Electrochemical Properties Research Articles

A sustainable solution: Conversion of distillers' grains waste into high-performance supercapacitor electrode materials for energy storage applications

The development of cost-effective biomass-derived carbon with good electrochemical properties is crucial for advancing energy storage devices sustainably. One feasible approach to producing supercapacitor electrode materials is the conversion of heteroatom-rich biomass waste into heteroatom self-doped hierarchical porous carbons with favorable electrochemical properties. In this study, distillers' grains with abundant crude fiber and protein were utilized as precursors to prepare N, S self-doped hierarchical porous carbon, which presents a high specific surface area of 3642.87 m2 g−1. The N, S doping could improve the interfacial wettability of electrode materials and enhance the pseudocapacitive effect of the materials. In three-electrode system, the carbon delivered a high capacitance of 347 F g−1 at 1 A g−1. Symmetrical capacitors assembled with PVA/KOH gel electrolytes delivered an ultrahigh energy density of 11.29 Wh kg−1 at a power density of 250 W kg−1. This strategy provides a practical, low-cost, and renewable design approach of carbon electrode for high-performance supercapacitors.

Tổng hợp vật liệu LiNi0,9Mn0,05Co0,05O2 bằng phương pháp phản ứng pha rắn (NMC9.5.5-PR) ứng dụng chế tạo pin ion liti

Nickel-manganese-cobalt (NMC) transition metal oxide-based layered structural materials are evaluated a promising material for applications as cathode in lithium-ion batteries. In this study, we have successfully synthesized nickel-rich NMC material LiNi0.9Mn0.05Co0.05O2 by solid-state reaction method (NMC9.5.5- PR). The CR2032-type lithium-ion battery is also successfully fabricated from NMC material to serve the study of electrochemical properties. The NMC9.5.5-PR material exhibits outstanding discharge specific capacity when providing a maximum specific capacity of up to 212.4 mAh/g at a current density of 10 mA/g. However, the cycle efficiency survey results show that the NMC9.5.5-PR material has some disadvantages (only maintaining 81.6% of the discharge specific capacity after 50 continuous charge-discharge cycles at current density of 10 mA/g). These electrochemical properties indicate that it is necessary to further improve the cyclic efficiency of NMC9.5.5-PR material but preserving its outstanding electrical energy storage capacity. Successfully accomplishing this goal, we believe that NMC-9.5.5-PR or a material based on NMC9.5.5-PR will be one of the suitable materials to fabricate positive electrodes used in lithium-ion batteries.

A facile synthesis of novel binder-free NiSe-SnSe electrode: With enhanced electrochemical performance and superior life span

Fossil fuels depletion and deteriorating environmental conditions have deepened the growing demand for new energy solution. The bimetallic transition metal selenides, which a smaller bandgap and greater electrical conductivity than nanometals, are the subject of recent research on hybrid supercapacitors, composite systems integrating battery-like energy storage capability with capacitive charging. Herein, a new binder NiSe-SnSe composite system for supercapacitors has been developed through facile hydrothermal method, and its structural features, morphological characteristics as well as electrochemical properties are systematically studies in this work. Additionally, a thorough understanding of the electrode physicochemical properties are presented. Practically, a NiSe-SnSe||AC|KOH ASC had excellent specific capacitance (618 F/g at 1 A g−1), mainly owing to fast charge transport in electrochemical action. More importantly, the NiSe-SnSe||AC|KOH ASC electrode exhibits a high specific power of 8400 W kg−1 at a high specific energy of 55.4 Wh kg−1 with remarkable cycling stability by 96.4 % maintenance of initial capacitance after 5500 cycles. Our findings provide a profound understanding and possible use of this newly developed asymmetric supercapacitor in energy storage.

Palladium effect on electrochemical hydrogen storage properties of nanoporous silicon

Coating porous silicon with metal catalysts such as palladium is considered a reliable method to improve the hydrogen storage performance of electrodes. Here, in order to evaluate the most effective use of Pd nanoparticle or Pd thin film, Pd nanoparticles with a size of 36 nm obtained by electroless method, and a Pd thin film with a thickness of 30 nm deposited by thermal evaporation were coated onto nanoporous silicon sample” and studied. The Pd deposits were confirmed by Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The obtained electrode materials: PS and Pd/PS were characterized by different electrochemical characterization techniques: cyclic voltammetry (CV) and galvanostatic charge/discharge. The results showed that Pd NPs/PS achieved the highest hydrogen storage capacity with a value of 425.9 mA h g-1. These results confirm that using Pd nanoparticles as catalyst metal is more suitable to improving the hydrogen storage capacity of electrode materials.

Engineering of Pt@Ni,N-doped graphene electrocatalyst based on recycled water bottles waste as an efficient cathode material for PEM fuel cells

Fuel cells (FCs) represent one of the most promising clean power sources. Their cost represents a considerable challenge to their widespread commercialization because of their sensitivity and the expensive cost of the employed platinum electrocatalysts. Accordingly, one feature of a fuel cell device that many interested parties are looking for is the engineering of catalysts with a low Pt content. Herewith, Pt supported on nickel loaded nitrogen-doped graphene (Pt@Ni,N-G) was synthesized through a simple pyrolysis process of mineral water bottles waste with urea and nickel metal at 800 °C followed by loading Pt in different proportions via a simple reduction method in aqueous solution at room temperature. The physicochemical and electrochemical properties of a promising Pt@Ni,N-G cathode electrocatalyst for polymer electrolyte membrane fuel cell (PEMFC) were characterized and evaluated using a number of specialized techniques. The results showed that the high Pt@Ni,N-G content enhanced the catalytic activity of the oxygen reduction reaction (ORR), with a specific activity of 3.13 mA cm−2 and a mass activity of 12.35 mA μg−1Pt at −0.1 V. A maximum power density of 87.8 mW cm−2 was achieved which is closest to that of commercial Pt/C. Designing Pt@Ni,N-G electrocatalysts by recycling waste bottles is not only expected to reduce the cost of fuel cells by ~30 % to raise the industry standard but also protect the environment and humanity from harmful pollutants.

Ionic liquid with hydrogen bonding reducing leakage charge for enhancing triboelectric performance

Refining the dielectric layer of a triboelectric nanogenerator (TENG) has been shown to maximize its output performance. Among the available strategies, utilizing an ionic dielectric can improve the output performance notably through the internal formation of an electrical double layer (EDL). However, ions dispersed in the ionic dielectric inevitably cause leakage charge between the surface charged layer and electrode of the ionic dielectric; this reduces the charge density, directly affecting output performance. Here, we investigate optimization of the ionic dielectric of a TENG using various ionic liquids (ILs), with the alkyl chain lengths of the cations and fluoride of anions with different size, to achieve power enhancement based on the EDL effect while concurrently suppressing leakage charge via hydrogen bonding. To elucidate the power enhancement working mechanisms within the ionic dielectric, we characterize the chemical, mechanical, and electrochemical properties of the ionic dielectric, including formation of hydrogen bonds, ionic conductivity, and dielectric constant. These parameters are investigated by varying the ion types, molecular sizes, and concentrations of the ILs within the ionic dielectric. As a results, our findings reveal that an IL of OMIM+PF6- dissolved in a base material of thermoplastic polyurethane (TPU) significantly enhances the voltage and current by 2.3 and 2.9 times, respectively, compared to those of a conventional TENG with TPU. These findings are expected to be implemented across a wide range of TENGs, paving the path for their advanced applications in next-generation energy harvesting.

Synthesis of BiDy composite oxide nanoflakes with good electrochemical properties

BiDy composite oxide nanoflakes with the thickness of about 50 nm were synthesized by one-step hydrothermal method. The electrodes modified with BiDy composite oxide nanoflakes exhibit superior electrochemical behavior for detecting L-cysteine using cyclic voltammetry (CV) method. The impact of scan rate, electrolyte, and concentration of L-cysteine for electrochemical behaviors were investigated. A pair of strong quasi-reversible CV peaks are observed at +0.03 V (cvp1) and –0.69 V (cvp1′) with peak current of 171.2 μA and 171.3 μA, respectively for the BiDy composite oxide nanoflake-modified GCE in 0.1 M KCl and 2 mM L-cysteine solution. GCE modified with the BiDy composite oxide nanoflakes displays broad range of linearity (0.001-2 mM) and low detection limit (0.29 μM) for L-cysteine. Using a hydrothermal approach as a synthesis technique for nanoflakes, as well as a facile and sensitive electro-chemical sensor based the nanoflakes was developed to detect L-cysteine, makes it a promising approach for practical application.

Investigating the Electrocatalytic Oxygen Evolution Reaction of Hydrothermally Synthesized NiFe2O4 Nanoparticles

In this study, nickel ferrite (NiFe2O4) nanoparticles were synthesized using the hydrothermal method at various pH values. The objective was to investigate the influence of pH variation on particle size and electrocatalytic activity. The formation of cubic phase nanoparticles was confirmed through X-ray diffraction (XRD) analysis. To characterize the electrochemical properties, the nickel ferrite nanoparticles were coated onto a stainless steel substrate using the doctor blade technique. The microstructural analysis was conducted using scanning electron microscopy (SEM). The samples were further analyzed using linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The average crystallite size, determined from the XRD pattern, was approximately 40 nm. SEM images revealed a conversion from nanoplates to a granular morphology. The synthesized electrode exhibited an overpotential of 392 mV at 10 mA/cm2 and demonstrated good stability for 5 hours. These findings highlight the excellent electrocatalytic activity of nickel ferrite nanoparticles for the oxygen evolution reaction (OER).

Review on Biomass Derived Activated Carbons as Electrochemical Electrode Material for Supercapacitor Device

Abstract: To face the challenge of the finite nature of fossil fuels and large energy crises across the globe, there is an urgent requirement for sustainable and renewable energy sources. Moreover, it is essential to focus on energy storage in order to meet the demand of future generations. Among various energy storage devices such as fuel cells, batteries, capacitors, supercapacitors, flywheels, etc., it is the supercapacitor device that has elicited extensive research interest recently because of prominent features like high power density, fast recharge capability, and long cycle life. The main objective of this article is to review the enhancement of the electrochemical performance of supercapacitor devices. The electrochemical properties of the supercapacitor device majorly depend on the electrode materials used, which include carbonaceous materials, metal oxides, and conducting polymers. In order to reduce energy shortages and environmental pressure, carbon materials derived from biomass/waste materials have been considered remarkable candidates for electrode materials with the advantages of high abundance, low cost, and environmental friendliness. This review shows the complied study of various methodologies for the preparation of activated carbons derived from different biomass residues such as plants, animals, and microorganisms, which have been investigated in the past few years as electrochemical electrode materials for supercapacitors. Further, ongoing challenges and potential improvements in this area for creating efficient energy storage devices are also discussed. The goal of this review article is to aid in the creation of new insights for energy storage applications of biomass-generated carbons that will lead to sustainable energy development.

Effect of Substrate Temperature on the Electrochemical and Supercapacitance Properties of Pulsed Laser-Deposited Titanium Oxynitride Thin Films

Abstract Electrocatalytically active titanium oxynitride (TiNO) thin films were fabricated on commercially available titanium metal plates using a pulsed laser deposition (PLD) method for energy storage applications. The elemental composition and nature of bonding were analyzed using x-ray photoelectron spectroscopy (XPS) to reveal the reacting species and active sites responsible for the enhanced electrochemical performance of the TiNO electrodes. Symmetric supercapacitor devices were fabricated using two TiNO working electrodes separated by an ion-transporting layer to analyze their real-time performance. The galvanostatic charge-discharge studies on the symmetric cell have indicated that TiNO films deposited on the polycrystalline titanium plates at lower temperatures are superior to TiNO films deposited at higher temperatures in terms of storage characteristics. For example, TiNO films deposited at 300°C exhibited the highest specific capacity of 69 mF/cm2 at 0.125 mA/cm2 with an energy density of 7.5 Wh/cm2. The performance of this supercapacitor (300°C TiNO) device is also found to be ∼ 22 % better compared to that of a 500°C TiNO supercapacitor with a capacitance retention ability of 90% after 1000 cycles. The difference in the electrochemical storage and capacitance properties is attributed to the reduced leaching away of oxygen from the TiNO films by the Ti plate at lower deposition temperatures, leading to higher oxygen content in the TiNO films and, consequently, a high redox activity at the electrode/electrolyte interface.

Study of structural, optical, surface and electrochemical properties of Co3O4 nanoparticles for energy storage applications

Study of structural, optical, surface and electrochemical properties of Co3O4 nanoparticles for energy storage applications

Incorporation of Pd Catalyst into Highly Effective Borophene Nanosheet Co-Catalyst for Electrokinetics and Electrochemical Oxygen Reduction Reactions

AbstractTo improve the performance of the system, it is of great importance to develop efficient catalysts for ethanol (EtOH) electro-oxidation. Pd/B electrocatalyst was synthesized using a sonochemical method. Structural and electrochemical properties of the prepared nanomaterial were investigated using electrochemical and physical techniques such as Raman spectroscopy, electrochemical impedance spectroscopy (EIS), x-ray diffraction (XRD), zetersizer, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and energy-dispersive x-ray spectroscopy (EDS) and cyclic voltammetry (CV). FTIR confirmed all the functional groups of carbon black, Pd/C, borophene, and Pd/B, and the crystallinity was investigated using XRD. EIS showed that Pd/B has a faster charge transfer and, through investigation using CV, Pd/B showed a more negative onset potential and higher current (−0.76 V vs. Ag|AgCl; 0.07 mA) than Pd/C (−0.65 V vs. Ag|AgCl; 0.05 mA), indicating a more catalytic behavior and tolerance of Pd/B. The active sites could be attributed to the addition of borophene. During the anodic sweeping direction of Pd/B electrocatalyst, it was observed that the ratio of backward peak current (Ibwd) to forward peak current (Ifwd), (Ibwd/Ifwd) of in a 2 M of NaOH + 2 M of EtOH is almost equal to (Ibwd/Ifwd) 1 which shows excellent tolerance of Pd/B to poisoning by ethanol intermediate species. The electron transfer rate (Ks) values for Pd/B at 0.1 M, 0.5 M, 1 M, 1.5 M, and 2 M were estimated to be 4.50 × 10−13 s−1, 1.08 × 10−12 s−1, 4.28 × 10−13 s−1, 5.25 × 10−14 s−1 and 9.35 × 10-14 s−1. At 2 M there is a faster electron transfer than at other concentrations which is also evidenced by the obtained diffusion values (D) of the system which were found to be 2.92 × 10−7 cm2 s−1, 4.72 × 10−8 cm2 s−1, 4.82 × 10−8 cm2 s−1, 1.22 × 10−7 cm2 s−1, and 9.12 × 10−8 cm2 s−1. The electrochemically active surface area (ECSA) is strongly related to intrinsic activity, Pd/B (1.85 cm2/mg × 10−5 cm2/mg) denotes the highest Pd-O stripping charge than Pd/C (1.13 cm2/mg × 10−5 cm2/mg).

Synergistic Enhancement of Supercapacitors with Cobalt–Copper Bimetal–Organic Framework

Metal–organic frameworks (MOFs), as high‐potential electrode materials for applications in supercapacitors, have received significant attention recently. Unfortunately, MOF materials still suffer from unsatisfactory specific capacitances due to poor conductivity and limited redox active sites. Herein, a novel cobalt–copper‐based bimetal–organic framework (CoCu‐MOF) is synthesized by a bottom‐up synthesis strategy, the material properties systematically characterized, and finally investigated as a supercapacitor electrode material. The synthesized CoCu‐MOF presents a high specific surface area of 62.4 m2 g−1, and 83% of the copper ions attains the +1 oxidation state contributing to the formation of additional redox active sites and leading to the formation of dual‐redox sites. The CoCu‐MOF displays an excellent specific capacitance of 618 F g−1 at a current density of 1 A g−1, which is more than twice that of Co‐MOF and four times that of Cu‐MOF. The CoCu‐MOF retains 75% of its original capacitance after 3000 charge–discharge cycles at the current density of 1 A g−1. Overall, this work demonstrates how the bimetallic synergistic strategy can effectively enhance the electrochemical properties of MOFs by providing a higher specific surface area and by the introduction of dual redox sites.

Anode-Free Aqueous Aluminum Ion Batteries.

Aqueous aluminum ion batteries (AAIBs) possess the advantages of high safety, cost-effectiveness, eco-friendliness and high theoretical capacity. However, the Al2O3 film on the Al anode surface, a natural physical barrier to the plating of hydrated aluminum ions, is a key factor in the decomposition of the aqueous electrolyte and the severe hydrogen precipitation reaction. To circumvent the obnoxious Al anode, a proof-of-concept of an anode-free AAIB is first proposed, in which Al2TiO5, as a cathode pre-aluminum additive (Al source), can replenish Al loss by over cycling. The Al-Cu alloy layer, formed by plating Al on the Cu foil surface during the charge process, possesses a reversible electrochemical property and is paired with a polyaniline (cathode) to stimulate the battery to exhibit high initial discharge capacity (175 mAh g-1), high power density (≈410Wh L-1) and ultra-long cycle life (4000 cycles) with the capacity retention of ≈60% after 1000 cycles. This work will act as a primer to ignite the enormous prospective researches on the anode-free aqueous Al ion batteries.

Synthesis, characterisation and voltammetric study of dimethylammonium lead iodide perovskite

In the last decade, the most investigated perovskite materials are the hybrid organic-inorganic perovskites (HOIPs) due to their optoelectronic properties and possible application in the production of photovoltaics. This interest has led to an ongoing search for new HOIP variants, alongside thorough investigations of the properties of existing HOIPs. That is why our research in the field of organic-inorganic perovskites is aimed at the synthesis, characterization, and investigation of the electrochemical properties of dimethylammonium lead iodide (DMAPbI3) using voltammetric studies. A modified synthesis of DMAPbI3, differing slightly from the one described in the literature, was performed by combining stoichiometric amounts of lead iodide (PbI2) and dimethylammonium iodide (DMAI) dissolved in acetonitrile. After conducting controlled evaporation, a yellow crystalline powder of DMAPbI3 was obtained. The identity and purity of the obtained compound were confirmed by powder X-ray diffraction (PXRD), infrared (IR) and Raman spectroscopy, and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX). Investigations on the electrochemical properties of DMAPbI3 by cyclic voltammetry were performed with dichloromethane (DCM) and tetrabutylammonium chloride (TBAC) as the electrolyte. A paraffin-impregnated graphite electrode (PIGE) was used as a working electrode, on which the perovskite microparticles were immobilized. The electrochemical activity of DMAPbI3 is recognized through an intense, broad, and irreversible anodic peak attributed to the oxidation of the constituents to different possible products and the decomposition of the perovskite structure.

Self‐Extinguishing and Low‐Cost Quasi‐Solid Polymer Electrolyte for Room Temperature Lithium Metal Batteries

Most modification strategies of polyethylene oxide (PEO)‐based solid polymer electrolyte focus on improving the room temperature ionic conductivity, while disregarding its inherent flammability that poses substantial safety hazard. Herein, a self‐extinguishing quasi‐solid‐state polymer electrolyte (PTTF‐SPE), which combines excellent room temperature electrochemical properties and high safety, has been developed by introducing triethyl phosphate (TEP) as a low‐cost and highly effective flame retardant. The cross‐linking structure derived from ‐CH2‐CH2‐O‐ segments of tetramethylene glycol dimethyl ether (TEGDME) and PEO makes a contribution to a high amorphous state of polymer. A robust solid electrolyte interphase (SEI) formed by preferential decomposition of fluoroethylene carbonate (FEC) that acts as a film‐forming additive, which can prevent TEP from degradation at lithium metal anode. The optimized PTTF‐SPE exhibits high ionic conductivity (0.54×10‐3 S/cm) and lithium transference number (0.71) at room temperature. The LiFePO4||Li battery demonstrates excellent cycle life over 500 cycles at 0.5 C with a high average discharge capacity of 131 mAh/g. A symmetric Li||Li battery that operating for 850 hours indicates a good compatibility of PTTF‐SPE towards lithium metal. This work provides a new idea for developing high‐energy‐density and high‐safety lithium‐metal batteries (LMBs) for room temperature.

Flexible Ni‐Based Bimetallic Spinel Oxide (NiM2O4, M = Mn, Fe, Co) Electrodes for Supercapacitor Applications

Herein, the single‐phase Ni‐based bimetallic spinel oxide (NiM2O4, M = Mn, Fe, Co) nanoparticles are successfully synthesized by sol–gel method and coated on a carbon cloth substrate to form flexible electrodes for supercapacitor applications. The effects of transition metal activity, calcination temperature, surface, and textural properties on the electrochemical properties of spinel electrode materials are demonstrated. It is found that lowering the calcination temperature results in a decrease in crystallite size and particle size, leading to an increase in surface area and pore volume. X‐Ray absorption spectroscopy reveals the presence of Mn2+/3+, Fe2+/3+, and Co2+/3+ in materials. According to the electrochemical studies, NiMn2O4 electrode in Na2SO4 electrolyte exhibits electrical double‐layer capacitance behavior, while NiFe2O4 and NiCo2O4 electrodes in KOH electrolyte exhibit pseudocapacitive behavior. All electrode materials have low solution resistance and charge transfer resistance. NiCo2O4 provides the highest specific capacitance (85.60 F g−1 at 2.5 A g−1) followed by NiFe2O4 and NiMn2O4. It seems likely that the high electrochemical activity of Co2+/3+ and small particle size of NiCo2O4 nanoparticles play an important role in improving the redox process and charge transfer, which may enhance the electrochemical performance of this electrode material.

Thermodynamic assessment of the Ce[sbnd]H and CeNi5[sbnd]H system

Interstitial metal hydrides (MHs) have attracted considerable attention in the field of hydrogen technology, particularly in the context of storage and compression applications. Because of their minor hysteresis effects, good cyclability, activation simplicity, and high volumetric storage density, LaNi5-based alloys are recognized as prominent candidates for hydrogen storage application. Additionally, the system’s thermodynamic and electrochemical properties can be modified to suit the requirements of a particular application by alloying specific substituents. To ascertain the thermodynamic effects of Ce addition within LaNi5, in this work the CeH and CeNi5H systems have been modeled with the CALPHAD method. For this reason, in this work, two different thermodynamic models have been developed and assessed using the same pressure-composition isotherms (PCIs) datasets obtained from literature and theoretical formation energies newly calculated employing periodic density functional theory (DFT). Direct comparison of the models against each other in terms of accuracy and physical plausibility revealed that extrapolation of thermodynamic properties to data-scarce regions is more reasonable with fewer model parameters and in agreement with other similar systems within the rare-earth (RE) metal-hydride class. In addition, the CeNi5H system was investigated by assessing the (Ce)(Ni)5(V a,H)7 phase model, which could accurately predict hydrogen storage properties while being compatible with previously developed LaNi5H models. Ultimately, the models developed in this study may be employed and extended to describe multi-component REH systems and allow for thermodynamic computations that are highly desirable for accurate predictions of hydrogen absorption/desorption properties and degradation characteristics within the (La,Ce)Ni5H metal hydride family.

Enhanced optical and electrochemical properties of FeBTC MOF modified TiO2 photoanode for DSSCs application

In this work, iron based 1, 3, 5-tricarboxylic acid (FeBTC) was prepared via microwave-assisted method and incorporated into TiO2 via ultrasonic assisted method. The TiO2–FeBTC nanocomposites were characterized by XRD, FTIR, Raman, BET, FESEM, HRTEM, TGA, UV‒vis DRS and PL to understand their crystallographic, surface morphology, and optical characteristics. The Raman spectra showed a blue shift of Eg, A1g, and B1g peaks upon incorporation of FeBTC MOF onto TiO2. HRTEM and XRD analysis confirmed a mixture of TiO2 nanospheres and hexagonal FeBTC MOF morphologies with high crystallinity. The incorporation of FeBTC onto TiO2 improved the surface area as confirmed by BET results, which resulted in improved absorption in the visible region as a results of reduced bandgap energy from 3.2 to 2.84 eV. The PL results showed a reduced intensity for TiO2–FeBTC (6%) sample, indicating improved separation of electron hole pairs and reduced recombination rate. After fabrication of the TiO2–FeBTC MOF photoanode, the charge transfer kinetics were enhanced at TiO2–FeBTC MOF (6%) with Rp value of 966 Ω, as given by EIS studies. This led to high performance due to low charge resistance. Hence, high power conversion efficiency (PCE) value of 0.538% for TiO2–FeBTC (6%) was achieved, in comparison with other loadings. This was attributed to a relatively high surface area which allowed more charge shuttling and thus better electrical response. Conversely, upon increasing the FeBTC MOF loading to 8%, significant reduction in efficiency (0.478%) was obtained, which was attributed to sluggish charge transfer and fast electron–hole pair recombination rate. The TiO2–FeBTC (6%) may be a good candidate for use in DSSCs as a photoanode materials for improved efficiency.

Rational Design of an Optimal Al-substituted Layered Oxide Cathode for Na-ion Batteries

Layered oxide cathodes, a promising avenue for Na-ion batteries, hold the highest potential for commercialization. Herein, we delve into the structural and electrochemical properties of Al-substituted layered oxides in our quest to pinpoint the optimal cathode composition in the Na3/4(Mn-Al-Ni)O2 pseudo-ternary system. The cathode materials investigated were synthesized in three distinct phase configurations, which include two monophasic configurations with P3 and P2-type structures and a third biphasic cathode with equal proportions of P3 and P2 phases. The fractions of the P3 and P2 type phases in the cathode materials were manipulated by adjusting the calcination temperature. The varying concentration of Mn3+ and Mn4+, confirmed by X-ray photoelectron spectroscopy, was found to impact the cyclic stability of these materials significantly. During electrochemical testing, the P3 cathodes showed impressive rate performance and exhibited an excellent specific capacity of 195 mAh g−1 at 0.1C. Regarding cyclic performance, the biphasic cathodes consistently outperformed their monophasic counterparts, with P3/P2-Na0.75Mn0.50Ni0.25Al0.25O2 exhibiting 82% capacity retention after 300 cycles. Analysis of operando Synchrotron XRD data revealed an absence of P3 to O3 type phase transition in the cathodes even at low voltages where large structural variations to the unit cell structure were observed. The absence of P3 to O3 transformations and the superior electrochemical performance of Na0.75Mn0.50Ni0.25Al0.25O2 underlines the importance of Al substitution and P3/P2 biphasic structure in enhancing the electrochemical performance of layered oxides.