Oxide Research Articles

Impact of water based nanofluids in heat exchanger type active solar PV cooling systems: A comparative CFD analysis

Solar photovoltaic technology is a fast growing form of renewable energy with many positive factors such as low cost, environmental friendliness, energy independence, etc. But, one of the major drawbacks of solar photovoltaic technology is the less efficiency compared to other forms of renewable energy technologies. There are many factors affecting the efficiency of a solar PV system such as temperature, solar irradiance, material quality, reflection losses, cell design etc. Researchers are focusing on different aspects to control the above factors to improve the efficiency of solar PV systems. Solar photovoltaic cooling system is one such solution which can be used to control the operating temperature of solar photovoltaic cells. The most common coolant used in these systems is water due to its superior thermo physical properties. In this research we are focusing on improvement of the thermophysical properties of water using nanotechnology. This article presents a CFD (Computational Fluid Dynamics) analysis conducted for a heat exchanger type solar PV cooling system integrated with a solar photovoltaic panel for water based nanofluids mainly focusing on three metal oxide nanoparticles Al2O3, CuO, and TiO2. Initially the heat exchanger model was developed using Solid Edge 2022 software and the thermo physical properties were simulated using Ansys 2019 software for different water based nanofluids. The obtained results were analyzed comparatively with the performance of water as a coolant in the same heat exchanger system. The results conclude that metal oxide/water based nanofluids have comparatively better thermal properties than water and can be suggested as possible alternatives for water in closed loop heat exchanger applications.

Protonolysis and Condensation Reactions of Alkoxido-Substituted Lindqvist {MW5} and Keggin {MPW11} Polyoxometalates: Comparative Experimental and Modeling Studies.

An understanding of proton transfer and migration at the surfaces of solid metal oxides and related molecular polyoxometalates (POMs) and metal alkoxides is crucial for the development of reactivity involving protonation or the absorption/binding of water. In this work, the hydrolysis of alkoxido Ti- and Sn-substituted Lindqvist [(MeO)MW5O18]3- (M = Ti, 1; M = Sn, 2) and Keggin [(MeO)MPW11O39]4- (M = Ti, 3; M = Sn, 4) type polyoxometalates (POMs) to hydroxido derivatives and subsequent condensation to μ-oxido species has been investigated in detail to provide insight into proton transfer reactions in these molecular metal oxide systems. Solution NMR studies revealed the dependence of reactions not only on the nature of the heteroatom (Ti or Sn) but also on the type of lacunary (W5 or PW11) POM and also on the solvent (MeCN or DMSO). Tin-substituted anions 2 and 4 were much more susceptible to protonolysis than the Ti analogues 1 and 3 while reactions of {MW5} anions were generally faster than those of the {MPW11} anions. Subsequent condensation of the resulting hydroxido derivatives [(HO)MW5O18]3- (M = Ti, 5; M = Sn, 6) and [(HO)MPW11O39]4- (M = Ti, 7; M = Sn, 8) was significantly more facile for 5 and 7 and, in all cases, condensation was inhibited in DMSO. Quantitative comparisons of equilibria and reaction rates were provided by analysis of NMR kinetic experiments, while DFT calculations on these and the analogous {NbW5} reactions provided comparative energetics and reaction profiles that are consistent with experimental observations. These results add to the fundamental understanding of proton migration in metal alkoxide hydrolysis/condensation and related reactions at metal oxide surfaces.

Pressure-Induced Engineering of Surface Oxygen Vacancies on Metal Oxides for Heterogeneous Photocatalysis.

Oxygen vacancies (OVs) spatially confined on the surface of metal oxide semiconductors are advantageous for photocatalysis, in particular, for O2-involved redox reactions. However, the thermal annealing process used to generate surface OVs often results in undesired bulk OVs within the metal oxides. Herein, a high pressure-assisted thermal annealing strategy has been developed for selectively confining desirable amounts of OVs on the surface of metal oxides, such as tungsten oxide (WO3). Applying a pressure of 1.2 gigapascal (GPa) on WO3 induces significant lattice compression, which would strengthen the W-O bonds and increase the diffusion activation energy for the migration of the O migration. This pressure-induced compression effectively inhibits the formation of bulk OVs, resulting in a high density of surface-confined OVs on WO3. These well-defined surface OVs significantly enhance the photocatalytic activation of O2, facilitating H2O2 production and aerobic oxidative coupling of amines. This strategy holds promise for the defect engineering of other metal oxides, enabling abundant surface OVs for a range of emerged applications.

Elucidating Thermal Decomposition Kinetic Mechanism of Charged Layered Oxide Cathode for Sodium-Ion Batteries.

The safety of the P2-type layered transition metal oxides (P2-NaxTMO2), a promising cathode material for sodium-ion batteries (SIBs), is a prerequisite for grid-scale energy storage systems. However, previous thermal runaway studies mainly focused on morphological changes resulting from gas production detection and thermogravimetric analysis, while the structural transition and chemical reactions underlying these processes are still unclear. Herein, a comprehensive methodology to unveil an interplay mechanism among phase structures, interfacial microcrack, and thermal stability of the charged P2-Na0.8Ni0.33Mn0.67O2 (NNMO) and the P2-Na0.8Ni0.21Li0.12Mn0.67O2 (NNMO-Li) at elevated temperatures is established. Combining a series of crystallographic and thermodynamic characterization techniques, the specific chemical reactions occurring in the NNMO materials during thermal runaway are clarified firstand solidly proved that Li doping effectively hinders the dissolution of transition metal ions, reduces oxygen release, and enhances thermal stability at elevated temperatures. Importantly, based on Arrhenius and nonisothermal kinetic equations, the kinetic triplet model is successfully constructed to in-depth elucidate the thermal decomposition reaction mechanism of P2-NaxTMO2, demonstrating that such thermodynamic assessment provides a new perspective for building high-safety SIBs.

Nanoclay-Mediated Crystal-Phase Engineering in Biofunctions to Balance Antibacteriality and Cytotoxicity.

The crystalline phase of metal oxides is a key determinant of the properties and functions of the nanomaterials. Traditional approaches have focused on replicating bulk-phase structures, with limited exploration of phase diversity due to challenges in controlling the crystal morphology. Here, we introduce a nanoclay-mediated strategy for crystal-phase engineering, using talc to modulate the morphology and phase of manganese oxide (MnOx) nanoparticles. This approach enhances the oxidase activity of the MnOx composite (M/T), optimizing the antimicrobial efficacy while minimizing cytotoxicity. M/T-190 demonstrated 99% bactericidal activity against Escherichia coli and Staphylococcus aureus, coupled with 84% cytocompatibility. Theory calculations suggest that talc modulates the charge distribution and d-band center tuning at the Mn3O4/MnOOH interface, enhancing oxygen activation. When integrated into gauze, M/T exhibits strong antimicrobial activity, low toxicity, and promotes wound healing in both in vitro and in vivo studies. These findings highlight the potential of natural minerals for crystal-phase engineering in biomedical applications.

Effective inhibition of antibiotic residues and bacterial pathogens in wastewater using TiO2 metal oxide photocatalyst

Antibiotic residues have become serious health concerns due to the development of antibiotic-resistant bacteria. The treatment of antibiotic pollutants in wastewater is necessary for reducing the issue of antibiotic resistance. In this work, the metal oxide photocatalyst titanium dioxide (TiO2) was evaluated for the removal of the tetracycline antibiotic (TC-A) and the deactivation of E. coli bacteria (E-B) from wastewater. Based on the oxidation process, TiO2 can successfully degrade TC-A in wastewater with an efficiency of up to 96.4%. It is also employed for the deactivation of E. coli, completely inactivating the bacteria within 30 min. Moreover, after five cycles of reuse, TiO2 demonstrated high removal efficiencies of over 80% and 95% for TC-A and E-B, respectively. Finally, the proposed mechanism for the removal of TC-A and the deactivation of E. coli using the TiO2 photocatalyst is presented. This work provides a simple method for removing antibiotic pollutants and deactivating bacteria in wastewater.

Reusable chemical catalysts for sustainable biodiesel production: The role of metallic elements

AbstractIn recent decades, biodiesel has emerged as a renewable and environmentally benign fuel compared with its fossil counterpart. From an industrial perspective, homogeneously‐catalyzed transesterification has been established as the principal method for biodiesel synthesis owing to the moderate reaction conditions. However, homogeneous catalysts cannot be reused, and large amounts of wastewater accompany their separation from the products, making the production process detrimental to the environment and contrary to the sustainable development objectives. This grim reality confronting green fuel can be avoided by using heterogeneous catalysts that can be recycled and reused several times. Metal elements have played a crucial role in the development of such catalysts. These species are readily available in the environment and provide solid catalysts with high activity. Due to their significant contribution to achieving a sustainable production method for biodiesel, this paper reviews the role of metallic elements in fabricating functional materials, including metal oxides, mixed metal oxides, and metal‐doped porous frameworks. The optimized reaction conditions focused on reusability were reported and analyzed for each class of catalysts. Challenges and future requirements for boosting the catalysts’ activity and reusability in the production process were also discussed. Leaching of active sites and pore blockage were the primary factors detrimental to reusability. These issues could be minimized by supported metal atoms on porous materials, providing a stronger bond of the metal sites and the support, and utilizing membrane reactors to continuously remove the products from a reaction mixture.

Catalytic Cu2O/Cu Site Trades off the Coupling and Etching Reactions of Carbon Intermediates for CO2-Assisted Graphene Synthesis.

In the chemical vapor deposition (CVD) synthesis of graphene, the surficial chemical state of the metal substrate has exerted key roles in all elemental reaction steps determining the growth mechanism of graphene. Herein, a CO2-participated annealing procedure is designed to construct catalytic Cu2O/Cu sites on Cu foil for the graphene CVD synthesis with CO2/CH4 as carbon sources. These Cu2O/Cu species can catalyze the CH4 decomposition and subsequent C─C coupling to form C2 intermediates for fast growth of monolayer hexagonal graphene domains with a diameter of ≈30µm within 0.5min. The graphene growth kinetics can be bidirectionally regulated merely with the variation of CO2 flow rate during annealing and growth stages, in association with the Cu+/Cu0 ratio, enabling simultaneous control over the size and shape of graphene domains. Density functional theory (DFT) calculations indicate that the catalytic Cu2O/Cu sites reduce the activation energy by ≈0.13eV for the first dehydrogenation of CH4, allowing the growing rate of graphene driven by coupling of C2 intermediates faster than their etching rate by O-containing *O and *OH species. The work provides novel insights into heterostructured nano-catalyst consisting of zero valent metal and variably valent metal oxide that facilitate the controllable synthesis of graphene materials.

Tailoring Metal–Oxide Interfaces via Selectively CeO2-Decorated Pd Nanocatalysts with Enhanced Catalytic Performance

Metal–oxide interfaces play a prominent role in heterogeneous catalysis. Tailoring the metal–oxide interfaces effectively enhance the catalytic activities and thermal stability of noble metal catalysts. In this work, polyvinyl alcohol-protected reduction and L-arginine induction methods are adopted to prepare Pd catalysts (Pd/Al2O3-xCeO2) that are selectively decorated by CeO2, which form core–shell-like structures and generate more Pd-CeO2 interfacial sites, so that the three-way catalytic activity of Pd/Al2O3-xCeO2 catalysts is obviously significantly enhanced due to more adsorption oxygen at the interface of Pd-CeO2 and good low-temperature reducibility. At the moment, the Pd/Al2O3-xCeO2 catalysts exhibit excellent thermal stability after being calcined at 900 °C for 5 h, owing to the Pd species being highly redispersed on CeO2 and part of the Pd species being incorporated into the lattice of CeO2. This is a major reason for the Pd/Al2O3-xCeO2 catalysts to maintain high catalytic activity after aging at high temperatures. It is concluded that the metal–oxide interfaces and the interaction between Pd NPs and CeO2 are responsible for the excellent catalytic performance and stability of Pd/Al2O3-xCeO2 catalysts in three-way reactions.

Fabrication of Cu: ZnO thin film sensor for ethanol vapor detection

For a long time, metal oxide semiconductor (MOS) based gas sensors have been widely used in domestic, commercial, and industrial sectors to detect harmful gases. The performance of such sensors is significantly enhanced by appropriate doping of suitable materials into MOS such as ZnO and SnO2. This work showcases the design, analysis, and use of a Cu-doped ZnO (Cu: ZnO) film tailored for detecting traces of ethanol vapor at lower temperatures. Herein, various Cu: ZnO films have been fabricated on glass substrates using a spin coater followed by annealing at 600 for 1 hour in a muffle furnace. So-prepared samples have been characterized using X-ray diffraction, Energy Dispersive Analysis X-ray (EDAX), UV-visible spectrophotometer, and Scanning Electron Microscopy (SEM). The XRD analysis showed a polycrystalline nature with preferred orientation along (100) and (002) crystal planes. The morphology study showed their porous and granular surface structure. These films' elemental analysis demonstrated the good incorporation of Cu into the ZnO matrix. The UV-visible results showed a significant decrease in the band gap from 3.28 eV for undoped ZnO to 3.20 eV for Cu: ZnO films. Ultimately, as-prepared Cu: ZnO thin films were used for sensing ethanol vapor at temperatures ranging from 100 to 300 . The result showed a maximum sensitivity of 70.60 at a reduced temperature of 140 at 4% Cu: ZnO thin, which implies that Cu: ZnO is suitable for developing the gas sensors for upcoming future generations.

Orbital and Electrical Dual Function of Polymer Intercalant for Promoting NH4+ Storage in Vanadium Oxide Anode

AbstractPolymer‐intercalated metal oxides have attracted considerable attention for ammonium ions (NH4+) storage due to their enhanced interlayer space, which, through the pillar effect, facilitates rapid and efficient transport of NH4+. However, the understanding remains limited regarding how polymer intercalants affect the intrinsic structure of host materials, especially the variations in atomic orbital and electronic structural induced by the intercalants. Herein, a polyaniline‐intercalated vanadium oxide (P‐VOx) is developed and, for the first time, its NH4+ storage behavior is validated as an anode material. Using various spectroscopy techniques combined with theoretical simulation, the changes are analyzed in atomic orbital and electronic structure induced by the intercalant. Spectroscopy studies reveal that the insertion of polyaniline optimizes the electronic structure of V2O5, promoting the transition of electrons to the V 3dxy state and increasing the occupation of the V t2g orbital, thereby enhancing electrical conductivity. Computational results confirm that P‐VOx lowers the NH4+ migration barrier, thereby enhancing electron/NH4+ transfer. As a result, the P‐VOx electrode demonstrates outstanding capacity and unprecedented long‐term cycling stability. This study provides new insights into the atomic and electronic structural changes induced by the polymer intercalant and underscores the advantages of polymer‐intercalated VOx as a high‐performance electrode for NH4+ storage.

Recent Developments in Synthesis Techniques and Microwave Absorption Performance of Materials Based on Molybdenum Disulfide (MoS<sub>2</sub>) with Metal Oxides: A Review

The widespread usage of various wireless equipment in many facets of life has significantly contributed to the serious pollution caused by electromagnetic radiation. Thankfully, scientists have created materials that can absorb microwave radiation and convert dangerous electromagnetic waves into other forms of energy, including heat energy. Many investigations regarding the development of materials that absorb microwaves with different constituents, morphologies, and architectures have been published recently. Microwave-absorbing materials (MAMs) are becoming more and more popular for use in a variety of aviation applications, including EMI prevention, information security, and reducing the risks of electromagnetic radiation to human health. Molybdenum di-sulphide (MoS2) is a transition metal sulphide extensively employed as a microwave absorption material (MAM) owing to its superior structural and physicochemical qualities. Because of its many flaws, huge specific surface area, and semiconductor qualities, MoS2 exhibits exceptional microwave loss properties. Using a number of various designs, MoS2 may efficiently boost the absorption and dispersion of microwaves inside the absorber. This study introduces the structure, characteristics, and synthesis method based on MoS2 material. The effectiveness of MoS2-based MAMs has been evaluated and analyzed in detail at the moment. Furthermore, the key problems and development challenges are examined, and the most recent advancements in MoS2-based MAMs are impartially assessed and discussed. As a result, it is anticipated that MoS2-based composites would provide excellent choices for very thin and light MAMs.

A short review on polysaccharide-based nanocomposite adsorbents for separation and biomedical applications.

Polysaccharides such as chitosan, alginate, cellulose, and carrageenan have emerged as promising adsorbents due to their biodegradability, abundant availability, and diverse chemical functionality. These biopolymers exhibit promising performance for adsorption of a wide range of pollutants including heavy metals (e.g., lead, cadmium), organic dyes (e.g., methylene blue, methyl orange), and even pathogenic microorganisms. However, inherent hydrophilicity and poor mechanical properties limit their broader application in environmental and biomedical fields. As an effective way to address the issues, recent advancements have focused on the incorporation of nanoparticles (e.g., metal oxides, carbon nanotubes and clays) into polysaccharides to obtain nanocomposite films. Generally, these nanocomposites offer enhanced surface area, tunable porous network, and improved chemical and mechanical resistances for adsorption and biomedical applications. The current review gives a focused overview of the recent progresses in polysaccharide-based nanocomposites, with particular attention to their fabrication methods, adsorption capacity and mechanism, and diverse applications in water purification, drug delivery, and antimicrobial treatments. Critical challenges such as the optimization of nanoparticle dispersion and the environmental impacts of nanocomposite biodegradation are also discussed to pave the road for the future research in this promising field.

The Stability of TiO2 Phases Studied Using r2SCAN in the Hubbard-Corrected Density Functional Theory

Titanium dioxide is a quintessential transition metal oxide with many technologically important applications. With its richness in phases, it has also been a testing ground for numerous theoretical studies including density functional theory. We investigated several phases of TiO2 using the all-electron density functional theory with a regularized–restored strongly constrained appropriately normed (r2SCAN) exchange–correlation functional, a popular choice of meta-generalized gradient approximation (meta-GGA). Specifically, the equilibrium lattice parameters were more accurate than those predicted by GGA and agreed well overall with the experimental data. With increasing pressure, the order of stability was determined as anatase < columbite < rutile < baddeleyite < orthorhombic I < cotunnite, as in the calculations using GGA. Including the Hubbard correction term, the correct ordering between rutile, anatase, and columbite can be achieved, consistent with experimental observations. The necessary U value using r2SCAN is much smaller than that using GGA+U. In addition, the Hubbard correction method using r2SCAN is substantially less sensitive to the size of the local projection space compared to the GGA+U study reported recently. We attribute these significantly improved results to the reduced self-interaction error in the r2SCAN functional.

Photoresponse Design in Metal Oxide Semiconductor TFTs toward Diverse Applications: Display Drivers, Photodetectors, and Optoelectronic Synapses.

Different application domains impose diverse and often conflicting requirements on the optoelectronic performance of metal oxide semiconductor (MOS) thin-film transistors (TFTs). These varying demands present substantial challenges in the selection of TFT materials and the optimization of device performance. This study begins by examining three primary application areas for TFTs: display drivers, photodetectors, and optoelectronic synapses. A comparative analysis of the optoelectronic properties is conducted among various MOS TFTs fabricated by magnetron sputtering, including indium-gallium-zinc-oxide (IGZO, In/Ga/Zn = 1:2:1), indium-gallium-oxide (IGO, In/Ga = 1:1), indium-zinc-oxide (IZO, In/Zn = 1:1), indium oxide (In2O3), and zinc oxide (ZnO). The investigation reveals the significant impact of material selection on key performance metrics essential for these applications, such as photoresponse, the decay rate of photocurrent (Iph), and negative bias illumination stress (NBIS). Additionally, a comprehensive summary of the applicable domains for each type of TFT is provided. The study also explores the correlation between activation energy (Ea) and TFT performance, indicating that higher Ea is associated with a stronger persistent photoconductivity (PPC) effect but poorer stability. Furthermore, the content of oxygen vacancy (VO) shows a positive correlation with the decay rate of Iph. Lastly, the photogenerated carrier lifetime (τ) is derived and compared among the five MOS materials, revealing the potential applications and performance characteristics of each in optoelectronic devices. The findings offer a nuanced understanding of the intrinsic relationships between material properties, defect states, and photoelectric performance, thereby guiding the selection and optimization of channel layer materials for specific application requirements.

Polymer Ligands with Multi-Nitrogen Heterocyclic Carbenes for Enhanced Stability and Reactivity in Nanoparticle Surface Functionalization.

Nitrogen heterocyclic carbenes (NHCs) are emerging as effective substitutes for conventional thiol ligands in surface functionalization of nanoparticles (NPs), offering exceptional stability to NPs under harsh conditions. However, the highly reactive feature of NHCs limits their use in introducing chemically active groups onto the NP surface. Herein, we develop a general yet robust strategy for the efficient surface functionalization of NPs with copolymer ligands bearing various functional groups. The polymer ligands consist of a multiple NHCs block, utilized for surface binding on NPs, alongside a poly(reactive ester) block intended for incorporating functional groups. The multiple NHCs block enables NPs with excellent colloidal stability across a broader range of pH values (0-14), temperature variations (-78°C-100°C), and electrolyte concentrations (0-1000 mM). Through the in situ ammonolysis of the poly(reactive ester) block, various active functional groups can be individually or together introduced on the NP surface. We further demonstrate the chemical reactivity of these functionalized NPs, including addition polymerization, Diels-Alder and Schiff base reactions. This method is applicable to various types of NPs, including metal NPs, metal oxide NPs, and even upconversion NPs, thereby paving new pathways for the design and creation of nanoparticle-based functional materials.

Implementing an Analytical Model to Elucidate the Impacts of Nanostructure Size and Topology of Morphologically Diverse Zinc Oxide on Gas Sensing

The development of state-of-the-art gas sensors based on metal oxide semiconductors (MOS) to monitor hazardous and greenhouse gas (e.g., methane, CH4, and carbon dioxide, CO2) has been significantly advanced. Moreover, the morphological and topographical structures of MOSs have significantly influenced the gas sensors by means of surface catalytic activities. This work examines the impact of morphological and topological networked assembly of zinc oxide (ZnO) nanostructures, including microparticles and nanoparticles (0D), nanowires and nanorods (1D), nanodisks (2D), and hierarchical networks of tetrapods (3D). Gas sensors consisting of vertically aligned ZnO nanorods (ZnO–NR) and topologically interconnected tetrapods (T–ZnO) of varying diameter and arm thickness synthesized using aqueous phase deposition and flame transport method on interdigitated Pt electrodes are evaluated for methane detection. Smaller-diameter nanorods and tetrapod arms (nanowire-like), having higher surface-to-volume ratios with reasonable porosity, exhibit improved sensing behavior. Interestingly, when the nanorods’ diameter and interconnected tetrapod arm thickness were comparable to the width of the depletion layer, a significant increase in sensitivity (from 2 to 30) and reduction in response/recovery time (from 58 s to 5.9 s) resulted, ascribed to rapid desorption of analyte species. Additionally, nanoparticles surface-catalyzed with Pd (~50 nm) accelerated gas sensing and lowered operating temperature (from 200 °C to 50 °C) when combined with UV photoactivation. We modeled the experimental findings using a modified general formula for ZnO methane sensors derived from the catalytic chemical reaction between methane molecules and oxygen ions and considered the structural surface-to-volume ratios (S/V) and electronic depletion region width (Ld) applicable to other gas sensors (e.g., SnO2, TiO2, MoO3, and WO3). Finally, the effects of UV light excitation reducing detection temperature help to break through the bottleneck of ZnO-based materials as energy-saving chemiresistors and promote applications relevant to environmental and industrial harmful gas detection.

Photocatalysis by Mixed Oxides Containing Niobium, Vanadium, Silica, or Tin

Nb-Sn, V-Sn mixed-metal oxides and Nb-Si, V-Si metal oxide–silicas were successfully synthesized through a “soft” templating method, in which appropriate amounts of metal salts (either niobium(V) chloride, or vanadium(IV) oxide sulfate hydrate or tin(II) chloride dihydrate) or tetraethyl orthosilicate (TEOS) were mixed with hexadecyltrimethylammonium chloride (HDTA) or sodium dodecyl sulfate (SDS) solutions to obtain a new series of mesoporous oxides, followed by calcination at different temperatures. As-obtained samples were characterized by SEM, TEM, XRD, and UV-Vis spectra techniques. The photocatalytic activities of the samples were evaluated by degradation of methyl orange II (MO) under simulated sunlight irradiation. The effects of metal species and calcination temperature on the physicochemical characteristic and photocatalytic activity of the samples were investigated in detail. The results indicated that, compared to pure oxides, mixed-metal oxide showed superior photocatalytic performance for the degradation of MO. A maximum photocatalytic discoloration rate of 97.3% (with MO initial concentration of 0.6·10−4 mol/dm3) was achieved in 300 min with the NbSiOx material, which was much higher than that of Degussa P25 under the same conditions. Additionally, the samples were tested in the photochemical oxidation process, i.e., advanced oxidation processes (AOPs) to treat the commercial non-ionic surfactant: propylene oxide ethylene oxide polymer mono(nonylphenyl) ether (N8P7, PCC Rokita). A maximum of 99.9% photochemical degradation was achieved in 30 min with the NbSiOx material.

Polymer Ligands with Multi‐Nitrogen Heterocyclic Carbenes for Enhanced Stability and Reactivity in Nanoparticle Surface Functionalization

Nitrogen heterocyclic carbenes (NHCs) are emerging as effective substitutes for conventional thiol ligands in surface functionalization of nanoparticles (NPs), offering exceptional stability to NPs under harsh conditions. However, the highly reactive feature of NHCs limits their use in introducing chemically active groups onto the NP surface. Herein, we develop a general yet robust strategy for the efficient surface functionalization of NPs with copolymer ligands bearing various functional groups. The polymer ligands consist of a multiple NHCs block, utilized for surface binding on NPs, alongside a poly(reactive ester) block intended for incorporating functional groups. The multiple NHCs block enables NPs with excellent colloidal stability across a broader range of pH values (0‐14), temperature variations (–78°C‐100°C), and electrolyte concentrations (0‐1000 mM). Through the in situ ammonolysis of the poly(reactive ester) block, various active functional groups can be individually or together introduced on the NP surface. We further demonstrate the chemical reactivity of these functionalized NPs, including addition polymerization, Diels‐Alder and Schiff base reactions. This method is applicable to various types of NPs, including metal NPs, metal oxide NPs, and even upconversion NPs, thereby paving new pathways for the design and creation of nanoparticle‐based functional materials.

Atomically thin high-entropy oxides via naked metal ion self-assembly for proton exchange membrane electrolysis

Designing efficient Ruthenium-based catalysts as practical anodes is of critical importance in proton exchange membrane water electrolysis. Here, we develop a self-assembly technique to synthesize 1 nm-thick rutile-structured high-entropy oxides (RuIrFeCoCrO2) from naked metal ions assembly and oxidation at air-molten salt interface. The RuIrFeCoCrO2 requires an overpotential of 185 mV at 10 m A cm−2 and maintains the high activity for over 1000 h in an acidic electrolyte via the adsorption evolution mechanism. We discuss the role of each element in the RuIrFeCoCrO2 and find that the Cr, Co, and Ir sites contribute to the catalytic activity, while the Cr atoms weaken the Ru-O bond covalency and improves the catalyst stability. The assembled proton exchange membrane electrolyzer operates stably for more than 600 h at a large current of 1 A cm−2. The naked ion assembly demonstrated in this work may provide an effective pathway for the controlled synthesis of a diversity of high-entropy materials.