Unraveling the Oxidation Kinetics Through Electronic Structure Regulation of MnCo2O4.5@Ni3S2 p-n Junction for Urea-Assisted Electrocatalytic Activity.

A promising strategy to boost electrocatalytic performance is via assembly of hetero-nanostructured electrocatalysts that delivers the essential specific surface area and also active sites by lowering the reaction barrier. However, the challenges associated with the intricate designs and mechanisms remain underexplored. Therefore, the present study constructs a p-n junction in a free-standing MnCo2O4.5@Ni3S2 on Ni-Foam. The space-charge region's electrical characteristics is dramatically altered by the formed p-n junction, which enhances the electron transfer process for urea-assisted electrocatalytic water splitting (UOR). The optimal MnCo2O4.5@Ni3S2 electrocatalyst results in greater oxygen evolution reactivity (OER) than pure systems, delivering an overpotential of only 240 mV. Remarkably, upon employing as UOR electrode the required potential decreases to 30 mV. The impressive performance of the designed catalyst is attributed to the enhanced electrical conductivity, greater number of electrochemical active sites, and improved redox activity due to the junction interface formed between p-MnCo2O4.5 and n-Ni3S2. There are strong indications that the in situ formed extreme-surface NiOOH, starting from Ni3S2, boosts the electrocatalytic activity, i.e., the electrochemical  surface reconstruction generates the active species. In conclusion, this work presents a high-performance p-n junction design for broad use, together with a viable and affordable UOR electrocatalyst.

CoOx @NiMoN/Ti3 C2 Tx Interface for Stable High-Performance Electrochemical Energy Storage Devices.

Transition metal nitrides (TMNs) are promising electrode materials for use in high-performance electrochemical energy storage devices due to their unique properties, which include a high conductivity, pseudocapacitance, and energy density. However, structural instability during electrochemical reactions has limited their practical deployment for energy storage devices. In this context, the present study fabricated a CoOx @NiMoN/Ti3 C2 Tx electrode via in situ growth on Ni foam using hydrothermal treatment with post-nitrogenization. The effect of atomic layer deposition (ALD) of CoOx on the TMN/Ti3 C2 Tx interface and the consequent electrochemical charge storage mechanisms are investigated in detail. The proposed CoOx @NiMoN/Ti3 C2 Tx electrode delivers an impressive specific capacity in a 2 m potassium hydroxide (KOH) electrolyte and is then employed in both a hybrid solid-state supercapacitor (HSSC) with reduced graphene oxide and a symmetric SC in a 2 m KOH + polyvinyl alcohol (PVA) gel electrolyte. Outstanding charge storage and high capacity retention during cyclic testing are observed for both energy storage devices. The exceptional electrochemical performance of the fabricated electrode is a result of its high conductivity and high number of active sites. Here a feasible new strategy is demonstrated for the fabrication of stable energy storage devices with a high energy density using TMNs and MXenes.

Recent Development Strategies for Bismuth-Driven Materials in Sustainable Energy Systems and Environmental Restoration.

Bismuth(Bi)-based materials have gained considerable attention in recent decades for use in a diverse range of sustainable energy and environmental applications due to their low toxicity and eco-friendliness. Bi materials are widely employed in electrochemical energy storage and conversion devices, exhibiting excellent catalytic and non-catalytic performance, as well as CO2 /N2 reduction and water treatment systems. A variety of Bi materials, including its oxides, chalcogenides, oxyhalides, bismuthates, and other composites, have been developed for understanding their physicochemical properties. In this review, a comprehensive overview of the properties of individual Bi material systems and their use in a range of applications is provided. This review highlights the implementation of novel strategies to modify Bi materials based on morphological and facet control, doping/defect inclusion, and composite/heterojunction formation. The factors affecting the development of different classes of Bi materials and how their control differs between individual Bi compounds are also described. In particular, the development process for these material systems, their mass production, and related challenges are considered. Thus, the key components in Bi compounds are compared in terms of their properties, design, and applications. Finally, the future potential and challenges associated with Bi complexes are presented as a pathway for new innovations.

Core-Shell Engineered WO3 Architectures: Recent Advances from Design to Applications.

Ongoing efforts to design novel materials with efficient structure-property-performance relations prove challenging. Core-shell structures have emerged as novel materials with controlled production routes and highly tailorable properties that offer extensive advantages in advanced oxidation processing, particularly in photocatalysis and photoelectrochemical applications. WO3 , which is an optoelectronically active semiconductor material, is a popular material in current studies in the field of photo(electro)catalysis. Considerable progress has been made using core-shell WO3 architectures, which warrants an evaluation in terms of processing and preparedness for their use in versatile catalytic and energy storage applications. This paper presents an in-depth assessment of core-shell WO3 architectures by highlighting the design challenges and protocols in powder and thin-film chemical processing. The development of specific core-shell designs for use in targeted applications, such as H2 production, CO2 reduction, wastewater treatment, batteries, supercapacitors, and sensing, is analyzed. The fundamental role of WO3 in core-shell structures to enhance efficiency is also discussed, along with the limitations and improvement strategies. Further, the prospects of core-shell WO3 architectures in energy conversion and environmental applications are suggested.

1D/2D constructed Bi2S3/Bi2O2CO3 direct Z-Scheme heterojunction: A versatile photocatalytic material for boosted photodegradation, photoreduction and photoelectrochemical detection of water-based contaminants.

In this work, two-dimensional Bi2O2CO3 disk is synthesized, followed by the growth of Bi2S3 over Bi2O2CO3 via topotactic transformation by controlling the amount of thiourea under hydrothermal conditions. The synthesized composite catalyst is investigated for photocatalytic oxidation and reduction of tetracycline hydrochloride and hexavalent chromium under visible light irradiation. High interfacial contact between the Bi2O2CO3 disk0 and Bi2S3 fiber is confirmed via high-resolution microscopic imaging. Enhanced light absorption and increased charge carrier separation is observed after the formation of the Bi2S3/Bi2O2CO3 composite. The Bi2S3/Bi2O2CO3 composite grown using 1 mmol of thiourea shows approximately 98% degradation of tetracycline hydrochloride after 120 min and 99% Cr(VI) reduction after 90 min of photochemical reaction under visible light irradiation. The charge separation is due to the formed internal electric field at the interface, which upon light irradiation follows a z-scheme charge transfer hindering the recombination at the Bi2S3 and Bi2O2CO3 interface, thereby contributing efficiently to the photochemical process. In addition, the mechanism of the photochemical reaction for the degradation of pollutants is supported using quencher and probe experiments. Furthermore, photoelectrochemical detection of antibiotic in aqueous solution is conducted to understand the sensing feasibility of the synthesized system.

Encapsulation of Co3 O4 Nanocone Arrays via Ultrathin NiO for Superior Performance Asymmetric Supercapacitors.

Designing of multicomponent transition metal oxide system through the employment of advanced atomic layer deposition (ALD) technique over nanostructures obtained from wet chemical process is a novel approach to construct rational supercapacitor electrodes. Following the strategy, core-shell type NiO/Co3 O4 nanocone array structures are architectured over Ni-foam (NF) substrate. The high-aspect-ratio Co3 O4 nanocones are hydrothermally grown over NF following the precision controlled deposition of shell NiO considering Co3 O4 nanocone as host. NiO thickness of 5 nm exhibits the highest specific capacity of 1242 C g-1 (2760 F g-1 ) at current density 2 A g-1 , which is greater than pristine Co3 O4 @NF (1045.8 C g-1 or 2324 F g-1 ). The rate capability with 5 nm NiO/Co3 O4 @NF nanocone structures is about 77% whereas Co3 O4 @NF retains 46 % of capability at 10 A g-1 . The ultrathin ALD 5 nm NiO accelerates both rate capability and 95.5% cyclic stability after 12 000 charge-discharge cycles. An asymmetric device fabricated between 5 nm NiO/Co3 O4 @NF (positive) || activated carbon (negative) achieves an energy density of 81.45 Wh kg-1 (4268 W kg-1 ) with good cycling device stability. Additionally, LEDs can be energized by two ASC device in series. This work opens the path in both advanced electrode material and surface modification of earth-abundant systems for efficient and real-time supercapacitor applications.

Synergistic construction of green tea biochar supported nZVI for immobilization of lead in soil: A mechanistic investigation.

Biochar-based nanocomposites with functional materials provide an excellent prospect in reactivity and stability. Most biochar reported have no reusability upon aging and offer the risk of release of immobilized components after short-term immobilization. To overcome this, we developed nano zero-valent iron (nZVI) impregnated magnetic green tea biochar (nZVI@GTBC) and studied its performance in immobilizing Pb and long-term effectiveness in the soil. The reactive nZVI units were obtained from iron oxide solution by reducing with polyphenol solution (green tea extract) and were successively stabilized by impregnation onto the remaining green tea waste matrix through co-precipitation technique. Finally, the magnetic biochar was developed from the above nZVI impregnated green tea waste through oven drying and slow pyrolysis technique in different temperature range (150-650 °C). The synthesized nZVI@GTBC biochar was characterized and studied by XRD, FTIR, Raman, UV-Vis, TG/DSC, XPS, SEM, and TEM. The nZVI@GTBC obtained with a particle size of 130 nm and surface charge of +2.8 C/m2 at 450 °C. Moreover, colloidal stability and mobility experiments were considered to explain the transport behavior and stability of bare nZVI and magnetic nZVI@GTBC in the soil. The immobilization of Pb by pristine nZVI, GTBC, and nZVI@GTBC was compared and explained under different soil pH conditions. The bioavailability of Pb content before and after immobilization was investigated through leaching experiments. Further, thirty days of soil incubation were carried out to examine different species of Pb according to the Tessier sequential extraction scheme. The study suggested that nZVI@GTBC enhanced the immobilization efficiency by 19.38% in comparison with pristine nZVI and 57.14% in comparison with bare GTBC biochar.

Interactive Fe2O3/porous SiO2 nanospheres for photocatalytic degradation of organic pollutants: Kinetic and mechanistic approach.

A uniformly distributed mesoporous silica nanospheres has been successfully synthesized. Silica nanospheres have been loaded with different content of Fe2O3 nanoparticles synthesized by the sol-gel process followed by calcination to form the Fe2O3 supported on silica nanospheres composite. The as-synthesized photocatalyst has been characterized for crystal structure, morphology, stability, surface area and also surface composition was determined. The photocatalytic oxidation ability of the composite photocatalyst was evaluated by degrading aqueous solutions of Methylene Blue and Congo red dyes under visible light having intense absorption in the wavelength range between 550 and 560 nm. The prime significance of silica is to act as catalyst support for uniform distribution of hematite particles for enhanced catalytic reactivity. Highest degradation has been achieved with 20 wt % loading of hematite nanoparticles indicating the less agglomeration and availability of more catalytic sites. Furthermore, colorless organic pollutants 2-chlorophenol and 2, 4-dichlorophenol have been degraded with high efficiency in the presence of H2O2 oxidizer. The scavenger experiments confirmed that hydroxyl radicals are the majorly participating species in this catalytic system. The composite system also shows good recyclability of the materials and advocates the promising nature of the designed system for multiple hazardous environmental contaminants.

Efficient interfacial charge transfer through plasmon sensitized Ag@Bi2O3 hierarchical photoanodes for photoelectrocatalytic degradation of chlorinated phenols.

The present work demonstrates an extremely proficient and robust study of efficient interfacial charge transfer through plasmonic Ag decorated Bi2O3 hierarchical photoanodes for the photoelectrochemical treatment of chlorinated phenols. Unique 2D flake-like Bi2O3 hierarchical nanostructures were grown onto a fluorine-doped tin oxide (FTO) substrate by a simple chemical bath deposition method using triethanolamine as complexing agent. The formation of Bi2O3 on FTO was governed by the decomposition of a nucleated bismuth-hydroxyl complex (Bi2O1-x(OH)x) and modification to the electrode was carried out by the deposition of Ag via a chemical reduction method using hydrazine hydrate. Both the fabricated electrodes were well characterized for their photo- and electro-optical properties. Efficient charge separation was observed due to the surface plasmon resonance phenomenon of silver nanoparticles with the favorable intrinsic properties of Bi2O3 under application of a small electric bias of 1 V preventing the recombination of charge carriers and thereby increasing the rate of photoelectrocatalytic degradation of the chlorinated phenols. PEC degradation using the Ag@Bi2O3 photoelectrode followed the trend 4-CP < 2,4-DCP < 2,4,6-TCP < P-CP due to efficient attack at the chlorinated positions by reactive oxygen species with increasing chlorine substitution and also due to the absence of an expected chain reaction of the generated chlorine radicals (Cl˙) during the PEC reaction. The PEC activity of Ag@Bi2O3 was 1.5 times higher than a Bi2O3 nanoflake electrode for 4-CP over 2 h. The fabricated Ag@Bi2O3 proved to be an efficient photoelectrode with synergistic solar-induced photoactivity. A detailed mechanistic study in the presence of scavengers suggests degradation by produced hydroxyl radical species. Thus, physical insights into the degradation of chlorinated phenols were obtained.

Role of Ni in hetero-architectured NiO/Ni composites for enhanced catalytic performance.

A facile, one-step combustion synthesis in solution is reported for preparing hetero-architectured NiO/Ni nanocomposites using different organic fuels. The prepared nanocomposites were physicochemically characterized for crystal structure, functional groups, and morphology. It was found that the content of Ni in the nanocomposite varied due to different combustion fuels. A photocatalytic (PC) investigation of these nanocomposites was performed using rhodamine 6G (RG) under UV light. A citric acid combusted NiO/Ni (N-CA) composite containing 20% Ni phase showed the highest photoactivity in comparison to pure NiO due to its large porous channels and high surface area (∼28 ± 2 m2 g-1). The N-CA catalyst was further evaluated for the degradation of cationic, anionic dyes and chloro/nitro-phenols under both UV and visible light. Photoelectrocatalysis (PEC) of RG with N-CA resulted in complete degradation of the dye. The mechanism governing the catalytic processes was determined from the trapping experiments. The potential reasons for the enhanced photoactivity of the NiO/Ni nanocomposite were that Ni acted as an electron sink, and the applied bias of +1.0 V separated the electron-hole, reducing its rate of recombination.

Solar-Light-Driven Improved Photocatalytic Performance of Hierarchical ZnIn2S4 Architectures.

In the quest for developing novel narrow band gap semiconductor materials, the research in metal chalcogenides has gained a strong attraction. In the present investigation, a surfactant-free hydrothermal route has been followed to design hierarchical self-assembled flower-like ZnIn2S4 structures through control over precursor concentration and hydrothermal processing parameters. Uniform hexagonal marigold flower-like ZnIn2S4 architectures (∼4 µm) were formed with self-assembly of petals (thickness ∼8-12 nm) forming rose-like structures and finally forming marigold flowers in 24 h duration. The hierarchical ZnIn2S4 flower structure has been used as photocatalysts for the degradation of dye and chlorinated phenols. Photodegradation demonstrates that the high surface area from the porous flower architecture (∼72 m2/g) with an enhanced visible light absorption giving low band gap energy (2.15 eV) is responsible for higher photocatalytic performance. Complete degradation of the organic pollutants has been observed within 90 min in the presence of natural sunlight. To understand the participating reactive species contributing to degradation, scavenger studies were performed for deducing the plausible photocatalytic degradation pathways. This study might open new insights into the design of novel hierarchical structures.

Hierarchical Design of CuS Architectures for Visible Light Photocatalysis of 4-Chlorophenol.

Hydrothermal-assisted CuS hierarchical architectures were grown in the presence of anionic sulfur sources, and the investigation of their degradation efficiency for a pesticide 4-chlorophenol (4-CP) under visible light irradiation was carried out. The dissociation of S2- from the sulfur compound governs the nucleation of CuS followed by a specific pattern of growth to produce different morphologies. The self-assembled covellite spherical CuS flower architecture assembles in the presence of thiourea and exhibits the highest photodegradation activity. The open architecture of ∼2.3 µm spherical CuS flowers consisting of a ∼100 nm thick sheet encompasses a comparatively high surface area and particle growth along the (110) plane that facilitates more active sites for catalytic activity enhancement. The catalyst loading for 4-CP degradation has been optimized, and a detailed trapping mechanism has been explored.

Synthesis, mechanical properties and bioactivity of nanostructured zirconia.

Yttria stabilized zirconia 3Y - TZP nanopowders (10-30 nm) are prepared through direct precursor calcination of mixed zirconium oxychloride and yttrium nitrate solutions at 600°C for 2h. Cuboid(50×25×20 mm(3)) zirconia blanks are fabricated through centrifuge casting and followed by sintering at 1350°C for 2h. Sintered zirconia blanks exhibit 24% volume shrinkage and 98% relative density with average grain size of 250 nm. Vickers hardness and indented fracture toughness of sintered blanks are measured as 13.5 GPa and 3.5 MPa.m(1/2), respectively. Bioactivity of nanostructured zirconia originates after four weeks incubation in simulated body fluid solution. An optimum time is required for the deposition of hydroxyapatite nanoparticles on stress-induced nucleation site of nanostructured zirconia.