Surface Facets Reconstruction in Copper-Based Materials for Enhanced Electrochemical CO2 Reduction.

The unavoidable and unpredictable surface reconstruction of metallic copper (Cu) during the electrocatalytic carbon dioxide (CO2) reduction process is a double-edged sword affecting the production of high-value-added hydrocarbon products. It is crucial to control the surface facet reconstruction and regulate the targeted facets/facet interfaces, and further understand the mechanism between activity/selectivity and the reconstructed structure of Cu for CO2 reduction. Based on the current catalyst design methods, a facile strategy combining chemical reduction and electro-reduction is proposed to achieve specified Cu(111) facets and the Cu(110)/(111) interfaces in reconstructed Cu derived from cuprous oxide (Cu2O). The surface facet reconstruction significantly boosted the electrocatalytic conversion of CO2 into multi-carbon (C2+) products comparing to the unmodified catalyst. Theoretical and experimental analyses show that the Cu(110)/(111)s interface between Cu(110) and a small amount of Cu(111) can tailor the reaction routes and lower the reaction energy barrier of C-C coupling to ethylene (C2H4). The work will guide the surface facets reconstruction strategy for Cu-based CO2 electrocatalysts, providing a promising paradigm to understand the structural variation in catalysts.

One-step hydrothermal synthesis of vanadium dioxide/carbon core-shell composite with improved ammonium ion storage for aqueous ammonium-ion battery.

Aqueous nonmetallic ion batteries have garnered significant interest due to their cost-effectiveness, environmental sustainability, and inherent safety features. Specifically, ammonium ion (NH4+) as a charge carrier has garnered more and more attention recently. However, one of the persistent challenges is enhancing the electrochemical properties of vanadium dioxide (VO2) with a tunnel structure, which serves as a highly efficient NH4+ (de)intercalation host material. Herein, a novel architecture, wherein carbon-coated VO2 nanobelts (VO2@C) with a core-shell structure are engineered to augment NH4+ storage capabilities of VO2. In detail, VO2@C is synthesized via the glucose reduction of vanadium pentoxide under hydrothermal conditions. Experimental results manifest that the introduction of the carbon layer on VO2 nanobelts can enhance mass transfer, ion transport and electrochemical kinetics, thereby culminating in the improved NH4+ storage efficiency. VO2@C core-shell composite exhibits a remarkable specific capacity of ∼300 mAh/g at 0.1 A/g, which is superior to that of VO2 (∼238 mAh/g) and various other electrode materials used for NH4+ storage. The NH4+ storage mechanism can be elucidated by the reversible NH4+ (de)intercalation within the tunnel of VO2, facilitated by the dynamic formation and dissociation of hydrogen bonds. Furthermore, when integrated into a full battery with polyaniline (PANI) cathode, the VO2@C//PANI full battery demonstrates robust electrochemical performances, including a specific capacity of ∼185 mAh·g-1 at 0.2 A·g-1, remarkable durability of 93 % retention after 1500 cycles, as well as high energy density of 58 Wh·kg-1 at 5354 W·kg-1. This work provides a pioneering approach to design and explore composite materials for efficient NH4+ storage, offering significant implications for future battery technology enhancements.

Anion Structure Regulation of Cobalt Silicate Hydroxide Endowing Boosted Oxygen Evolution Reaction.

Transition metal silicates (TMSs) are attempted for the electrocatalyst of oxygen evolution reaction (OER) due to their special layered structure in recent years. However, defects such as low theoretical activity and conductivity limit their application. Researchers always prefer to composite TMSs with other functional materials to make up for their deficiency, but rarely focus on the effect of intrinsic structure adjustment on their catalytic activity, especially anion structure regulation. Herein, applying the method of interference hydrolysis and vacancy reserve, new silicate vacancies (anionic regulation) are introduced in cobalt silicate hydroxide (CoSi), named SV-CoSi, to enlarge the number and enhance the activity of catalytic sites. The overpotential of SV-CoSi declines to 301 mV at 10 mA cm-2 compared to 438 mV of CoSi. Source of such improvement is verified to be not only the increase of active sites, but also the positive effect on the intrinsic activity due to the enhancement of cobalt-oxygen covalence with the variation of anion structure by density functional theory (DFT) method. This work demonstrates that the feasible intrinsic anion structure regulation can improve OER performance of TMSs and provides an effective idea for the development of non-noble metal catalyst for OER.

Topochemical behavior of ferrocene embedded in V2O5·nH2O with weak hydrogen bonding enhancing ammonium-ion storage.

Aqueous ammonium ion batteries (AAIBs) are garnering increasing attention due to their utilization of abundant resources, cost-effectiveness, safety, and unique energy storage mechanism. The pursuit of high-performance cathode materials has become a pressing issue. In this study, we propose and synthesize ferrocene-embedded hydrated vanadium pentoxide (Fer/VOH) for implementation in AAIBs. The inclusion of ferrocene serves to expand the interlayer spacing, mitigate interlayer forces, and introduce the electron-rich environment characteristic of ferrocene. This augmentation facilitates the creation of additional oxygen vacancies, substantially enhancing the capacity and efficiency of ammonium ion storage. Notably, our investigation reveals that the incorporation of ferrocene attenuates the hydrogen bonding interactions associated with ammonium ions, rendering them more amenable to the interlayer embedding and release processes. Building upon these advantages, Fer/VOH exhibits a specific capacity of 313 mAh/g at a current density of 0.2 A/g, representing the highest reported performance among vanadium oxides utilized in AAIBs to date. Even after 2000 charge/discharge cycles at a current density of 2 A/g, Fer/VOH maintains a reversible specific capacity of 89 mAh/g, with a capacity retention rate of 54.8%. This study confirms the viability of Fer/VOH as a cathode material for AAIBs and offers a novel approach to enhancing the electrical conductivity and diminishing the hydrogen bonding forces in vanadium oxide intercalation through the embedding of electron-rich species and positronic groups.

Heterostructured Bimetallic MOF-on-MOF Architectures for Efficient Oxygen Evolution Reaction.

Electron modulation presents a captivating approach to fabricate efficient electrocatalysts for the oxygen evolution reaction (OER), yet it remains a challenging undertaking. In this study, an effective strategy is proposed to regulate the electronic structure of metal-organic frameworks (MOFs) by the construction of MOF-on-MOF heterogeneous architectures. As a representative heterogeneous architectures, MOF-74 on MOF-274 hybrids are in situ prepared on 3D metal substrates (NiFe alloy foam (NFF)) via a two-step self-assembly method, resulting in MOF-(74 + 274)@NFF. Through a combination of spectroscopic and theory calculation, the successful modulation of the electronic property of MOF-(74 + 274)@NFF is unveiled. This modulation arises from the phase conjugation of the two MOFs and the synergistic effect of the multimetallic centers (Ni and Fe). Consequently, MOF-(74 + 274)@NFF exhibits excellent OER activity, displaying ultralow overpotentials of 198 and 223 mV at a current density of 10 mA cm-2 in the 1.0 and 0.1 M KOH solutions, respectively. This work paves the way for manipulating the electronic structure of electrocatalysts to enhance their catalytic activity.

La-doped NiWO4 coupled with reduced graphene oxide for effective electrochemical determination of diphenylamine.

Diphenylamine (DPA) is a harmful pesticide widely used to control post-harvest scald of fruits. In this study, rapid and sensitive determination of DPA was realized by the development of an effective electrochemical sensor, which was fabricated by coupling La-doped NiWO4 nanoparticles (La/NiWO4) with reduced graphene oxide (rGO), and the obtained rGO/La/NiWO4 nanocomposite was modified on glassy carbon electrodes (GCEs). The morphologies, structures and compositions were well characterized, and the effects of La doping and the introduction of rGO on the crystal structure and electrochemical performance were discussed. The incorporation of both La and rGO was found to enhance the active surface area and improve conductivity, resulting in the enhanced electrocatalytic performance of rGO/La/NiWO4/GCE, including a wide linear range (0.01-500 µM), a low detection limit (0.0058 µM) and high sensitivity (1.778 µA µM-1 cm-2). The fabricated sensor was further used for DPA detection in fresh apple extract to evaluate its practicality and demonstrated excellent recoveries ranging from 99.52 to 104.70%.

Phosphate-modified cobalt silicate hydroxide with improved oxygen evolution reaction.

Oxygen Evolution Reaction (OER) has gained significant attention due to its crucial role in renewable energy systems. The quest for efficient and low-cost OER catalysts remains a challenge of significant interest and importance. In this work, phosphate-incorporated cobalt silicate hydroxide (denoted as CoSi-P) is reported as a potential electrocatalyst for OER. The researchers first synthesized hollow spheres of cobalt silicate hydroxide Co3(Si2O5)2(OH)2 (denoted as CoSi) using SiO2 spheres as a template through a facile hydrothermal method. Phosphate (PO43-) was then introduced to layered CoSi, leading to the reconstruction of the hollow spheres into sheet-like architectures. As expected, the resulting CoSi-P electrocatalyst demonstrated low overpotential (309 mV at 10 mA·cm-2), large electrochemical active surface area (ECSA), and low Tafel slope. These parameters outperform CoSi hollow spheres and cobaltous phosphate (denoted as CoPO). Moreover, the catalytic performance achieved at 10 mA cm-2 is comparable or even better than that of most transition metal silicates/oxides/hydroxides. The findings indicate that the incorporation of phosphate into the structure of CoSi can enhance its OER performance. This study not only provides a non-noble metal catalyst CoSi-P but also demonstrates that the incorporation of phosphates into transition metal silicates (TMSs) offers a promising strategy for the design of robust, high-efficiency, and low-cost OER catalysts.

Vanadate ion promoting the transformation of α-phase molybdenum trioxide (α-MoO3) to h-phase MoO3 (h-MoO3) for boosted Zn-ion storage.

Molybdenum trioxide (MoO3) has been widely studied in the energy storage field due to its various phase states and unique structural advantages. Among them, lamellar α-phase MoO3 (α-MoO3) and tunnel-like h-phase MoO3 (h-MoO3) have attracted much attention. In this study, we demonstrate that vanadate ion (VO3-) can transform α-MoO3 (a thermodynamically stable phase) to h-MoO3 (a metastable phase) by altering the connection of [MoO6] octahedra configurations. h-MoO3 with VO3- inserted (referred to as h-MoO3-V) as the cathode material for aqueous zinc ion batteries (AZIBs) exhibits excellent Zn2+ storage performances. The improvement in electrochemical properties is attributed to the open tunneling structure of the h-MoO3-V, which offers more active sites for Zn2+ (de)intercalation and diffusion. As expected, the Zn//h-MoO3-V battery delivers specific capacity of 250 mAh·g-1 at 0.1 A·g-1 and rate capability (73% retention from 0.1 to 1 A·g-1, 80 cycles), well exceeding those of Zn//h-MoO3 and Zn//α-MoO3 batteries. This study demonstrates that the tunneling structure of h-MoO3 can be modulated by VO3- to enhance the electrochemical properties for AZIBs. Furthermore, it provides valuable insights for the synthesis, development and future applications of h-MoO3.

Enzyme-Inspired Coordination Polymers for Selective Oxidization of C(sp3)-H Bonds via Multiphoton Excitation.

Nature's blueprint provides the fundamental principles for expanding the use of abundant metals in catalysis; however, mimicking both the structure and function of copper enzymes simultaneously in one artificial system for selective C-H bond oxidation faces marked challenges. Herein, we report a new approach to the assembly of artificial monooxygenases utilizing a binuclear Cu2S2Cl2 cluster to duplicate the identical structure and catalysis of the CuA enzyme. The designed monooxygenase Cu-Cl-bpyc facilitates well-defined redox potential that initially activated O2via photoinduced electron transfer, and generated an active chlorine radical via a ligand-to-metal charge transfer (LMCT) process from the consecutive excitation of the in situ formed copper(II) center. The chlorine radical abstracts a hydrogen atom selectively from C(sp3)-H bonds to generate the radical intermediate; meanwhile, the O2•- species interacted with the mimic to form mixed-valence species, giving the desired oxidization products with inherent product selectivity of copper monooxygenases and recovering the catalyst directly. This enzymatic protocol exhibits excellent recyclability, good functional group tolerance, and broad substrate scope, including some biological and pharmacologically relevant targets. Mechanistic studies indicate that the C-H bond cleavage was the rate-determining step and the cuprous interactions were essential to stabilize the active oxygen species. The well-defined structural characters and the fine-modified catalytic properties open a new avenue to develop robust artificial enzymes with uniform and precise active sites and high catalytic performances.

Metal silicates for supercapacitors derived from the multistep treatment of natural green algaes.

Natural green algaes (GAs) was treated with NaCl solution to prepare metal- silicates (S-C-FeSi-3 and S-C-CuSi-3) with high electrochemical performance. Then, the as-synthesized samples were soaked in NaOH solution to obtain etched metal silicates (e-S-C-FeSi-3 and e-S-C-CuSi-3). This novel method was used to generate a more porous structure with a higher specific surface area. In the three-electrode system, e-S-C-FeSi-3 and e-S-C-CuSi-3 showed the best electrochemical performance (476 F g-1 and 458 F g-1 at 0.5 A g-1, 96 % and 97% after 10,000 cycles, respectively). The solid-state hybrid supercapacitor (HSC) devices (denoted as e-S-C-FeSi-3//AC and e-S-C-CuSi-3//AC), manufactured by metal- silicates and activated carbon (AC), were tested in a two-electrode system. e-S-C-MSi-3//AC exhibited much better electrochemical properties such as areal specific capacitances (603 and 615 mF cm-2 at 2 mA cm-2), energy densities (4.57 and 4.43 Wh m-2 at the power density of 19.2 and 21.0 W m-2) and cycle performances (74.5 % and 76.3 % after 6,000 cycles) than those of C-MSi-3//AC, e-C-MSi-3//AC and S-C-MSi-3//AC (M = Fe and Cu). This study confirms that supercapacitors with excellent electrochemical performance can be prepared by naturally polluted GAs. Furthermore, treatment with porogens is shown to be an effective method to enhance the electrochemical properties of metal- silicates and to prepare electrode materials applied for high-performance supercapacitors.

Synthesis of V2O5·nH2O nanobelts@polyaniline core-shell structures with highly efficient Zn2+ storage.

Aqueous zinc-ion batteries (AZIBs) are regarded as attractive candidates for next-generation energy storage devices. Among various cathode materials, V2O5·nH2O (VOH) possesses a high theoretical capacity but poor cycle stability due to the susceptibility of its open structure to damage by the quick shuttling of Zn2+. Herein, the structural stability of VOH is directly improved by wrapping polyaniline (PANI) on the VOH nanobelts (VOH@PANI). As a cathode material for AZIBs, the VOH nanobelts@PANI core-shell structures exhibit an outstanding cycle stability of 98% after 2000 cycles at 2 A g-1. The improved conductivity and additional energy storage contribution of the PANI endow VOH@PANI with a specific capacity as high as 440 mAh g-1 at 0.1 A g-1, substantially higher than pure VOH (291 mAh g-1). At the same time, high energy and power densities of 349 Wh kg-1 and 3347 W kg-1 are achieved. This work not only demonstrates that p-type doped PANI coatings on VOH can boost the Zn2+ storage of VOH, but also provides a novel method to enhance cathode materials for high electrochemical performance.

Rational Design of Silicon Nanodots/Carbon Anodes by Partial Oxidization Strategy with High-Performance Lithium-Ion Storage.

Silicon (Si) is considered a promising anode material for rechargeable lithium-ion batteries (LIBs) due to its high theoretical capacity, low working potential, and safety features. However, the practical use of Si-based anodes is hampered by their huge volume expansion during the process of lithiation/delithiation, and they have relatively low intrinsic electronic conductivity, therefore seriously restricting their application in energy storage. Here, we propose a facile approach to directly transform siliceous biomass (bamboo leaves) into a porous carbon skeleton-wrapped Si nanodot architecture through a partial oxidization strategy and magnesium thermal reaction to obtain a high Si nanodot component composite (denoted as Si/C-O). With the synergistic effect of the porous carbon skeleton structure and uniformly dispersed Si nanodots, the Si/C-O composite anode with a stable structure that can avoid pulverization and accommodate volume expansion during cycling is fabricated. As expected, the biomass-converted Si/C-O anode not only presents a high Si component (59.7 wt %) by TGA but also exhibits an excellent capacity of 1013 mAh g-1 at 0.5 A g-1 and robust cycling stability with a capacity retention of 526 mAh g-1 after 650 cycles. Moreover, the Si/C-O anode demonstrates considerable performance in practical LIBs when assembled with a commercial LiNi0.8Co0.1Mn0.1O2 cathode. This work provides an effective strategy and long-term insights into the utilization of porous Si-based materials converted by biomass to design and synthesize high-performance LIB materials.

In situ growth of hierarchical phase junction CdS on a H-mordenite zeolite for enhanced photocatalytic properties.

A kind of cadmium sulfide (CdS) nanocomposite with different crystalline phases was grown on the surface of H-mordenite zeolite (HMOR) by a chemical liquid-phase co-precipitation method. In this work, 2 wt% CdS@HMOR photocatalytic material with the coexistence phase (hexagonal phase and cubic phase) of cadmium sulfide was grown on the surface of HMOR by controlling the reaction temperature and ammonia concentration. Photocatalytic degradation of methylene blue (MB) was used as an index to detect the photocatalytic performance of materials. The results indicated that the photocatalytic degradation efficiency of the system with HMOR was significantly improved in comparison to that without HMOR (CdS, 40.34%, 0.2578 h-1). It was found that 2 wt% CdS@HMOR had the best photocatalytic activity. The degradation rate of MB was 84.15% in 2 h, and the degradation rate constant was 0.8884 h-1. When 1.5 ml H2O2 was introduced into the system, the degradation rate of MB was increased to 98.98%, and the degradation rate constant was 1.9976 h-1. SEM, HRTEM, PL, EIS and photocurrent showed that the cubic and hexagonal phases of CdS were in contact with each other on the HMOR surface, forming a good electron transport. By XRD, XPS and SEM tests, the results of materials after four cycles of reactions showed that the structure of the 2 wt% CdS@HMOR was still stable. Therefore, HMOR may provide a good support for CdS, and the synergistic effect between them is beneficial for the occurrence of photocatalytic reactions. HMOR can act as an electron receptor to inhibit the recombination of carriers. The homo-junction between different phases of CdS on the surface of HMOR is beneficial to the separation of photo-induced carriers. These results indicate that the construction of phase heterojunctions on zeolites and the synergism among them are a method for improving the photocatalytic activity.

Defect-Guided Synthesis of Hierarchical Sn-B-Beta Zeolite with Highly Exposed Sn Sites.

Selectively anchoring active centers on the external surface for forming highly exposed acid sites is a highly desirable but challenging task in zeolite catalyst synthesis. Herein, a defect-guided etching-regrowth strategy is rationally designed for facilely positioning Sn Lewis acid sites on the outer surface of the Sn-B-Beta while fabricating a bifunctional hierarchical structure. The synthesis was conducted by hydrothermal treatment of the as-made B-Beta (uncalcined), which has intrinsic defects of the BEA structure, with Sn source and basic organic structure directing agent (SDA). Under a moderate SDA concentration, with blocked micropore channels, such SDA-triggered etching-regrowth will proceed along the defect defined pathway, which ensures Sn selectively anchored on the external surface. Moreover, this methodology has exclusively introduced tetrahedrally coordinated framework Sn with open Sn sites as the predominated species. Mono- and disaccharide isomerizations in ethanol over different Sn-Beta catalysts proved the prominent advantages of the hierarchical structure with highly exposed and synergetic acid sites.

Coadsorption Interfered CO Oxidation over Atomically Dispersed Au on h-BN.

Similar to the metal centers in biocatalysis and homogeneous catalysis, the metal species in single atom catalysts (SACs) are charged, atomically dispersed and stabilized by support and substrate. The reaction condition dependent catalytic performance of SACs has long been realized, but seldom investigated before. We investigated CO oxidation pathways over SACs in reaction conditions using atomically dispersed Au on h-BN (AuBN) as a model with extensive first-principles-based calculations. We demonstrated that the adsorption of reactants, namely CO, O2 and CO2, and their coadsorption with reaction species on AuBN would be condition dependent, leading to various reaction species with different reactivity and impact the CO conversion. Specifically, the revised Langmuir-Hinshelwood pathway with the CO-mediated activation of O2 and dissociation of cyclic peroxide intermediate followed by the Eley-Rideal type reduction is dominant at high temperatures, while the coadsorbed CO-mediated dissociation of peroxide intermediate becomes plausible at low temperatures and high CO partial pressures. Carbonate species would also form in existence of CO2, react with coadsorbed CO and benefit the conversion. The findings highlight the origin of the condition-dependent CO oxidation performance of SACs in detailed conditions and may help to rationalize the current understanding of the superior catalytic performance of SACs.

Dual intercalation of inorganics-organics for synergistically tuning the layer spacing of V2O5·nH2O to boost Zn2+ storage for aqueous zinc-ion batteries.

Possessing a 2D zinc-ion transport channel, layered vanadium oxides have become good candidates as cathode materials for aqueous rechargeable zinc-ion batteries (ARZIBs). Tuning the lamellar structure of vanadium oxides to enhance their zinc-ion storage is a great challenge. In the present study, we proposed and investigated a "co-intercalation mechanism" in which Mg2+ and polyaniline (PANI) were simultaneously intercalated into the layers of hydrated V2O5 (MgVOH/PANI) by a one-step hydrothermal method. Inorganic-organic co-intercalation could tune the layer spacing of VOH, and this combination played a synergistic role in enhancing the zinc-ion storage in MgVOH/PANI. It showed an extremely large layer spacing of 14.2 Å, specific capacity of up to 412 mA h g-1 at 0.1 A g-1, and the capacity retention rate could reach 98% after 1000 cycles. PANI itself has a zinc-storage capacity, and Mg2+ intercalated with PANI can improve the conductivity of the material and enhance its stability. Further first-principles calculations clearly revealed the structural changes and improved electrochemical performance of vanadium oxides. This method of inorganic and organic co-regulation of the VOH structure opens a new strategy for tuning the lamellar structure of layered materials to boost their electrochemical performances.

Chromophore-Inspired Design of Pyridinium-Based Metal-Organic Polymers for Dual Photoredox Catalysis.

2,4,6-Triphenylpyrylium (TPT+ ) functions as a classic organic photocatalyst and exhibits a noteworthy absorption in the visible range, strongly oxidizing excited states, and a somewhat unstable structure. Inspired by the nuclear chromophore and dual catalysis strategy, herein, we report a universal photoredox platform constructed by TPT+ -mimic bridging ligands and reductive metal ions on the basis of metal-organic supramolecular systems for various organic couplings and molecular oxygen activation under visible-light irradiation. Significant photoinduced electron transfer and ligand-to-metal charge-transfer events are both integrated and regulated by the spatial and kinetic confinement effects of the structurally confined microenvironments, effectively improving the efficiency of electron transfer and radical-radical coupling processes in photocatalysis. This package deal provides a promising way for the design of novel photocatalysts and the development of versatile and sustainable synthetic chemistry.

Pd speciation on black phosphorene in a CO and C2H4 atmosphere: a first-principles investigation.

Deposited transition metal clusters and nanoparticles are widely used as catalysts and have long been thought stable in reaction conditions. We investigated the electronic structure and stability of freestanding and black phosphorene supported small Pd clusters containing 1 to 6 atoms in a CO or C2H4 atmosphere by extensive first-principles based calculations. We showed that, driven by the thermodynamics, subnanometric Pd clusters and single Pd atom on phosphorene may evolve for a better balance among metal-metal, metal-support and metal-adsorbate interactions, etc., resulting in atomic dispersion of Pd in reaction conditions. The strong interfacial Pd-P interactions would deform preformed Pd clusters into atomic strips of various lengths with enhanced stability comparable to bulk Pd. The diffusion barriers of terminal Pd atoms in the zigzag direction on phosphorene are small (<0.3 eV) and vary within ∼0.1 eV with the length of these atomic strips. Further adsorption of CO or C2H4 alters the Pd-P and Pd-Pd interactions and forms thermodynamically stable surface Pd species with decreased diffusion barriers, suggesting that atomic dispersion of Pd can be achieved on phosphorene, especially in a CO or C2H4 atmosphere. The current work may help to understand the superior catalytic performance of supported subnanometric transition metal catalysts in reaction conditions and pave the way for fabrication of single atom catalysts with the desired performance.

Electrolyte additive strategy enhancing the electrochemical performance of a soft-packed LiCoO2//graphite full cell.

During the development of high-capacity, ultra-stable battery electrode materials, battery performance, and safety issues are proved to be related to the properties of the electrolyte used. The employment of electrolyte additives is to improve the battery electrolyte properties. Representative commercial two-electrode LiCoO2//graphite pouch cells are used to study electrolyte additives represented by fluoroethylene carbonate (FEC) to improve the electrochemical stability of a commercial pouch full cell. The study reveals that a 1.5% FEC electrolyte additive has the best stability in the voltage range of 3.0-4.2 V.

Alkali etching zinc and manganese silicates derived from natural green algaes for supercapacitors with enhanced electrochemical properties.

A facile novel method of alkali etching was proposed to enhance the application of metal-silicates in supercapacitors. First, 3D N, S, P-doped C-zinc-silicate (C-ZnSi), and C-manganese-silicate (C-MnSi) were derived from calcined green algaes (GAs) in a N2 atmosphere. Second, the synthesized products were soaked in a 3.0 M NaOH aqueous solution for alkali etching (soaked for 6, 12 and 24 h) to obtain the etching metal silicates (e-C-ZnSi and e-C-MnSi). This method can yield a higher specific surface area and more pores, and this in turn can improve the electrochemical performance. In the three-electrode system, e-C-ZnSi and e-C-MnSi, which were soaked in NaOH solution for 12 h, exhibited the highest specific capacitances and cycling performance. Solid-state hybrid supercapacitor (HSC) devices were manufactured using C-MSi, e-C-MSi (M = Zn and Mn), and activated carbon (AC) (denoted as C-MSi//AC and e-C-MSi//AC). In the two-electrode system, the e-C-MSi//AC HSC devices exhibited higher areal specific capacitances and energy densities and better cycle performance than those of C-MSi//AC, especially e-C-MSi//AC-12 h HSC devices, which exhibited the best electrochemical properties. This study demonstrated that the naturally polluted GAs can be used as a reusable silica source for the synthesis of supercapacitors. Furthermore, alkali etching can enhance the electrochemical performance of metal silicates and can be used to prepare electrode materials applied for high-performance supercapacitors.