Lower Charge Transfer Resistance Research Articles

Toward Efficient Hydrogen Generation Using Nickel-Molybdenum Catalyst and Its Environmental Sustainability.

In this study, a catalyst with Ni-Mo combination was synthesized using the electric heating/reductive tempering method. Nickel (II) nitrate hexahydrate and ammonium molybdate were combined in a ratio of 1.1 in this approach. The mixture was milled into a fine powder. It was heated to 950°C to 1000°C in a seething hood. The disappearance of green shading and emission of brownish-yellow fumes indicated that the reaction was completed. XRD has been used to determine the crystallinity of the combined Ni-Mo amalgam, SEM was used to investigate the surface morphology of the orchestrated Ni-Mo compound, and inductively coupled plasma examinations were carried out to evaluate elemental percentage (%) of the integrated sample of Ni-Mo combination. In addition, an electrical impedance analysis of as-synthesized Ni-Mo alloy was conducted to estimate hydrogen production in an electrochemical reaction. The electrical impedance results indicate that the synthesized Ni-Mo catalyst exhibited an efficient charge-transfer kinetics with a low charge-transfer resistance (5.35 Ω). The onset potential value achieved was 18 mV with overpotential of -100 mV in IM KOH, possessing a turnover frequency of 0.91H2 s-1. These findings underscore Ni-Mo catalyst as a promising catalyst for hydrogen generation studies. The results of this study are anticipated to be of potential significant importance in providing a cost-effective approach towards the synthesis of Ni-bimetallic catalyst, which in the future can serve as a promising candidate for applications involving sustainable hydrogen generation. Additionally, the proposed method's study of its greenness using the Analytical Greenness Calculator (AGREE) can help advance the usage of renewable and environmentally friendly energy sources.

Rare earth doped CeO2 uniformly enwraps graphite felt as high current density electrode for all vanadium redox flow battery

Although the introduction of metal oxides can solve the problem of poor electrochemical activity of graphite felt electrode, their low conductivity, poor dispersibility, and difficulty in nanocrystallization restrict their application development. Herein, a uniform distributed Gd or Sm doped CeO2 nanoparticle decorated graphite felt electrode is successfully prepared by hydrothermal method. The incorporation of Gd3+ or Sm3+ into the lattice of CeO2 results in the formation of numerous oxygen vacancies, acting not only as reaction sites for redox reactions but also enhancing the charge transfer rate. Compared to CeO2/GF, Ce0.8Gd0.2O2/GF and Ce0.8Sm0.2O2/GF exhibits superior electrochemical activity and lower charge transfer resistance. Correspondingly, the energy efficiency of Ce0.8Gd0.2O2/GF and Ce0.8Sm0.2O2/GF increases 4.5 % and 7.8 % at 160 mA cm−2, respectively. The maximum operating current density of Ce0.8Sm0.2O2/GF is 200 mA cm−2, while Ce0.8Gd0.2O2/GF is 160 mA cm−2. Ce0.8Sm0.2O2/GF achieves an energy efficiency of 69.3 % using a flow-by flow field at 200 mA cm−2. The optimal doping concentration for Sm is 20 %. The Ce0.8Sm0.2O2/GF stably operate for 500 cycles at 100 mA cm−2 and the Ce0.8Sm0.2O2 nanoparticles adhere firmly to the GF without observed detachment. These results demonstrate that Ce0.8Sm0.2O2/GF with high activity and stability is a promising electrode for VRFB.

Enhanced electrocatalytic performance and exceptional durability facilitate the effective degradation of m-dinitrobenzene wastewaters utilizing a novel SS/PbO2-Y2O3-SiC electrode

The intrinsic toxicity of m-dinitrobenzene (m-DNB) to human health and the environment has made dealing with m-DNB pollution a major concern. Herein, a novel hydrophobic anodic electrode SS/PbO2-Y2O3-SiC doped with Y and SiC was constructed via a simple electrodeposition strategy for efficient degradation of m-DNB. With a dense-uniform structure and hydrophobic surface, such SS/PbO2-Y2O3-SiC electrode exhibits obviously lower activation energy (8.17kJmol−1) and charge transfer resistance (1.15 Ω cm2), higher electrochemical active area (46.14 cm2) and stability (359 d), in comparison to SS/PbO2. The m-DNB removal efficiency of the as-prepared SS/PbO2-Y2O3-SiC anode was significantly increased to 96.4% in 180minutes, and the degradation reaction-order was determined to be 0.9559, which was in accordance with the quasi-first-order reaction kinetics. These are the possible degradation pathways of m-DNB under the action of both cathodic and anodic reactions, according to the GC-MS results. The -NO2 group of m-DNB was first reduced to the -NH2 group at the cathode surface, and then the m-phenylenediamine generated at the cathode was sequentially oxidised by the hydroxyl radicals generated from the anodic electrochemical process, resulting in the generation of H2O and CO2 at the anode surface. Additionally, the Assessment Software Tool (TEST) shows that the SS/PbO2-Y2O3-SiC anode can effectively reduce the risk and harm of m-DNB to the overall environment. This study offers novel perspectives on the development of a highly efficient PbO2 electrode for the degradation of m-DNB pollutants.

One-pot synthesis of 2D-Ni-MOF from waste PET plastic in aqueous medium for selective electrooxidation of glycerol, ethanol, and methanol

This study investigates the electrochemical performance and selectivity of a nickel-based metal-organic framework (Ni-MOF) catalyst synthesized from waste PET plastic using a one-pot approach in aqueous media. The Ni-MOF electrode was evaluated for glycerol electrooxidation reaction (GEOR), ethanol electrooxidation reaction (EEOR), and methanol electrooxidation reaction (MEOR). Linear sweep voltammetry (LSV) revealed current densities of 30mA/cm² at 0.5639V for GEOR, 50.07mA/cm² at 0.35V for EEOR, and 45.73mA/cm² at 0.39V for MEOR, indicating superior catalytic activity. Nyquist plots showed lower charge transfer resistance (Rct) values of 11.0 Ω for GEOR, 2.79 Ω for EEOR, and 2.69 Ω for MEOR, confirming efficient electron transfer. Bode impedance plots demonstrated lower impedance for alcohol electrooxidation compared to oxygen evolution reaction (OER). Chronoamperometry (CA) tests indicated excellent stability with 75.72% glycerol conversion for GEOR and selectivities of 94% for glyceric acid, 65.59% for acetic acid in EEOR, and 70.54% for formic acid in MEOR. These results highlight the potential of Ni-MOF derived from recycled PET plastic for sustainable and efficient electrooxidation of C1-C3 alcohols.

Efficient nano-size ZnM/rGO (M = Ni, Cu, and Fe) electrocatalysts for oxygen electrode reactions in alkaline media

Herein, zinc with nickel, copper, and iron was deposited on reduced graphene oxide (rGO) (ZnM/rGO, M = Cu, Ni, Fe) and examined as novel bifunctional electrocatalysts for oxygen evolution (OER) and oxygen reduction (ORR) reaction in alkaline media. Fourier-transform infrared and X-ray photoelectron spectroscopy, X-ray powder diffraction analysis, transmission, and scanning electron microscopy with energy-dispersive X-ray spectroscopy were used for the examination of structural and morphological properties of ZnM/rGO. ZnFe/rGO showed the lowest OER overpotential and Tafel slope, the highest OER current density with the lowest charge-transfer resistance. Furthermore, ORR at ZnFe/rGO proceeds by mixed 2e/4e mechanism, and by 2e mechanism at the other materials. Still, ZnCu/rGO showed the most positive onset potential and low Tafel slope during ORR. Hence, ZnFe/rGO presents the best OER activity with further improvements needed in terms of its ORR performance to reach full potential for rechargeable metal-air batteries and unitized regenerative fuel cells.

Electro-sorption/-desorption with bio-sourced granular activated carbon electrode for phenols recovery and combination with advanced electro-oxidation for residual olive mill wastewater treatment

To face the releasing of hazardous solid and liquid wastes into the environment from the olive oil production industry, it is newly proposed a circular economy approach by implementing electro-sorption of value-added phenolic compounds (PCs) followed by electro-desorption using a bio-sourced granular activated carbon (GAC) electrode made of olive pomace waste. The remaining organic compounds present in the real olive mill wastewater (OMWW) were treated by advanced electrooxidation.The PCs electro-sorption study highlighted efficiency around 72 % in synthetic matrix against 68 % in real effluents, whose electro-sorption capacities could be partly attributed to the high electroactive surface area (7.8 × 103 cm2), high exchange current intensity (I0) value (5.5 × 10−3 A), and low charge transfer resistance (RCT) value (4 Ω) compared to the literature. The study further emphasized the fact that the electro-sorption selectivity was not only dependent on pKa of PCs with respect to solution pH, but also on the size of adsorbed molecules relative to the pore size distribution of GAC. The maximal percentage of PCs recovered from GAC after electro-desorption experiments was 34.5 %, while the global chemical oxygen demand (COD) removal efficiency was 92 % of the pre-filtered real effluent at the cost of scaling during advanced electrooxidation of residual OMWW.

Synthesis of nitrogen-doped carbon dot/ tin disulfide nanosheet composite electro-catalysts for dye-sensitized solar cells.

Nitrogen-doped carbon dots (N-CDs) and vertically-grown tin disulfide (SnS2) nanosheets are synthesized via hydrothermal method and chemical vapor deposition (CVD) technique, respectively. The SnS2 nanosheets are directly fabricated on flexible carbon cloth (CC), and then their basal planes are decorated with N-CDs. The as-prepared composite electrodes are used as the counter electrode for the application in dye-sensitized solar cells (DSSCs). The characterizations of N-CDs and SnS2 nanosheets are studied by high resolution transmission electron microscopy (HR-TEM), scanning electron microscopic (SEM), energy dispersive X-ray spectrometer (EDS), Raman spectrometer and X-ray photoelectron spectroscopy (XPS) ect. Moreover, the cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and photocurrent-density voltage (J-V) are utilized to understand the electro-catalytic performance of N-CDs/SnS2/CC composite counter electrode. The N-CDs/SnS2/CC composite electrode shows higher cathodic reduction current density and lower charge transfer resistance in CV and EIS measurements, respectively, as compared to those of the electrodes with N-CDs or SnS2 alone. Meanwhile, the DSSC using N-CDs/SnS2/CC exhibits cell efficiency (η) of 7.68%, which is higher than those of cells having SnS2/CC (η=7.54%) and N-CDs/CC (η=5.66%) counter electrodes, repectively; it also reaches 94% cell efficiency of the cell using Pt/CC counter electrode (η=8.15%). The design concept of the modification of the basal planes by defect-rich carbon dots (i.e., N-CDs) and highly-exposed edge sites (i.e., vertically-grown SnS2 nanosheets) makes promising route to enhance the performance of two-dimensional electro-catalysts.

Photoelectron-Promoted Sulfate Reduction for Heavy Metal Removal without Organic Carbon Addition.

Sulfate-reducing microorganisms (SRMs) show promise for heavy metal removal from contaminated environments, but their scalability is limited by reliance on organic carbon, sludge formation, and CO2 emissions. This study investigates using photoelectrons from biogenic (Bio-ZnS) and abiogenic (Abio-ZnS) sphalerite nanoparticles to enhance the activity of Desulfovibrio desulfuricans G20 (G20) for sulfate reduction and lead removal without organic substrates. Both Abio-ZnS and Bio-ZnS NPs promote sulfate reduction and energy production in G20 cells under illumination without the addition of organic substrates, with Bio-ZnS achieving 1.6 times greater sulfate reduction and 3.1 times higher ATP production compared to Abio-ZnS. This superior performance of Bio-ZnS NPs is due to their wider band gap, higher photoconversion efficiency, lower charge-transfer resistance, and closer proximity to cells, which enable more efficient photoelectron uptake, enhanced intracellular electron transfer, and reduced energy consumption for motion and filamentation. The uptake of photoelectrons also promotes G20s resistance to high Pb2+ concentrations through enhanced PbS precipitation, biofilm formation, enzymatic detoxification, and Pb2+ efflux, thus improving long-term and cyclic lead removal by G20 under substrate-depleted conditions. This approach harnesses solar energy, reduces reliance on organic substrates, and lowers costs and CO2 emissions, offering a sustainable solution for utilizing SRMs in bioremediation.

A comparative study on exploring sputtered titanium nitride thin films for high-performance supercapacitors

Magnetron sputtered titanium nitride (TiN) thin films possessed desirable electrochemical and physical characteristics making them attractive candidates for supercapacitor electrodes. Herein, the electrochemical performance of TiN films prepared via direct and reactive sputtering methods is investigated as electrodes for supercapacitor. Microstructural analysis revealed distinct morphologies, topographies, and crystal structures for each film type, with reactively sputtered TiN (RS) displaying a pyramidal structure indicative of (111) orientation, whereas directly sputtered TiN (DS) exhibited a granular structure. Electrochemical techniques like cyclic voltammetry, galvanic charge-discharge, and electrochemical impedance spectroscopy clarified the charge storage mechanisms and capacitance behavior. RS exhibited a quasi-rectangular CV profile with pseudo-capacitive behavior with low charge transfer resistance and peak specific capacitance of 90 mF cm−2 along with superior cyclic stability and ion conductivity. Supercapattery configuration was setup to validate those findings using reactive sputtered thin films. It demonstrated enhanced capacitance retention and low charge transfer resistance, highlighting their potential for practical applications in energy storage systems.

Balancing Surface Chemistry and Flake Size of MXene-Based Electrodes for Bioelectrochemical Reactors.

MXenes have excellent properties as electrode materials in energy storage devices or fuel cells. In bioelectrochemical systems (for wastewater treatment and energy harvesting), MXenes can have antimicrobial characteristics in some conditions. Here, different intercalation and delamination approaches to obtain Ti3C2Tx MXene flakes with different terminal groups and lateral dimensions are comprehensively investigated. The effect of these properties on the energy harvesting performance from wastewater is then assessed. Regardless of the utilized intercalant molecules, MXene flakes obtained using soft delamination approaches are much larger (up to 10µm) than those obtained using mechanical delamination methods (<1.5nm), with a relatively higher content of ─O/─OH surface terminations. When employed in microbial fuel cells, electrodes made of these large MXene flakes have demonstrated a power density of over 400% higher than smaller MXene flakes, thanks to their lower charge transfer resistance (0.38Ω). These findings highlight the crucial role of selecting appropriate intercalation and delamination methods when synthesizing MXenes for bioelectrochemical applications.

Enhancing the electrochemical efficiency of metal-organic frameworks through integration of chromium nitride interfacial layer for efficient hybrid supercapacitors

Transition metal nitrides are highly stable and electrochemically efficient, making them a promising material for supercapacitor electrodes. Herein, for assessing the synergistic effects of metal-organic framework via transition metal nitrides, we synthesized chromium nitride electrode using magnetron sputtering followed by the deposition of copper-trimesic acid. Electrochemical testing in half and full cell configurations reveals that chromium nitride/copper-trimesic acid has the lowest charge transfer resistance, indicating its quick charge transport pathways, leading to an increased specific capacity (1651C/g at 1.5 A/g) and notable rate capability. Persuaded by the exceptional capacitive and charge storage potential, a two-cell mode-based hybrid supercapacitor was fabricated using activated carbon and chromium nitride/copper-trimesic acid. This combination demonstrated the highest energy density of 94.5 Wh/kg, maximum power density of 7750 W/kg while functioning at 1.6 V with cycling stability of 97.9 % after 3000 galvanostatic charge discharge cycles. Additionally, for examining the diffusive and capacitive behaviors of devices, two different semi-empirical models were further used and compared, which shed light on the special characteristics and implementation of supercapattery device.

Efficient Photocatalytic Hydrogen Production Using In-Situ Polymerized Gold Nanocluster Assemblies.

Gold nanoparticles (NPs) are widely recognized as co-catalysts in semiconductor photocatalysis for enhancing hydrogen production efficiency, but they are often overlooked as primary catalysts due to the rapid recombination of excited-state electrons. This study presents an innovative gold-based photocatalyst design utilizing an in situ dopamine polymerization-guided assembly approach for efficient H2 generation via water splitting. By employing gold superclusters (AuSCs; ≈100nm) instead of ultra-small gold nanoclusters (AuNCs; ≈2nm) before polymerization, unique nanodisk-like 3D superstructures consisting of agglomerated 2D polydopamine (PDA) nanosheets with a high percentage of uniformly embedded AuNCs are created that exhibit enhanced metallic character post-polymerization. The thin PDA layer between adjacent AuNCs functions as an efficient electron transport medium, directing excited-state electrons toward the surface and minimizing recombination. Notably, the AuSCs@PDA structure shows the largest potential difference (26.0mV) compared to AuSCs (≈18.4mV) and PDA NPs (≈14.6mV), indicating a higher population of accumulated photo-generated carriers. As a result, AuSCs@PDA achieves a higher photocurrent density, improved photostability, and lower charge transfer resistance than PDA NPs, AuSCs, or AuNCs@PDA, with the highest hydrogen evolution rate of 3.20mmol g-1h-1. This work highlights a promising in situ polymerization strategy for enhancing photocatalytic hydrogen generation with metal nanoclusters.

Synthesis and characterization of a nanocomposite consisting of Ti3C2Tx (MXene) and WS2 nanosheets for potential use in supercapacitors

With the growing demand for high-performance supercapacitor materials, this study explores the synthesis and electrochemical evaluation of Ti3C2Tx (MXene), WS2 nanosheets, and MXene/WS2 nanocomposites. The aim is to develop materials with enhanced energy storage capabilities. To this end, the performance of MXene/WS2 nanocomposites was compared to that of the individual materials. MXene, WS2 nanosheets, and MXene/WS2 nanocomposites were synthesized through chemical and hydrothermal methods, and their morphology was characterized using scanning electron microscopy and energy-dispersive X-ray spectroscopy, while Fourier transform infrared spectroscopy confirmed the presence of functional groups. Electrochemical analysis of WS2, MXene, and MXene/WS2 was conducted in a 1 M H2SO4 electrolyte using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). The specific capacitance (Cs) values for WS2 were 58 F/g (at 5 mV/s) and 47 F/g (at 0.4 A/g); for MXene, the Cs values were 98 F/g (at 5 mV/s) and 71 F/g (at 0.4 A/g), while MXene/WS2 exhibited much higher Cs values of 322 F/g (at 5 mV/s) and 373 F/g (at 0.4 A/g). EIS results indicated a lower charge transfer resistance (Rct) for MXene/WS2 (2.29 Ω) compared to WS2 (5.25 Ω) and MXene (3.41 Ω). These findings demonstrate that MXene/WS2 nanocomposites have superior electrochemical properties, making them promising candidates for high-energy supercapacitor applications.

Partial Selenization Strategy for Fabrication of Ni0.85Se@NiCr-LDH Heterostructure as an Efficient Bifunctional Electrocatalyst for Overall Water Splitting.

NiCr-LDH and its partial selenization as Ni0.85Se@NiCr-LDH heterostructure is established here as an alkaline water electrolyzer for achieving enhanced overall water splitting efficiency. The hydrothermally synthesized optimized batch of Ni0.85Se@NiCr-LDH is thoroughly characterized to elucidate its structure, morphology, and composition. Compared to pristine NiCr-LDH, the batch of Ni0.85Se@NiCr-LDH exhibits exceptional alkaline OER and HER activity with low overpotentials of 258 and 85 mV at 10 mA cm-2, respectively. Besides, Ni0.85Se@NiCr-LDH also exhibits excellent acidic HER with an overpotential of only 61 mV at 10 mA cm-2, indicating that Ni0.85Se@NiCr-LDH can operate effectively across a wide pH range. The excellent electrochemical stability of Ni0.85Se@NiCr-LDH for 24 h operation is attributed to the formation of a thin layer of SeOx during OER operation. The role of selenization and the effect of Cr in the LDH lattice toward enhanced electrocatalytic water splitting is discussed. The outstanding OER and HER performances of Ni0.85Se@NiCr-LDH are attributed to the higher electrochemical active surface area, favorable conditions for adsorption of HER/OER intermediates, low charge transfer resistance, and improved conductivity. The practical application ofNi0.85Se@NiCr-LDHas a bifunctionalelectrocatalyst for overall water splitting is reflected from the low cell voltage of 1.548 V at 10 mA cm-2.

Synergistic modification of Ti/PbO2 electrodes with metal ions (Nd, Al, Bi) and STAB surfactant for electrocatalytic treatment of desulfurization wastewater

In this study, PbO2 electrodes are modified by co-doping with different metallic elements (Nd, Al, Bi) and stearyl trimethyl ammonium bromide (STAB) using the electrodeposition method. The modified electrodes, designated as Ti/PbO2-Nd-STAB, Ti/PbO2-Al-STAB, and Ti/PbO2-Bi-STAB, are then applied in the electrochemical degradation of desulfurization wastewater. The surface morphology, crystal structure, and elemental valence of the prepared electrodes are analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Their electrochemical performance and stability are assessed by linear sweep voltammetry (LSV), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and accelerated life testing (ALT). The results reveal that modification with metallic elements and STAB significantly enhances the physicochemical and electrocatalytic performance of the Ti/PbO2 electrode. Among the modified electrodes, the Ti/PbO2-Nd-STAB electrode exhibits the most compact and homogeneous surface morphology, the highest oxygen evolution potential (OEP, 2.33 V vs. SCE), the lowest chlorine evolution potential (CEP, 1.44 V vs. SCE), the largest electrochemically active surface area, the lowest charge transfer resistance, the highest electrochemical stability, and a prolonged accelerated life (65 h, which is 17 h longer than that of the unmodified electrode). Further, the optimal electrochemical oxidation process parameters for desulfurization wastewater are determined as follows: current density = 50 mA/cm2, temperature = 35 ℃, electrode spacing = 3.0 cm, and stirring rate = 300 rpm. After 300 min of electrolysis, the Ti/PbO2-Nd-STAB electrode achieves a Cl− removal rate of 86.9 % and a chemical oxygen demand (COD) removal rate of 71.2 %. After 10 cycles, the Cl− and COD removal rates decrease by 2.8 % and 1.8 %, respectively. Besides, Tafel curve analysis indicates that the chlorine evolution reaction follows the Volmer-Tafel mechanism, with the recombination of adsorbed Cl− ions on the surface oxidation film being the rate-determining step. Overall, the Ti/PbO2-Nd-STAB anode exhibits immense application potential in the treatment of desulfurization wastewater.

Preparation of amorphous TiO2 films by RF magnetron sputtering: Process optimization and effect of sputtering pressure on electrochromic properties

In this study, radio frequency (RF) magnetron sputtering was utilized to fabricate Titanium dioxide (TiO2) thin films at a room temperature. Scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, electrochemical workstation, and UV–Vis spectrophotometry were employed to analyze and characterize the microstructure, compositional components, and electrochromic properties of the films. The main focus is on exploring the microstructure and electrochromic properties of films produced under diverse sputtering pressures. The results show that the TiO2 films fabricated at a sputtering pressure of 1.2 Pa exhibit the most desirable surface morphology, with an optical modulation amplitude of up to 49.18 % (@550 nm), coloring time of 1.28 s, bleaching time of 0.79 s, and a coloration efficiency of 21.07 cm2/C. After 1000 cyclic voltammetry tests, the Q decay rate is 51.75 %. Electrochemical impedance spectroscopy (EIS) measurements reveal that TiO2 films prepared under these process parameters have lower charge transfer resistance and ion diffusion impedance, which facilitate ion injection and extraction.

Carbazolyl-Decorated Metal-Organic Framework with a High Fluorescent Quantum Yield for Detection and Photocatalytic Degradation of Organic Contaminants.

A carbazolyl-based fluorescent metal-organic framework with deep-blue light emission and a high quantum yield (88%) has been screened out by changing the ratio of mixed ligands, named Cz-MOF-2, which was constructed by ZrO4(OH)4 clusters, 3-(9-ethyl-9H-carbazol-3-yl)-4-methylthieno[2,3-b]thiophene-2,5-dicarboxylate (H2ECMTDC) and 3,4-dimethyl-dihydrothieno[2,3-b]thiophene-2,5-dicarboxylate (H2DMTDC). Cz-MOF-2 has excellent sensitivity in fluorescent sensing of 2,6-dichloro-4-nitroaniline (DCN), nitrofurazone (NZF), and nitrofurantoin (NFT) with detection limits of 3.37 × 10-7, 1.64 × 10-5, and 1.76 × 10-5 M, respectively. The quenching mechanisms involving electron transfer and competitive absorption were comprehensively elucidated through DFT calculations and UV absorption experiments. Cz-MOF-2 has been fabricated into a rapidly regenerated composite membrane with PVDF as a visualized fluorescent sensor for DCN. Furthermore, the carbazolyl groups covalently modified in the framework endowed Cz-MOF-2 with a suitable band gap (2.58 eV) for photocatalytic degradation of organic contaminants. It demonstrated superior photocatalytic efficiency compared to UiO-66 and NH2-UiO-66 in the degradation of tetracycline (TC), and the removal efficiency was up to 85% (20 mg of catalyst, 50 mL, 20 mg/L TC solution and 180 min) under simulated sunlight irradiation using a 300 W Xe lamp. Photoelectrochemical tests demonstrate that Cz-MOF-2 exhibits high photocurrent density and low charge transfer resistance, which provide evidence for the efficient charge separation capability. Radical trapping experiments and ESR detection have substantiated that ·O2- and h+ are the primary active species involved in this photocatalytic reaction. This work highlights the potential of MOFs in the targeted design and development of fluorescent sensors and photocatalysts for environmental detection and remediation.

Enhanced oxygen evolution reaction in flexoelectric thin-film heterostructures

Recently, the flexoelectric effect has triggered considerable interest in energy-related applications, such as flexo-actuation, flexo-photovoltaic, and flexo-catalysis, because of its ubiquitous feature allowing the creation of electric polarity, i.e., the flexoelectric polarization (Pflexo), in non-polar materials by strain gradient. Here, we show a flexoelectric strategy in electrocatalytic water splitting. Remarkably enhanced oxygen evolution reaction (OER) properties are achieved in strain-gradient LaFeO3 (LFO) thin-film heterostructures owing to the promotion of kinetic processes by Pflexo. The improved OER is demonstrated by increased current density of ∼300% in linear sweep voltammetry and lowered charge transfer resistance by two orders of magnitude in electrochemical impedance spectroscopy. These are ascribed to the flexoelectric-induced downward bending of the LFO band, as revealed by density functional theory calculations and band structure measurements. With Pflexo in the thin-film heterostructure catalysts, the adsorption of hydroxyl ions is strengthened on the polar LFO surface, and the transfer of electrons is accelerated from the reactants/key intermediates to the catalyst across the band-tilted LFO layer. These findings indicate the significance of flexoelectric effect in OER kinetics and open a new perspective for exploiting catalytic mechanisms and performances in water splitting.

Harnessing the Potential of Morphologically Tailored ZnSn(OH)6 Nanograss Photoanode for Solar‐Driven Water Splitting

AbstractHydrothermal growth of ZnSn(OH)6 nanograss on ZnO‐coated FTO substrates is demonstrated. Effect of surfactants addition (polyvinylpyrrolidone and polyethylene glycol), precursor concentration, and reaction temperature on surface morphology of ZnSn(OH)6 nanograss are investigated. Addition of surfactant in precursor solution results in growth of approximately 20–30 nm thick nanograss morphology with varying orientation. The nanograss grow longer by increasing the concentration of precursors solution. The grown ZnSn(OH)6, exhibits XRD peaks corresponding to cubic phase ZnSn(OH)6. Optical bandgap of the grown nanograss are calculated in the range from ∼3.0 to 3.5 eV. The nanograss photoanode grown with PEG surfactant (at 200 °C) has shown the highest photocurrent of 2.2 mA/cm2 at RHE 1.23VRHE and photoconversion efficiency of 1.4% at 0.46 VRHE. The longer nanograss has shown lower charge transfer resistance and higher charge carrier concentration, which is favorable for enhancing the PEC performance.

Stabilizing Lithium Superoxide Formation in Lithium-Air Batteries by Janus Chalcogenide Catalysts

Solid lithium peroxide (Li2O2) is the major discharge product in Li-air batteries. However, the electronically insulating nature of Li2O2 tends to affect the battery’s performance such as the polarization gap and cyclability. On the other hand, lithium superoxide (LiO2), generated through a one-electron transfer process, offers greater electronic conductivity, lower charge transfer resistance, and thus reduced charge potential. Nevertheless, LiO2 long-term stabilization as a final product remains a significant challenge. In this study, we present the molybdenum (Mo)-based Janus chalcogenide family featuring asymmetric structures as a new generation of cathode catalysts for Li-air batteries. These catalysts demonstrate remarkable efficacy in stabilizing LiO2 discharge products, even under high current densities of 5000mA/g (corresponding to 0.5mA/cm2). Our density functional calculations provide an understanding of why the asymmetric Mo-Janus chalcogenides result in LiO2 formation whereas the symmetric Mo-dichalcogenides produce Li2O2 as the discharge product. These results pave the way to explore a new generation of advanced catalysts for superoxide-based Li-air batteries.