Enhancing deep visible-light photoelectrocatalysis with a single solid-state synthesis: Carbon nitride/TiO2 heterointerface

Visible-light responsive, stable, and abundant absorbers are required for the rapid integration of green, clean, and renewable technologies in a circular economy. Photoactive solid-solid heterojunctions enable multiple charge pathways, inhibiting recombination through efficient charge transfer across the interface. This study spotlights the physico-chemical synergy between titanium dioxide (TiO2) anatase and carbon nitride (CN) to form a hybrid material. The CN(10%)-TiO2(90%) hybrid outperforms TiO2 and CN references and literature homologs in four photo and photoelectrocatalytic reactions. CN-TiO2 achieved a four-fold increase in benzylamine conversion, with photooxidation conversion rates of 51, 97, and 100 % at 625, 535, and 465 nm, respectively. The associated energy transfer mechanism was elucidated. In photoelectrochemistry, CN-TiO2 exhibited 23 % photoactivity of the full-spectrum measurement when using a 410 nm filter. Our findings demonstrate that CN-TiO2 displayed a band gap of 2.9 eV, evidencing TiO2 photosensitization attributed to enhanced charge transfer at the heterointerface boundaries via staggered heterojunction type II.

Recent achievements and performance of nanomaterials in microwave absorption and electromagnetic shielding

Due to the swift advancement of the electronic industry and information technology, electromagnetic wave absorption materials are gaining significance in the field of intelligent equipment and weaponry. Nanomaterials were developed to investigate wave absorbing materials that can achieve both impedance matching and attenuation balance. Nanomaterials possess the properties of being thin, lightweight, and capable of absorbing microwave radiation across a wide range of frequencies. This work aims to present a systematic overview of the recent advancements in core-shell materials, specifically carbon, oxide, and sulfide nanomaterials, with regards to their applications in electromagnetic absorption and electromagnetic shielding. This review intends to emphasize the core principles of electromagnetic interference (EMI) shielding and microwave absorption in different systems documented in the literature, along with diverse methods of synthesis and fabrication for creating effective wideband electromagnetic absorbers/shields. Lastly, we also endeavor to offer a comprehensive view and insight into the areas where future research will thrive. This study provides a comprehensive assessment of the current advancements in the field of microwave absorption and electromagnetic shielding of nanomaterials.

Ideal Photothermal Materials Based on Ge Subwavelength Structure

Photothermal materials often prioritize solar absorption while neglecting thermal radiation losses, which diminishes thermal radiation conversion efficiency. This study addresses this gap by introducing a germanium (Ge) subwavelength structure (SWS) designed to optimize both solar absorption and infrared emissivity. Using a self-masked reactive ion etching (RIE) technique, we achieved a peak absorption of 98.8% within the 300 nm to 1800 nm range, with an infrared emissivity as low as 0.32. Under solar illumination of 1000 W/m2, the structure's temperature increased by 50 °C, generating a heating power of 800 W/m2. Additionally, it demonstrated good mechanical and thermal stability at high temperatures and possessed a hydrophobic angle of 132°, ensuring effective self-cleaning. These characteristics make the Ge SWS suitable for application in solar panels, displays, sensors, and other optoelectronic devices.

Nanoribbon Yarn with Versatile Inorganic Materials

Nanomaterial-based yarns have been actively developed owing to their advantageous features, namely, high surface-area-to-volume ratios, flexibility, and unusual material characteristics such as anisotropy in electrical/thermal conductivity. The superior properties of the nanomaterials can be directly imparted and scaled-up to macro-sized structures. However, most nanomaterial-based yarns have thus far, been fabricated with only organic materials such as polymers, graphene, and carbon nanotubes. This paper presents a novel fabrication method for fully inorganic nanoribbon yarn, expanding its applicability by bundling highly aligned and suspended nanoribbons made from various inorganic materials (e.g., Au, Pd, Ni, Al, Pt, WO3, SnO2, NiO, In2O3, and CuO). The process involves depositing the target inorganic material on a nanoline mold, followed by suspension through plasma etching of the nanoline mold, and twisting using a custom-built yarning machine. Nanoribbon yarn structures of various functional inorganic materials are utilized for chemical sensors (Pd-based H2 and metal oxides (MOx)-based green gas sensors) and green energy transducers (water splitting electrodes/triboelectric nanogenerators). This method is expected to provide a comprehensive fabrication strategy for versatile inorganic nanomaterials-based yarns.

An Online Nanoinformatics Platform Empowering Computational Modeling of Nanomaterials by Nanostructure Annotations and Machine Learning Toolkits

Modern nanotechnology has generated numerous datasets from in vitro and in vivo studies on nanomaterials, with some available on nanoinformatics portals. However, these existing databases lack the digital data and tools suitable for machine learning studies. Here, we report a nanoinformatics platform that accurately annotates nanostructures into machine-readable data files and provides modeling toolkits. This platform, accessible to the public at https://vinas-toolbox.com/, has annotated nanostructures of 14 material types. The associated nanodescriptor data and assay test results are appropriate for modeling purposes. The modeling toolkits enable data standardization, data visualization, and machine learning model development to predict properties and bioactivities of new nanomaterials. Moreover, a library of virtual nanostructures with their predicted properties and bioactivities is available, directing the synthesis of new nanomaterials. This platform provides a data-driven computational modeling platform for the nanoscience community, significantly aiding in the development of safe and effective nanomaterials.

Nanoconfinement Effect in Water Processable Discrete Molecular Complex-Based Hybrid Piezo- and Thermo-Electric Nanogenerator

Water-processable hybrid piezo- and thermo-electric materials have an increasing range of applications. We use the nanoconfinement effect of ferroelectric discrete molecular complex [Cu(l-phe)(bpy)(H2O)]PF6·H2O (1) in a nonpolar polymer 1D-nanofiber to envision the high-performance flexible hybrid piezo- and thermo-electric nanogenerator (TEG). The 1D-nanoconfined crystallization of 1 enhances piezoelectric throughput with a high degree of mechano-sensitivity, i.e., 710 mV/N up to 3 N of applied force with 10,000 cycles of unaffected mechanical endurance. Thermoelectric properties analysis shows a noticeable improvement in Seebeck coefficient (∼4 fold) and power factor (∼6 fold) as compared to its film counterpart, which is attributed to the enhanced density of states near the Fermi edges as evidenced by ultraviolet photoelectric spectroscopy and density functional based theoretical calculations. We report an aqueous processable hybrid TEG that provides an impressive magnitude of Seebeck coefficient (∼793 μV/K) and power factor (∼35 mWm-1K-2) in comparison to a similar class of materials.

Recent progresses in synthesis and modification of g-C3N4 for improving visible-light-driven photocatalytic degradation of antibiotics

Graphitic carbon nitride (g-C3N4) is a widely studied visible-light-active photocatalyst for low cost, non-toxicity, and facile synthesis. Nonetheless, its photocatalytic efficiency is below par, due to fast recombination of charge carriers, low surface area, and insufficient visible light absorption. Thus, the research on the modification of g-C3N4 targeting at enhanced photocatalytic performance has attracted extensive interest. A considerable amount of review articles have been published on the modification of g-C3N4 for applications. However, limited effort has been specially contributed to providing an overview and comparison on available modification strategies for improved photocatalytic activity of g-C3N4-based catalysts in antibiotics removal. There has been no attempt on the comparison of photocatalytic performances in antibiotics removal between modified g-C3N4 and other known catalysts. To address these, our study reviewed strategies that have been reported to modify g-C3N4, including metal/non-metal doping, defect tuning, structural engineering, heterostructure formation, etc. as well as compared their performances for antibiotics removal. The heterostructure formation was the most widely studied and promising route to modify g-C3N4 with superior activity. As compared to other known photocatalysts, the heterojunction g-C3N4 showed competitive performances in degradation of selected antibiotics. Related mechanisms were discussed, and finally, we revealed current challenges in practical application.

Updates on Hydrogen Value Chain: A Strategic Roadmap

A strategic roadmap for noncarbonized fuels is a global priority, and the reduction of carbon dioxide emissions is a key focus of the Paris Agreement to mitigate the effects of rising temperatures. In this context, hydrogen is a promising noncarbonized fuel, but the pace of its implementation will depend on the engineering advancements made at each step of its value chain. To accelerate its adoption, various applications of hydrogen across industries, transport, power, and building sectors have been identified, where it can be used as a feedstock, fuel, or energy carrier and storage. However, widespread usage of hydrogen will depend on its political, industrial, and social acceptance. It is essential to carefully assess the hydrogen value chain and compare it with existing solar technologies. The major challenge to widespread adoption of hydrogen is its cost as outlined in the roadmap for hydrogen. It needs to be produced at the levelized cost of hydrogen of less than $2 kg-1 to be competitive with the established process of steam methane reforming. Therefore, this review provides a comprehensive analysis of each step of the hydrogen value chain, outlining both the current challenges and recent advances.

Catalytically Active Carbon for Oxygen Reduction Reaction in Energy Conversion: Recent Advances and Future Perspectives

The shortage and unevenness of fossil energy sources are affecting the development and progress of human civilization. The technology of efficiently converting material resources into energy for utilization and storage is attracting the attention of researchers. Environmentally friendly biomass materials are a treasure to drive the development of new-generation energy sources. Electrochemical theory is used to efficiently convert the chemical energy of chemical substances into electrical energy. In recent years, significant progress has been made in the development of green and economical electrocatalysts for oxygen reduction reaction (ORR). Although many reviews have been reported around the application of biomass-derived catalytically active carbon (CAC) catalysts in ORR, these reviews have only selected a single/partial topic (including synthesis and preparation of catalysts from different sources, structural optimization, or performance enhancement methods based on CAC catalysts, and application of biomass-derived CACs) for discussion. There is no review that systematically addresses the latest progress in the synthesis, performance enhancement, and applications related to biomass-derived CAC-based oxygen reduction electrocatalysts synchronously. This review fills the gap by providing a timely and comprehensive review and summary from the following sections: the exposition of the basic catalytic principles of ORR, the summary of the chemical composition and structural properties of various types of biomass, the analysis of traditional and the latest popular biomass-derived CAC synthesis methods and optimization strategies, and the summary of the practical applications of biomass-derived CAC-based oxidative reduction electrocatalysts. This review provides a comprehensive summary of the latest advances to provide research directions and design ideas for the development of catalyst synthesis/optimization and contributes to the industrialization of biomass-derived CAC electrocatalysis and electric energy storage.

Constructing a P2W18O626--Containing Hybrid Photocatalyst via Noncovalent Interactions for Enhanced H2 Production

Polyoxometalates (POMs) have gained significant research attention because of their excellent properties in photocatalytic (PC) hydrogen production. Exploring POM-based compounds for heterogeneous photocatalysis is an ongoing task. Here, we obtain a water-insoluble inorganic-organic hybrid compound, (P2W18O62)3(C12N3H10)6(C12N3H11)6·9.5H2O (P-PW), formed by Dawson-type POM P2W18O626- (P2W18) anions and protonated 2-(pyridin-4-yl)-1H-benzo[d]imidazole (PHB) cations via noncovalent interactions. In the presence of the sacrificial agent triethanolamine, P-PW exhibits a PC H2 generation rate of 0.418 mmol/g/h, surpassing that of P2W18 and PHB by 15 and 17 times, respectively. This enhancement in PC performance of P-PW can be attributed to its band structure change from the precursor compounds, leading to increased light absorption and therefore more efficient PC hydrogen production.

Enhanced-Performance Triboelectric Nanogenerator Based on Polydimethylsiloxane/Barium Titanate/Graphene Quantum Dot Nanocomposites for Energy Harvesting

Triboelectric nanogenerators (TENGs) have been developed as promising energy-harvesting devices to effectively convert mechanical energy into electricity. TENGs use either organic or inorganic materials to initiate the triboelectrification process, followed by charge separation. In this study, a high-performance composite-based triboelectric nanogenerator (CTENG) device was fabricated, comprising polydimethylsiloxane (PDMS) as a polymeric matrix, barium titanite (BTO) nanopowders as dielectric fillers, and graphene quantum dots (GQDs) as conductive media. The PDMS/BTO/GQD composite film was prepared with GQDs doped into the mixture of PDMS/BTO and mechanically stirred. The composition of the GQD varied from 0 to 40 wt %. The composite was spin-coated onto flexible ITO on a PET sheet and dried in an oven at 80 °C for 24 h. The output performance of TENGs is enhanced by the increased concentration of 30 wt % GQD, which is 2 times higher than nanocomposite films without GQD. The PDMS/BTO/G30 TENG film depicted an increase in open-circuit voltage output (VOC), short-circuit current output (ISC), and power density reaching ∼310.0 V, ∼23.0 μA, and 1.6 W/m2, respectively. The simple and scalable process for the PDMS/BTO/GQD TENGs would benefit as a sustainable energy-harvesting system in small electronic devices.

Sputtered Silicon-Coated Graphite Electrodes as High Cycling Stability and Improved Kinetics Anodes for Lithium Ion Batteries

Amorphous Si thin films with different thicknesses were deposited on synthetic graphite electrodes by using a simple and scalable one-step physical vapor deposition (PVD) method. The specific capacities and rate capabilities of the produced electrodes were investigated. X-ray diffraction, scanning electron microscopy, Raman spectroscopy, profilometry, cyclic voltammetry, galvanostatic techniques, and in situ Raman spectroscopy were used to investigate their physicochemical and electrochemical properties. Our results demonstrated that the produced Si films covered the bare graphite electrodes completely and uniformly. Si-coated graphite, Si@G, with an optimal thickness of 1 μm exhibited good stability, with an initial discharge capacity of 628.7 mAhg-1, a capacity retention of 96.2%, and a columbic efficiency (CE) higher than 99% at C/3. A discharge capacity of 250 mAh g-1 was attained at a high current rate of 3C, which was over 2.5 times that of a bare graphite electrode, thanks to the high activated surface area (1.5 times that of pristine graphite) and reduced resistance during cycling.

Progress and Advances in Porous Silica-based Scaffolds for Enhanced Solid-state Hydrogen Storage: A Systematic Literature Review

Hydrogen plays a crucial role in the future energy landscape owing to its high energy density. However, finding an ideal storage material is the key challenge to the success of the hydrogen economy. Various solid-state hydrogen storage materials, such as metal hydrides, have been developed to realize safe, effective, and compact hydrogen storage. However, low kinetics and thermodynamic stability lead to a high working temperature and a low hydrogen sorption rate of the metal hydrides. Using scaffolds made from porous materials like silica to confine the metal hydrides is necessary for better and improved hydrogen storage. Therefore, this article reviews porous silica-based scaffolds as an ideal material for improved hydrogen storage. The outcome showed that confining the metal hydrides using scaffolds based on porous silica significantly increases their storage capacities. It was also found that the structural modifications of the silica-based scaffold into a hollow structure further improved the storage capacity and increased the affinity and confinement ability of the metal hydrides, which prevents the agglomeration of metal particles during the adsorption/desorption process. Hence, the structural modifications of the silica material into a fibrous and hollow material are recommended to be crucial for further enhancing the metal hydride storage capacity.

Selective Gas-Phase Hydrogenation of CO2 to Methanol Catalysed by Metal-Organic Frameworks

Large scale production of green CH3 OH obtained from CO2 and green H2 is a highly wanted process due to the role of CH3 OH as H2 /energy carrier and for producing chemicals. Starting with a short summary of the advantages of metal-organic frameworks (MOFs) as catalysts in liquid-phase reactions, the present article highlights the opportunities that MOFs may offer also for some gas-phase reactions, particularly for the selective CO2 hydrogenation to CH3 OH. It is commented that there is a temperature compatibility window that combines the thermal stability of some MOFs with the temperature required in the CO2 hydrogenation to CH3 OH that frequently ranges from 250 to 300 °C. The existing literature in this area is briefly organized according to the role of MOF as providing the active sites or as support of active metal nanoparticles (NPs). Emphasis is made to show how the flexibility in design and synthesis of MOFs can be used to enhance the catalytic activity by adjusting the composition of the nodes and the structure of the linkers. The influence of structural defects and material crystallinity, as well as the role that should play theoretical calculations in models have also been highlighted.

Controlled Growth of WO3 Photoanode under Various pH Conditions for Efficient Photoelectrochemical Performance

Herein, the effects of the precursor solution's acidity level on the crystal structure, morphology, nucleation, and growth of WO3·nH2O and WO3 nanostructures are reported. Structural investigations on WO3·nH2O using X-ray diffraction and Fourier-transform infrared spectroscopy confirm that the quantity of hydrate groups increases due to the interaction between H+ and water molecules with increasing HCl volume. Surface analysis results support our claim that the evolution of grain size, surface roughness, and growth direction on WO3·nH2O and WO3 nanostructures rely on the precursor solution's pH value. Consequently, the photocurrent density of a WO3 photoanode using a HCl-5 mL sample achieves the best results with 0.9 mA/cm2 at 1.23 V vs. a reversible hydrogen electrode (RHE). We suggest that the improved photocurrent density of the HCl-5 mL sample is due to the efficient light absorption from the densely grown WO3 nanoplates on a substrate and that its excellent charge transport kinetics originate from the large surface area, low charge transfer resistance, and fast ion diffusion through the photoanode/electrolyte interface.

Data-Driven Predetermination of Cu Oxidation State in Copper Nanoparticles: Application to the Synthesis by Laser Ablation in Liquid

Copper-based nanocrystals are reference nanomaterials for integration into emerging green technologies, with laser ablation in liquid (LAL) being a remarkable technique for their synthesis. However, the achievement of a specific type of nanocrystal, among the whole library of nanomaterials available using LAL, has been until now an empirical endeavor based on changing synthesis parameters and characterizing the products. Here, we started from the bibliographic analysis of LAL synthesis of Cu-based nanocrystals to identify the relevant physical and chemical features for the predetermination of copper oxidation state. First, single features and their combinations were screened by linear regression analysis, also using a genetic algorithm, to find the best correlation with experimental output and identify the equation giving the best prediction of the LAL results. Then, machine learning (ML) models were exploited to unravel cross-correlations between features that are hidden in the linear regression analysis. Although the LAL-generated Cu nanocrystals may be present in a range of oxidation states, from metallic copper to cuprous oxide (Cu2O) and cupric oxide (CuO), in addition to the formation of other materials such as Cu2S and CuCN, ML was able to guide the experiments toward the maximization of the compounds in the greatest demand for integration in sustainable processes. This approach is of general applicability to other nanomaterials and can help understand the origin of the chemical pathways of nanocrystals generated by LAL, providing a rational guideline for the conscious predetermination of laser-synthesis parameters toward the desired compounds.

Interfacial Effect-Induced Electrocatalytic Activity of Spinel Cobalt Oxide in Methanol Oxidation Reaction

In this study, spinel cobalt oxide (Co3O4) nanoparticles without combining with any other metal atoms have been decorated through the influence of two hard templating agents, viz., zeolite-Y and carboxy-functionalized multiwalled carbon nanotubes (COOH-MWCNT). The adornment of the Co3O4 nanoparticles, through the combined impact of the aluminosilicate and carbon framework has resulted in quantum interference, causing the reversal of signatory Raman peaks of Co3O4. Apart from the construction of small Co3O4 nanoparticles at the interface of the two matrices, the particles were aligned along the direction of COOH-MWCNT. The catalyst Co3O4-Y-MWCNT exhibited excellent catalytic activity toward the methanol oxidation reaction (MOR) in comparison to Co3O4-Y, Co3O4-MWCNT, and bared Co3O4 with the current density of 0.92 A mg-1 at an onset potential of 1.33 V versus RHE. The material demonstrated persistent electrocatalytic activity up to 300 potential cycles and 20,000 s without substantial current density loss. High surface area of zeolite-Y in combination with the excellent conductivity of the COOH-MWCNT enhanced the electrocatalytic performance of the catalyst. The simplicity of synthesis, scale-up, and remarkable electrocatalytic activity of the catalyst Co3O4-Y-MWCNT provided an effective way toward the development of anode materials for direct methanol fuel cells.

Development of Electrochemical Cells and Their Application for Spatially Resolved Analysis Using a Multitechnique Approach: From Conventional Experiments to X-Ray Nanoprobe Beamlines

Real (electro)catalysts are often heterogeneous, and their activity and selectivity depend on the properties of specific active sites. Therefore, unveiling the so-called structure-activity relationship is essential for a rational search for better materials and, consequently, for the development of the field of (electro-)catalysis. Thus, spatially resolved techniques are powerful tools as they allow us to characterize and/or measure the activity and selectivity of different regions of heterogeneous catalysts. To take full advantage of that, we have developed spectroelectrochemical cells to perform spatially resolved analysis using X-ray nanoprobe synchrotron beamlines and conventional pieces of equipment. Here, we describe the techniques available at the Carnaúba beamline at the Sirius-LNLS storage ring, and then we show how our cells enable obtaining X-ray (XRF, XRD, XAS, etc.) and vibrational spectroscopy (FTIR and Raman) contrast images. Through some proof-of-concept experiments, we demonstrate how using a multi-technique approach could render a complete and detailed analysis of an (electro)catalyst overall performance.

Controllable synthesis of Fe3C-reinforced petal-like lignin microspheres with boosted electrochemical performance and its application in high performance supercapacitors

One more effective measure to solve the energy crisis caused by the shortage of fossil energy is to convert natural renewable resources into high-value chemical products for electrochemical energy storage. Lignin has broad application prospects in this field. In this paper, three kinds of lignin with different molecular weights were obtained by the ethanol/water grading of Kraft lignin (KL). Then, different surface morphology lignin microspheres were prepared by spray drying. Finally, petal-like microspheres were successfully prepared by mixing and grinding the above four kinds of surface morphology lignin microspheres with potassium ferrate and cyanogen chloride and carbonizing at 800 °C and were later used as electrode materials for supercapacitors. Compared with the other microspheres, LMS-F3@Fe3C has the highest specific surface area (1041.42 m2 g-1), the smallest pore size (2.36 nm) and the largest degree of graphitization (ID/IG = 1.06). At a current density of 1 A g-1, the maximum specific capacitance is 786.7 F g-1. At a power density of 1000 W kg-1, the high energy density of 83.3 Wh kg-1 is displayed. This work provides a novel approach to the modulation of surface morphology and structure of lignin microspheres.

Cobalt Ferrite Surface-Modified Carbon Nanotube Fibers as an Efficient and Flexible Electrode for Overall Electrochemical Water Splitting Reactions

One of the most practical and environmentally friendly ways to deal with the energy crises and global warming is to produce hydrogen as clean fuel by splitting water. The central obstacle for electrochemical water splitting is the use of expensive metal-based catalysts. For electrocatalytic hydrogen production, it is essential to fabricate an efficient catalyst for the counterpart oxygen evolution reaction (OER), which is a four-electron-transfer sluggish process. Here in this study, we have successfully fabricated cobalt-based ferrite nanoparticles over the surface of carbon nanotube fiber (CNTF) that was utilized as flexible anode materials for the OER and overall electrochemical water splitting reactions. Scanning electron microscopy images with elemental mapping showed the growth of nanoparticles over CNTF, while electrochemical characterization exhibited excellent electrocatalytic performance. Linear sweep voltammetry revealed the reduced overpotential value (260 mV@η10mAcm-2) with a small Tafel slope of 149 mV dec-1. Boosted electrochemical double layer capacitance (0.87 mF cm-2) for the modified electrode also reflects the higher surface area as compared to pristine CNTF (Cdl = 0.022 mF cm-2). Charge transfer resistance for the surface-modified CNTF showed the lower diameter in the Nyquist plot and was consequently associated with the better Faradaic process at the electrode/electrolyte interface. Overall, the as-fabricated electrode could be a promising alternative for the efficient electrochemical water splitting reaction as compared to expensive metal-based electrocatalysts.

Stability Modification of Dye-sensitized Solar Cells by Ruthenium Dyes Embedded on Eggshell Membranes

Dye-sensitized solar cells (DSSCs) have been one of the most promising technologies to convert sunlight into electricity repeatedly based on the mechanism that dyes inject/accept electron into the metal oxides/from redox mediator. Specifically, N719 ([RuL2(NCS)2], L: 4,4'-dicarboxy-2,2'-bipyridine), immobilized on TiO2 through the interaction between its ligands (-COO- and -NCS) and the oxygen on the TiO2 surface, has been used as a conventional DSSC dye with high voltage. Nevertheless, -NCS ligands have been removed from Ru2+ in N719 due to UV irradiation and exchanged with H2O or OH- in electrolyte, resulting in voltage drop. In this work, we developed the first DSSC using the N719-adsorbed Eggshell (ESM)-TiO2 composite to maintain the immobilization of N719 on TiO2 through electrostatic interaction between the protein of ESM and N719. The DSSC using the composite maintained the voltage even after 12 h light irradiation, although the voltage of DSSC without ESM dropped drastically. It means that the ESM contributed to stable photovoltaic performances of DSSCs through the protection of NCS ligands of N719.

Functionalization of Fluorine on the Surface of SnO2-Mg Nanocomposite as an Efficient Photocatalyst for Toxic Dye Degradation

This work reports on the photocatalytic activity of tin oxide (SnO2)-doped magnesium (Mg) and fluorine (F) nanoparticles for methyl orange and safranin dye degradation under sunlight irradiation. Nanocatalysis-induced dye degradation was examined using UV-visible spectroscopy and a pseudo-first-order kinetics model. The results indicate that the prepared nanoparticles exhibit superior photocatalytic activity, and the degradation of methyl orange (MO) dye is approximately 82%. In contrast, the degradation of safranin dye is 96% in the same time interval of 105 min. The calculated crystallite size of the SnO2-Mg-F nanocomposite is 29.5 nm, which respects the particle size found in the DLS analysis with a tetragonal structure and spherical morphology affirmed. The optical characteristics were assessed, and their respective bandgap energies were determined to be 3.6 eV. The influence of F in Mg and SnO2 is recognized with the XRD and FT-IR spectra of the prepared particles.

Efficient Photoelectrochemical Hydrogen Generation Using Eco-Friendly "Giant" InP/ZnSe Core/Shell Quantum Dots

InP quantum dots (QDs) are promising building blocks for use in solar technologies because of their low intrinsic toxicity, narrow bandgap, large absorption coefficient, and low-cost solution synthesis. However, the high surface trap density of InP QDs reduces their energy conversion efficiency and degrades their long-term stability. Encapsulating InP QDs into a wider bandgap shell is desirable to eliminate surface traps and improve optoelectronic properties. Here, we report the synthesis of "giant" InP/ZnSe core/shell QDs with tunable ZnSe shell thickness to investigate the effect of the shell thickness on the optoelectronic properties and the photoelectrochemical (PEC) performance for hydrogen generation. The optical results demonstrate that ZnSe shell growth (0.9-2.8 nm) facilitates the delocalization of electrons and holes into the shell region. The ZnSe shell simultaneously acts as a passivation layer to protect the surface of InP QDs and as a spatial tunneling barrier to extract photoexcited electrons and holes. Thus, engineering the ZnSe shell thickness is crucial for the photoexcited electrons and hole transfer dynamics to tune the optoelectronic properties of "giant" InP/ZnSe core/shell QDs. We obtained an outstanding photocurrent density of 6.2 mA cm^-1 for an optimal ZnSe shell thickness of 1.6 nm, which is 288% higher than the values achieved from bare InP QD-based PEC cells. Understanding the effect of shell thickness on surface passivation and carrier dynamics offers fundamental insights into the suitable design and realization of eco-friendly InP-based "giant" core/shell QDs toward improving device performance.

Exchanging Anion in CuCo-Carbonate Double Hydroxide for Faradaic Supercapacitors: A Case Study

A systematic synthetic method involving the anion exchange process was designed and developed to fabricate the superior functioning three-dimensional (3-D) urchin-architectured copper cobalt oxide (CuCo₂O₄; CCO) and copper cobalt sulfide (CuCo₂S₄; CCS) electrode materials from copper-cobalt carbonate double hydroxide [(CuCo)₂(CO₃)(OH)₂; CCH]. The effective tuning of chemical, crystalline, and morphological properties was achieved during the derivatization process of CCH, based on the anion exchange effect and phase transformation without altering the 3-D spatial assembly. Benefiting from morphological and structural advantages, CCO and CCS exhibited superior electrochemical activity with capacity values of 1508 and 2502 C g^-1 at 10 A g^-1 to CCH (1182 C g^-1 at 10 A g^-1). The thermal treatment of CCH has generated a highly porous nature in nanospikes of 3-D urchin CCO structures, which purveys betterment in electrochemical phenomena than pristine smooth-surfaced CCH. Meanwhile, the sulfurization reaction induced the anion effect to a greater extent in the CCS morphology, resulting in hierarchical 3-D urchins formed by 1-D nanospikes constituting coaxially swirled 2-D nanosheets with high exposure of active sites, specific surface areas, and 3-D electron/ion transportation channels. The asymmetric supercapacitor was constructed with a superior CCS electrode as a cathode and an activated carbon electrode as an anode, showing a high specific capacity of 287.35 C g^-1 at 7 A g^-1 and durability for 5000 cycles with 94.2% retention at a high current density of 30 A g^-1. The ultrahigh energy and power density of 135.3 W h kg^-1 (10 A g^-1) and 44.35 kW kg^-1 (30 A g^-1) were harvested during the PC device performance. Our finding proposes an idea about the importance of anions and phase transformation as a versatile tool for engineering high-functioning electrode materials and their endeavor toward overwhelming the major demerit of SCs by aggrandizing the energy density value and rate performance.

MgIn2S4/UiO-66-NH2 MOF-Based Heterostructure: Visible-Light-Responsive Z-Scheme-Mediated Synergistically Enhanced Photocatalytic Performance toward Hydrogen and Oxygen Evolution

Hydrogen and oxygen evolution via photocatalytic water splitting remains the quintessential alternative to fossil fuels. Photocatalysts must be sufficiently robust, competent, and productive toward harnessing sunlight in order to utilize the solar spectrum for maximal photocatalytic output. Herein, we have fabricated the MgIn₂S₄/UiO-66-NH₂ composite via a facile solvothermal route and have determined its efficacy toward light-induced H₂ and O₂ generation reactions through water splitting with the aid of different sacrificial agents. Initially, the formation of pristine and composite materials was ascertained by PXRD, FTIR, etc. Moreover, with the aid of sophisticated morphological characterization techniques (FESEM and HRTEM), the intricate interaction between MgIn₂S₄ and UiO-66-NH₂ was revealed. Additionally, the XPS studies suggested the effective interaction between the individual components with binding energy shifting suggesting the transfer of electrons from Zr-MOF to MgIn₂S₄. The PL and electrochemical aspects supported the effective photogenerated charge segregation in the prepared composite leading to superior photocatalytic outputs. Amidst the prepared composites of (3, 5, and 7 wt %) MgIn₂S₄/UiO-66-NH₂, the 5 wt % or UM-2 composite displays optimal H₂ and O₂ evolution performances of 493.8 and 258.6 μmol h^-1 (4-fold greater than for pristine MgIn₂S₄ and UiO-66-NH₂), respectively. The nanocomposite's enhanced performance is indeed a consequence of the coadjuvant interaction among pristine UiO-66-NH₂ and MgIn₂S₄ components that transpires via the Z-scheme-mediated charge transfer by enabling facile exciton segregation and channelization. Moreover, the composite inherited the remarkable framework stability of parent Zr-MOF, and the MgIn₂S₄ insertion had a negligible impact on the framework integrity. This work will offer a valuable model for developing robust Zr-MOF-based nanocomposite photocatalysts and evaluating their superior performance toward photocatalytic water redox reactions.

Photothermal Nanomaterials: A Powerful Light-to-Heat Converter

All forms of energy follow the law of conservation of energy, by which they can be neither created nor destroyed. Light-to-heat conversion as a traditional yet constantly evolving means of converting light into thermal energy has been of enduring appeal to researchers and the public. With the continuous development of advanced nanotechnologies, a variety of photothermal nanomaterials have been endowed with excellent light harvesting and photothermal conversion capabilities for exploring fascinating and prospective applications. Herein we review the latest progresses on photothermal nanomaterials, with a focus on their underlying mechanisms as powerful light-to-heat converters. We present an extensive catalogue of nanostructured photothermal materials, including metallic/semiconductor structures, carbon materials, organic polymers, and two-dimensional materials. The proper material selection and rational structural design for improving the photothermal performance are then discussed. We also provide a representative overview of the latest techniques for probing photothermally generated heat at the nanoscale. We finally review the recent significant developments of photothermal applications and give a brief outlook on the current challenges and future directions of photothermal nanomaterials.

Recent Advances in Electrochemical, Photochemical, and Photoelectrochemical Reduction of CO2 to C2+ Products

Environmental problems such as global warming are one of the most prominent global challenges. Researchers are investigating various methods for decreasing CO₂ emissions. The CO₂ reduction reaction via electrochemical, photochemical, and photoelectrochemical processes has been a popular research topic because the energy it requires can be sourced from renewable sources. The CO₂ reduction reaction converts stable CO₂ molecules into useful products such as CO, CH₄ , C₂ H₄ , and C₂ H₅ OH. To obtain economic benefits from these products, it is important to convert them into hydrocarbons above C₂ . Numerous investigations have demonstrated the uniqueness of the CC coupling reaction of Cu-based catalysts for the conversion of CO₂ into useful hydrocarbons above C₂ for electrocatalysis. Herein, the principle of semiconductors for photocatalysis is briefly introduced, followed by a description of the obstacles for C₂₊ production. This review presents an overview of the mechanism of hydrocarbon formation above C₂ , along with advances in the improvement, direction, and comprehension of the CO₂ reduction reaction via electrochemical, photochemical, and photoelectrochemical processes.

Integrating structure annotation and machine learning approaches to develop graphene toxicity models

Modern nanotechnology provides efficient and cost-effective nanomaterials (NMs). The increasing usage of NMs arises great concerns regarding nanotoxicity in humans. Traditional animal testing of nanotoxicity is expensive and time-consuming. Modeling studies using machine learning (ML) approaches are promising alternatives to direct evaluation of nanotoxicity based on nanostructure features. However, NMs, including two-dimensional nanomaterials (2DNMs) such as graphenes, have complex structures making them difficult to annotate and quantify the nanostructures for modeling purposes. To address this issue, we constructed a virtual graphenes library using nanostructure annotation techniques. The irregular graphene structures were generated by modifying virtual nanosheets. The nanostructures were digitalized from the annotated graphenes. Based on the annotated nanostructures, geometrical nanodescriptors were computed using Delaunay tessellation approach for ML modeling. The partial least square regression (PLSR) models for the graphenes were built and validated using a leave-one-out cross-validation (LOOCV) procedure. The resulted models showed good predictivity in four toxicity-related endpoints with the coefficient of determination (R2) ranging from 0.558 to 0.822. This study provides a novel nanostructure annotation strategy that can be applied to generate high-quality nanodescriptors for ML model developments, which can be widely applied to nanoinformatics studies of graphenes and other NMs.

Functionalized MOF-Based Photocatalysts for CO2 Reduction

Metal-organic frameworks (MOFs) materials have become a research forefront in the field of photocatalytic CO₂ reduction attributed to their ultra-high specific surface area, adjustable structure, and abundant catalytic active sites. Particularly, MOFs can be facilely tuned to match CO₂ photoreduction by utilizing post-modification of metal nodes, functionalization of organic linkers, and combination with other active materials. Herein, the recent advances in the construction strategy of MOF-based photocatalysts materials for CO₂ reduction are highlighted. Some systematic modification strategies on MOF-based photocatalysts are also discussed, such as modification of metal sites and organic ligands, construction of heterojunction, introduction of single/dual-atom, and strain engineering. Finally, the future development directions of MOF-based photocatalysts in the field of CO₂ reduction are presented.

Coffee-waste templated CeOx/TiO2 nanostructured materials for selective photocatalytic oxidations

An environmentally friendly solvent-free approach was tested using spent coffee as a biomass sacrificial template for the preparation of TiO₂ modified with CeO_x. The use of coffee as a template pursues the preparation of a nanostructured heterojunction without the need for a solvent. Two variables were optimized in the synthesis process, i.e. calcination temperature and proportion of CeO_x. Firstly, bare coffee-template titania was prepared to explore the effect of the calcination temperature, within 500-650 °C. The anatase phase was obtained up to 600 °C. Higher temperatures, i.e. 650 °C, led to the appearance of rutile (10%) and efficient removal of the sacrificial agent (0.6% residue). The maximum photocatalytic activity in terms of conversion, in the oxidation of benzyl alcohol, was achieved employing the bare coffee-template TiO₂ at 650 °C, and it was found comparable to the benchmarked P25. The incorporation of ceria in the solvent-free approach considerably improved photocatalytic benzaldehyde production. No changes in the XRD pattern of TiO₂ were appreciated in the presence of ceria due to the low amount added, within 1.5-6.0%, confirmed by XPS as superficial Ce³⁺/Ce⁴⁺. The UV-visible absorption spectra were considerably redshifted in the presence of Ce, reducing the bandgap values of bare titania. An optimum amount of ceria in the structure within 3-0% was found. In this case, the selectivity towards benzaldehyde was ca. 75%, 3 times higher than the selectivity value registered for the benchmarked P25 or the bare prepared TiO₂.

Fight for carbon neutrality with state-of-the-art negative carbon emission technologies

After the Industrial Revolution, the ever-increasing atmospheric CO2 concentration has resulted in significant problems for human beings. Nearly all countries in the world are actively taking measures to fight for carbon neutrality. In recent years, negative carbon emission technologies have attracted much attention due to their ability to reduce or recycle excess CO2 in the atmosphere. This review summarizes the state-of-the-art negative carbon emission technologies, from the artificial enhancement of natural carbon sink technology to the physical, chemical, or biological methods for carbon capture, as well as CO2 utilization and conversion. Finally, we expound on the challenges and outlook for improving negative carbon emission technology to accelerate the pace of achieving carbon neutrality.

Effect of Ag-Decorated BiVO4 on Photoelectrochemical Water Splitting: An X-ray Absorption Spectroscopic Investigation

Bismuth vanadate (BiVO₄) has attracted substantial attention on account of its usefulness in producing hydrogen by photoelectrochemical (PEC) water splitting. The exploitation of BiVO₄ for this purpose is yet limited by severe charge recombination in the bulk of BiVO₄, which is caused by the short diffusion length of the photoexcited charge carriers and inefficient charge separation. Enormous effort has been made to improve the photocurrent density and solar-to-hydrogen conversion efficiency of BiVO₄. This study demonstrates that modulating the composition of the electrode and the electronic configuration of BiVO₄ by decoration with silver nanoparticles (Ag NPs) is effective in not only enhancing the charge carrier concentration but also suppressing charge recombination in the solar water splitting process. Decoration with a small number of Ag NPs significantly enhances the photocurrent density of BiVO₄ to an extent that increases with the concentration of the Ag NPs. At 0.5% Ag NPs, the photocurrent density approaches 4.1 mA cm^-2 at 1.23 V versus a reversible hydrogen electrode (RHE) under solar simulated light illumination; this value is much higher than the 2.3 mA cm^-2 of pure BiVO₄ under the same conditions. X-ray absorption spectroscopy (XAS) is utilized to investigate the electronic structure of pure BiVO₄ and its modification by decoration with Ag NPs. Analytical results indicate that increased distortion of the VO₄ tetrahedra alters the V 3d-O 2p hybridized states. Additionally, as the Ag concentration increases, the oxygen vacancy defects that act as recombination centers in BiVO₄ are reduced. In situ XAS, which is conducted under dark and solar illumination conditions, reveals that the significantly enhanced PEC performance is attributable to the synergy of modulated atomic/electronic structures and the localized surface plasmon resonance effect of the Ag nanoparticles.

Discovery of Two-Dimensional Multinary Component Photocatalysts Accelerated by Machine Learning

Searching for novel and high-performance two-dimensional (2D) materials is an important task for photocatalytic applications. Although multinary compounds exhibit more diversity in structure and properties in comparison to binary 2D materials, they are comparatively under-studied. Herein, using a machine-learning (ML) technique and high-throughput screening, we develop an efficient approach to accurately predict 2D multicomponent photocatalysts. Over 4000 monolayers are examined, and 75 multinary compounds are identified for photocatalytic applications. Considering our predictions, we find that the ternary and quaternary compounds A₂P₂X₆ and ABP₂X₆ with A = Cu/Zn/Ge/Ag/Cd, B = Ga/In/Bi, and X = S/Se exhibit superior properties, making them promising candidates for overall water splitting. Thus, our work provides an efficient way to explore novel photocatalysts, which could stimulate further theoretical and experimental investigations on 2D multinary compounds for application in photocatalytic water splitting.

Enhanced Photocatalytic Hydrogen Production Activity by Constructing a Robust Organic-Inorganic Hybrid Material Based Fulvalene and TiO2

A novel redox-active organic-inorganic hybrid material (denoted as H₄TTFTB-TiO₂) based on tetrathiafulvalene derivatives and titanium dioxide with a micro/mesoporous nanomaterial structure has been synthesized via a facile sol-gel method. In this study, tetrathiafulvalene-3,4,5,6-tetrakis(4-benzoic acid) (H₄TTFTB) is an ideal electron-rich organic material and has been introduced into TiO₂ for promoting photocatalytic H₂ production under visible light irradiation. Notably, the optimized composites demonstrate remarkably enhanced photocatalytic H₂ evolution performance with a maximum H₂ evolution rate of 1452 μmol g⁻¹ h⁻¹, which is much higher than the prototypical counterparts, the common dye-sensitized sample (denoted as H₄TTFTB-5.0/TiO₂) (390.8 μmol g⁻¹ h⁻¹) and pure TiO₂ (18.87 μmol g⁻¹ h⁻¹). Moreover, the composites perform with excellent stability even after being used for seven time cycles. A series of characterizations of the morphological structure, the photoelectric physics performance and the photocatalytic activity of the hybrid reveal that the donor-acceptor structural H₄TTFTB and TiO₂ have been combined robustly by covalent titanium ester during the synthesis process, which improves the stability of the hybrid nanomaterials, extends visible-light adsorption range and stimulates the separation of photogenerated charges. This work provides new insight for regulating precisely the structure of the fulvalene-based composite at the molecule level and enhances our in-depth fundamental understanding of the photocatalytic mechanism.

Achieving high selectivity towards electro-conversion of CO2 using In-doped Bi derived from metal-organic frameworks

Metal-organic frameworks (MOFs) and their derivatives have shown great potential as electrocatalysts, in virtue of their ease of functionalization and abundance of active sites. Here, we report a series of indium-doped bismuth MOF-derived composites (BiIn_X-Y@C) for the direct conversion of carbon dioxide (CO₂) to hydrocarbon derivatives. Amongst the catalysts studied, BiIn₅-500@C demonstrated high selectivity for the production of formate and intrinsic activity in a wide potential window, ranging from - 1.16 to - 0.76 V vs. RHE (V_RHE). At - 0.86 V_RHE, the Faradaic efficiency and total current density were determined as 97.5% and - 13.5 mA cm^-2, respectively. In addition, a 15-h stability test shows no obvious signs of deactivation. Complementary density functional theory (DFT) calculations revealed that the In-doped Bi₂O₃ are the predominant active centers for HCOOH production in the reduction of CO₂ under the action of the BiIn_X-Y@C catalyst. This work provides new detailed insights into reaction mechanism, and selectivity for reduction of CO₂via MOFs, which are expected to inspire and guide the design of novel, selective and efficient catalysts.

Progress in Preparation of Sea Urchin-like Micro-/Nanoparticles

Urchin-like microparticles/nanoparticles assembled from radial nanorods have a good appearance and high specific surface area, providing more exposed active sites and shortening the diffusion path of photoexcited carriers from the interior to the surface. The interfacial interaction and physical and chemical properties of the materials can be improved by the interfacial porous network induced by interlacing nano-branches. In addition, multiple reflections of the layered microstructure can absorb more incident light and improve the photocatalytic performance. Therefore, the synthesis and functionalization of three-dimensional urchin-like nanostructures with controllable size, shape, and hierarchy have attracted extensive attention. This review aims to provide an overview to summarize the structures, mechanism, and application of urchin-like microparticles/nanoparticles derived from diverse synthesis methods and decoration types. Firstly, the synthesis methods of solid urchin-like micro-/nanoparticles are listed, with emphasis on the hydrothermal/solvothermal method and the reaction mechanism of several typical examples. Subsequently, the preparation method of composite urchin-like micro-/nanoparticles is described from the perspective of coating and doping. Then, the research progress of urchin-like hollow microspheres is reviewed from the perspective of the step-by-step method and synchronous method, and the formation mechanism of forming urchin-like hollow microspheres is discussed. Finally, the application progress of sea urchin-like particles in the fields of photocatalysis, electrochemistry, electromagnetic wave absorption, electrorheological, and gas sensors is summarized.

Relationship between the Formation of Magnetic Clusters and Hexagonal Phase of Gold Matrix in AuxFe1-x Nanophase Thin Films

AuxFe1-x nanophase thin films of different compositions and thicknesses were prepared by co-deposition magnetron sputtering. Complex morpho-structural and magnetic investigations of the films were performed by X-ray Diffraction, cross-section Transmission Electron Microscopy, Selected Area Electron Diffraction, Magneto Optical Kerr Effect, Superconducting Quantum Interference Device magnetometry and Conversion Electron Mössbauer Spectroscopy. It was proven that depending on the preparation conditions, different configurations of defect α-Fe magnetic clusters, i.e., randomly distributed or auto-assembled in lamellar or filiform configurations, can be formed in the Au matrix. A close relationship between the Fe clustering process and the type of the crystalline structure of the Au matrix was underlined, with the stabilization of a hexagonal phase at a composition close to 70 at. % of Au and at optimal thickness. Due to different types of inter-cluster magnetic interactions and spin anisotropies, different types of magnetic order from 2D Ising type to 3D Heisenberg type, as well as superparamagnetic behavior of non-interacting Fe clusters of similar average size, were evidenced.

Environment Friendly g-C3N4-Based Catalysts and Their Recent Strategy in Organic Transformations

Organic molecules synthesized in an environmentally friendly manner have excellent therapeutic potential. The entire preparation technique was examined in the existence of a light source, implying that light has been replaced by heating and the usage of dangerous chemicals has decreased, resulting in less pollution of the environment. The advantages of these nanocarbon catalysts include high efficiency, environmentally friendly synthesis, eco-friendly, inexpensive, and non-corrodible. In organic transformations, solid metal base/metal-free catalysts produce better results. Here, the metal-free semiconductor g-C₃N₄ was used to demonstrate the catalytic behavior of organic conversions. g-C₃N₄ is a two-dimensional material and a p‑type semiconductor to enhance the photocatalytic activity. The excellent properties of g-C₃N₄ sheet lead to the support of metals to form metal-organic frameworks. Most of the reactions gained positive response under visible light irradiation. This review will inspire readers in widen the applications of g-C₃N₄ based catalyst in various organic transformation reactions.

A bone implant with NIR-responsiveness for eliminating osteosarcoma cells and promoting osteogenic differentiation of BMSCs

Incomplete removal of tumor cells and insufficient osseointegration are the main causes of bone tumor recurrence and implantation failure. In the present study, a multifunctional titanium-based bioactive implant for near-infrared-triggered synergy therapy to overcome these hurdles is engineered, composed of titanium dioxide (TiO₂) nanoparticles doped with fluorine (F)/dopamine (PDA)/collagen. The TiO₂ nanoparticles designed in this work can simultaneously exhibit excellent near-infrared-activated photothermal and photocatalytic properties. Besides, the layer designed in this work show excellent anti-tumor activity under irradiation with 808 nm light due to the synergetic effect of hyperthermia and reactive oxygen species (ROS), and Saos-2 cells can be eradicated within 10 min. Moreover, modification of PDA and collagen endue the Ti alloy excellent osteogenic activity.

Recent Advancement of the Current Aspects of g-C3 N4 for its Photocatalytic Applications in Sustainable Energy System

Being one of the foremost enticing and intriguing innovations, heterogeneous photocatalysis has also been used to effectively gather, transform, and conserve sustainable sun's radiation for the production of efficient and clean fossil energy as well as a wide range of ecological implications. The generation of solar fuel-based water splitting and CO₂ photoreduction is excellent for generating alternative resources and reducing global warming. Developing an inexpensive photocatalyst can effectively split water into hydrogen (H₂ ), oxygen (O₂ ) sources, and carbon dioxide (CO₂ ) into fuel sources, which is a crucial problem in photocatalysis. The metal-free g-C₃ N₄ photocatalyst has a high solar fuel generation potential. This review covers the most recent advancements in g-C₃ N₄ preparation, including innovative design concepts and new synthesis methods, and novel ideas for expanding the light absorption of pure g-C₃ N₄ for photocatalytic application. Similarly, the main issue concerning research and prospects in photocatalysts based g-C₃ N₄ was also discussed. The current dissertation provides an overview of comprehensive understanding of the exploitation of the extraordinary systemic and characteristics, as well as the fabrication processes and uses of g-C₃ N₄ .