Search

This study demonstrates the impact of water-in-salt (WIS) electrolytes on the performance of a supercapacitor using nitrogen and sulphur co-doped activated carbon as the electrode material, highlighting its potential for enhanced energy storage capabilities. The electrolyte (WIS) used is 12 m NaNO3 and the electrode material is a previously reported nitrogen and sulphur co-doped activated carbon sourced from mangosteen shells (NS-MSAC). Furthermore, the three-electrode test of NS-MSAC demonstrates a high specific capacitance of 206 F g−1 at a current density of 0.5 A g−1 within a potential window of 0 to −1.0 V. The symmetric supercapacitor built with NS-MSAC achieved a voltage range of 0–2.0 V by exploiting the beneficial electrochemical properties of 12 m NaNO3, which include a higher potential window, low viscosity, high conductivity, and electrochemical stability. The assembled symmetric device featuring NS-MSAC//NS-MSAC delivered a specific energy of 25 W h kg−1 at a power density of 512 W kg−1. Additionally, after 8000 charge/discharge cycles, approximately 85% of the capacitance was retained. This highly concentrated aqueous electrolyte strategy is promising for achieving remarkable supercapacitor performance. [ABSTRACT FROM AUTHOR]

The electrocatalytic CO2 reaction with other gases to synthesize value-added products at high current densities is challenging due to the limited diffusion rate for low-solubility gases in aqueous electrolytes. To enhance the mass transfer process, herein, a membrane electrode assembly (MEA) electrolyzer is employed to achieve high-rate electrochemical C–C coupling of CO2 and gaseous formaldehyde. Based on the simultaneous gas-phase delivery of reactants to the catalytic surface, an acetate production rate of 654 mg L−1 h−1 is achieved at a current density over 150 mA cm−2 on a Cu-MOF coated Cu2O catalyst. In situ FT-IR, Raman spectroscopy, and in situ XAFS combined with DFT suggest that the energy barrier of C–C coupling between *CO and *CH2OH is significantly lowered due to the insertion of Cu-MOF, thus promoting the production of acetate. This work provides a novel strategy for electrochemical treatment of waste gas coupling to synthesize high-value products with potential industrial applications. [ABSTRACT FROM AUTHOR]

Redox flow batteries (RFBs) are gaining significant attention due to the growing demand for sustainable energy storage solutions. In contrast to conventional aqueous vanadium RFBs, which have a restricted voltage range resulting from the use of water and vanadium, the utilization of redox-active organic molecules (ROMs) as active materials broadens the range of applicable liquid media to include non-aqueous electrolyte solutions. The extended voltage range of non-aqueous media, exceeding 2 V, facilitates the establishment of high-energy storage systems. Additionally, considering the higher cost of non-aqueous solvents compared to water, the objective in developing non-aqueous electrolyte solution-based organic RFBs (NRFBs) is to efficiently install these systems in a compact manner and explore unique applications distinct from those associated with aqueous RFBs, which are typically deployed for grid-scale energy storage systems. This review presents recent research progress in ROMs, electrolytes, and membranes in NRFBs. Furthermore, we address the prevailing challenges that require revolution, encompassing a narrow cell voltage range, insufficient solubility, chemical instability, and the crossover of ROMs. Through this exploration, the review contributes to the understanding of the current landscape and potential advancements in NRFB technology and encourages researchers and professionals in the energy field to explore this emerging technology as a potential solution to global environmental challenges. [ABSTRACT FROM AUTHOR]

Electrochemistry plays a pivotal role in a vast number of domains spanning from sensing and manufacturing to energy storage, environmental conservation, and healthcare. Electrochemical applications encompassing gaseous or organic substrates encounter shortcomings ascribed to high mass transfer/internal resistances and low solubility in aqueous electrolytes, resulting in high overpotentials. In practice, strong acids and expensive organic electrolytes are required to promote charge transfer in electrochemical cells, resulting in a high carbon footprint. Liquid–liquid (L–L) and gas–liquid (G–L) dispersions involve the dispersion of a nano/micro gas or liquid into a continuous liquid phase such as micelles, (macro)emulsions, microemulsions, and microfoams stabilised by surface-active agents such as surfactants and colloidal particles. These dispersions hold promise in addressing the drawbacks of electrochemical reactions by fostering the interfacial surface area between immiscible reagents and mass transfer of electroactive organic and gas reactants and products from/to the bulk to/from the electrode surface. This tutorial review provides a taxonomy of liquid–liquid and gas–liquid dispersions for applications in electrochemistry, with emphasis on their assets and challenges in industrially relevant reactions for fine chemistry and depollution. [ABSTRACT FROM AUTHOR]

Nanostructures are critical for improving the contact area with an electrolyte and catalytic efficiency for the CO2 reduction reaction (CO2RR). However, their hydrophobicity conflicts with the intended increase in the contact area and complicates the determination of the active contact area. Here, bismuth–nickel (BiNi) micro–nano hierarchical catalysts for the CO2RR were studied to understand the effects of electrolyte–catalyst contact area variation with the immersion duration in an aqueous electrolyte. The immersed BiNi samples showed about 13.4-fold higher formate production compared to the pristine BiNi sample. The 2-day pre-immersed BiNi sample exhibited faradaic efficiencies (FE%) of ∼80.1% for formate and ∼10% for H2 with a current density of 10.2 mA cm−2 at −1.5 V vs. Ag/AgCl. In contrast, the pristine BiNi catalysts exhibited an FE% of ∼12.9% for formate and ∼76.3% for H2 with a current density of 5.38 mA cm−2. Our experimental results reveal that the improved contact between the electrolyte and the catalyst surface through pre-immersion can lead to enhanced CO2RR efficiency for formate production using hierarchical BiNi catalysts. [ABSTRACT FROM AUTHOR]

Combining different metals in coordination compounds is an efficient strategy to improve their various properties. Herein, mixed nickel–cobalt hexacyanoferrate (NixCoyHCF) microcubes of varying x : y molar ratios are synthesized via a co-precipitation route and comprehensively characterized to study their material and electrochemical properties. NixCoyHCF microcubes display the battery-type electrochemical energy storage mechanism in aqueous electrolytes. Among the samples, Ni1Co2HCF microcubes deliver the highest specific capacity of 134 mA h g−1 (1068 F g−1) at a specific current of 1 A g−1. This significant enhancement in the capacity indicates the synergistic and cooperative effects between Ni and Co sites in Ni1Co2HCF microcubes. The asymmetric supercapacitor device assembled with Ni1Co2HCF microcubes delivers an excellent energy density of 74.4 μW h cm−2 at a power density of 750 μW cm−2 and retains 87.7% of its initial capacity after 2000 cycles at a current density of 5 mA cm−2, indicating its robust structural integrity and electrochemical durability. This study highlights the promising potential of mixed-metal hexacyanoferrates as high-performance electrodes for aqueous supercapacitors. [ABSTRACT FROM AUTHOR]

Aqueous zinc-ion batteries (AZIBs) have garnered significant attention in the realm of large-scale and sustainable energy storage, primarily owing to their high safety, low cost, and eco-friendliness. Aqueous electrolytes, serving as an indispensable constituent, exert a direct influence on the electrochemical performance and longevity of AZIBs. Nonetheless, conventional aqueous electrolytes often encounter formidable challenges in AZIB applications, such as the limited electrochemical stability window and the zinc dendrite growth. In response to these hurdles, a series of advanced aqueous electrolytes have been proposed, such as "water-in-salt" electrolytes, aqueous eutectic electrolytes, molecular crowding electrolytes, and hydrogel electrolytes. This comprehensive review commences by presenting an in-depth overview of the fundamental compositions, principles, and distinctive characteristics of various advanced aqueous electrolytes for AZIBs. Subsequently, we systematically scrutinizes the recent research progress achieved with these advanced aqueous electrolytes. Furthermore, we summarizes the challenges and bottlenecks associated with these advanced aqueous electrolytes, along with offering recommendations. Based on the optimization of advanced aqueous electrolytes, this review outlines future directions and potential strategies for the development of high-performance AZIBs. This review is anticipated to provide valuable insights into the development of advanced electrolyte systems for the next generation of stable and sustainable multi-valent secondary batteries. [ABSTRACT FROM AUTHOR]

For a reliable evaluation of the electrocatalytic ammonia oxidation reaction (EAOR), we revised the standard electrode potentials in both aqueous and nonaqueous electrolytes using the solvation energies of ammonia. Moreover, we developed an improved assessment protocol for EAOR systems, particularly for those employing nonaqueous electrolytes and/or nitrogen-containing materials. [ABSTRACT FROM AUTHOR]

Aqueous electrolyte additives are considered one of the most promising agents for improving the cycling stability and practicality of aqueous zinc-ion batteries (AZIBs) due to their multiple functions, low cost, and easy operation. The application of these electrolyte additives could significantly suppress the corrosion reaction, dendrite growth, and the hydrogen evolution reaction originating from the zinc anodes. In light of the intensive research of electrolyte additives and the significant progress that have been made in recent years, this review will focus on the mechanism and nature behind the improved performance contributed by the additives. A comprehensive overview of the origins of the challenges above will be presented firstly. Furthermore, the basic function principles of most reported additives are summarized and categorized, aiming to induce a deep and logical consideration of the use of the electrolyte additives in practical or large capacity cells. Finally, this review outlines the prospective advancement of electrolyte additives, inspiring the application of advanced characterization techniques in enhancing the understanding of AZIBs and laying the groundwork for the possibility of commercialization of AZIBs. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) and deep eutectic solvents (DESs) have tremendous potential for reactive capture and conversion (RCC) of CO2 due to their wide electrochemical stability window, low volatility, and high CO2 solubility. There is environmental and economic interest in the direct utilization of the captured CO2 using electrified and modular processes that forgo the thermal- or pressure-swing regeneration steps to concentrate CO2, eliminating the need to compress, transport, or store the gas. The conventional electrochemical conversion of CO2 with aqueous electrolytes presents limited CO2 solubility and high energy requirement to achieve industrially relevant products. Additionally, aqueous systems have competitive hydrogen evolution. In the past decade, there has been significant progress toward the design of ILs and DESs, and their composites to separate CO2 from dilute streams. In parallel, but not necessarily in synergy, there have been studies focused on a few select ILs and DESs for electrochemical reduction of CO2, often diluting them with aqueous or non-aqueous solvents. The resulting electrode–electrolyte interfaces present a complex speciation for RCC. In this review, we describe how the ILs and DESs are tuned for RCC and specifically address the CO2 chemisorption and electroreduction mechanisms. Critical bulk and interfacial properties of ILs and DESs are discussed in the context of RCC, and the potential of these electrolytes are presented through a techno-economic evaluation. [ABSTRACT FROM AUTHOR]

Aqueous Zn–metal batteries have attracted increasing interest for large-scale energy storage owing to their outstanding merits in terms of safety, cost and production. However, they constantly suffer from inadequate energy density and poor cycling stability due to the presence of zinc ions in the fully hydrated solvation state. Thus, designing the dehydrated solvation structure of zinc ions can effectively address the current drawbacks of aqueous Zn–metal batteries. In this case, considering the lack of studies focused on strategies for the dehydration of zinc ions, herein, we present a systematic and comprehensive review to deepen the understanding of zinc-ion solvation regulation. Two fundamental design principles of component regulation and pre-desolvation are summarized in terms of solvation environment formation and interfacial desolvation behavior. Subsequently, specific strategy based distinct principles are carefully discussed, including preparation methods, working mechanisms, analysis approaches and performance improvements. Finally, we present a general summary of the issues addressed using zinc-ion dehydration strategies, and four critical aspects to promote zinc-ion solvation regulation are presented as an outlook, involving updating (de)solvation theories, revealing interfacial evolution, enhancing analysis techniques and developing functional materials. We believe that this review will not only stimulate more creativity in optimizing aqueous electrolytes but also provide valuable insights into designing other battery systems. [ABSTRACT FROM AUTHOR]

I+ hydrolysis, sluggish iodine redox kinetics and the instability of Zn anodes are the primary challenges for aqueous four-electron zinc–iodine batteries (4eZIBs). Herein, the OTf− anion chemistry in aqueous electrolyte is essential for developing advanced 4eZIBs. It is elucidated that OTf− anions establish weak hydrogen bonds (H bonds) with water to stabilize I+ species while optimizing a water-lean Zn2+ coordination structure to mitigate Zn dendrites and corrosion. Moreover, the interaction of the OTf− anions with the iodine species results in an increased equilibrium average intermolecular bond length of the iodine species, facilitating the 4e redox kinetics of iodine with improved reversibility. [ABSTRACT FROM AUTHOR]

Electrolytes play a significant role in improving the stability and specific capacity of supercapacitors; however, they have gained less attention compared to the designing of electrode materials. This study presents the supercapacitor application of novel Prussian blue analog (PBA)-based fabricated electrodes in different electrolytes. PBA was derived by the ligand substitution of sodium pentacyanonitrosyl ferrate(III) dihydrate followed by precipitation with cobalt salt to yield cobalt pentacyano(methylaniline)ferrate(II) (CoPCF). The fabricated electrode exhibited specific capacity of 390, 233, 175, and 83 mA h g−1 in 3 M KOH, 1 M NaOH, 1 M LiOH, and 1 M KNO3 at 1 A g−1 with capacity retention of 88.80%, 89.95%, 92.42%, and 90.80%, respectively, after 1000 continuous charge–discharge cycles. Furthermore, a solid-state asymmetric supercapacitor (ASC) device was fabricated using a PVA/KOH polymer gel electrolyte that exhibited a specific capacity of 56 mA h g−1 with a specific energy density of 71 W h kg−1 and a specific power density of 2560 W kg−1 at a current density of 1 A g−1, with excellent capacity retention of 93% over 2000 continuous (dis)charge cycles. These results demonstrated that the introduction of organic ligands in the framework of PBAs along with the selection of the right electrolyte is an effective strategy in the development of high-capacity and stable supercapacitor electrodes. [ABSTRACT FROM AUTHOR]

A dual-additive-based aqueous electrolyte was designed with a pH-buffering additive (Zn(OAc)2) and an electrostatic shielding additive (TMAOAc) for high Zn plating/stripping efficiency. The buffering pair, OAc−/HOAc, can stabilize the pH value to suppress side hydrogen evolution reactions. Meanwhile, TMA+ acts as a competitive cation being preferentially adsorbed on the uneven surface of the Zn anode and exerts an electrostatic shielding effect to facilitate flat Zn deposition. Such a dual-additive-based electrolyte promotes an ultra-high Zn plating/stripping efficiency of 99.9% at 1 mA cm−2 and long-term cycling stability for 3600 h at 0.5 mA cm−2, offering valuable insights for advanced aqueous batteries. [ABSTRACT FROM AUTHOR]

One of the major problems affecting the energetic characteristics and cycle life of electrochemical capacitors (ECs) utilizing aqueous electrolytes is the narrow operating voltage range, which is limited by the thermodynamic stability of water (1.23 V). An improvement in the EC energy can be realized by a capacitance and/or voltage increase. For that purpose, cost-effective and environmentally friendly iodides have been added to aqueous electrolytes to improve the redox activity. Moreover, buffer agents (acetate, citrate, and phosphate) that are well known for adjusting the pH of an electrolyte have been applied, which enabled ECs to reach a stable operating voltage of 1.5 V. After adding iodide to the buffer system, the conductivity increased notably, whereas the pH values remained nearly the same. Galvanostatic charge/discharge test (0.5 A g−1 ) for ECs operating in buffer electrolytes containing 0.2 mol L−1 NaI showed that this additive noticeably increased the specific capacitance values from 91 to 149 F g−1 for acetate buffer, from 7 to 101 F g−1 for citrate buffer, and from 22 to 132 F g−1 for phosphate buffer. The long-time performance of the ECs was investigated through accelerated potentiostatic floating. The electrochemical performance was studied using various activated carbons. During the floating aging test, the YP50F-based EC working in acetate buffer with 0.2 mol L−1 NaI displayed the best long-term performance (310 h) compared to YP80F and BP2000 carbons, which exhibited 212 h and 126 h, respectively. The highly microporous YP50F carbon in the acetate buffer/iodide electrolyte revealed the best wettability. Interestingly, the citrate buffer/iodide EC system with YP50F demonstrated an extremely long floating performance (1006 h). Thus, this study presents a new strategy for improving the energetic metrics and cycling performance of carbon-based ECs operating in buffer electrolytes with an iodide redox pair. [ABSTRACT FROM AUTHOR]

Self-assembled monolayers (SAM) are ubiquitous in studies of modified electrodes for sensing, electrocatalysis, and environmental and energy applications. However, determining their adsorptive stability is crucial to ensure robust experiments. In this work, the stable potential window (SPW) in which a SAM-covered electrode can function without inducing SAM desorption was determined for aromatic SAMs on gold electrodes in aqueous and non-aqueous solvents. The SPWs were determined by employing cyclic voltammetry, attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), and surface plasmon resonance (SPR). The electrochemical and spectroscopic findings concluded that all the aromatic SAMs used displayed similar trends and SPWs. In aqueous systems, the SPW lies between the reductive desorption and oxidative desorption, with pH being the decisive factor affecting the range of the SPW, with the widest SPW observed at pH 1. In the non-aqueous electrolytes, the desorption of SAMs was observed to be slow and progressive. The polarity of the solvent was the main factor in determining the SPW. The lower the polarity of the solvent, the larger the SPW, with 1-butanol displaying the widest SPW. This work showcases the power of spectroelectrochemical analysis and provides ample future directions for the use of non-polar solvents to increase SAM stability in electrochemical applications. [ABSTRACT FROM AUTHOR]

Aqueous lithium-ion batteries (ALIBs) featuring high-safety, low-cost, and environmental friendliness have dramatic potential in the area of energy storage batteries. The progress of aqueous lithium-ion batteries is restricted by the advanced electrode materials, which can maintain a robust structure after long-term cycling. In this work, we report a novel "rocking-chair" type aqueous full lithium-ion battery with titanium phosphate nanosheets (Ti(HPO4)2·H2O) as the anode material. The fabricated aqueous full lithium-ion battery achieves a high capacity retention of 83% after 1000 cycles even at the high-voltage of 2.4 V, as well as an excellent rate performance. [ABSTRACT FROM AUTHOR]

Aqueous zinc (Zn) batteries have attracted global attention for energy storage. Despite significant progress in advancing Zn anode materials, there has been little progress in cathodes. The predominant cathodes working with Zn2+/H+ intercalation, however, exhibit drawbacks, including a high Zn2+ diffusion energy barrier, pH fluctuation(s) and limited reproducibility. Beyond Zn2+ intercalation, alternative working principles have been reported that broaden cathode options, including conversion, hybrid, anion insertion and deposition/dissolution. In this review, we report a critical assessment of non-intercalation-type cathode materials in aqueous Zn batteries, and identify strengths and weaknesses of these cathodes in small-scale batteries, together with current strategies to boost material performance. We assess the technical gap(s) in transitioning these cathodes from laboratory-scale research to industrial-scale battery applications. We conclude that S, I2 and Br2 electrodes exhibit practically promising commercial prospects, and future research is directed to optimizing cathodes. Findings will be useful for researchers and manufacturers in advancing cathodes for aqueous Zn batteries beyond Zn2+ intercalation. [ABSTRACT FROM AUTHOR]

Manganese dioxide nanorods (Na0.4MnO2) with a typical 2 × 4 tunnel structure are successfully synthesized by the simple hydrothermal method in the presence of 5 M NaCl. The nanorods are about 30 nm in diameter. ZIBs (zinc-ion batteries) with Na0.4MnO2 display a specific capacity of 274.6 mA h g−1 at 0.2 A g−1 and have a high reversible capacity of 182.6 mA h g−1 after 1400 charge–discharge cycles at 1 A g−1 with a capacity retention of 96.5%. The unique morphology endows abundant electrochemical active sites and facile ion diffusion kinetics, which contributes to high specific capacity and stability. Both Zn2+ and H+ are inserted/extracted during the discharging/charging processes, and the crystalline structure and morphology of the nanorods do not change after repetitive cycling. The Na0.4MnO2 with the 2 × 4 tunnel structure is a promising candidate as the electrode material for ZIBs. [ABSTRACT FROM AUTHOR]

Aqueous zinc ion batteries (AZIBs) are regarded as a promising alternative for energy storage due to their safety, cost-effectiveness and environmental friendliness. Manganese dioxide is considered a promising cathode material for energy storage because of its abundant reserves and high energy density. However, its inherent low electronic conductivity and limited cycling performance due to structural instability hinder its further development. Herein, a silver and manganese dioxide composite (Ag@MnO2) enriched with oxygen vacancies was prepared by a simple liquid-phase reduction method. The introduction of silver particles facilitates the improvement of electrical conductivity, and the incorporation of oxygen vacancies helps change the surface properties of manganese dioxide, providing additional active sites for ion transport, enhancing the overall electrochemical kinetics, and further improving the battery performance. As a result, the Ag@MnO2 cathode exhibits an astonishingly high capacity of 353 mAh g−1 at a current density of 0.1 A g−1 and a capacity retention of 78% after 1500 cycles. Additionally, electrochemical and structural analyses have revealed that the Ag@MnO2 cathode undergoes a reversible and stable process of H+ and Zn2+ insertion/extraction. [ABSTRACT FROM AUTHOR]

This work investigates the impact of alloy composition on the microstructure and phase distribution of rapidly solidified Al–Zn alloys. The results demonstrate that the size and distribution of α-Al grains vary with the Zn content, and a Zn-rich phase precipitates along the grain boundaries with Zn content over 15 at%. Furthermore, the alloy composition of the Al–Zn precursors significantly influences the formation, microstructure, crack appearance and length scale of ligaments in nanoporous zinc (NP-Zn) prepared by dealloying. Additionally, the activity and selectivity of NP-Zn in CO2 electroreduction were explored in an aqueous KHCO3 electrolyte. The results indicate that a smaller ligament size of NP-Zn is more conducive to enhancing the catalytic performance. The research underscores the potential for adjusting the nanostructure of NP-Zn by controlling the composition of precursor alloys, providing valuable insights for designing efficient Zn-based electrocatalysts. [ABSTRACT FROM AUTHOR]

Zinc metal is widely considered as the primary option for constructing various aqueous batteries due to its cost-effectiveness, safety, and environmental friendliness. However, the Zn anode continues to be plagued by parasitic reactions and dendrite growth in aqueous electrolytes, limiting the practical implementation of zinc ion batteries (ZIBs) for large-scale energy storage. Herein, a foveolate ZnTe nanoarray is developed as a protective layer to enhance the chemical reversibility during Zn plating/stripping. The semi-conductive ZnTe with excellent ionic conductivity and hydrophobicity can effectually prevent the corrosion reactions, hydrogen generation and dendritic growth on the surface of the Zn anode. As a result, the Zn@ZnTe symmetrical cells achieve ultrahigh cycling stability (over 2800 h at 2 mA cm−2 and 1 mA h cm−2) and simultaneously deliver a low voltage hysteresis of 28 mV. Additionally, the durable Zn@ZnTe//V2O5 cells exhibit a remarkable capacity retention of 96.7% after 3000 cycles, surpassing that of the Zn//V2O5 cells. This work provides a straightforward and low-cost strategy to regulate the interface chemistry of the Zn anode, which may open a way for the development of practical ZIBs. [ABSTRACT FROM AUTHOR]

Delamination of the electron-transporting polymer N2200 from indium tin oxide (ITO) in aqueous electrolytes is mitigated by modifying ITO with an azide-functionalized phosphonic acid (PA) which, upon UV irradiation, reacts with the polymer. The optical, electrochemical, and spectroelectrochemical properties of N2200 thin films are retained in aqueous and non-aqueous media. [ABSTRACT FROM AUTHOR]

We report the electrochemistry of Al3+ ion storage in copper tetrathiovanadate (Cu3VS4) in an aqueous electrolyte for the first time. It is found that Cu3VS4 could deliver an initial discharge capacity of 111 mA h g−1 at a current rate of 0.5 A g−1 and 77 mA h g−1 up to the 300th cycle at 2 A g−1 along with an excellent rate capability. The better electrochemical performance may be attributed to the high theoretical capacity of sulfur and the superior conductivity of copper which allows facile Al3+ ion diffusion in Cu3VS4. The electrochemical mechanism of Al3+ ion storage is also illustrated. [ABSTRACT FROM AUTHOR]

The direct electrochemical conversion of captured CO2 technology has received global attention as an alternative to the current energy-demanding amine solvent regeneration and separation processes of the conventional carbon capture process; however, the identification of the potential advantages of this process from both the economic and environmental perspectives is not straightforward. Here, we present process designs of two commercial-scale carbon capture and utilization (CCU) processes: a direct electrochemical conversion process via the captured CO2 reduction reaction (cCO2RR) in a monoethanolamine (MEA)-based medium and an electrochemical conversion process via the CO2 reduction reaction (CO2RR) in aqueous electrolyte media. As a result of the techno-economic analysis, the levelized cost of product CO (LCOC) of the cCO2RR process, which reflects the current technology level, is 3.5 times higher than that of the CO2RR process, resulting in low economic feasibility. However, if the technology of cCO2RR develops to the same level as that of the CO2RR, the LCOC can be 6.1% lower than that of the CO2RR process, which shows that the cCO2RR technology has good economic potential. Furthermore, the life cycle assessment revealed that when using renewable electricity, the cCO2RR process can have a much more positive environmental impact than CO2RR, even at the current technological performance level. We highlighted that the analysis of the proposed cCO2RR technology will become a good guideline for the development of an integrated and new type of CCU technology without being complacent with the current CCU technology. [ABSTRACT FROM AUTHOR]

Mesoporous activated carbons (ACs) and microporous ACs are prepared through physical activation from one-pot hydrothermal product carbon dots (CDs) and hydro-chars, respectively. The CD-derived ACs exhibit a low surface area of ∼200 g m−2 but a high percentage of mesopores, while the hydrochar-derived ACs (ACSs) are typically microporous with a much higher surface area. Using different activation agents, the N and O components are introduced or adjusted. With symmetric supercapacitor (SC) cells, the mesoporous ACs exhibit superior electrochemical performances than the corresponding ACSs in both aqueous and organic electrolytes, although the surface area is much lower. Higher N contents benefit the electrochemical properties in both aqueous and organic systems. In comparison, the O component is only favored for the aqueous system. The ACs derived from CDs by ammonia exhibit an optimum specific capacitance of 175 F g−1 at 1 A g−1 with 74% capacitance retention at 40 A g−1 in an aqueous system and 153.84 F g−1 at 1 A g−1 with 60% capacitance retention at 40 A g−1 in an organic system. By defining a specific capacitance per surface area, the synergetic effects of porous structures and surface functionality are analyzed, which may help predict the theoretical capacitance of the ACs and design highly effective electrode materials. [ABSTRACT FROM AUTHOR]

Aqueous zinc–sodium hybrid batteries with a Prussian blue cathode have been extensively studied in recent years. However, less research has been conducted on low-cost ferric ferricyanide (FeFe(CN)6) cathode materials. Considering that both Zn2+ and Na+ can be reversibly embedded in FeFe(CN)6 crystals, here we focus on mixed electrolytes with different concentrations of ZnSO4 and Na2SO4 in deionized water to explore the preference of FeFe(CN)6 towards Zn2+ and Na+. As a result, by using 0.1 M ZnSO4 + 1 M Na2SO4 electrolyte, a superior battery performance is obtained, which reveals that the co-function of Zn2+ and Na+ in this electrolyte promotes Zn//FeFe(CN)6 cells to exert a superior specific capacity. In this work, FeFe(CN)6 is synthesized by a co-precipitation method and is analyzed by XRD, SEM, etc., and then used as the cathode material in Zn–Na hybrid batteries. Cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) tests show that FeFe(CN)6 in 0.1 M ZnSO4 + 1 M Na2SO4 electrolyte delivers the highest discharge/charge capacities of 165.2/165.9 mA h g−1 (theoretical specific capacity: 212.2 mA h g−1) at a 0.1 C current density, with good capacity retention of 84% after 200 cycles at 15 C, outperforming many of the reported Zn–Na hybrid cells. [ABSTRACT FROM AUTHOR]

This document is the contents list for an issue of the journal Chemical Communications, published by the Royal Society of Chemistry. It provides a summary of calixarene-based fluorescent sensors developed in the past five years, as well as feature articles on precision nanoengineering for functional self-assemblies across length scales. The document also includes information for authors who wish to submit material for publication, guidelines for reproducing published contributions, and a list of featured articles and communications that have been published in the journal. It covers a range of topics in chemistry, including the synthesis of complex oxide thin films, self-assembled perovskite quantum dots, and regioselective synthesis of indazolo[2,3-a]-quinazolines. The document concludes with information about copyright and the use of the journal's content. [Extracted from the article]

Herein, ammonium fluoride is reported as an additive within 1 M ZnSO4 aqueous electrolyte to improve zinc anodes. The as-formed electrostatic shielding layer and ZnF2-rich solid-state interphase layer can jointly inhibit side reactions and dendrite growth. Consequently, symmetric Zn‖Zn cells, asymmetric Zn‖Cu cells and Zn‖MnO2 cells with the additives present dramatically enhanced performance in comparison to the ones with pure ZnSO4 electrolyte counterparts. This work proposes a facile but effective method to achieve highly reversible zinc anodes. [ABSTRACT FROM AUTHOR]

Trace Sc3+ additive (1.0 mol%) is shown to greatly improve the Coulombic efficiency and cycling stability of Zn metal anodes in aqueous ZnSO4 electrolyte due to the decreased nucleation overpotential and increased kinetics for Zn plating/stripping. Both Zn‖Zn and Zn‖V2O5 cells show enhanced cycling stability and rate capability in the Sc3+-modified electrolyte. [ABSTRACT FROM AUTHOR]

Supercapacitors (SCs) have drawn much attention owing to their unique superiorities. The selection of electrode materials is significantly crucial as it influences SC performance. Defects such as low specific capacitance and poor rate performance need to be settled urgently to achieve enhanced SC performance. Here, we have developed an effective and facile strategy to prepare a binder-free nitrogen-doped graphene hydrogel (NDGH) as an electrode material. The electrochemical performance of NDGH was measured in three different electrolytes (2 M KOH, 1 M Na2SO4 and 1 M H2SO4), and it showed superior performance in 2 M KOH. NDGH had an outstanding specific capacitance of 224.1 F g−1 at 1 A g−1 and retained 80.7% of the capacitance at 10 A g−1. Meanwhile, NDGH possessed good cycling stability, with 93% capacitance retention after 6000 cycles. The contributions of surface-controlled and diffusion-controlled processes to NDGH capacitance were analyzed in different electrolytes. Compared with 1 M Na2SO4 (52%) and 1 M H2SO4 (13%), superior surface-controlled contribution was observed in the 2 M KOH (73%) electrolyte at 10 mV s−1. The symmetric supercapacitor (SSC) consisting of NDGH delivered an energy density of 14.3 W h kg−1 at a power density of 582.8 W kg−1 in the KOH electrolyte. These excellent electrochemical performance parameters could be achieved due to the synergistic effect of the multistage pore structure, nitrogen doping and binder-free hydrogel, which allow abundant electrochemical reactions to take place at the interface between the electrode materials and the electrolyte. This strategy may be further broadened to prominently enhance the specific capacitance and rate performance of graphene oxide. [ABSTRACT FROM AUTHOR]

This study investigates a salt design principle for aqueous battery electrolytes by combining chaotropic ions, guanidium cations (Gdm) and bis(trifluoromethanesulfonyl)imide anions (TFSI), forming GdmTFSI. This salt's crystal structure was solved via single-crystal X-ray diffraction and characterized using Fourier-transform infrared spectroscopy. Study reveals that GdmTFSI salt disrupts the hydrogen bonding network of aqueous solutions, impacting water reactivity at electrochemical interfaces. [ABSTRACT FROM AUTHOR]

This study introduces a versatile electrolyte additive, nicotinamide, for zinc anodes, aiming to facilitate uniform deposition and suppress water-induced side reactions. The molecular structure, consisting of a pyridine ring and an amide function group, endows NTA molecules with the ability to regulate electrolyte pH, enhance nucleation overpotential, and constrain 2D diffusion of Zn2+. As a result, the full battery configuration with this additive achieved an impressive lifespan of over 10 000 cycles. [ABSTRACT FROM AUTHOR]

Developing effective electrocatalysts for the oxygen evolution reaction (OER) that are highly efficient, abundantly available, inexpensive, and environmentally friendly is critical to improving the overall efficiency of water splitting and the large-scale development of water splitting technologies. We, herein, introduce a facile synthetic strategy for depositing the self-supported arrays of 1D-porous nanoneedles of a manganese cobalt oxide (Mn0.21Co2.79O4: MCO) thin film demonstrating an enhanced electrocatalytic activity for OER in an alkaline electrolyte. For this, an MCO film was synthesized via thermal treatment of a hydroxycarbonate film obtained from a hydrothermal route. The deposited films were characterized through scanning electron microscopy (SEM), X-ray diffractometry (XRD), energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). In contrast to a similar 1D-array of a pristine Co3O4 (CO) nanoneedle film, the MCO film exhibits a remarkably enhanced electrocatalytic performance in the OER with an 85 mV lower overpotential for the benchmark current density of 10 mA cm−2. In addition, the MCO film also demonstrates long-term electrochemical stability for the OER in 1.0 M KOH aqueous electrolyte. [ABSTRACT FROM AUTHOR]

Aqueous electrolytes are attractive as energy storage devices due to their high conductivity, environmental friendliness, and sustainability. However, their use is limited by the evolution potential of 1.23 V. A Tween 20-based sustainable microemulsion electrolyte has been proposed; the hydrophobic tail of the surfactant could array on the surface of a hydrophobic electrode, concentrating an oil layer to increase the operating potential, achieving 2.9 V operating voltage (same level as organic electrolyte), while persevering the odds of aqueous electrolytes. [ABSTRACT FROM AUTHOR]

Understanding multiple lengthscale correlations in the pair distribution functions (PDFs) of aq. electrolytes is a persistent challenge. Here, the coordination chemistry of polyoxoanions supports an ion-network of cation-coordination polyhedra in NaNO3(aq) and NaNO2(aq) that induce long-range solution structure. Oxygen correlations associated with Na+-coordination polyhedra have two characteristics lengthscales; 3.5–5.5 Å and 5.5–7.5 Å, the latter solely associated oligomers. The PDF contraction between 5.5–7.5 Å observed in many electrolytes is attributed to the distinct O⋯O correlation found in dimers and dimer subunits within oligomers. [ABSTRACT FROM AUTHOR]

Although non-alkaline rechargeable Zn–air batteries (RZABs) are promising for energy storage, their chemistry is still underdeveloped and unclear. It was suggested that using Zn(OAc)2 or Zn(OTf)2 aqueous solutions as electrolytes enables reversible, corrosion-free charge–discharge processes, but the anodic stability of carbon in these cells has remained poorly studied. We report that CO2 evolution is manifested during the oxygen evolution reaction in non-alkaline RZABs, which is associated with the corrosion of carbon scaffolds. This corrosion is observed for different electrolyte compositions, such as Zn(OAc)2, ZnSO4 and Zn(OTf)2 solutions of various concentrations. The corrosion rate decreases when the overpotentials during the oxygen evolution reaction are lower. This study underlines the importance of addressing the anodic instability of carbon in non-alkaline RZABs. [ABSTRACT FROM AUTHOR]

Nickel–cobalt Prussian blue analogues (Ni–Co PBAs) suffer from structural instability in neural and alkaline electrolytes due to the dissolution of metal cations and cyanide anions caused by external H2O attack, resulting in capacity degradation and restricted life span. Herein, in this work, Ni–Co PBA quantum dots embedded in N-doped carbon (CC-Ni–Co PBA) were synthesized via a facile coprecipitation method and in situ polymerization followed by calcination under a nitrogen atmosphere. The obtained electrode provided a high specific capacity of 333.7 C g−1 and still retained 188.8 C g−1 when the current density increased by 40 times. Remarkably, it exhibited outstanding cycling stability with 82% retention of capacity after 10 000 cycles in an aqueous alkaline electrolyte, which benefited from the inner Ni–Co PBA quantum dots that provided a surrounding space and significantly accommodated the volume change during the repeated charge–discharge process, and the outer carbon layer that served as a protective barrier to hinder the Ni–Co PBA from dissolving into the electrolyte, thus realizing the durability of the electrode. Furthermore, an asymmetric alkaline battery device was assembled which achieved a maximum energy density of 33.2 W h kg−1 and a power density of 3.1 kW kg−1. Our work contributed to the development of PBA-based electrode materials with improved cycling stability as battery-type electrodes in aqueous electrolytes. [ABSTRACT FROM AUTHOR]

For the purpose of expanding the working potential window and reducing the self-discharge for a Zn-ion hybrid supercapacitor, a positive electrode (cathode) of the Mn–Co-sulfide–polyaniline (MCS–PANi) composite coated on porous graphite paper was prepared using the reverse voltage pulse electrodeposition method. The electrode first achieved a high specific capacitance of 1048.8 F g−1 at a scan rate of 5 mV s−1 in the 1 M ZnSO4 and 0.1 M MnSO4 electrolyte solution. The Zn negative electrode (anode) was modified by organic fatty alcohol additives to reduce oxidation and dendrite growth. A hydrophilic modified polypropylene (PP) nonwoven fabric was used as a separator. The MCS–PANi-Zn-ion hybrid supercapacitor (MPZHSC) exhibited a very wide potential window of 2 V in aqueous electrolytes, a high specific capacitance value of 586.7 F g−1 at a scan rate of 5 mV s−1, an excellent durability of 98.3% after 11 232 cycles and a low self-discharge rate, retaining over 60% of its initial voltage value after 7 days. In addition, a device with a small active area of 2 cm2 can be used to light a 2.5 W LED module for about 15 min, suggesting MPZHSC's potential practical applications. [ABSTRACT FROM AUTHOR]

Silicon (Si) is a commercially available semiconductor used for photoelectrochemical (PEC) hydrogen production, which has various advantages of earth-abundant element, non-toxicity, broad absorption of the solar spectrum, high saturation current and industrial applicability. However, it suffers from surface light reflection, short carrier-transport distance, slow charge transfer at the electrode–electrolyte interface, and poor stability in aqueous electrolytes, resulting in decreased photocurrent density and elevated overpotential. In this work, a surface-modified nanoporous Si photocathode, called black Si (b-Si), was fabricated with a large electrochemical surface area for loading of Co(dmgH)2(py)Cl catalyst. Under the illumination of simulated sunlight, the optimal b-Si/[Co] photocathode exhibited a high photocurrent density of −4.15 mA cm−2 (0 VRHE), a value 319 times that of the f-Si electrode under the same conditions. Moreover, the onset potential positively shifted to 0.31 VRHE and the driving force required for H2 production was significantly decreased. The enhanced water splitting was attributed to the rapid transfer of charge across the electrode–electrolyte interface and efficient HER reactivity via the [Co] molecular catalyst. The surface engineering of the nanoporous structure and the deposition of molecular catalyst on the Si electrode have provided insights into the construction of semiconductor/catalyst hybrid photoelectrodes, and were concluded to synchronously improve the charge transfer at the electrode/electrolyte interface, reduce the overpotential, and speed up the PEC water splitting. [ABSTRACT FROM AUTHOR]

The capacitance of electrode materials is directly influenced by their surface area. In this work, we synthesized three-dimensional interconnected honeycomb-like carbon nanosheets (RTK-3) utilizing a homemade phenolic resin along with KOH etching and in situ doping of thiourea. These nanosheets possess a large surface area (2277.71 m2 g−1) and are rich in heteroatoms, which results in outstanding electrochemical performance, with specific capacitances of 349 F g−1 at 0.5 A g−1 and 217 F g−1 at 10 A g−1. Additionally, the assembled symmetric supercapacitor (RTK-3//RTK-3) exhibits exceptional performance in different aqueous electrolytes. Specifically, it delivers an energy density of 6.11 W h kg−1 at a power density of 249.61 W kg−1 in alkaline electrolytes, while it achieved a preeminent energy density of 36.34 W h kg−1 at 810.11 W kg−1 in neutral electrolytes due to its larger potential window (0–1.8 V). The utilization of resin-based carbon materials to prepare high-performance supercapacitors represents a novel approach and could potentially lead to the application of other large surface area and heteroatom-doped materials in energy storage. [ABSTRACT FROM AUTHOR]

The self-discharge and effumability of supercapacitors with aqueous electrolytes are prevalent problems. In this study, we used Na2S2O3·5H2O as the electrolyte for aqueous supercapacitors. Na2S2O3 in Na2S2O3·5H2O can dissolve in crystalline water molecules by itself and the transformation between the solid and liquid states of Na2S2O3·5H2O electrolytes is reversible. The electrolyte based on liquating Na2S2O3 in 5H2O electrolytes has better thermal stability than that based on 2 M Na2S2O3 and 2 M KOH electrolytes. The electrochemical result indicates that the energy storage mechanism of a supercapacitor based on liquating Na2S2O3 in 5H2O leads to a double-layer supercapacitor via Na+ and S2O32− ion adsorption. The self-discharge behavior of the supercapacitor using liquating Na2S2O3 in 5H2O is effectively suppressed by the slow charge redistribution of Na+ and S2O32− ions in solid electrolytes formed from the liquid state. Finally, the supercapacitor using liquating Na2S2O3 in 5H2O has good cycling stability. [ABSTRACT FROM AUTHOR]

Nickel-based metal–organic frameworks (Ni-MOFs) have attracted considerable attention as a potential electrode material for supercapacitors due to their unique structure, high specific surface area, and tuneable electronic and chemical properties. Herein, for the first time an N-trimellitylimido dicarboxylic acid linker is used to develop a novel Ni-MOF material via a simple solvothermal method. The prepared Ni-MOF nanoflakes are characterized using various techniques, including, NMR, XRD, SEM, TEM, and BET. The electrochemical performance of the Ni-MOF nanoflakes was investigated in 3M KOH aqueous electrolyte. The three-electrode measurements disclosed a specific capacity of 21 mA h at 1 A g−1. The supercapacitor achieved an energy density of 11 W h kg−1 and a power density of 6396 W kg−1, highlighting the superior energy storage capability of the Ni-MOF nanoflakes. Moreover, the supercapacitor retained nearly 89% of its capacity even after 3400 cycles, demonstrating good cycling stability and long-term durability. These results indicate that the conductive-layered Ni-MOF nanoflakes are a promising electrode material for practical applications in energy storage systems. [ABSTRACT FROM AUTHOR]

Spinel oxides are promising for high-potential cathode materials of photo-rechargeable batteries. However, LiMn1.5M0.5O4 (M = Mn) shows a rapid degradation during charge/discharge under the illumination of UV-visible light. Here, we investigate various spinel-oxide materials by modifying the composition (M = Fe, Co, Ni, Zn) to demonstrate photocharging in a water-in-salt aqueous electrolyte. LiMn1.5Fe0.5O4 exhibited a substantially higher discharge capacity compared to that of LiMn2O4 after long-term photocharging owing to enhanced stability under illumination. This work provides fundamental design guidelines of spinel-oxide cathode materials for the development of photo-rechargeable batteries. [ABSTRACT FROM AUTHOR]

The development of new catalysts with high selectivity and efficiency for the electrocatalytic nitrate reduction reaction (NtRR) to produce ammonia (NH3) at room temperature and ambient pressure is still a challenge. Herein, we report a simple in situ growth method for the controlled synthesis of a GDY–MnOx heterointerface by selectively anchoring and growing MnOx on GDY surfaces. Experimental results show that the incomplete charge-transfer between GDY and Mn atoms at the interface structures largely increases the number of active sites, improves the electrical conductivity, and therefore results in excellent electrocatalytic performance for NH3 synthesis with a maximum FE of 95.4%, an NH3 yield rate of 463.4 μmol h−1 cm−2 and high long-term stability in 0.1 M KOH + 0.1 M NO3− aqueous electrolytes at room temperature and ambient pressure. [ABSTRACT FROM AUTHOR]

A pH-neutral aqueous organic redox flow battery (AORFB) is one of the most attractive redox flow battery systems due to its non-corrosivity and low-cost as well as a wider electrochemical stability potential window than the acidic and alkaline electrolytes. Herein, by incorporating two quaternary ammonium groups into an anthraquinone nucleus, a water-soluble redox-active molecule, 2,2′-((9,10-dioxo-9,10-dihydroanthracene-1,4-diyl)bis(azanediyl))bis(N,N,N-trimethylethan-1-aminium)dichloride (BDEAQCl2), was achieved that could serve as an anolyte material in pH-neutral AORFBs. The BDEAQCl2 displays a highly negative redox-potential of −0.554 V (vs. SHE) in pH-neutral aqueous electrolytes, rapid electrochemical kinetics and high aqueous-solubility (∼1.2 M in H2O) as well as low permeability. The pH-neutral AORFB with BDEAQCl2 as the anolyte and potassium ferrocyanide as the catholyte yields open-circuit voltage approaching ∼1.04 V. Long-term charge–discharge cycling measurements were conducted to determine the efficiency, capacity, and chemical stability of BDEAQCl2. Post-analysis indicates that BDEAQCl2 undergoes a hydrolytic side reaction during charge–discharge cycling, which is mainly responsible for capacity degradation. [ABSTRACT FROM AUTHOR]

Rechargeable aqueous zinc (Zn)-ion batteries are regarded as a suitable candidate for large-scale energy storage due to their high safety and the natural abundance of Zn. However, the Zn anode in the aqueous electrolyte faces the challenges of corrosion, passivation, hydrogen evolution reaction, and the growth of severe Zn dendrites. These problems severely affect the performance and service life of aqueous Zn ion batteries, making it difficult to achieve their large-scale commercial applications. In this work, the sodium bicarbonate (NaHCO3) additive was introduced into the zinc sulfate (ZnSO4) electrolyte to inhibit the growth of Zn dendrites by promoting uniform deposition of Zn ions on the (002) crystal surface. This treatment presented a significant increase in the intensity ratio of (002) to (100) from an initial value of 11.14 to 15.31 after 40 cycles of plating/stripping. The Zn//Zn symmetrical cell showed a longer cycle life (over 124 h at 1.0 mA cm−2) than the symmetrical cell without NaHCO3. Additionally, the high capacity retention rate was increased by 20% for Zn//MnO2 full cells. This finding is expected to be beneficial for a range of research studies that use inorganic additives to inhibit Zn dendrites and parasitic reactions in electrochemical and energy storage applications. [ABSTRACT FROM AUTHOR]

Vanadium oxide (V2O5) is intercalated by tetrachlorobenzoquinone (TCB) through a one-step solvothermal method in an N-methylpyrrolidone (NMP)/water solvent mixture. The insertion and synergy of TCB and NMP widen the lattice and expand crystal particles, promoting Zn2+ ion transfer and coordination, which endow s-NMP–TCB–V2O5 with an improved capacity of 452 mA h g−1 as well as outstanding capacity retention of 85.6% after 1500 cycles. [ABSTRACT FROM AUTHOR]

The limited mass transfer of CO2 and the competitive hydrogen evolution reaction (HER) during photoelectrochemical (PEC) CO2 reduction usually result in low CO2 reduction activity. Here, we constructed a Cu2O/Sn/PTFE photocathode with a hydrophobic surface based on Cu2O by physical vapor deposition and a dipping method. The CO faradaic efficiency (FE) increased from 34.5% (Cu2O) to 95.1% (Cu2O/Sn/PTFE) at −0.7 V vs. RHE, and the FEH2 decreased from 27.9% (Cu2O) to 3.8% (Cu2O/Sn/PTFE). The introduction of the hydrophobic layer enhances the local CO2 concentration on the electrode surface and effectively isolates H+ from the aqueous electrolyte, thereby enhancing the CO2 reduction activity. [ABSTRACT FROM AUTHOR]