X-ray Raman Spectroscopy Research Articles

The development of titanium dioxide nanotube-supported CdTe catalysts for photocatalytic enzymatic glucose fuel cell and response surface methodology optimization

Energy is one of the critical needs for human life and well-being. Alternative energy sources are essential due to the increase in energy demand with the rise in population the development of industrialization, and the damage caused by fossil fuels to the environment. Fuel cells, an alternative energy source, are a clean and environmentally friendly technology that converts chemical energy into electrical energy. In this study, titanium dioxide (TiO2) nanotube (TNT)-support CdTe catalysts were synthesized by the wet impregnation (WI) method. Glucose oxidase (GOD) and laccase (LAC) enzymes were modified by incubation on CdTe/TNT catalysts. These enzymatic and non-enzymatic catalysts were characterized by scanning electron microscope-energy dispersive X-ray (SEM-EDX) and mapping, X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscope (TEM) analyses. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA) analyses were used to examine the activity, resistance, and stability of catalysts for enzymatic photocatalytic glucose electrooxidation. The 3 % CdTe(50-50)-TNT-GOD/GCE electrode exhibited the highest activity, resistance, and stability under UV illumination compared to other electrodes. The modification parameters of the electrodes, incubation time, amount of catalyst ink, and drying time were found to be 136.96 min, 8.94 µL, and 21.30 min with response surface method (RSM) analysis, respectively. The estimated specific activity value was obtained as 0.754 mA/cm2 under optimized conditions.

Pressure-induced phase transition in nanostructured cation-deficient Zn0.34Fe2.53☐0.13O4 ferrite

The crystal structure and vibrational spectra of cation-deficient nanostructured zinс ferrite Zn0.34Fe2.53☐0.13O4 (where ☐ denotes the cation vacancies) have been studied using X-ray diffraction and Raman spectroscopy methods in the pressure range of 0–34 GPa. Our results indicate a phase transition from the initial cubic phase with space group Fd3‾m to a high-pressure phase with orthorhombic symmetry of Bbmm at pressures above 18 GPa. This phase transition is accompanied by changes in lattice parameters, unit cell volume, interatomic bond lengths, and vibration mode frequencies.

Exploring the photocatalytic and photodetection potential of undoped and nickel-doped molybdenum trioxide nanoplates: Synthesis and characterization

Orthorhombic stable phase of MoO3 and Ni-doped MoO3 with different weight percentages (2 %,5 % and 10 %) were successfully synthesized by following a surfactant free acid-assisted chemical co-precipitation method under optimized experimental conditions. Structural and compositional investigation using tools like X-ray diffraction and Raman spectroscopy verified the orthorhombic phase and structure quality of the prepared samples with findings from Raman consistent with those from XRD. The optical characteristics analysed using UV–Vis diffused reflectance spectroscopy and photoluminescence spectroscopy revealed that Ni2+ may act as a shallow acceptor at lower doping concentrations. It was observed that the structure and characteristics of MoO3 dramatically altered as a function of Ni doping concentration, suggesting that Ni ions migrated from lattice substitution to grain boundaries. Images from field emission scanning electron microscope revealed the formation of layer-by-layer growth of micro-plate like morphology of the prepared samples with increasing agglomeration influenced by grain boundaries. EDAX spectrum confirmed the presence of Mo, O and Ni and their compositional proportion. Based on the properties analysed, the photocatalytic properties of the synthesized samples were analysed for degradation of Alizarin Red dye and kinetic studies were conducted. The optical characterization revealed defect induced emissions and the feasibility of MoO3 acting as a photodetector was studied along with Ni-doping proving the versatility of material for multifunctional applications.

Characterize and Mediate Assembly of Triptycenes on Au(111) Surface.

Herein, we report the assembly behavior of triptycenes with aldehyde (Trip-1) and amino (Trip-2) groups on pristine and iodine-passivated Au(111) surfaces by a combination of scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and density functional theory (DFT) calculation. On Au(111) surface, Trip-1 forms long trimer chains and two-dimensional islands via aldehyde-aldehyde hydrogen bonding in one dimension and π-π stacking of adjacent benzene rings in the other dimension. In contrast, Trip-2 lies as individuals or in disorderly stacked islands. Trip-2 and Trip-1 can be mixed in an arbitrary ratio. And Trip-2 molecules disrupt the ordered self-assembly structure of Trip-1 due to the formation of stronger aldehyde-amino hydrogen bonding. DFT, XPS, and Raman spectra confirm the conformational difference of Trip-1 and -2, as well as the aldehyde-amino hydrogen bonding formation in Trip-1 and Trip-2 mixture. On the iodine-passivated Au(111) surface, Trip-1 forms single-molecule chains and a hexagonal closely packed structure due to iodine interlayer mediation. Trip-2 molecules disrupt the hexagonal closely packed structure of Trip-1.

Room temperature detection of aspergillus flavus volatile organic compounds (VOCs) under simulated conditions using graphene oxide and tin oxide Nanorods (SnO2 NRs-GO)

This study investigated the application of a hybrid nanocomposite of tin oxide nanorods (SnO2 NRs) and graphene oxide (GO) for the chemoresistive detection of some volatile compounds (hexanal, benzaldehyde, octanal, 1-octanol, and ethyl acetate vapours) emitted by Aspergillus flavus under simulated conditions. The synthesised materials were characterised using various analytical techniques, including high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, and Fourier transform infrared spectroscopy (FTIR). Three sensors were fabricated: individual nanomaterials (i.e., SnO2 and GO) and composites (SnO2-GO). The results showed that SnO2 NRs had limited sensitivity as a sensor, while GO-based sensors responded to various analyte vapours. However, the incorporation of SnO2 NRs into GO layers resulted in synergistic effects and improved sensor performance. The sensors' sensitivity, selectivity, recovery, and response times were quantitatively determined from the sensors' response curves. The nanocomposite sensor demonstrated superior sensitivity and selectivity for analyte vapours with acceptable response and recovery times. In addition, the sensor was insensitive to humidity and showed robust performance up to 62% RH, although sensor drift occurred at 70% RH. This study highlights the promising potential of using SnO2 NRs-GO composite-based sensor for sensitive and selective detection of analyte vapours, which has significant implications for food safety and environmental monitoring applications.

Enhanced electrochemical performance of MgFeO4 spinel as anode materials for Lithium-ion batteries through manganese doping

Existing graphite anode materials are reaching their limits, and iron-based AB2O4 spinel materials are considered as potential anodes for Li-ion batteries owing to their significant theoretical capacities. In this work, novel nanocrystalline MgFe2-xMnxO4 (x = 0, 0.1, 0.2, and 0.3) spinel ferrites were evaluated as anode materials for high-capacity Li-ion batteries. The Mn-doped MgFe2-xMnxO4 (x = 0, 0.1, 0.2, and 0.3) spinel ferrites were synthesized through a facile sol-gel synthesis method coupled with an annealing process. Their crystal structure, morphology, and purity were examined via X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). The X-ray diffraction analyses with Rietveld refinement of the synthesized ferrites reveal pure cubic structure with a characteristic Fd3̅m space group for all prepared samples. This was confirmed by Raman spectroscopy by revealing five spinel Raman active modes. The SEM images showed interconnected nanosized particles for all compositions, which led to a porous morphology. Their electrochemical proprieties as anode materials for Li-ion batteries were examined by cyclic voltammetry and galvanostatic charge-discharge tests. For all compositions, the cyclic voltammetry plots demonstrate the conversion type for the Li-ion storage mechanism. At an applied current density of 150 mA g−1, the compositions x = 0, 0.1, 0.2, and 0.3 show initial discharge/charge capacities of 1235/712, 1187/680, 1542/938, and 1239/768 mAh g−1, respectively. After 100 operational cycles, their galvanostatic charge/discharge capacities remain 529/534, 612/606, 642/663, and 700/700 mAh g−1. However, the compositions x = 0.2 and 0.3 exhibit excellent cycling stability during 100 cycles, even at higher rates. As a result, the Mn doping led to enhanced specific capacity and cycling stability of the MgFe2O4 spinel. The optimized compositions with x = 0.2 and 0.3 are, thus, proposed as promising anodes materials compositions for Li-ion batteries.

Fabrication of a coral-like barium titanate nano-piezoelectric coating and its effect on promoting osteogenic differentiation of rat bone marrow mesenchymal stem cells in vitro

Objective: To investigate the biocompatibility of coral-like barium titanate nano-piezoelectric coatings and the influence of ultrasound-excited piezoelectric effect on the early osteogenic differentiation. Methods: The barium titanate nano-piezoelectric coating (the coating group) was prepared on the surface of titanium metal by anodic oxidation, hydrothermal reaction and high-temperature annealing, and polished titanium specimens were used as control group. The surface morphology, composition, and crystal phase and hydrophilicity of the two groups of titanium specimens were characterized using scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and contact angle meter. The piezoelectric properties of the materials were characterized by piezoresponse force microscopy. Rat bone marrow mesenchymal stem cells (BMSC) were cultured and identified and seeded the surface of titanium specimens in two groups. The cells seeded on blank culture plates were used as blank group. After low intensity pulsed ultrasound intervention, cell proliferation and live/dead staining were detected to evaluate cytocompatibility of the coatings. Alkaline phosphatase (ALP) activity of each group was detected by ALP staining kit, and the expression of osteogenesis-related genes [integrin, bone morphogenetic protein 2 (BMP-2), Runt-related transcription factor 2 (RUNX2)] was detected by real-time fluorescent quantitative PCR (RT-qPCR) to evaluate the effect of the coating on promoting the early osteogenic differentiation of BMSC. Results: The surface of titanium specimens in the coating group showed a uniform coral-like morphology, and the diameter of the coral tentacles was 70-100 nm. The main component was tetragonal barium titanate. The surface hydrophilicity of the coating group (water contact angle 10.12°± 0.93°) was significantly better than that of the control group (water contact angle 78.32°±0.71°) (F= 10 165.91, P<0.001). The coating has a stable piezoelectric property with a piezoelectric constant of about 5 pC/N. Cell experiments showed that, with or without ultrasound, the cell proliferation activity of the coating group was significantly lower than that of the blank group and the control group on the third day (P<0.05). On the fifth day, with or without ultrasound, there was no significant difference in cell proliferation activity between the three groups (P>0.05). After 7 days of culture, the ALP activity of the coating group was significantly higher than that of the blank group and the control group (P<0.05). The results of RT-qPCR showed that the mRNA expression of integrin and BMP-2 in the coating group with ultrasound was significantly higher than that in the other groups with ultrasound, and was higher than that of the coating group without ultrasound (P<0.05). The expression of integrin mRNA in the control group with ultrasound was significantly higher than that in the control group without ultrasound (P<0.05). The expression of RUNX2 mRNA in the coating group with ultrasound was significantly higher than that in the coating group without ultrasound (P<0.05). Conclusions: The coral-like barium titanate nano-piezoelectric coating exhibits favorable biocompatibility and stable piezoelectric property, and facilitates the early osteogenic differentiation of BMSC under the excitation of low-intensity pulsed ultrasound.

Erosion behaviors and mechanisms of Ti3AlC2 material under arc discharge in various mixed atmospheres

The present study establishes an experimental platform for investigating arc erosion and explores the erosion characteristics of Ti3AlC2 material under a voltage of 10 kV in SF6/N2, SF6/CO2, and N2/CO2 environments. Our findings reveal that the arc energy and duration exhibit a gradual increase in the sequence of SF6/N2, SF6/CO2, and N2/CO2, while the breakdown strength decreases. Scanning electron microscopy (SEM) and a three-dimensional laser confocal microscope were employed to observe uneven erosion morphology. Additionally, high-speed camera footage captures the arc bending and drifting phenomenon caused by Rayleigh-Taylor instability between the arc and gas. X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) analysis were utilized to characterize the composition of eroded surfaces. Erosion models were proposed for each mixed atmosphere along with comprehensive discussions on their underlying mechanisms. This work expands the application scope of MAX phase materials while providing a theoretical foundation for designing electrical contact materials.

Enhanced n-Type Thermoelectric Properties and Structure Evolution of Carbonized Metal-Coordination Polydopamine.

Carbonized polydopamine (cPDA) exhibits a nitrogenous graphite-like structure with n-type semiconductor property. However, the low electrical conductivity and Seebeck coefficient of cPDA cannot meet the needs of flexible thermoelectric devices. In this study, a series of metal ions were coordinated with cPDA to enhance n-type thermoelectric properties. At 300 K, all metal-coordination cPDA (metal-cPDA) samples obtain lower thermal conductivity compared to cPDA. Mn-cPDA exhibits the greatest Seebeck coefficient of -25.94 μV K-1, which is almost six times higher than cPDA. Fe-cPDA shows the best electrical conductivity of 2.45 × 105 S m-1. An optimal power factor (PF) value of 11.93 μW m-1 K-2 is achieved in Ca-cPDA with the enhanced electrical conductivity of 9.5 × 104 S m-1 and Seebeck coefficient of -11.24 μV K-1. Using Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM), we revealed the structural characterization of metal-cPDA. Our results indictate that the different metal ions (Mn2+, Zn2+, Mg2+, Al3+, Ca2+, and Fe3+) exert varying influences on the growth of graphite-like structure within metal-cPDA, which lead to the evolution of electrical conductivity. We observe that the carrier density and carrier mobility depend on both the degree of graphitization and the metal-ion coordination, which work together on electrical conductivity and Seebeck coefficient. These findings and understanding of the thermoelectric properties of PDA-based materials will help to realize high-performance n-type thermoelectric materials for flexible electronic device applications.

Impacts of radiation sources on structures and electrochemical performance of SiO2/C composite anodes for Li-ion batteries

Application of radiation with highly energetic electrons and ions can be an alternative method to modify structures of crystalline materials. This radiation can potentially induce phase transformations while preserving some physical characteristics and morphology of the materials, hence impacting their useful properties. Here, we report the impacts of e-beam and gamma radiation on the structures and electrochemical performance of SiO2/C anodes for Li-ion batteries (LIB) obtained from rice husk ash (RHA). The effects of radiation sources on structural and physical properties are investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence spectrometry (XRF), electron microscopy, and Raman spectroscopy. After irradiation-induced processes using e-beam and gamma radiation at 1000 kGy, the mean diameters of the SiO2 particles were around 30 ± 10 and 27 ± 10 nm, respectively, while retaining their round-shaped particle morphology. Both radiation sources induce formation of disordered carbon structure as indicated by the higher ID/IG Raman peaks ratios than the pristine sample. Electrochemical properties were studied using half-coin type cells. The modified structure of SiO2/C anodes caused by irradiation showed improved electrochemical performance, compared with pristine material.

Carbon fiber recovery from carbon fiber reinforced polymer matrix composite by microwave pyrolysis

The recovery of high-value carbon fibers (CFs) from carbon fiber-reinforced polymers (CFRP) is essential for advancing sustainability goals. In this study, CFs were extracted from CFRP using a microwave pyrolysis method known for its efficiency and environmental friendliness. The pyrolysis process was optimized through the response surface methodology to minimize carbon residue accumulation on the CFs' surface. The microwave pyrolysis of CFRP was simulated using COMSOL software to analyze temperature distribution patterns. The optimal parameters for microwave pyrolysis were determined as follows: a temperature of 543.7 °C, a holding time of 22.8 minutes, and a microwave power of 840.9 W, resulting in a residual carbon rate of only 3.7 %. Scanning electron microscopy (SEM) examination revealed no visible surface damage to the CFs. Analysis using X-ray diffraction (XRD) and Raman spectroscopy indicated a slight reduction in the crystallinity and graphitization level of the CFs due to the presence of deposited carbon. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) results suggested increased oxygen-containing functional groups. The comparative microstructural analysis between the pyrolyzed and pristine CFs showed no significant disparities. These results demonstrate the successful recovery of CFs through rapid resin pyrolysis in CFRP using microwave irradiation.

Nb2O5 film optical properties and laser-induced damage by phase-change-driven tuning

Niobium oxide (Nb2O5) is widely used in optical and electrical fields because of its high refractive index, wide band gap, high laser-induced damage threshold (LIDT) and high transparency in the ultraviolet to middle-infrared-wavelength range (0.35–7 μm). In this study, Nb2O5 films with different crystalline phases were successfully prepared on BK7 and Si substrates through electron beam evaporation (EB) and post-annealing. Based on the results of X-ray diffraction (XRD) and Raman spectroscopy analysis, the impact of the post-annealing technique on the structure, and optical and physical properties of Nb2O5 films was thoroughly discussed at the molecular level. The crystal phase of an Nb2O5 film and its molecular bonds considerably affect its properties. The Nb2O5(-12 1 2) film prepared in this study exhibited a higher LIDT (17.72 J/cm2) and a higher RMS (0.447 nm) than the corresponding films prepared in previous studies. Following the post-annealing process, the band gap and refractive index of the prepared films were significantly higher than those of the as-deposited film. Thus, this study has significant guiding implications for Nb2O5 film applications and the development costs of the films.

Research on Improved Crystallization Properties and Underlying Mechanism of the Sb2Te3 Phase-Change Thin Film by Inserting Sn15Sb85 Layers.

As a non-volatile semiconductor memory technology, phase-change memory has a wide range of application prospects as a result of the excellent comprehensive performance. In this paper, multilayer thin films based on Sb2Te3 material were designed and prepared by inserting the Sn15Sb85 layer. The thermal and electrical properties of superlattice-like Sb2Te3/Sn15Sb85 phase-change films can be adjusted by controlling the thickness ratio of Sb2Te3/Sn15Sb85. In comparison to the monolayer Sb2Te3 film, the multilayer layer Sb2Te3/Sn15Sb85 materials have a higher crystallization temperature, larger crystallization activation energy, and longer data lifetime, indicating the great improvement of thermal stability. The changes in the phase structure and vibrational modes of multilayer Sb2Te3/Sn15Sb85 films were characterized by X-ray diffraction and Raman spectroscopy, respectively. The presence of Sn15Sb85 layers restrains grain growth and refines the grain size. The multilayer Sb2Te3/Sn15Sb85 films exhibit better surface flatness, smaller surface potential undulation, and lower thickness variations than single-layer Sb2Te3. Phase-change memory cells based on the [Sb2Te3 (1 nm)/Sn15Sb85 (9 nm)]5 thin film has a lower threshold voltage (1.9 V) and threshold current (3.1 μA) compared to the Ge2Sb2Te5 film. Meanwhile, the electrical heating model of a phase-change memory cell based on a [Sb2Te3 (1 nm)/Sn15Sb85 (9 nm)]5 multilayer structure was established by multiphysics coupling analysis, proving the great improvement in heat transfer performance and efficiency. The experimental and theoretical studies confirm that the insertion of the Sn15Sb85 layer can significantly improve the crystallization properties of Sb2Te3 films, paving the way for optimizing the phase-change materials by regulating the microstructural parameters.

Ethane under pressure revisited using x-ray diffraction, Raman spectroscopy, infrared absorption, and abinitio calculations up to 150 GPa.

Ethane (C2H6) is anticipated to be the most stable compound within the carbon-hydrogen system under the 100GPa pressure range. Nevertheless, the properties of ethane under pressure are still poorly documented. Here, we present a comprehensive study of the structural and vibrational properties of C2H6 in a diamond anvil cell at pressures up to 150GPa. To obtain detailed data, ethane single-crystal was grown in a helium pressure-transmitting medium. Utilizing single-crystal x-ray diffraction, the distortion mechanism between the tetragonal and monoclinic phases, occurring over the 3.2-5.2GPa pressure range, is disclosed. Subsequently, no phase transition is observed up to 150GPa. The accurately measured compression curve is compared to various computational approximations. The vibrational modes measured by Raman spectroscopy and infrared absorption are well identified, and their evolution is well reproduced by abinitio calculations. In particular, an unusual anticrossing phenomenon occurs near 40GPa between a rocking and a stretching mode, likely attributable to intermolecular interactions through hydrogen bonding.

Onion husk-derived high surface area graphene-like carbon for supercapacitor electrode material application

In this study, we report the synthesis of graphene-like carbon derived from onion husk, with potential application as an electrode material in energy storage devices. Graphene-like carbon (GLC) was synthesized from onion husk (OH) by preliminary carbonization at 550 °C, followed by thermochemical activation at various temperatures to determine the optimal activation parameters. The surface morphology of graphene-like carbon from onion husk (GLC-OH) samples after carbonization shows distinct thermal exfoliation of the material. This layering upon activation in KOH promotes the formation of highly porous graphene-like carbon flakes. According to the Brunauer-Emmett-Teller (BET) method, the specific surface area at 850 °C was 1924 m2/g. The X-ray diffraction (XRD) and Raman spectroscopy results reveal the emergence of few-layer graphene with a significant amount of structural defects at 850 °C. As the temperature increases, the formation shifts towards multilayer graphene, which leads to a decrease in the specific surface area of the carbon material. The electrochemical characterization of the assembled GLC–OH–based supercapacitor synthesized at 850 °C revealed a markedly higher specific capacitance value of 131 F/g, along with a Coulombic efficiency of 98 % at a gravimetric current density of 1 A/g. Additionally, it exhibited a low charge transfer resistance (RCT) of approximately 1.4 Ω.Our study investigates the influence of structural changes on the electrochemical performance of biomass-derived activated carbon, highlighting the potential of graphene-like carbon from onion husk as a promising and low-cost material for future energy storage devices.

Assessment of acoustic shock wave resistance of SiO2 (α-cristobalite): A potential material for aerospace and defense industry applications

In the present research article, the acoustic shock wave-resistant efficiency of silica microparticles (SiO2-α-cristobalite)) has been experimentally evaluated in terms of structural, optical and morphological stability against the impact of shock waves. The required SiO2 particles were synthesized by a hydrothermal method which was subjected to a different number of shock pulses such as 200,400 and 600 with Mach number 2.2. Shocked samples’ structural, morphological and optical stabilities have been evaluated by utilizing a powder X-ray diffractometer (PXRD), Ultraviolet–Diffuse reflectance spectrometer (DRS) while the surface morphological analysis has been scrutinized by the field emission scanning electron microscopic technique (FESEM) and transmission electron microscopy (TEM). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy techniques are utilized to evaluate oxidation states and crystallographic structural stability. The above-mentioned analytical techniques provide convincing proofs whereby the synthesized SiO2 particles are authentically proven to possess outstanding structural, optical and morphological stability against the impact of shock waves. The implicated experimental results and the arguments strongly suggest that the SiO2 particles are suitable candidates for aerospace and defense industry applications due to their outstanding shock wave-resistant properties.

Effect of sandblasting and acid surface pretreatment on the specific capacitance of CuO nanostructures grown by hot water treatment for supercapacitor electrode applications

Crystalline copper oxide (CuO) nanostructures with micro, nano, and micro-nano surface roughness were grown on Cu sheet substrates by a facile, scalable, low-cost, and low-temperature hot water treatment (HWT) method that simply involved immersing Cu sheet in DI water at 75 °C for 24 h without any chemical additives. Various morphological features and sizes of CuO nanostructures were tuned by using different surface pretreatment techniques including acid treatment, sandblasting, or a combination of those two. The surface morphology of the prepared samples was analyzed by scanning electron microscopy. The crystal structure of the CuO nanostructures was investigated by x-ray diffraction XRD and Raman spectroscopy. To study the pseudocapacitive behavior, their potential supercapacitor performance, and equivalent series resistance, electrochemical analysis was done by cyclic voltammetry and electrochemical impedance spectroscopy for all the CuO/Cu samples in 1 M of Na2SO4 electrolyte. Among all, the best supercapacitive performance was achieved for CuO/Cu samples pretreated with Sandblasting followed by Acid treatment resulting in a specific capacitance of about 104 F g−1. The electrode with the sandblasted + acid pretreated sample showed a maximum of ∼69% capacitive retention after 2000 consecutive cycles. Our results indicate that CuO nanostructures on Cu substrates prepared with different surface pretreatment conditions and grown by HWT can be promising electrodes for supercapacitor device applications.

Controlled reaction dynamics of cellulose: Revealing the dual morphology nanocrystals

Cellulose nanocrystals exhibit diverse morphology with embedded crystallinity derived from the ordered crystalline regimes of cellulose fibers. Acid hydrolysis parameters controls the morphology of nanocrystals and is the primary efficient route for the synthesis of cellulose nanocrystals. In this study, we explored the impact of temperature on the morphology engineering of cellulose nanocrystals derived from banana pseudostem by oxalic acid hydrolysis, an underexplored method. Confirmation of successful cellulose extraction was achieved through fibrous morphology observed in FESEM and TEM analyses. X-ray diffraction and Raman spectroscopy affirmed the presence of type II cellulose. Notably, for the first time, we report the derivation of toroidal and spherulitic sheet-like morphologies in cellulose nanocrystals synthesized by hydrothermal method from banana psuedostem. Our investigation revealed that cellulose hydrolysis at 120 °C yields nanocrystals characterized by toroidal and spherulitic sheet-like morphologies with excellent crystallinity, as confirmed by FESEM and TEM analyses, with average thicknesses of 13.70 nm and 18.05 nm, respectively. Interestingly, elevating the hydrolysis temperature to 180 °C led to the collapse of these structures into carbon dots, exhibiting notable cyan emission.

Carbon coated iron pyrite (C–FeS2) photo-electrode for photo-electrochemical water splitting

In this paper, we present fabrication of ‘FeS2’ and carbon coated FeS2 (C–FeS2) photo-electrodes and demonstrated that coating of carbon on FeS2 significantly enhanced photo-electrochemical properties. The hydrothermal method has been adopted for the synthesis of FeS2 and carbon coating on FeS2 was achieved by CVD technique. The materials are subsequently characterized using X-ray diffraction, Raman spectroscopy and Field enhanced scanning electron microscope (FESEM) techniques for phase identification and morphological studies, respectively. The photo-electrochemical measurements revealed significant enhancement in the current density from ∼2 to 3.7 mA/cm2 (∼1.8 times higher) for C–FeS2 in comparison to the FeS2 photo-electrode under visible light. The enhancement in FeS2 after carbon coating has been attributed to reduction in recombination of photo generated charge carriers, enhancement in the band bending and lowering the charge transfer resistance at the semiconductor/electrolyte interface. To date, very few studies have been reported on FeS2 based composites for water splitting applications and use of carbon coating can be a novel approach for developing efficient solar to hydrogen conversion devices. The mechanism for the photocurrent enhancement was supported by Mott-Schottky and electrochemical impedance spectroscopy measurements.

Steering the Reaction Pathway of CO2 Electroreduction by Tuning the Coordination Number of Copper Catalysts.

Cu-based catalysts are optimal for the electroreduction of CO2 to generate hydrocarbon products. However, controlling product distribution remains a challenging topic. The theoretical investigations have revealed that the coordination number (CN) of Cu considerably influences the adsorption energy of *CO intermediates, thereby affecting the reaction pathway. Cu catalysts with different CNs were fabricated by reducing CuO precursors via cyclic voltammetry (Cyc-Cu), potentiostatic electrolysis (Pot-Cu), and pulsed electrolysis (Pul-Cu), respectively. High-CN Cu catalysts predominantly generate C2+ products, while low-CN Cu favors CH4 production. For instance, over the high-CN Pot-Cu, C2+ is the main product, with the Faradaic efficiency (FE) reaching 82.5% and a partial current density (j) of 514.3 mA cm-2. Conversely, the low-CN Pul(3)-Cu favors the production of CH4, achieving the highest FECH4 value of 56.7% with a jCH4 value of 234.4 mA cm-2. In situ X-ray absorption spectroscopy and Raman spectroscopy studies further confirm the different *CO adsorptions over Cu catalysts with different CN, thereby directing the reaction pathway of the CO2RR.