Conversion Applications Research Articles

Photoredox catalysis of acridinium and quinolinium ion derivatives

AbstractPhotoredox catalysis has attracted increasing attention because of wide range of synthetic transformations and solar energy conversion applications. Reviews on photoredox catalysis have so far focused predominantly on the synthetic applications. This review highlights how organic photoredox catalysts were developed and how they function as efficient photocatalysts in mechanistic point of views. In particular, 9‐mesityl‐10‐methylactidinium (Acr+–Mes) has been highlighted as one of the best organic photoredox catalysts. Acr+–Mes was originally developed as a model compound of the photosynthetic reaction center to mimic the long lifetime of the charge‐separated state in which the energy is converted to chemical energy in photosynthesis. The reason why Acr+–Mes acts as one of the most efficient photoredox catalyst is clarified in terms of the one‐electron redox potentials and long lifetimes of the electron‐transfer state (Acr•–Mes•+) produced upon photoexcitation of Acr+–Mes in different solvents. The reason why the mesityl substituent at the 9‐position of the Acr+ moiety is essential for the efficient photoredox catalysis is discussed in comparison with acridinium ions with different substituents R (Acr+–R) including 10‐methylacridinium ion with no substituent (AcrH+). The mechanisms of photoredox catalysis of Acr+–Mes are discussed in various synthetic transformations and solar energy conversion reactions mimicking photosynthesis. Photoredox catalysis of quinolinium ion and its derivatives is also discussed in comparison with that of Acr+–Mes. Finally, immobilization of Acr+–Mes and quinolinium ions to form the composite catalysts with redox catalyst is discussed to improve the photoredox catalytic activity and stability.

APPLICATION OF Eco-Enzyme CONVERSION RESULTS INTO DISHWASHER SOAP

The application of the conversion results from Eco-Enzyme into dishwashing soap, the fermentation process lasts for one months, where the resulting liquid is dark brown in color and has a very strong sweet and sour fermented aroma. There is a lack of public knowledge about the very profitable benefits of Eco-Enzyme, such as as a multi-purpose cleaner as a multi-functional liquid which can be converted, one of the ways, into dishwashing soap. This research aims to determine the application of the results of converting Eco-Enzyme into dishwashing soap. This research used experimental methods and a research period of 3 months. This Eco-Enzyme is made with a ratio of organic ingredients: sugar: water 3:1:10. The Eco-Enzyme harvest is converted into dishwashing soap by adding lerak and Methyl Ester Sulfonate (MES). Eco-Enzyme conversion soap was then applied to several treatment groups: plastic plates, cans and glass. The results of the application show that the dishes washed with Eco-Enzyme using lerak have not completely removed dirt, oil and odors in each treatment, whereas Eco-Enzyme using Methyl Ester Sulfonate (MES) when compared with Sunlight brand liquid soap sold on the market shows that there are similarities both in terms of cleanliness, tapestry and smell. The research conclusion is that the application of the Eco-Enzyme conversion results has significant potential to be developed into an active ingredient for environmentally friendly dishwashing soap.

3 kV monolithic bidirectional GaN HEMT on sapphire

Abstract 3-kV breakdown voltage was demonstrated in monolithic bidirectional GaN HEMTs having potential applications in 1200V or 1700V-class power converters. The on-resistance of the fabricated transistors was ~20 Ω.mm (~11 mΩ.cm2). The breakdown voltage was optimized with two field plates on either side of the transistor. Shorter first field plate lengths (≤ 2μm) resulted in higher breakdown voltage and the possible reason was discussed. The transistors had a steep subthreshold swing of 92 mV/ dec. The fabricated transistor was benchmarked against the state-of-the-art monolithic bidirectional GaN HEMTs in the performance matrices of breakdown voltage – on resistance, that showed crucial progress.

Efficient Second-Harmonic Generation in Thin-Film Lithium Tantalate Through Modal Phase-Matching

Lithium tantalate (LT) exhibits nonlinear optical properties that are comparable to those of lithium niobate (LN), yet the former surpasses the latter in several respects. These include an enhanced optical damage threshold, a wider transparency range, and lower birefringence. Consequently, LT is an excellent material for optical frequency conversion applications. In this study, we have devised a novel device based on thin-film lithium tantalate (TFLT) for the efficient generation of second-harmonic waves. The design employs modal phase-matching (MPM), which circumvents the intricacies of conventional poling techniques, and attains a normalised conversion efficiency of 120% W−1cm−2. In order to address the challenges presented by higher-order modes, a mode converter with an insertion loss of less than 0.1 dB has been developed, thereby ensuring the efficient utilisation of the second harmonic. This study not only demonstrates the potential of TFLT for high-performance SHG, but also promotes the development of integrated nonlinear TFLT platforms.

Combined In Situ X‐Ray Spectroscopic and Theoretical Study on Trimetal Synergistic Enhancement of Water Oxidation

AbstractElectrochemical water‐splitting is vital in energy storage and conversion applications. However, the sluggish kinetics of the oxygen evolution reaction (OER) hinders the electrochemical water‐splitting. Therefore, developing efficient catalysts and understanding the OER mechanism are highly desirable. This study successfully synthesized a new quadruple perovskite oxide CaCu3Co2Ru2O12 (CCCRO) catalyst exhibiting high OER activity with overpotential 198 mV at 10 mA cm−2, a Tafel slope of 37 mV dec−1, and long‐term operational stability with a current density of 500 mA cm−2 for >500 h. The in situ X‐ray absorption near‐edge structure (XANES) indicated that a part of high‐spin (HS) Co3+ ions and low‐spin (LS) Ru5+ ions transitioned to the tetravalent Co (IV) and hexavalent Ru (VI) valence states under OER. However, the Cu2+ valence state remained unchanged. Furthermore, the density functional theory (DFT) calculations reveal that the lattice‐oxygen oxidation mechanism (LOM) rather than conventional adsorbate evolution mechanism (AEM) is responsible for high OER activity in Ru (VI)‐O‐Co (IV) network, and that the Cu(A’)/Co(B)/Ru(B’) three sites synergistically facilitate the OER activity for CCCRO.

A Geometric Interpretation of Kinetic Zone Diagrams in Electrochemistry.

Electrochemical systems with increasing complexity are gaining importance in catalytic energy conversion applications. Due to the interplay between transport phenomena and chemical kinetics, predicting optimization is a challenge, with numerous parameters controlling the overall performance. Zone diagrams provide a way to identify specific kinetic regimes and track how variations in the governing parameters translate the system between either adverse or optimal kinetic states. However, the current procedures for constructing zone diagrams are restricted to simplified systems with a minimal number of governing parameters. We present a computationally based method that maps the entire parameter space of multidimensional electrochemical systems and automatically identifies kinetic regimes. Once the current output over a discrete set of parameters is interpreted as a geometric surface, its geometry encodes all of the information needed to construct a zone diagram. Zone boundaries and limiting zones are defined by curved and flat regions, respectively. This geometric framework enables a systematic exploration of the parameter space, which is not readily accessible by analytical or direct numerical methods. This will become increasingly valuable for the rational design of electrochemical systems with intrinsically high complexity.

Speed control analysis of voltage source inverter fed brushless DC motor

The brushless DC (BLDC) motor requires to be controlled at the preferred speed in order to operate. A brushless DC motor's speed can be adjusted by adjusting the input voltage. In general, speed increases with voltage. The application of a Luo converter is made to satisfy the load demand, get rid of output voltage ripples, and reduce parasitic effects. The magnitude of stator input voltage to BLDC motor is controlled through the pulses applied by ATMEGA 328P micro controller to voltage source Inverter which in turn controls the magnitude of speed of BLDC motor. The position of the brushless DC (BLDC) motor is continually monitored by infrared sensors, which are then processed by a PIC16F872 microcontroller to produce the necessary pulses for BLDC motor speed regulation. The BLDC motor speed can be regulated by the pulses applied to voltage source inverter through the IR sensors placed at the motor. The outcomes of controlling the speed of a BLDC motor using voltage variation values have been shown.

In situ preparation of carbon/zeolite composite materials derived from coal gasification fine slag for removing malachite green: Performance evaluation and mechanism insight

The stockpiling of coal gasification fine slag (CGFS) and the discharge of organic wastewater pose serious environmental threats. The complex synthesis process and limited pollutant removal capacity of CGFS-based adsorbents impede their efficient utilization in organic wastewater purification. In this work, carbon/zeolite composite materials (CZCM) derived from CGFS were prepared in situ using a one-pot method without further crystallization, achieving an ultra-high adsorption capacity (9705 mg/g) and excellent renewability for malachite green (MG). CZCM was identified as a typical mesoporous material with an abundant pore structure, facilitating the migration of MG within the material. Notably, various metal elements (e.g., iron and calcium) and chemical groups (e.g., carboxyl and hydroxyl) from CGFS were retained through this novel preparation method, providing additional adsorption sites and enhancing MG adsorption. The adsorption kinetics and thermodynamics results indicated that physisorption and multilayer adsorption were the primary adsorption modes of MG by CZCM, with the adsorption rate limited by internal diffusion. Furthermore, the adsorption process was found to be exothermic, spontaneous, and entropy-decreasing. Mechanistic investigations revealed that the exceptional adsorption performance of MG by CZCM was primarily attributed to electrostatic attraction and ion exchange, with hydrogen bonding and π-π interactions also playing significant roles. This study provides new insights into the development of CGFS-based adsorbents for organic wastewater treatment, promoting the efficient conversion and practical application of CGFS.

A New Strategy for Photo‐Electrochemical Reduction of Carbon Dioxide Using a Carbazole‐BODIPY Based Metal‐Free Catalyst

AbstractIn this study, a cross‐linked boron dipyrromethene (BODIPY) photocatalyst containing a carbazole donor group designed for photoelectrocatalytic carbon dioxide (CO2) reduction is synthesized and characterized. The BODIPY‐based system, coated onto a platinum surface, is evaluated for its electrochemical and photocatalytic performance under light illumination. Cyclic voltammetry (CV) and chronoamperometry measurements reveals enhanced photocurrent responses, confirming the catalyst's ability to effectively drive CO2 reduction. Gas chromatography/mass spectrometry (GC‐MS) analysis identifies the formation of ethanol (C2H5OH) as a major reaction product, showing that its yield increased with extended reaction times. Additionally, the photocatalyst demonstrates remarkable performance with significantly increasing turnover numbers (TON) and turnover frequencies (TOF) over time, indicating stable and sustained catalytic activity. With a Faradaic efficiency of 34.79% at a potential of ‐1.15 V, this BODIPY system exhibits both high activity and long‐term stability. The combination of efficient electron transfer and visible light absorption by the carbazole‐BODIPY donor‐acceptor structure positions this system as a highly promising candidate for sustainable CO2 conversion applications.

Effect of differently shaped spiral inductors on micro power integrated circuit

Abstract This paper investigates the impact of parasitic effects on the performance of on-chip planar spiral inductors for DC-DC converter applications, focusing on three geometries: square, hexagonal, and octagonal. Detailed electromagnetic simulations in MATLAB are employed to analyze the frequency-dependent behavior of key parasitic components, including ohmic resistance (Rs), substrate resistance (Rsub), oxide capacitance (Cox), and substrate capacitance (Csub) across a frequency range of 1 GHz to 10 GHz. The study reveals that the octagonal spiral inductor outperforms the others, demonstrating a 29% reduction in ohmic resistance at 1.5 GHz compared to the square geometry and achieving the highest substrate resistance, which helps reduce current leakage. Additionally, the octagonal inductor exhibits the lowest parasitic capacitance and a high-quality factor, peaking at 30 at 4.2 GHz. These results underscore the significant impact of inductor geometry on minimizing energy dissipation and electromagnetic interference, positioning the octagonal spiral inductor as a compelling choice for enhancing efficiency and miniaturization in DCDC converter designs.

Water process/treatment by a S-scheme Fe2O3/TiO2 heterojunction photocatalyst for excellent antibiotic degradation/CO2 reduction/H2 production; process optimization and mechanistic insights

A facile synthesis approach was employed to fabricate a binary Fe2O3/TiO2 nanocomposite (FeTi4-400) for enhanced photocatalytic hydrogen (H2) production, cephalexin degradation and CO2 reduction under visible light irradiation. Compared to pristine TiO2, FeTi4-400 exhibited improved visible light absorption and promoted charge carrier separation, leading to increased H2 production rate and CO2 conversion into CH4 and CO. This improvement can be attributed to the formation of an S-scheme heterojunction, along with the desirable properties of FeTi4-400, including visible light activity, high surface area, and strong CO2 adsorption. The photocatalyst achieved a maximum H2 production rate of 649 μmol/g·h−1, exceeding that of pure TiO2. Similarly, the highest CO production rate of 16.44 μmol/g·h−1 was attained with FeTi4-400. Furthermore, FeTi4-400 achieved excellent cephalexin degradation (96 %) under optimal conditions, with a degradation rate constant of 0.01 min−1. A plausible cephalexin degradation pathway over FeTi4-400 is proposed. Transient photocurrent measurements and EIS analysis corroborated a significant enhancement in photocatalytic activity for FeTi4-400, attributed to the efficient separation of photogenerated electron-hole pairs. Stability studies demonstrated consistent cephalexin degradation by FeTi4-400 over five consecutive cycles without noticeable photocatalyst deactivation. This work presents a novel strategy for fabricating low-cost, efficient, and readily synthesized nanomaterials for applications in solar energy conversion and environmental remediation.

Low-temperature rapid fabrication of crosslinked poly(quaterphenyl piperidine) membrane for anion exchange membrane water electrolyzers

While nonsolvent-induced phase separation (NIPS) is widely recognized as an established method for creating porous polymer membranes, this study uniquely employs a nonsolvent to produce a dense, nonporous membrane instead. Specifically, the membranes were rapidly fabricated at low temperatures using dimethyl sulfoxide (DMSO), a high-boiling-point solvent, and water as the nonsolvent. We successfully prepared a series of crosslinked poly(quaterphenyl piperidine) (PQP-BM) network membranes with high crosslinking degrees (up to 47.2 %). By combining a hydrophobic extended polyaromatic backbone with a hydrophilic piperidine-based crosslinker, we achieved distinct microphase separation, which enhanced ion transport, dimensional stability, and thermal and mechanical properties compared to the linear uncrosslinked membranes. The optimized AEM exhibited exceptional mechanical strength (tensile strength >63 MPa), high ion conductivity (151.5 mS cm⁻¹ at 80 °C), and excellent alkaline durability. In single-cell water electrolyzer tests, the PQP-BM membrane demonstrated a remarkable current density of 3.99 A cm⁻² at 2.0 V in 1 M KOH at 50 °C, outperforming the commercial FAA-3–50 membrane by 126 %. This study highlights the potential of the energy-efficient NIFF process as a scalable method for producing advanced AEMs for energy conversion applications.

One-pot synthesis of lactones from ketoacids involving microwave heating and sodium borohydride: application in biomass conversion.

A metal-free one-pot cascade method involving NaBH4 and microwave (MW)-heating efficiently synthesized lactones, including the industrially significant γ-valerolactone at 90% yield. The process directly converts methyl levulinate, succinic acid and a wide range of aliphatic and aromatic ketoacids, in H2O or THF, proceeding via reduction, COOH proton exchange, cyclization, and dehydration, showing promise for biomass conversion.

Village-level hydropower for developing economies: Accelerating access to electricity using low-cost hydrokinetic technology for remote community: 1. Laboratory flume experiment

ABSTRACT This article presents the feasibility of a low-cost hydrokinetic turbine technology developed and experimentally tested in the laboratory for enhancing electricity access in isolated off-grid communities in the rural areas. The research and development involved using e-waste and locally available materials to develop a modular energy conversion system using rivers’ kinetic flow. A decommissioned boat motor with a 0.24 m diameter rotor is operated as a turbine. Four augmentation structures were developed and tested in a flume to evaluate their performance for flow acceleration and application for energy conversion. The four varied configurations produced distinctive performances in an overflow test condition at an approach velocity of 0.25 m/s such that: nozzle 1(8.111 ± 0.107 V DC, 7.116 ± 0.098 V AC), Nozzle 2 (10.038 ± 0.103 V DC, 8.804 ± 0.123 V AC), nozzle 3 (8.523 ± 0.009 V DC, 7.543 ± 0.008 V AC) and Diffuser_type 1 (8.053 ± 0.082 V DC, 7.147 ± 0.144 V AC). Only nozzle 1 was tested in dammed condition and produced 13.248 ± 0.123 V DC and 11.395 ± 0.008 V AC. Nozzle 2 produced a promising performance serving as a reference in comparison to the other three configurations under similar flow conditions.

Enhanced photo-thermal conversion in phase change materials by Cu-Zn Bi-metallic metal-organic framework and expanded graphite

Photothermal phase change materials (PCM) are employed for the efficient conversion and storage of solar energy. In this work, a Cu-Zn bi-metallic metal-organic framework (MOF) was synthesized and combined with expanded graphite (EG), followed by high-temperature carbonization to prepare the supporting material for polyethylene glycol (PEG). Through the high-temperature carbonization process, nano-metallic copper is uniformly dispersed on the surface of the EG, accompanied by the formation of a new porous structure resulting from the evaporation of Zn vapour. The nano metallic copper particles enhance the thermal conductivity and photo-thermal conversion efficiency of the composite PCM, while the porous structure generated by Zn vapour improves the adsorption capacity of PEG. The composite PCM demonstrated a high phase change enthalpy of 174.6 J/g and excellent thermal reliability, with only a 2.29 % reduction in enthalpy after 200 melting-freezing cycles. Additionally, the thermal conductivity of the composite PCM reached 6.096 W/(m·K) which is 26.1 times higher than that of pure PEG, while the photo-thermal conversion efficiency achieved was 88.69 %. These properties indicate that the PEG/EG/Cu-Zn-MOF derived carbon composite PCM has great potential for applications in solar energy storage and conversion.

One-pot construction of highly active defective g-C3N4 via hydrogen bond of the biomass for the improvement of CO2 conversion

Graphitic carbon nitride (g-C3N4) containing conjugated tri-s-triazine units has a high abundance of amine and guanidine groups, which are ideal for the application of CO2 conversion. However, absolute g-C3N4 is inherently scarce in Lewis base sites, which leads to low catalytic activities. In this study, we present a simple and green method to in situ construct chrysanthemum stalk-derived porous carbon/ highly active defective g-C3N4 (PC/g-C3N4) through hydrogen bond, increasing the surface area and a high density of Lewis base sites. The chrysanthemum stalk contains cellulose, hemicellulose and lignin, which possess a significant number of hydroxyl functional groups and drain channels, thereby providing more hydrogen bonding for highly active defective g-C3N4. The XPS spectra revealed that, in comparison to PC/g-C3N4–1 and PC/ g-C3N4–2.5, PC/g-C3N4–2 exhibited a higher C-NH2 content at the edge of the nitrogen element. PC/g-C3N4–2 had a high specific surface area to expose more active sites for absorbing CO2. The quantification of the base sites is determined by the peak area of the thermal programmed desorption of CO2 and is 229.6 μmol/g for PC/g-C3N4–2. PC/g-C3N4–2 demonstrated excellent catalytic activity in the cycloaddition with hierarchical pores. The yield of cyclic carbonate was up to 99% with a selectivity of 99% under mild solvent-free conditions. The mechanistic studies indicate that PC/g-C3N4–2 not only captured CO2, but also provided hydrogen bonds to activate the oxygen atom of epichlorohydrin (ECH). It is our contention that the multifunctional organic-inorganic hybrid materials have considerable potential for the production of cyclic carbonate.

Strategic defect engineering in TiO2 catalysts through electron beam irradiation: Unraveling enhanced photocatalytic pathways for multicomponent VOCs degradation

Defect engineering improves catalytic activity, electron transport efficiency, and stability by introducing defects such as oxygen vacancies, offering significant potential for applications in environmental remediation and energy conversion. Electron beam (EB) irradiation has emerged as a key technique in defect engineering, renowned for its mild reaction conditions and precise defect construction capabilities. This study synthesized defect-rich commercial TiO2 catalysts (P25) using high-energy EB irradiation to investigate the photodegradation efficiency of multicomponent VOCs. The EB irradiation technique promoted the formation of oxygen vacancies, which played a key role in the adsorption and activation of pollutant molecules. DFT calculations further confirmed the superior photocatalytic activity of the irradiated P25 catalyst. The photodegradation experiments showed that the 300P25 degraded pure ethyl acetate up to 99.05 % (40 min) and acetone up to 97.14 % (60 min), but toluene only up to 7.34 % (60 min). Interestingly, in acetone and toluene mixture, 300P25 achieved toluene removal as high as 68 % (60 min) with a rate constant (k) of 0.0181 min−1, a 12.1-fold than pure toluene (0.0015 min−1). In-situ infrared spectroscopy analysis revealed that during the simultaneous degradation of toluene and acetone, acetone significantly promoted the deep oxidation of toluene, leading to the rapid oxidation of intermediate products (benzyl alcohol and benzaldehyde) to benzoic acid and smaller molecules. This work provides important guidance for developing efficient and stable photocatalysts for degrading multicomponent VOCs.

Impact of a tri-dimensional conical structure made of composite materials

This paper investigates the impact strength of a three-dimensional conical structure constructed from composite materials, focusing on its application in wave energy converters. Two glass fibre-reinforced polymers, unidirectional and bi-axial stitched fabrics, are analysed. The study includes an experimental low-velocity impact of plates with solid objects, simulating low-velocity impact with floating debris, and an experimental bottom wave slamming test where the structure is dropped from a height of 1.5 m onto a calm water surface equivalent to an initial velocity of 5.43 (m/s). In addition, a destructive buckling test is carried out by applying pressure to the conical to assess the buckling strength of both laminates. Furthermore, the experimental buckling pressure failure is compared with the pressure peak determined by a numerical simulation, based on the Arbitrary Lagrangian Eulerian formulation, and with a design pressure suggested by a classification society recommended practice. Results demonstrate that the biaxial stitched fabric reveals a higher impact strength on both impacts with solids and fluids and a higher buckling strength. Moreover, the peak pressure determined by the numerical simulation is slightly higher than that a conservative design approach predicted.

Facile and ecofriendly green synthesis of Co3O4/MgO-SiO2 composites towards efficient asymmetric supercapacitor and oxygen evolution reaction applications.

The development of low-cost, eco-friendly, and earth-friendly electrode materials for energy storage and conversion applications is a highly desirable but challenging task for strengthening the existing renewable energy systems. As part of this study, orange peel extract was utilized to synthesize a magnesium oxide-silicon dioxide hybrid substrate system (MgO-SiO2) for coating cobalt oxide nanostructures (Co3O4) via hydrothermal methods. A variety of MgO-SiO2 compositions were used to produce Co3O4 nanostructures. The purpose of using MgO-SiO2 substrates was to increase the porosity of the final hybrid material and enhance its compatibility with the electrode material. This study investigated the morphology, chemical composition, optical properties, and functional group properties. In hybrid materials, the shape structure is inherited from nanoparticles with uniform size distributions that are well compacted. A relative decrease in the optical band was observed for Co3O4 when deposited onto an MgO-SiO2 substrate. An improvement in the electrochemical properties of Co3O4/MgO-SiO2 composites was observed during the measurements of supercapacitors and oxygen evolution reaction (OER) in alkaline solutions. The Co3O4/MgO-SiO2 composite prepared on 0.4 g of the MgO-SiO2 substrate (sample 2) demonstrated excellent specific capacitance, high energy density, and recycling stability for 40 000 galvanic charge-discharge cycles. The assembled asymmetric supercapacitor (ASC) device demonstrated a specific capacitance of 243.94 F g-1 at a current density of 2 A g-1. Co3O4/MgO-SiO2 composites were found to be highly active towards the OER in 1 M KOH aqueous solution with an overpotential of 340 mV at 10 mA cm-2 and a Tafel slope of 88 mV dc-1. It was found that the stability and durability were highly satisfactory. Based on the use of orange peel extract, a roadmap was developed for the synthesis of porous hybrid substrates for the development of efficient electrode materials for energy storage and conversion.

Modulating the Doping Effect for Carbon Nanotube-Based Thermoelectric Composites by Radical-Containing Naphthalene Diimides

Modulating the Doping Effect for Carbon Nanotube-Based Thermoelectric Composites by Radical-Containing Naphthalene Diimides