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Electrochemical energy devices serve as a vital link in the mutual conversion between chemical energy and electrical energy. This role positions them to be essential for achieving high-efficiency utilization and advancement of renewable energy. Electrochemical reactions, including anodic and cathodic reactions, play a crucial role in facilitating the connection between two types of charge carriers: electrons circulating within the external circuit and ions transportation within the internal electrolyte, which ensures the completion of the circuit in electrochemical devices. While electrons are uniform, ions come in various types, we herein propose the concept of hybrid electrochemical energy technologies (h-EETs) characterized by the utilization of different ions as charge carriers of anodic and cathodic reactions. Accordingly, this review aims to explore the fundamentals of emerging hybrid electrochemical energy technologies and recent research advancements. We start with the introduction of the concept and foundational aspects of h-EETs, including the proposed definition, the historical background, operational principles, device configurations, and the underlying principles governing these configurations of the h-EETs. We then discuss how the integration of hybrid charge carriers influences the performance of associated h-EETs, to facilitate an insightful understanding on how ions carriers can be beneficial and effectively implemented into electrochemical energy devices. Furthermore, a special emphasis is placed on offering an overview of the research progress in emerging h-EETs over recent years, including hybrid battery capacitors that extend beyond traditional hybrid supercapacitors, as well as exploration into hybrid fuel cells and hybrid electrolytic synthesis. Finally, we highlight the major challenges and provide anticipatory insights into the future perspectives of developing high-performance h-EETs devices.
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Nature seems to favor the formation of closed anion-templated silver clusters. How precisely to create non-closed sliver clusters remains an interesting challenge. In this work, we propose that the use of transition-metal-coordination-cluster substituted polyoxometalates (TMCC-substituted POMs) as templates is an effective synthetic strategy for creating the non-closed silver clusters, as demonstrated by the obtainment of four types of rare non-closed silver cluster species of Ag38-TM (TM = Co, Ni or Zn), Ag37-Zn, {Ag37-Zn}∞ and Ag36-TM (TM = Co, Ni). The idea of the strategy is to employ the TMCC-substituted POMs containing cluster modules with different bond interactions with Ag+ ions as templates to guide the formation of the non-closed silver clusters. For example, TMCC-substituted POM clusters are used as templates in this work, which contain POM modules that can coordinate with the Ag+ ions and TMCC moieties that are difficult to coordinate with the Ag+ ions, leading to the Ag+ ions being unable to form closed clusters around TMCC-substituted POM templates. The work demonstrates a promising approach to developing intriguing and unexplored non-closed silver clusters.
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Atomically precise low-nuclearity (n<10) silver nanoclusters (AgNCs) have garnered significant interest due to their size-dependent optical properties and diverse applications. However, their synthesis has remained challenging, primarily due to their inherent instability. The present study introduces a new feasible approach for clustering silver ions utilizing highly negative and redox-inert polyoxoniobates (PONbs) as all-inorganic ligands. This strategy not only enables the creation of novel Ag-PONb composite nanoclusters but also facilitates the synthesis of stable low-nuclearity AgNCs. Using this method, we have successfully synthesized a small octanuclear rhombic [Ag8]6+ AgNC stabilized by six highly negative [LiNb27O75]14- polyoxoanions. This marks the first PONb-protected superatomic AgNC, designated as {Ag8@(LiNb27O75)6} (Ag8@Nb162), with an aesthetically spherical core-shell structure. The crystalline Ag8@Nb162 is stable under ambient conditions, What's more, it is water-soluble and able to maintain its molecular cluster structure intact in water. Further, the stable small [Ag8]6+ AgNC has interesting temperature- and pH-dependent reversible fluorescence response, based on which a multiple optical encryption mode for anti-counterfeit technology was demonstrated. This work offers a promising avenue for the synthesis of fascinating and stable PONb-protected AgNCs and sheds light on the development of new-type optical functional materials.
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In this work, a novel organodiphosphate-containing inorganic-organic hybrid polyoxoniobate (PONb) ring {(PO3CH2CH2PO3H)4Nb8O16}4- (Nb8P8) has been achieved by a one-pot hydrothermal method. The ring is constructed from a tetragonal {Nb8O36} motif and four {PO3CH2CH2PO3H} ligands. Interestingly, Nb8P8 can be joined together via K-H2O clusters {K2(H2O)4(OH)2} to form one-dimensional chains {[K2(H2O)4(OH)2]Nb8P8}n and further linked by {Cu(en)2}2+ (en = ethylenediamine) complexes, resulting in a three-dimensional supramolecular framework {[Cu(en)2]2[K2(H2O)4(OH)2]Nb8P8}·3en·H2O (1). 1 exhibits good chemical and thermal stability and has a high water vapor adsorption capacity of ≤224 cm3 g-1 (22.71 mol·mol-1) at 298 K, outperforming most of the known polyoxometalate-based materials. Impedance measurements prove that 1 can transfer protons with moderate conductivity. This study not only contributes to the structural diversity of organodiphosphate-containing PONbs and PONb rings but also provides a reference for the development of PONb-based materials with unique performance.
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Rechargeable Zn-air batteries (ZABs) are considered highly competitive technologies for meeting the energy demands of the next generation, whether for energy storage or portable power. However, their practical application is hindered by critical challenges such as low voltage, CO2 poisoning at the cathode, low power density, and poor charging efficiency Herein, a rechargeable hybrid alkali/acid Zn-air battery (h-RZAB) that effectively separates the discharge process in an acidic environment from the charging process in an alkaline environment, utilizing oxygen reduction reaction (ORR) and glycerol oxidation reaction (GOR) respectively is reported. Compared to previously reported ZABs, this proof-of-concept device demonstrates impressive performance, exhibiting a high power density of 562.7 mW cm-2 and a high operating voltage during discharging. Moreover, the battery requires a significantly reduced charging voltage due to the concurrent utilization of biomass-derived glycerol, resulting in practical and cost-effective advantages. The decoupled system offers great flexibility for intermittently generated renewable power sources and presents cost advantages over traditional ZABs. As a result, this technology holds significant promise in opening avenues for the future development of renewable energy-compatible electrochemical devices.
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Inspired by the metal-oxo cluster structural feature and charge separation behaviour of the oxygen evolving center (OEC) in photosystem II (PS-II) under photoirradiation, a new crystalline photochromic polyoxomolybdate, MV2 [ß-Mo8 O26 ] (1, MV=methyl viologen cation), is designed as a biomimetic oxygen evolution reaction (OER) catalyst in neutral electrolytes. After photoinduced electron transfer (PIET) with colour change from colourless to grey, it remains in an ultra-stable charge-separated state over a year under ambient conditions. The observed overpotential at 10â mA â cm-2 and Tafel slope decrease by 49â mV and 62.8â mV â dec-1 after coloration, respectively. The outstanding OER performance of the coloured state in neutral electrolytes even outperforms the commercial RuO2 benchmark. Experimental and theoretical studies show that oxygen holes within polyanions after irradiation serve as sites for enhancing direct O-O coupling, thus effectively promoting OER. This is the first successful application of electron-transfer photochromism to realize OER activity gain.
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A unique heteropolyoxotantalate (hetero-POTa) cluster [P2O7Ta5O14]7- (P2Ta5) was first developed using pyrophosphate as a key to open the ultrastable skeleton of the classical Lindqvist-type [Ta6O19]8- precursor. The P2Ta5 cluster can serve as a general and flexible secondary building unit to create a family of brand-new multidimensional POTa architectures. This work not only promotes the limited structural diversity of hetero-POTa but also provides a practical strategy for new extended POTa architectures.
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Covalent organic frameworks (COFs), thanks to their adjustable porous structure and abundant build-in functional motifs, have been recently regarded as promising electrode materials for a variety of batteries. There still remain grand opportunities to further utilizing their merits for developing advanced COFs-based batteries. In this paper, we propose a hybrid acid/alkali all-COFs battery by coupling pyrene-4,5,9,10-tetraone based COF cathode with anthraquinone based COF anode. In such a hybrid acid/alkali all-COFs battery, the cathodic COF favorably works in acid with a relatively positive potential, while the anodic COF preferably runs in alkali with a relatively negative potential. It thus can deliver a decently high discharge capacity of 92.97â mAh g-1 with a wide voltage window of 2.0â V, and exhibit high energy density of 74.2â Wh kg-1 along with a considerable cyclic stability over 300 cycles. The development of the proof-of-concept all-COFs battery may drive forward the improvement of newly cost-effective and performance-reliable energy storage devices.
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The development of high-efficiency oxygen evolution reaction (OER) electrocatalysts is of great importance for electrolytic H2 generation. In this work, we report in-situ growth of MnCo2O4 nanoneedles and NiFeRu layered double hydroxide (LDH) nanosheets on nickel foam (NF) (MnCo2O4@NiFeRu-LDH/NF) that can function a highly efficient electrode toward electrocatalysis of OER. Such electrode demands an overpotential of as low as 205 mV to reach 10 mA cm-2 in alkaline electrolyte and can run stably over 120-hours continuous operation. A hybrid flow acid/alkali electrolyzer is set up by using the Pt/C as the acidic cathode coupling with the MnCo2O4@NiFeRu-LDH/NF as the alkaline anode, which only requires an applied voltage of 0.59 V and 0.94 V to attain an electrolytic current density of 10 mA cm-2 and 100 mA cm-2, respectively. The present work could push forward the further development of the electricity-saving electrolytic technique for H2 generation.
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Aqueous Zn-based batteries hold multiple advantages of eco-friendliness, easy accessibility, high safety, easy fabrication, and fast kinetics, while their widespread applications have been greatly limited by the relatively narrow thermodynamically stable potential windows (i. e., 1.23â V) of water and the mismatched pH conditions between cathode and anode, which presents challenges regarding how to maximize the output voltage and the energy density. Recently, aqueous OH- /H+ dual-ion Zn-based batteries (OH- /H+ -DIZBs), where the Zn anode reacts with hydroxide ions (OH- ) in alkaline electrolyte while hydrogen ions (H+ ) are involved in the cathode reaction in the acidic electrolyte, have been reported to be capable of broadening the working voltage and improving the energy density, which offers practical feasibility toward overcoming the above limitations. This Review thus takes this chance to investigate the recent progress on aqueous OH- /H+ -DIZBs. First, the concept and the history of such OH- /H+ -DIZBs are introduced, and then special emphasis is put on the working mechanisms, the progress of the development of new batteries, and how the electrolytes improve their performance. Finally, the challenges and opportunities in this field are discussed.
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The development of flexible energy devices is envisaged to revolutionize the next generation of the wearable electronics industry, the practical application yet faces critical issues of low power density, poor cycling stability, and low energy density. Herein, the authors report a newly flexible hybrid Zn-quinone battery (h-ZnQB) with acidic gel in the cathode and alkaline gel in the anode, in which proton (H+ ) and hydroxide ions (OH- ) are served as the ion charge carriers for acidic quinone cathode and alkaline Zn anode. To this end, the nanohybrids of sub-1 nm MoC quantum dots decorating nitrogen-doped ultrathin graphene (MoC QDs/NG) are developed as the advanced cathode electrocatalysts toward redox conversion between quinone and hydroquinone (H2 Q/Q). Comprehensive characterization studies and density functional theory (DFT) calculations reveal that high valent Mo species originating from the size-effects serve as the active sites for the conversion of H2 Q/Q, contributing to the impressive catalytic performance. The as-developed flexible h-ZnQB displays a high open-circuit voltage of 1.74 V with a specific capacity of 223.3 mAh g-1 and an energy density of 350 Wh kg-1 at 0.2 A g-1 , thanks to the fast kinetics of charge carriers (H+ and OH- ), the high activity of the catalyst, and the elaborate design of alkali-acid gel electrolytes.
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The continuously increasing CO2 released from human activities poses a great threat to human survival by fluctuating global climate and disturbing carbon balance among the four reservoirs of the biosphere, earth, air, and water. Converting CO2 to value-added feedstocks via electrocatalysis of the CO2 reduction reaction (CO2RR) has been regarded as one of the most attractive routes to re-balance the carbon cycle, thanks to its multiple advantages of mild operating conditions, easy handling, tunable products and the potential of synergy with the rapidly increasing renewable energy (i.e., solar, wind). Instead of focusing on a special topic of electrocatalysts for the CO2RR that have been extensively reviewed elsewhere, we herein present a rather comprehensive review of the recent research progress, in the view of associated value-added products upon selective electrocatalytic CO2 conversion. We initially provide an overview of the history and the fundamental science regarding the electrocatalytic CO2RR, with a special introduction to the design, preparation, and performance evaluation of electrocatalysts, the factors influencing the CO2RR, and the associated theoretical calculations. Emphasis will then be given to the emerging trends of selective electrocatalytic conversion of CO2 into a variety of value-added products. The structure-performance relationship and mechanism will also be discussed and investigated. The outlooks for CO2 electrocatalysis, including the challenges and opportunities in the development of new electrocatalysts, electrolyzers, the recently rising operando fundamental studies, and the feasibility of industrial applications are finally summarized.
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Aqueous electrochemical devices such as batteries and electrolytic cells have emerged as promising energy storage and conversion systems owing to their environmental friendliness, low cost, and high safety characteristics. However, grand challenges are faced to address some critical issues, including how to enhance the potential window and energy density of electrochemical power devices (e.g. fuel cells, batteries, and supercapacitors), and how to minimize the energy consumption in electrolysis. The use of decoupled acid-base asymmetric electrolytes shows great potential in improving the performance of aqueous devices by electrochemically converting the conventional thermal energy of acid-base neutralization into electricity, i.e., electrochemical neutralization energy (ENE). This review aims to introduce the little-known concept of the ENE, including its development history, thermodynamic fundamentals, operating principles, device configurations, and applications. The recent progress made in ENE-assisted electrochemical energy devices emphasizing fuel cells, batteries, supercapacitors, and electrolytic cells is summarized specifically. Finally, the challenges and future perspectives of ENE associated technology are discussed. It is believed that this tutorial review will give a better understanding of the mechanism and operating principles of the ENE to newcomers, which would shed light on the innovative design and fabrication of ENE-assisted devices and thus pave the way for the development of high-performance aqueous electrochemical energy devices.
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Aqueous rechargeable batteries have attracted attention owning to their advantages of safety, low cost, and sustainability, while the limited electrochemical stability window (1.23â V) of water leads to their failure in competition with organic-based lithium-ion batteries. Herein, we report an alkali-acid Zn-PbO2 hybrid aqueous battery obtained by coupling an alkaline Zn anode with an acidic PbO2 cathode. It shows the capability to deliver an impressively high open-circuit voltage (Voc ) of 3.09â V and an operate voltage of 2.95â V at 5â mA cm-2 , thanks to the contribution of expanding the voltage window and the electrochemical neutralization energy from the alkali-acid asymmetric-electrolyte hybrid cell. The hybrid battery can potentially deliver a large area capacity over 2â mAh cm-2 or a high energy density of 252.39 Wh kg-1 and shows almost no fading in area capacity over 250â charge-discharge cycles.
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It remains great challenge to develop precious-metal-free electrocatalysts to implement high-activity electrochemical conversion of O2 into value-added hydroperoxide species (HO2 - ), which are vulnerable when exposed to various transition-metal-based catalysts. A strategy based on steric hindrance and layered nickel-based layered double hydroxide (Ni-LDH) induction has been developed for one-pot inlaying high-density ultrathin 2 D Ni-LDH chips on inâ situ-grown carbon nanosheets (Ni-LDH C/CNSs). The resulting material exhibits high electrocatalytic selectivity with a faradaic efficiency up to 95 % for oxygen reduction into peroxide and attains a fairly high mass activity of approximately 22.2â A g-1 , outperforming most metal-based catalysts reported previously. Systematic studies demonstrate that the greatly increased defect concentration at Ni edge sites of Ni-LDH chips results in more active sites, which contributes a favorable thermodynamically neutral adsorption of OOH* and adsorbed H2 O2 molecules relatively weakly. Additionally, the modified CNSs effectively suppress H2 O2 decomposition and avoid O-O bond cleavage to produce H2 O by steric effects. The synergistic effect of CNSs and Ni-LDH chips therefore leads to high activity and high selectivity in a two-electron pathway. A proof-of-concept zinc-air fuel cell is proposed and set up to demonstrate the feasibility of green synthesis of peroxide, generating an impressive H2 O2 production rate of 5239.67â mmol h-1 gcat. -1 .
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Although a solar-thermal conversion technique shows great potential for seawater desalination, there remains a grand challenge in exploring low-cost and high-efficiency photothermal materials. We report here a molten salt assisted galvanic replacement method for preparing a hollow black TiAlOx composite, which features a high solar absorptivity with up to 90.2% and has a high efficiency of 71.1% in a high salinity solution containing 15.3 wt% NaCl (â¼5 times more concentrated than seawater). We exemplify the practical application of such hollow black TiAlOx composites as photothermal composites by setting up the automatic and manual tracking of solar desalination devices with a photic area of â¼1.0 m2, which can produce purified water with a rate of above 4.0 L m-2 day-1 in high-salinity water under natural light irradiation, and maintains good stability upon 5 days of continuous running. The advantages of the as-developed hollow black TiAlOx composites, including scalability, low cost, and high photothermal conversion efficiency, may open up a promising avenue practical application in seawater desalination.
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Exploiting effective electrocatalysts toward electrochemical conversion of CO2 into valued-added chemicals is highly desirable for achieving the global carbon cycle. In this work, we report the synthesis of Cu3P/C nanocomposites by phosphatizing the copper-based metal organic framework precursor. Systematic electrochemical characterizations demonstrate the Cu3P/C nanocomposites hold high activity and favorable selectivity towards CO2 reduction reaction (CO2RR) into CO, as manifested by an onset potential is about -0.25 V versus reversible hydrogen electrode (RHE) and a faradic efficiency (FE) of 47% for CO production at a relatively low potential (-0.3 V). The attractive catalytic properties might be attributed to the synergistic effect of cooper and phosphorus elements, as well as the unique structure of Cu3P. Furthermore, we propose an asymmetrical-electrolyte Zn-CO2 battery with the Cu3P/C as cathode catalyst, demonstrating a decent performance with an open-circuit voltage of 1.5 V and a power density of 2.6 mW cm-2 (at 10 mA cm-2).
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An unprecedented asymmetric-electrolyte electrolyzer is proposed using an acidic cathode for the hydrogen evolution reaction (HER) and an alkaline anode for the urea oxidation reaction (UOR), which significantly decreases the electrical energy required for electrolytic hydrogen production.
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An alkaline-acid Zn-H2 O fuel cell is proposed for the simultaneous generation of electricity with an open circuit voltage of about 1.25â V and production of H2 with almost 100 % Faradic efficiency. We demonstrate that, as a result of harvesting energy from both electrochemical neutralization and electrochemical Zn oxidation, the as-developed hybrid cell can deliver a power density of up to 80â mW cm-2 and an energy density of 934â Wh kg-1 and maintain long-term stability for H2 production with an output voltage of 1.16â V at a current density of 10â mA cm-2 .
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A novel OER electrocatalyst, namely oxygen-incorporated amorphous cobalt sulfide porous nanocubes (A-CoS4.6 O0.6 PNCs), show advantages over the benchmark RuO2 catalyst in alkaline/neutral medium. Experiments combining with calculation demonstrate that the desirable O* adsorption energy, associated with the distorted CoS4.6 O0.6 octahedron structure and the oxygen doping, contribute synergistically to the outstanding electrocatalytic activity.