Screening Ultra-Stable (Phenazine)dioxyalkanocic Acids with Varied Water-Solubilizing Chain Lengths for High-Capacity Aqueous Redox Flow Batteries.

Aqueous redox flow batteries (ARFBs) hold great potential for large-scale energy storage. Recently, research on aqueous flow batteries has shifted toward water-soluble organic molecules with redox capabilities to reduce the use of mineral resources. The chemical and electrochemical stabilities of organic compounds are heavily influenced by their functional groups and reaction sites. In this study, we present a low-cost synthesis of the O-alkyl-carboxylate-functionalized derivatives of 2,3-dihydroxyphenazine, namely, phenazine-(2,3-diyl) dioxy dibutyric acid (DBEP) and phenazine-(2,3-diyl)dioxy diacetic acid (DAEP), which serve as negolytes and exhibit good reversibility and high redox kinetics. The evidence is provided to clarify the capacity degradation mechanisms of DAEP and DBEP by a series of comprehensive characterizations. Similar to anthraquinones functionalized with alkyl chains, the main degradation mechanism of DAEP modified with acetic acid is due to side chain loss. Longer side chains are more stable and can withstand long-term electrochemical reactions. DBEP modified with butyric acid exhibits superior chemical and electrochemical stability. Our results demonstrate that rational molecular design and suitable membranes, such as the alkaline ARFBs based on DBEP negolyte, potassium ferrocyanide (K4Fe(CN)6) posolyte, and custom sulfonated poly(ether ether ketone) membrane, can deliver a high open-circuit voltage of 1.17 V and high capacity retention of 99.997% per cycle for over 1000 cycles at 50 mA cm-2. This study highlights the importance of not only considering the modification position of the molecules but also focusing on the influence of various side chains on the redox core's stability toward sustainable grid-scale energy storage applications.

Ternary Eutectic Electrolyte-Assisted Formation and Dynamic Breathing Effect of the Solid-Electrolyte Interphase for High-Stability Aqueous Magnesium-Ion Full Batteries.

Aqueous rechargeable magnesium batteries hold immense potential for intrinsically safe, cost-effective, and sustainable energy storage. However, their viability is constrained by a narrow voltage range and suboptimal compatibility between the electrolyte and electrodes. Herein, we introduce an innovative ternary deep eutectic Mg-ion electrolyte composed of MgCl2·6H2O, acetamide, and urea in a precisely balanced 1:1:7 molar ratio. This formulation was optimized by leveraging competitive solvation effects between Mg2+ ions and two organic components. The full batteries based on this ternary eutectic electrolyte, Mn-doped sodium vanadate (Mn-NVO) anode, and copper hexacyanoferrate cathode exhibited an elevated voltage plateau and high rate capability and showcased stable cycling performance. Ex-situ characterizations unveiled the Mg2+ storage mechanism of Mn-NVO involving initial extraction of Na+ followed by subsequent Mg2+ intercalation/deintercalation. Detailed spectroscopic analyses illuminated the formation of a pivotal solid-electrolyte interphase on the anode surface. Moreover, the solid-electrolyte interphase demonstrated a dynamic adsorption/desorption behavior, referred to as the "breathing effect", which substantially mitigated undesired dissolution and side reactions of electrode materials. These findings underscore the crucial role of rational electrolyte design in fostering the development of a favorable solid-electrolyte interphase that can significantly enhance compatibility between electrode materials and electrolytes, thus propelling advancements in aqueous multivalent-ion batteries.

Rapid and Green Electric-Explosion Preparation of Spherical Indium Nanocrystals with Abundant Metal Defects for Highly-Selective CO2 Electroreduction.

Electrochemical conversion of CO2 into high-value-added chemicals has been considered a promising route to achieve carbon neutrality and mitigate the global greenhouse effect. However, the lack of highly efficient electrocatalysts has limited its practical application. Herein, we propose an ultrafast and green electric explosion method to batch-scale prepare spherical indium (In) nanocrystals (NCs) with abundant metal defects toward high selective electrocatalytic CO2 reduction (CO2RR) to HCOOH. During the electric explosion synthesis process, the Ar atmosphere plays a significant role in forming the spherical In NCs with abundant metal defects instead of highly crystalline In2O3 NCs formed under an air atmosphere. Analysis results reveal that the In NCs possess ultrafast catalytic kinetics and reduced onset potential, which is ascribed to the formation of rich metal defects serving as effective catalytic sites for converting CO2 into HCOOH. This work provides a feasible strategy to massively produce efficient In-based electrocatalysts for electrocatalytic CO2-to-formate conversion.

Interfacial Reduction Nucleation of Noble Metal Nanodots on Redox-Active Metal-Organic Frameworks for High-Efficiency Electrocatalytic Conversion of Nitrate to Ammonia.

Electrochemically converting nitrate to ammonia is a promising route to realize artificial nitrogen recycling. However, developing highly efficient electrocatalysts is an ongoing challenge. Herein, we report the construction of stable and redox-active zirconium metal-organic frameworks (Zr-MOFs) based on Zr6 nanoclusters and redox-reversible tetrathiafulvalene (TTF) derivatives as inorganic nodes and organic linkers, respectively. The redox-active Zr-MOF can facilitate the in situ reduction of noble metal precursors free of external reductants and realize the uniform nucleation of noble metal nanodots (NDs) on Zr-MOF, achieving the preparation of M-NDs/Zr-MOF (M = Pd, Ag, or Au). The highly porous Zr-MOF with good conductivity can facilitate the mass transfer process. Among the M-NDs/Zr-MOF catalysts, Pd-NDs/Zr-MOF exhibits the highest electrocatalytic activity, delivering a NH3 yield of 287.31 mmol·h-1·g-1cat. and a Faradaic efficiency of 58.1%. The proposed interfacial reduction nucleation strategy for anchoring M NDs on Zr-MOFs can be applied to other challenging energy conversion reactions.

Redox-Active Covalent Organic Frameworks with Nickel-Bis(dithiolene) Units as Guiding Layers for High-Performance Lithium Metal Batteries.

Combining the chemistry of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) can bring new opportunities for the design of advanced materials with enhanced tunability and functionality. Herein, we constructed two COFs based on Ni-bis(dithiolene) units and imine bonds, representing a bridge between traditional MOFs and COFs. The Ni-bis(dithiolene)tetrabenzaldehyde as the 4-connected linker was initially synthesized, which was further linked by 4-connected tetra(aminophenyl)pyrene (TAP) or 3-connected tris(aminophenyl)amine (TAA) linkers into two COFs, namely, Ni-TAP and Ni-TAA. Ni-TAP shows a two-dimensional sql network, while TAA is a twofold interpenetrated framework with an ffc topology. They both exhibit a high Brunauer-Emmett-Teller surface area (324 and 689 m2 g-1 for Ni-TAP and Ni-TAA, respectively), a fairly good conductivity (1.57 × 10-6 and 9.75 × 10-5 S m-1 for Ni-TAP and Ni-TAA, respectively), and high chemical stability (a stable pH window of 1-14 for Ni-TAA). When applied in lithium metal batteries as an intermediate layer for guiding the uniform Li electrodeposition, Ni-TAP and Ni-TAA displayed impressive lithiophilicity and high Li-ion conductivity, enabling the achievement of smooth and dense Li deposition with a clear columnar morphology and stable Li plating/stripping behaviors with high Li utilization, which is anticipated to pave the way to upgrade Li metal anodes for application in high-energy-density battery systems.

Batch-Scale Synthesis of Nanoparticle-Agminated Three-Dimensional Porous Cu@Cu2O Microspheres for Highly Selective Electrocatalysis of Nitrate to Ammonia.

The electrochemical nitrate reduction reaction (NITRR), which converts nitrate to ammonia, is promising for artificial ammonia synthesis at mild conditions. However, the lack of favorable electrocatalysts has hampered its large-scale applications. Herein, we report the batch-scale synthesis of three-dimensional (3D) porous Cu@Cu2O microspheres (Cu@Cu2O MSs) composed of fine Cu@Cu2O nanoparticles (NPs) using a convenient electric explosion method with outstanding activity and stability for the electrochemical reduction of nitrate to ammonia. Density functional theory (DFT) calculations revealed that the Cu2O (111) facets could facilitate the formation of *NO3H and *NO2H intermediates and suppress the hydrogen evolution reaction (HER), resulting in high selectivity for the NITRR. Moreover, the 3D porous structure of Cu@Cu2O MSs facilitates electrolyte penetration and increases the localized concentration of reactive species for the NITRR. As expected, the obtained Cu@Cu2O MSs exhibited an ultrahigh NH3 production rate of 327.6 mmol·h-1·g-1cat. (which is superior to that of the Haber-Bosch process with a typical NH3 yield <200 mmol h-1g-1cat.), a maximum Faradaic efficiency of 80.57%, and remarkable stability for the NITRR under ambient conditions. Quantitative 15N isotope labeling experiments indicated that the synthesized ammonia originated from the electrochemical reduction of nitrate. Achieving the batch-scale and low-cost production of high-performance Cu@Cu2O MSs electrocatalysts using the electric explosion method is promising for the large-scale realization of selective electrochemical reduction of nitrate toward artificial ammonia synthesis.

Visual/CVG-AFS/ICP-MS multi-mode and label-free detection of target nucleic acids based on a selective cation exchange reaction and enzyme-free strand displacement amplification.

Conventional atomic spectrometry biosensors usually require labeling and separation of signaling molecules. Visual assays have direct and effective characteristics; however, they have poor accuracy. We intended to improve the analytical performance of our previous work and simplify the experimental operation while maintaining the advantages of simple operation and low cost. Herein, we describe the development of a visual, chemical vapor generation-atomic fluorescence spectrometry (CVG-AFS) and inductively coupled plasma-mass spectrometry (ICP-MS) three-mode method for the analysis of nucleic acids via CdTe quantum dot (QD)-assisted selective cation exchange reaction and enzyme-free strand displacement amplification. This work mainly utilized the ability of CdTe QDs to selectively differentiate free Hg2+ from the T-Hg2+-T complex in addition to the simple selective membrane filtration separation of Cd2+ from CdTe QDs to improve the performance of label-free bioassay methods. Due to the superior optical features of CdTe QDs, they can not only be used as a signal molecule for atomic spectroscopy, but also for direct use in visual readings. Under optimal experimental conditions, the developed strategy displayed a wide linear range along with limits of detection (LODs) of 10 fM and 3 fM (2 fM) in the linear concentration ranges of 10 fM-100 pM and 10 fM-1 nM with the naked eye and CVG-AFS (ICP-MS) assays, respectively. This method also exhibited excellent DNA sequence specificity. This assay had advantageous characteristics such as an easy operation, simple design, high sensitivity, and diversified signal readout manner, which demonstrate its great potential in medical diagnosis applications.

Target-promoted specific activation of m6A-DNAzyme for SPEXPAR-amplified and highly sensitive non-label electrochemical assay of FTO demethylase.

The demethylase of fat mass and obesity related protein (FTO) is critical to regulate the dynamic N6-methyladenosine (m6A) modification of eukaryotic mRNAs, and its overexpression has found to be closely related to the initiation of several cancers. On the basis of a target-promoted specific activation of DNAzyme strategy coupled with self-primer exponential amplification reaction (SPEXPAR) cycles and DNA supersandwich assemblies, the highly sensitive and label-free electrochemical FTO assay approach is established. The modification of the catalytic core nucleobase of the DNAzyme probe by m6A can inhibit its cleavage activity. The presence of target FTO catalyzes the elimination of the methyl group to restore the DNAzyme activity, which cleaves the hairpin substrates to trigger the SPEXPAR for yielding many ssDNAs. The capture of these DNAs on the sensor electrode leads to the initiation of supersandwich assembly formation of long dsDNAs. Tremendous electrochemical signal probe of [Ru(NH3)6]Cl3 are then absorbed on these dsDNAs to produce highly amplified catalytic currents with the assistance of K3[Fe(CN)6] for detecting trace FTO with 63.1 fM detection limit. Furthermore, the sensor can be employed for selective assay of FTO in cell lysates, revealing the great potential of this sensing strategy for biomedical and biological study applications.

Electrochemical label-free biomolecular logic gates regulated by distinct inputs.

In current work, with elaborate designs of G-quadruplex containing "Y" junction structures, we demonstrate the construction of several new and label-free electrochemical logic gate operations (OR, AND, NOR, and NAND) by defining two distinct biomolecules, human 8-oxo-7,8-dihydroguanine DNA glycosylase 1 (hOGG1) and microRNA-141 (miRNA-141), as the inputs. The "Y" junction structures are immobilized onto the surface of gold electrode as the signal transduction platform. The presence of the input molecules with different combinations can alter the "Y" junction structures to disrupt the formation of the complete G-quadruplexes via 8-oxoG-site specific cleavage and miRNA-141-triggered displacement of the "Y" junctions. Subsequent association of hemin with the G-quadruplex sequences thus yields significant current variation outputs upon electrochemical reduction of hemin on the electrode, leading to the successful function of different logic operations without the involvement of labeling the DNA sequences with electro-active species. Featured with the advantages of multiple logic operations with distinct inputs and the label-free electrochemical format, such molecular logic gates can potentially provide promising opportunities for the development of simple and robust biological logic gates for various applications.

Apamer-based sensitive and label-free electrochemical detection of neutrophil gelatinase-associated lipocalin via recycling amplification cascades.

Sensitive and selective detection of neutrophil gelatinase-associated lipocalin (NGAL) is critical for the prediction and early diagnosis of acute renal injury. In this work, the establishment of an aptamer-based, highly sensitive and label-free method for detecting NGAL in diluted human serums via metal ion-dependent DNAzyme- and exonuclease III (Exo III)-triggered recycling signal amplification cascades is described. NGAL binds with the aptamer strands in the DNAzyme/aptamer duplexes and results in the liberation of the metal ion-dependent DNAzyme sequences to cleave the hairpin signal probes on the electrode to liberate the G-quadruplex and intermediate strands. The released intermediate strands further complement with the DNAzyme/aptamer duplexes to form favorable substrate for Exo III, which digests the duplexes to release the DNAzyme strands to initiate the cascaded recycling cycles for the yield of plenty of G-quadruplex strands. Hemin can associate with G-quadruplex strands to produce many G-quadruplex/hemin complexes and electrochemical reduction of hemin thus generates highly amplified current for detecting NGAL with the detection limit of 4.45 ng mL-1. Such biosensor also shows high selectivity and can be utilized for monitoring NGAL spiked in diluted serum, indicating its extension potential for detecting various protein biomarkers with different aptamers for disease diagnosis.

Crystalline Modulation Engineering of Ru Nanoclusters for Boosting Ammonia Electrosynthesis from Dinitrogen or Nitrate.

Developing highly efficient nitrogen reduction reaction (NRR) and nitrate reduction reaction (NITRR) electrocatalysts is an ongoing challenge. Herein, we report the in situ growth of ultrafine amorphous Ru nanoclusters with a uniform diameter of ∼1.2 nm on carbon nanotubes as a highly efficient electrocatalyst for both the NRR and the NITRR. The amorphous Ru nanoclusters were prepared via a convenient ambient chelated co-reduction method, in which trisodium citrate as a chelating agent played a key role to form amorphous Ru instead of crystalline Ru. The strong d-π interaction between Ru metal and carbon nanotubes led to the homogeneous distribution and good long-term stability of ultrafine Ru nanoclusters. Compared with crystalline Ru, amorphous Ru nanoclusters with abundant low-coordinate atoms can provide more catalytic sites. The amorphous Ru nanoclusters exhibited an NH3 yield of 10.49 µg·h-1·mgcat.-1 and a FENH3 of 17.48% at -0.2 V vs reversible hydrogen electrode (RHE) for NRR. For the NITRR, an NH3 yield of 145.1 µg·h-1·mgcat.-1 and a FENH3 of 80.62% were also achieved at -0.2 V vs RHE. This work provides new insights into crystalline modulation engineering of metal nanoclusters for electrocatalytic ammonia synthesis.

Cooperative Cationic and Anionic Redox Reactions in Ultrathin Polyvalent Metal Selenide Nanoribbons for High-Performance Electrochemical Magnesium-Ion Storage.

Rechargeable magnesium batteries (RMBs) are considered as potential energy storage devices due to their high volumetric specific capacity, good safety, as well as source abundance. Despite extensive efforts devoted to constructing an efficient magnesium battery system, the sluggish Mg2+ diffusion in conventional cathode materials often leads to slow rate kinetics, low capacity, and poor cycling lifespan. Although transition metal selenides with soft anion frameworks have attracted extensive attention, their Mg2+ storage mechanism still needs to be clarified. Herein, we demonstrate that the ultrathin CoSe2 nanoribbons can be used as a robust cathode material for RMBs and reveal a novel Mg2+ storage mechanism based on cooperative cationic (Co) and anionic (Se) redox processes via systematic ex-situ characterizations. Compared to other metal selenide cathodes based on conversion reactions of solely metal cations, the cooperative cationic-anionic redox reactions of the CoSe2 cathode contribute to obtaining an enhanced specific capacity and boosted electrochemical kinetics. Moreover, on one hand, the ultrathin nanoribbon structure enables effective contact between the electrode material and electrolyte and on the other hand significantly reduces the length and time consumption of Mg2+ diffusion, leading to dominated surface-driven capacitance-controlled Mg2+ storage behavior and rapid Mg2+ storage kinetics. As a result, the ultrathin CoSe2 nanoribbon cathode exhibits a reversible discharge capacity of ∼130 mAh g-1 at 100 mA g-1, good rate capability (116 mAh g-1 at 300 mA g-1), and long cyclability over 600 cycles. This finding confirms the development potentiality of polyvalent metal selenide cathode materials based on a cooperative cationic-anionic redox mechanism for the construction of next-generation multivalent secondary batteries.