Successive Reaction Research Articles

Co-pyrolysis of Baltic wheat straw and low-density polyethylene bags and its kinetic and thermodynamic behaviour

Wheat cultivation represents about 42 % of the total cereal cultivation area in the Baltic Sea region, generating huge amounts of wheat straw (WS) that needs to be optimally managed. In this context, this research aims to investigate the extent of using pyrolysis process in WS valorization. The experiments were performed using a thermogravimetric (TG) analyzer on WS and its mixtures with low-density polyethylene (LDPE) bags at different mixing ratios (1:1, 1:2, 1:3, 1:4). The released TG vapours were monitored using TG-Fourier transform infrared spectroscopy (TG-FTIR) and chromatography-mass spectrometry (GC-MS). The thermochemical activation energy (Ea) were studied by Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa, Friedman, and Vyazovkin models. The pyrolysis results showed that WS and LDPE could be completely decomposed as a single reaction up to 600 °C and 520 °C, respectively. Aromatic-carbonyl and CO2 were the main FTIR functional group for WS vapour versus -CH2- for LEDP vapour. The GC/MS analysis of WS showed various compounds such as sec-Butylamine (11.88 %), acetic acid (10.68 %), etc., while LDPE showed many compounds without specific trend even when the heating rate was changed. While the co-pyrolysis results showed that WS/LDPE could be decomposed individually in two successive reactions at 335 °C (WS) and 495 °C (LDPE). These results were confirmed by FTIR and GC/MS which showed that the functional groups and chemical compounds of vapour generated at these decomposition zones have similar characteristics to those obtained from pyrolysis of WS and LDPE. Finally, kinetic analysis showed that WS-Baltic (227–250 kJ/mol) is more complex compared to WS-Asian (163–217 kJ/mol) due to its higher ash content. While Ea of WS/LDPE was increases upto 274–291 kJ/mol (1:1), 266–297 kJ/mol (2:1), 268–289 kJ/mol (3:1), and 278–299 kJ/mol (1:4). Also, the enthalpy, and Gibbs free energy coefficients of WS were increased by mixing (1:1) up to 272 J/mol K, while its entropy does not change much by mixing (367 J/mol K). Accordingly, the co-pyrolysis process is a key technology in valorization of WS and convert into value-added chemicals and a sustainable energy source.

Successive ionic layer adsorption and reaction grown silver nanoflowers as an efficient flexible SERS substrate

The detection limitations of surface-enhanced Raman spectroscopy (SERS) sensors largely depend on the nano tip structure, yet the methods for constructing it are often overly complex. Here, we introduce a method using successive ionic layer adsorption and reaction (SILAR) to synthesize silver nanoflowers (AgNFs) within and on the surface of soft cellulose filter paper. This synthesis relies on a redox reaction involving silver nitrate (AgNO3) and ascorbic acid (AA), with no surfactants or additional agents utilized. Key synthesis parameters were investigated, such as the molar concentration of reactants and the number of synthesis cycles performed. As a result, the detection limit for rhodamine 6G (R6G) using SERS approached 10−11 M when deposited on the optimally synthesized AgNFs sample, yielding a corresponding enhancement factor of 8.9 × 108. The growth mechanism of AgNFs was analyzed by examining morphological changes over the initial five reaction cycles, and differences in X-ray diffraction (XRD) peak intensity ratios of (111) and (200) among the samples were considered. These findings pave a way for the development of high performance, Ag-based flexible SERS substrates.

Citizen-Led Disaster Preparedness: Adaptive Survival and Safety Techniques in the Face of Limited Resources

Citizens proactively preparing themselves and working together at the neighbourhood level are often key to a successful disaster reaction. When communities don't have a lot of outside help after a disaster, this article looks at how grassroots organising and adaptive survival techniques can help them stay alive and get back on their feet. Texas tornadoes and Hurricane Katrina are two examples of how citizen-led planning and mutual help can fill in important gaps in response. When official first responders are too busy, Oklahomans help each other out by giving each other emergency supplies, a place to stay, and search and rescue services. People in the community came together during Hurricane Katrina in 2005 to give out supplies and provide housing for people who were stuck for days without help. With decentralised preparation, this book suggests flexible methods that people and communities can use to become more resilient. Communication networks should be set up using all available channels; complete emergency supply kits should be put together and updated on a regular basis; backup power and clean water sources should be made sure of; shelters should be strengthened to withstand high winds and flooding; and coordinated evacuation and neighbourhood watch plans should be made. Citizens can help each other on their own if reaction capabilities are exceeded by setting up localised chains of command, stockpiling supplies, and making it clear who is responsible for sheltering who. In order to better coordinate their efforts and get back on their feet faster after a disaster, communities that establish clear roles and mutual deals are better organised. By applying adaptive strategies, citizens can overcome resource limitations and environmental vulnerabilities through self-sufficiency and mutual aid. Widespread civilian preparation and cooperation builds resilience to withstand catastrophic events when facing delayed or restricted formalized relief efforts.

Chemical Bath Deposition of ZnO/ZnGa2O4 Core-Shell Nanowire Heterostructures Using Partial Chemical Conversion.

The development of innovative heterostructures made of ZnO nanowires is of great interest for enhancing the performances of many devices in the fields of optoelectronics, photovoltaics, and energy harvesting. We report an original fabrication process to form ZnO/ZnGa2O4 core-shell nanowire heterostructures in the framework of the wet chemistry techniques. The process involves the partial chemical conversion of ZnO nanowires grown via chemical bath deposition into ZnO/ZnGa2O4 core-shell nanowire heterostructures with a high interface quality following their immersion in an aqueous solution containing gallium nitrate heated at a low temperature. The double-step process describing the partial chemical conversion relies on successive dissolution and reaction mechanisms. The present finding offers the possibility to fabricate ZnO/ZnGa2O4 core-shell nanowire heterostructures at low temperatures and over a wide variety of substrates with a large surface area, which is attractive for nanostructured solar cells, deep-UV photodetectors, and piezoelectric devices.

A Core/Shell Bi2S3/BiVO4 Nanoarchitecture for Efficient Photoelectrochemical Water Oxidation.

The construction of nanostructured heterostructure is a potent strategy for achieving high-performance photoelectrochemical (PEC) water splitting. Among these, constructing BiVO4-based heterostructure stands out as a promising method for optimizing light-harvesting efficiency and reducing severe charge recombination. Herein, we present a novel approach to fabricate a type II heterostructure of core/shell Bi2S3/BiVO4 using electrolytic deposition and successive ionic layer adsorption and reaction (SILAR) methods. We identify the type II heterostructure and the difference in fermi energy using UV-Vis spectroscopy, X-ray photoelectron spectroscopy, and PEC measurements. This redistribution of charges due to the fermi energy difference induces an interfacial built-in electric field from BiVO4 to Bi2S3, reinforcing the photogenerated hole transfer kinetics from BiVO4 to Bi2S3. The Bi2S3/BiVO4 heterostructure exhibits a superior photocurrent (6.0 mA cm-2), enhanced charge separation efficiency (85 %), and higher open-circuit photovoltage (350 mV). Additionally, the heterostructure displays a prolonged average lifetime of charge (1.63 ns), verifying this heterojunction could boost interfacial carriers' migration via an additional nonradiative quenching pathway. Furthermore, the lower photoluminescence (PL) intensity demonstrates the interfacial built-in electric field is beneficial for boosting charge migration.

Synthesis and characterization of copper tin sulfide counter electrode for enhanced performance in third-generation solar cells

This paper presents the fabrication of a copper tin sulfide (CTS) counter electrode for application in third-generation solar cells. The fabrication process involved modified chemical bath deposition (M-CBD) or a successive ionic layer adsorption reaction (SILAR). Initially, a ZnO seed layer was deposited onto a fluorine-doped tin oxide (FTO) substrate via CBD. Subsequently, a mesoporous layer of ZnO was deposited onto the FTO substrate using the doctor-blade method. The mesoporous ZnO layer was sensitized with CdS nanocrystals deposited using the SILAR method. Various characterization techniques, including UV–Vis spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM), were employed to analyze the optical, structural, and morphological properties of the photoanode and CTS counter electrode. The results demonstrate the successful synthesis of a CTS counter electrode with desirable properties for solar-cell applications. The fabricated CTS counter electrode exhibited a conversion efficiency of 0.49%, which was significantly higher than that of carbon-based counter electrodes.

SnS thin films deposited at room temperature – Efficient and reusable dark catalyst for water remediation at ambient conditions

This study describes the dark catalytic degradation of cationic, anionic, and commercial dyes by SnS thin films under dark ambient conditions without the assistance of any external stimuli. The thin films were deposited by a modified SILAR (Successive Ionic Layer Adsorption and Reaction) method at room temperature and characterised using XRD, XPS, FESEM, TGA, and UV–visible spectrophotometers. The dark catalytic degradation of methylene blue (MB) dye was investigated using a spectrophotometer and validated by LCMS analysis and an adsorption desorption test. Within 15 min, 48 % of the MB dye (original concentration: 10 mg/l) had been degraded by the catalyst, and by 90 min, the degeneration was almost complete. The ROS (reactive oxygen species) scavenger test and indicator test confirmed the role of the hydroxyl radical in the degradation process. The influence of initial dye concentration, magnetic stirring, and the composition of the catalyst on the degradation efficiency was also studied. The same catalyst was used five times in succession to test its reusability, and it was then structurally and thermally characterised to test its stability. This study emphasises the possible use of SnS thin film as an effective, reliable, and reusable around-the-clock catalyst for the degradation of dye-contaminated waste water without the assistance of light or any chemical additives.

Synthesis of N-vinylcarbazole from acetylene by a continuous high-pressure liquid-phase process with inherent safety

In this study, a continuous high-pressure liquid-phase acetylene microreaction process is rationally designed and successfully realized by employing the strategy of decoupling the acetylene dissolution and successive reaction. As the acetylene reaction is operated in a pure liquid phase with high acetylene concentration, the safety and efficiency of the acetylene conversion process are greatly improved. As a result, N-vinylcarbazole (NVC) is continuously synthesized from dissolved acetylene at 165 °C and 4.5 MPa. Compared to the conventional batch process, the reaction time is reduced to 5–20 min from 5 to 6 h, the amount of catalyst is reduced by 14.8 times, and the specific activity (g carbazole /g KOH /min) is increased by 220 times. To further increase the yield of NVC, 4-tert-butylcatechol (TBC) is added to the feedstock as a polymerization inhibitor, which improves the yield of NVC to 88 %. Several other vinyl compounds, in addition to NVC, are also continuously synthesized from acetylene using this method, which suggests that the process decoupling reaction strategy is widely applicable to acetylene-involved reactions.

Fabrication of cobalt-doped ZnS thin films by successive ionic layer adsorption and reaction for UV–visible photodetectors on flexible substrate

Photodetectors are widely employed in research and innovation, necessitating swift response times, precision, and stability. However, their application in commercial and industrial settings is hindered by limited flexibility and a constrained capacity to respond across a broad spectrum. In this study, we adopted a facile, cost-effective, and room temperature Successive Ionic Layer Adsorption and Reaction (SILAR) technique to craft thin films of Cobalt-doped ZnS on a flexible paper substrate. The Cobalt doping, with varying wt.% (0, 0.5, 1, and 1.5) exhibiting excellent responsivity to both UV and visible spectra. Zinc Sulfide (ZnS), renowned for its wide bandgap, serves as a versatile semiconductor, making it an ideal candidate for photodetectors. The introduction of Cobalt broadened the responsivity of ZnS, covering a wide spectrum, including UV and visible regions. Structural confirmation of the material was achieved through XRD and Raman analyses. Scanning Electron Microscopy revealed the aggregated spherical nanostructure of ZnS on the cellulose substrate. Verification of Cobalt presence in the ZnS thin film and assessment of elemental oxidation states were conducted using XPS. Temporal response and I–V characteristics of the device were evaluated under varying light conditions, specifically at wavelengths of 325 nm and 700 nm at different intensities. Responsivity calculations yielded values of 22.5 mA/W for UV illumination (light intensity 0.6 mW/cm2) and 37.6 mA/W (light intensity 0.4 mW/cm2) for visible light, with corresponding response times recorded as 1.45 s and 2.13 s, respectively. In addition to performance assessments, bending cycle studies were conducted, demonstrating the excellent flexibility of the device up to 800 cycles. The Cobalt-doped ZnS device, as fabricated, emerges as a promising material for energy harvesting.

Encapsulation of Cu-modified SnO2 yolk-shell in V2O5-amalgamated wrinkled g-C3N4 lamella for boosting antibiotic photodegradation

The remarkable application of tin oxide in various domains is indebted to its photoelectronic merits. However, significant efforts to discover its photocatalytic potential were restricted through arduous challenges, which were the amelioration of light-harvesting and -utilizing. In fact, the uncommon light absorption energy has drawn veil over the brilliance of astounding oxidation potential, which is much more than that of TiO2. Herein, our attention was focused on the taking advantages of self-template structure for simultaneously enjoying the two sides of photoelectronic justification as well as the S-step system for eminent charge dissociation. In this regard, the optimized Cu-modified SnO2 yolk-shell ((5)YS-CuSnO) spheres were engineered through the copper modulation into glycerate-assisted metal-organic structure. As a result, the exceptional light-harvesting was achieved through desirable defects and oxygen vacancy resulted from Cu-doping, and also efficient light-utilization was obtained by the multi-scattering/reflection effect resulted from multi-shell configuration. After the effectual incorporation (40 wt⁒) of (5)YS-CuSnO was encapsulated into the V2O5-decorated wrinkled g-C3N4 lamella (VO–WCN), the dual S-step VO-WCN@(5)YS-CuSnO introduced unprecedented levofloxacin (LFC) decontamination performance, which was kinetically 5.2 and 30.2-times greater than of the (5)YS-CuSnO and bare SnO2 yolk-shell. The conspicuous fulfillment of nanocomposite was manifested in the LFC mineralization, pharmaceutical effluent treatment within 360 min, and successive cycling reactions. The fusion of the extraordinary architecture of YS-CuSnO with S-Step system not only initiates the facile and practical photocatalytic exploitation, but shade light on some undeveloped side of tin oxide.

(Invited) CdS/Ti-Si-O Composite Photoanode for Photoelectrochemical Hydrogen Generation

Advancements in clean energy drive socio-economic development and foster a sustainable future by restructuring energy systems and promoting low-carbon development. In this paper, we presented a comprehensive investigation on the design and performance characterization of CdS/Ti-Si-O composite photoanodes for photoelectrochemical (PEC) hydrogen generation. Silicon-doped TiO2 nanotube arrays were fabricated through anodization of Ti-5Si alloy, followed by the deposition of CdS using the SILAR (successive ionic layer adsorption and reaction) process, resulting in nanostructured Ti-Si-O photoanodes modified with CdS. The composite photoanodes were characterized in terms of their composition, microstructure, optical properties and photoelectrochemical hydrogen production performance. The composite photoanodes revealed a notable enhancement in PEC hydrogen generation properties with a photocurrent density of 7.86 mA/cm2，which was 19.15 times and 9.59 times to those of the undoped TiO2 photoanode and Ti-Si-O photoanode, respectively. The Si-doping mechanism of the photoanodes was elucidated through Density Functional Theory (DFT) calculations. The synergistic combination of Si-doping and CdS modification represents a novel and promising approach for the design of efficient nanostructured photoanodes.

Interface-modulated kinetic differentials in electron and hole transfer rates as a key design principle for redox photocatalysis by Sb2VO5/QD heterostructures.

The efficient conversion of solar energy to chemical energy represents a critical bottleneck to the energy transition. Photocatalytic splitting of water to generate solar fuels is a promising solution. Semiconductor quantum dots (QDs) are prime candidates for light-harvesting components of photocatalytic heterostructures, given their size-dependent photophysical properties and band-edge energies. A promising series of heterostructured photocatalysts interface QDs with transition-metal oxides which embed midgap electronic states derived from the stereochemically active electron lone pairs of p-block cations. Here, we examine the thermodynamic driving forces and dynamics of charge separation in Sb2VO5/CdSe QD heterostructures, wherein a high density of Sb 5s2-derived midgap states are prospective acceptors for photogenerated holes. Hard-x-ray valence band photoemission spectroscopy measurements of Sb2VO5/CdSe QD heterostructures were used to deduce thermodynamic driving forces for charge separation. Interfacial charge transfer dynamics in the heterostructures were examined as a function of the mode of interfacial connectivity, contrasting heterostructures with direct interfaces assembled by successive ion layer adsorption and reaction (SILAR) and interfaces comprising molecular bridges assembled by linker-assisted assembly (LAA). Transient absorption spectroscopy measurements indicate ultrafast (<2ps) electron and hole transfer in SILAR-derived heterostructures, whereas LAA-derived heterostructures show orders of magnitude differentials in the kinetics of hole (<100ps) and electron (∼1ns) transfer. The interface-modulated kinetic differentials in electron and hole transfer rates underpin the more effective charge separation, reduced charge recombination, and greater photocatalytic efficiency observed for the LAA-derived Sb2VO5/CdSe QD heterostructures.

Highly stable flexible ozone gas sensors using Mn3O4 nanoparticles-decorated IGZO thin films through the SILAR method

Metal or semiconductor nanoparticles (NPs) can enhance the device performance of gas sensors due to their high surface area and unique electronic properties. However, this method requires additional thermal bonding with high temperatures to secure the NPs, making it unsuitable for flexible substrates. In this study, we develop a room-temperature flexible ozone (O3) gas sensor using Mn3O4 NPs on an amorphous InGaZnO (a-IGZO) film. The Mn3O4 NPs are synthesized by a successive ionic layer adsorption and reaction (SILAR) method at low temperatures. The sensor with Mn3O4 NPs exhibits a gas response of 4.06 against 5 ppm O3 gas at room temperature, which is much higher than that of its pristine counterpart. It also shows excellent selectivity for O3 over toxic gases and maintains stability over 60 days, with reproducible folding even after 500 bending cycles. Thus, the combination of SILAR-synthesized Mn3O4 NPs and a-IGZO films provides an effective way to fabricate flexible O3 gas sensors.

Fabrication and characterization of ZnWO4/CoWO4 heterojunction for multispectral photodetection on flexible substrate

Flexible photodetectors hold significant interest across diverse applications, such as imaging, communication, healthcare, and environmental monitoring. This work reports a broad-band photodetector comprising Zinc tungstate (ZW) and Cobalt tungstate (CW) on a flexible paper substrate. CW thin film was fabricated by a facile successive ionic layer adsorption and reaction(SILAR) technique and the ZW nanoparticles, synthesised via simple co-precipitation method, were drop casted on it to form a heterojunction. Structural characterization of the materials was conducted using X-ray diffraction (XRD), Raman spectroscopy, and Fourier-transform infrared spectroscopy (FTIR), while scanning electron microscopy was employed for detailed morphology analysis. CW is a p type semiconductor with its bandgap of 2.6 eV, exhibits impressive sensitivity across both visible and infrared segments of the electromagnetic spectrum. In contrast, ZW which is n type contributes UV-responsive, attributes effectively broadening the overall spectral sensitivity from Ultraviolet (UV) to Infrared (IR) spectra within a single compact device. The photodetector demonstrates remarkable responsivity of 1.66 mA/W (UV), 24.58 mA/W (Visible), and 0.024 mA/W (IR) under respective light intensities of 0.6 mW/cm², 0.4 mW/cm², and 4.41 mW/cm. The detectivity metrics are equally impressive, measuring at 9.9×1010 Jones (UV), 5.01×1011 Jones (Visible), and 4.48×1010 Jones (IR). The successful combination of Zinc tungstate and Cobalt tungstate on a paper substrate represents an advancement in photodetector technology, offering enhanced sensitivity, extended spectral range, and the potential for seamless integration into wearable electronics and portable devices.

Research Progress of Heavy-Metal-Free Quantum Dot Light-Emitting Diodes.

At present, heavy-metal-free quantum dot light-emitting diodes (QLEDs) have shown great potential as a research hotspot in the field of optoelectronic devices. This article reviews the research on heavy-metal-free quantum dot (QD) materials and light-emitting diode (LED) devices. In the first section, we discussed the hazards of heavy-metal-containing quantum dots (QDs), such as environmental pollution and human health risks. Next, the main representatives of heavy-metal-free QDs were introduced, such as InP, ZnE (E=S, Se and Te), CuInS2, Ag2S, and so on. In the next section, we discussed the synthesis methods of heavy-metal-free QDs, including the hot injection (HI) method, the heat up (HU) method, the cation exchange (CE) method, the successful ionic layer adsorption and reaction (SILAR) method, and so on. Finally, important progress in the development of heavy-metal-free QLEDs was summarized in three aspects (QD emitter layer, hole transport layer, and electron transport layer).

Formation of a potential barrier by a ZnSXSe1−X electron-blocking layer to improve the efficiency of CdSe0.3S0.7/CdSe quantum dot sensitized solar cells

We designed and fabricated multilayer quantum dots sensitized solar cells (QDSCs) with TiO2 NPs/CdSe0.3S0.7/CdSe/ZnSXSe1−X, X = S/S + Se = 0, 0.7, 0.8, 0.9, and 1 photoelectrodes to achieve optimum power conversion efficiency (PCE). In the corresponding structure, incoming light is absorbed by the CdSe0.3S0.7 and CdSe quantum dots (QDs), while the ZnSXSe1−X QDs act as an electron blocking layer or passivation layer, forming an energy barrier that restricts electron mobility from the light absorbers to the polysulfide electrolyte. The beneficial effect of the alloyed ZnSXSe1−X layer is the adjustability of its nanoparticle size/bandgap energy proportional to variations in the concentration of anionic precursors X, according to optical results. The PCE value of the reference cell with the TiO2 NPs/CdSe0.3S0.7/CdSe photoanode is 4.15 %. Following the coating of ZnSe, ZnS0.7Se0.3, ZnS0.8Se0.2, ZnS0.9Se0.1, and ZnS QDs via two successive ionic layer adsorption and reaction (SILAR) cycles (2Sc) on the CdSe0.3S0.7/CdSe co-sensitized photoelectrode increasing stability and improving the PCE value to 4.9 %, 5.40 %, 5.70, 5.25 %, and 5.05 %, respectively. Next, by modifying the thickness of the champion cell's passivation layer, the QDSCs with TiO2 NPs/CdSe0.3S0.7/CdSe/ZnS0.8Se0.2 (3Sc) photoelectrode exhibit maximum photovoltaic performance parameters of short circuit current density (JSC) = 26.25 mA/cm2, open circuit voltage (VOC) = 560 mV, fill factor (FF) = 0.42 % and PCE = 6.15 %. This improvement in performance is the result of decreased internal energy loss and recombination of charge carriers at the interface between the electrolyte and photoelectrode, which increases electron collection efficiency and electron injection efficiency in the visible region according to the external and internal quantum efficiency curves.

Exceeding Three-Electron Reactions in Polyanionic Cathode To Achieve High-Energy Density for Sodium-Ion Batteries.

Activating multielectron reactions of sodium superionic conductor (NASICON)-type cathodes toward higher energy density remains imperative to boost their application feasibility. However, multisodium storage with high stability is difficult to achieve due to the sluggish reaction kinetics, irreversible phase transitions, and negative structural degradation. Herein, a kind of NASICON-type Na2.5V1.5Ti0.5(PO4)3/C (NVTP-0.5) hierarchical microsphere consisting of abundant primary nanoparticles is designed, realizing a reversible 3.2-electron reaction with high stability. The optimized NVTP-0.5 cathode demonstrates an ultrahigh discharge capacity of 192.42 mAh g-1, energy density of up to 497.3 Wh kg-1 at 20 mA g-1, and capacity retention ratio of 94.1% after 1000 cycles at 1 A g-1. Additionally, the NVTP-0.5 cathode delivers excellent tolerance to extreme temperatures while also achieving a high-energy density of 400 Wh kg-1 (based on the cathode mass) in a full-cell configuration. Systematic in situ/ex situ analysis results confirm the multisodium storage processes of NVTP-0.5 involving successive redox reactions (V2+/V3+, Ti3+/Ti4+, and V3+/V4+ redox couples) and reversible structure evolution (solid-solution and biphasic mechanisms), which contribute to the high capacity and excellent cycling stability. This work indicates that the rational regulation of components with different functions can unlock more possibilities for the development of NASICON-type cathodes.

Modified successive ionic layer adsorption and reaction for interconnected bismuth vanadate nanograins: Highly active visible light harvesting photoanodes

A modified successive ionic layer adsorption and reaction (SILAR) method is developed for depositing interconnected bismuth vanadate (BiVO4) nanoparticles with improved visible light harvesting activity. Facile control of preparative parameters like deposition cycles, anionic precursor, pH and deposition temperature significantly altered BiVO4 surface morphology. BiVO4 thin films prepared with Na3VO4 anionic precursor show dispersed nanoparticles type morphology and that deposited with NaVO3 precursor displays 3D interconnected nanoparticles morphology. The BiVO4 photoanodes with 3D interconnected nanoparticles morphology exhibits an excellent photocurrent density of 5.19 mA cm−2 at 1.23 V vs. RHE with superior photostability and improved applied bias photon to current efficiency (ABPE) (1.50 %) compared to dispersed nanostructured BiVO4 photoanodes. The excellent photoelectrochemical (PEC) characteristics of BiVO4 photoanodes with 3D interconnected nanoparticle morphology can be ascribed to porous morphology, optimum thickness, narrow band gap energy and favorable electronic band structure for water splitting. The current study illustrates the usefulness of the modified SILAR approach for depositing 3D interconnected BiVO4 nanoparticle morphology in a single step that is superior and efficient to previously reported multistep processes.

Coating effect of metal organic complex (Co-DTPMP) layer on enhancing PEC water oxidation performance of BiVO4 photoanode

Photoelectrochemical (PEC) water splitting is a promising method for transforming solar energy into clean and sustainable energy. However, PEC is severely limited, and they cannot achieve the predicted photocurrent density owing to the severe photochemical deterioration of the electrode and the recombination of photogenerated carriers. In this study, BiVO4/Co-diethylenetriamine Penta (methylene phosphonic acid) (BVO/Co-DTPMP) co-catalyst was successfully prepared as a nanoporous photoanode. Diethylenetriamine Penta (methylene phosphonic acid) was crosslinked with Co ions and coated on the BiVO4 surface by successive ionic layer adsorption and reaction (SILAR) to reduce fast recombination, which correlated with the BiVO4 photoanode. Various characterization and PEC measurements were conducted, revealing that the co-catalyst thin layer enhanced the charge separation and electrons transfer which significantly affected on the PEC performance of BiVO4, and the current density by BVO/Co-DTPMP was 4 mA cm−2 at 1.23 V vs. RHE. Furthermore, the co-catalyst exhibited improved charge transport and long-term stability.

A role for conformational changes in enzyme catalysis

The role played by conformational changes in enzyme catalysis is controversial. In addition to examining specific enzymes, studying formal models can help identify the conditions under which conformational changes promote catalysis. Here, we present a model demonstrating how conformational changes can break a generic trade-off due to the conflicting requirements of successive steps in catalytic cycles, namely high specificity for the transition state to accelerate the chemical transformation and low affinity for the products to favor their release. The mechanism by which the trade-off is broken is a transition between conformations with different affinities for the substrate. The role of the effector that induces the transition is played by a substrate “handle,” a part of the substrate that is not chemically transformed but whose interaction with the enzyme is nevertheless essential to rapidly complete the catalytic cycle. A key element of the model is the formalization of the constraints causing the trade-off that the presence of multiple states breaks, which we attribute to the strong chemical similarity between successive reaction states—substrates, transition states, and products. For the sake of clarity, we present our model for irreversible one-step unimolecular reactions. In this context, we demonstrate how the different forms that chemical similarities between reaction states can take impose limits on the overall catalytic turnover. We first analyze catalysts without internal degrees of freedom and then show how two-state catalysts can overcome their limitations. Our results recapitulate previous proposals concerning the role of conformational changes and substrate handles in a formalism that makes explicit the constraints that elicit these features. In addition, our approach establishes links with studies in the field of heterogeneous catalysis, where the same trade-offs are observed and where overcoming them is a well-recognized challenge.