groups such as phenolic and amino groups, in the present work, dopamine and natural sepiolite were utilized as raw materials to prepare polydopamine-modified sepiolite composite (SEP/PDA) by simple co-precipitation method. According to Langmuir isotherm model, the maximum adsorption capacity of SEP/PDA for Cd2+ can reach 203.21 mg/g at 298 K. At the initial concentration of 100 mg/L, the adsorption capacity was 2.9 times that of natural sepiolite. The composite material has good reusability and anti-cationic interference performance and has 100 % removal ability of low concentration Cd2+ in actual electroplating wastewater. Density Functional Theory (DFT) calculations were performed to obtain the electronic structure information. To elucidate the microscopic mechanism, molecular surface analyses, Interaction Region Indicator (IRI), Atom In Molecules (AIM) theory, Bond Order Density (BOD), and Electron Localization Function (ELF) were conducted. These analyses revealed that the amino nitrogen and phenolic oxygen atoms in the dopamine molecules donate lone pair electrons to coordinate with cadmium ions. Polydopamine, which possesses multiple oxidation states, contains catechol, quinone, and indole or a lesser extend pyrrole groups that can complex with cadmium ions, resulting in the formation of a surface complex. This coordination significantly enhances the adsorption properties of the SEP/PDA composite.

Synthesis of multifunctional NiFe2O4-Zns-Ag nanocomposite for sunlight driven photocatalytic dye degradation and solar cells applications: Structural, magnetic and optical properties

This article focuses on the fabrication and investigation of the novel multifunctional NiFe2O4-Zns-Ag core-bi-shell nanocomposite and their magnetic optical properties. The nanocomposite was prepared by a simple co-precipitation method and characterized using various techniques such as XRD, SEM, TEM, UV–Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR) and VSM. The results showed that the nanocomposite had a spinel cubic structure with an average crystallite size of 29 nm. The SEM and TEM images revealed that the nanocomposite had a spherical shape with an average particle size of 61 nm. The optical study demonstrated that the nanocomposite had high absorption in the visible region, indicating its potential for photocatalytic applications. The magnetic study showed that the nanocomposite was superparamagnetic in nature, which could be useful in magnetic separation processes. Furthermore, the potential application of the nanocomposite in solar cells was explored by studying its optical absorption properties. Finally, the photocatalytic activity of the nanocomposite was evaluated using two different azoic dyes under sunlight irradiation. The results showed that the nanocomposite exhibited excellent photocatalytic activity, with a degradation efficiency of 96.22 % within 90 min. Overall, this study provides insights into the potential use of NiFe2O4-Zns-Ag nanocomposite as an efficient photocatalyst for environmental remediation.

Capacity augmentation strategy in α-Fe2O3 nanoparticles through multifaceted structural and electrochemical analyses

Hematite (α-Fe₂O₃) has garnered significant research interest for supercapacitor applications, but capacity fading and limited cyclic life remain serious challenges. In this context, the present research provides a comprehensive study of the factors that significantly impact charge kinetics within the electrode and at the solid/electrolyte interface. By integrating structural and electrochemical analyses, this study offers an effective strategy to enhance the capacity of α-Fe₂O₃ nanoparticles through rigorous scientific analysis and identification of various qualitative and quantitative factors that influence charge storage capacity. A simple one-step co-precipitation method was adopted to synthesize porous α-Fe₂O₃ nanoparticles. The quantitative analysis of charge kinetics demonstrated the domination of diffusion-controlled charge storage as the main contributor to the total charge storage. The α-Fe₂O₃ nanoparticles-based electrode delivered a high energy density of 24.6 Wh kg⁻1 at an impressive power density of 478.7 W kg⁻1. Additionally, it displayed a capacity retention of 79 % over 10,000 cycle operations. The choice of electrode material and the superior porous nanoarchitecture have proven to be advantageous for high-performance supercapacitor applications, offering fast electron/ion transport.

Durably Superhydrophobic Magnetic Cobalt Ferrites for Highly Efficient Oil-Water Separation and Fast Microplastic Removal.

Microplastic pollution has become a primary global concern in the 21st century. Recyclable magnetic particles with micro-nanostructures are considered an efficient and economical way to remove microplastics from water. In this study, superhydrophobic magnetic cobalt ferrite particles were prepared by using a simple coprecipitation method combined with surface functionalization. The micromorphology, chemical composition, hysteresis loop, and surface contact angle of the functionalized cobalt ferrite were characterized. The separation efficiency and absorption capacity of cobalt ferrite particles in water-oil separation and microplastic removal were investigated. The results showed that the saturation magnetic field intensity of cobalt ferrite was 65.52 emu/g, the residual magnetization intensity (Mr) was 18.79 emu/g, and the low coercivity was 799.83 Oe. Cobalt ferrites had stable superhydrophobicity in the pH range of 1-13. The separation efficiency of cobalt ferrite powder for four oil-water mixture separations was higher than 94.2%. The separation efficiency was as high as 99.6% in the separation of the hexane and water mixtures. Due to the synergistic effect of the hydrophobic effect and van der Waals force, the functionalized magnetic cobalt ferrite had a high and stable microplastic removal efficiency and capture capacity. The removal efficiency of microplastics was close to 100%, and the capture capacity was 2.56 g/g. After ten microplastic removal cycles, the removal efficiency reached more than 98%, and the surface contact angle was still greater than 150°.

Visible-light-response organic-inorganic hybrid CdS/MIL-101-NH2 S-scheme heterostructures for high-efficient photo-Fenton application

Developing artificial-photosynthesized heterostructures for solar energy conversion has inspired extensive interest, but the organic-inorganic hybrid Fe-based MOF photocatalyst is still in shortage. Here we report a visible-light response CdS/MIL-101-NH2 hybrid S-scheme heterostructure to exhibit efficient photocatalytic and photo-Fenton functionalities under the simulated solar-driven irradiation. In our work, the 0D CdS nanoparticles have in-situ anchored on the 3D NM101 octahedron to form well interface connection by a mild and simple co-precipitation method, which effectively promoted to shorten the carrier transfer distance as well as to promote charge separation. The whole photo-physics process has been revealed by systemically characterizations and the artificial-photosynthesized S-scheme heterostructure has been confirmed by the results of electrochemical measurements and density functional theory (DFT) calculations. By comparison, the as-prepared CdS/MIL-101-NH2 photocatalysts have more potential applications in Fenton-like advanced oxidation techniques considering their stability and element with variable valency, furthermore, the corresponding mechanism has been discussed. Our work extends the territory of organic-inorganic hybrid heterostructures and hopes to provide a new viewpoint for fabricating efficient artificial-photosynthesized photocatalysts.

Effect of Cu substitution on morphological optical and electrochemical properties of Co3O4 nanoparticles by co-precipitation method

In this present study, pure Co3O4 and Cu-substituted Co3O4 nanoparticles (NPs) were prepared by a simple co-precipitation method and their structural, morphological, optical, and electrochemical properties were assessed. X-ray diffraction (XRD) analysis indicated that the synthesized samples had a cubic structure with the formation of a secondary phase (CuO) was detected at a higher Cu concentration. The average crystallite was decreased with increasing Cu content. Fourier transform infra-red (FT-IR) analysis revealed that the presence of vibrational bands in Cu-substituted Co3O4 NPs. The morphological study of the pure Co3O4 and Cu-substituted Co3O4 NPs revealed that the hexagonal structure with porous morphology confirmed by Field emission scanning electron microscopy (FESEM). High resolution transmission electron microscope (HR-TEM) analysis with spotty diffraction rings showed that pure Co3O4 and Cu-substituted Co3O4 NPs were polycrystalline in nature. The optical properties of synthesized samples exhibited strong absorption edges, and bandgap values were found to be increased from 3.60 to 3.75 eV. Cyclic voltammetry (CV) was employed to investigate the electrochemical properties of the synthesized materials. The CV curves exhibited pseudocapacitive behavior, and 2 % Cu substituted Co3O4 electrode had a high higher specific capacitance value than pure Co3O4 electrode.

Study of an enhanced photocatalytic hybrid MnO2@SnO2 core-shell Z-scheme nano heterojunction for efficient H2 production

The usage of non-renewable carbon-base fuel energy have created multiple issues such as global warming, environmental degradations etc. Replacing these non-renewable sources of energy with renewable energy (photocatalytic H2 production) is a hot topic for researchers due to its sustainability and eco-friendliness. In this work MnO2, SnO2 and their nanocomposites have been synthesized through simple hydrothermal and co-precipitation methods. The purpose of such nanocomposite fabrication is to synthesize a suitable heterostructure for maximum solar energy harvesting in water splitting. All the prepared samples of pure MnO2, SnO2, and nanocomposites have been characterized through various techniques, which confirm the structure, functional groups, absorbance, morphology, elemental compositions, chemical compositions, and increase in photo-induced current as well as the photostability of such nanocomposites. The highest apparent quantum yield of the optimized MnO2@SnO2 (first time reported as photocatalyst for H2 production) were 21.7% at wavelength 420 nm, which is the highest ever reported for such (MnO2@SnO2) nanocomposite. The enhanced photocatalytic behavior for H2 production has been observed which is 3.67 times greater than pristine MnO2. Such an enhancement is due to the synergistic effect of SnO2 NPs decorated on the NTs of MnO2. The present work provides a novel approach to produce hydrogen with high performance as efficient solar harvesting.

Efficient transformation of CO2 into α-alkylidene cyclic carbonates over Cu0/Cu+ derived from CuAl layered double hydroxide/reduced graphene oxide hybrid

A simple liquid-phase co-precipitation method was used to achieve a good dispersion of CuAl layered double hydroxide (CuAl-LDH) on the surface of graphene oxide (GO), and Cu2+ in the lattice of CuAl-LDH was in-situ reduced to Cu0 and Cu+ species, resulting in the preparation of R-CuAl-LDH/rGO catalyst. It could effectively catalyze the cyclization of CO2 and propargylic alcohols under mild conditions (50 °C and 1 bar), and the yield exceeded 99 % within only 40 min. Systematic characterization revealed that two-dimensional LDH nanosheets were grown on the rGO surface in an irregular orientation, leading to a higher specific surface area and more abundant surface active sites. Meanwhile, the synergistic catalysis of Cu0 and Cu+ dual-active sites greatly enhanced the catalytic efficiency. In addition, the catalyst had excellent recycling properties with no significant loss of activity after 5 cycles of continuous operation.

Selective Photocatalytic Oxidation of 5‐Hydroxymethylfurfural using Ce doped TiO2: A Crucial Role of Defective Sites

AbstractTransforming platform compounds with conventional catalysts, such as homogeneous and heterogeneous, into valuable chemicals encounters challenges associated with entailing high temperature/pressure and reusability during the reaction. To address these challenges, photocatalysis is one of the promising approaches, especially with visible‐light‐driven photocatalysts for selective transformation. A series of cerium‐doped TiO2 (CexTiO2; x=0.5, 1, 3 and 5 wt %) are prepared via a simple coprecipitation method for the cocatalyst‐free selective oxidation of 5‐hydroxymethylfurfural (HMF) to 2,5‐diformylfuran (DFF) under visible light illumination. Introducing Ce into the network to TiO2 generates impurity energy levels, reduces the band gap, and extends the spectral response range. This also causes slight distortion to the surface structure, thereby originating defective sites and various surface oxygen species, confirmed by X‐ray photoelectron spectroscopy and electron paramagnetic resonance studies. The HMF adsorption studies infer that HMF forms a surface complex with CeTiO2, facilitating the formation of ligand‐to‐metal charge transfer complex (LMCT) under visible light (~420 nm), which efficiently catalyzes the conversion of HMF (54.4 %) to DFF with a selectivity of >99 %. In‐situ DRIFTS and surface passivation studies provide insight into the interaction between HMF and surface acidic/basic sites along with hydroxyl groups of CeTiO2, which subsequently convert selectively to DFF.