Publication on 2D research

Stereodivergent, Kinetically Controlled Isomerization of Terminal Alkenes via Nickel Catalysis

2024-03-18T13:09:30+00:00March 18th, 2024|Categories: Publications|

Because internal alkenes are more challenging synthetic targets than terminal alkenes, metal-catalyzed olefin mono-transposition (i.e., positional isomerization) approaches have emerged to afford valuable E- or Z- internal alkenes from their complementary terminal alkene feedstocks. However, the applicability of these methods has been hampered by lack of generality, commercial availability of precatalysts, and scalability. Here, we report a nickel-catalyzed platform for the stereodivergent E/Z-selective synthesis of internal alkenes at room temperature. Commercial reagents enable this one-carbon transposition of terminal alkenes to valuable E- or Z-internal alkenes via a Ni–H-mediated insertion/elimination mechanism. Though the mechanistic regime is the same in both systems, the underlying pathways that lead each of the active catalysts are distinct, with the Z-selective catalyst forming from comproportionation of an oxidative addition complex followed by oxidative addition with substrate and the E-selective catalyst forming from protonation of the metal by the trialkylphosphonium salt additive. In each case, ligand sterics and denticity control stereochemistry and prevent over-isomerization.

Published in: "Angewandte Chemie International Edition".

Upcycling of Carbon Fiber/Thermoset Composites into High‐Performance Elastomers and Repurposed Carbon Fibers

2024-03-16T13:08:01+00:00March 16th, 2024|Categories: Publications|Tags: |

Recycling of carbon fiber-reinforced polymer composites (CFRCs) based on thermosetting plastics is difficult. In the present study, high-performance CFRCs are fabricated through complexation of aromatic pinacol-cross-linked polyurethane (PU-AP) thermosets with carbon fiber (CF) cloths. PU-AP thermosets exhibit a breaking strength of 95.5 MPa and toughness of 473.6 MJ m-3 and contain abundant hydrogen-bonding groups, which can have strong adhesion with CFs. Because of the high interfacial adhesion between CF cloths and PU-AP thermosets and high toughness of PU-AP thermosets, CF/PU-AP composites possess a high tensile strength of >870 MPa. Upon heating in N,N-dimethylacetamide (DMAc) at 100 °C, the aromatic pinacols in the CF/PU-AP composites can be cleaved, generating non-destructive CF cloths and linear polymers that can be converted to high-performance elastomers. The elastomers are mechanically robust, healable, reprocessable, and damage-resistant with an extremely high tensile strength of 74.2 MPa and fracture energy of 149.6 kJ m-2. As a result, dissociation of CF/PU-AP composites enables the recovery of reusable CF cloths and high-performance elastomers, thus realizing the upcycling of CF/PU-AP composites.

Published in: "Angewandte Chemie International Edition".

Vinyl‐Groups‐Anchored Covalent Organic Framework for Promoted Photocatalytic Hydrogen Peroxide Generation

2024-03-16T13:07:59+00:00March 16th, 2024|Categories: Publications|Tags: |

Artificial photosynthesis of H2O2 from water and oxygen using semiconductor photocatalysts has attracted growing attention because of its green, environmentally friendly, and energy-saving characteristics. Although covalent organic frameworks (COFs) are promising materials for photocatalytic H2O2 production by virtue of their structural and functional diversities, they typically suffer from low charge generation and transfer efficiency as well as rapid charge recombination, which restricts their uses as catalysts for photocatalytic H2O2 production seriously. Herein, we report a strategy for anchoring the vinyl moieties into the skeleton of a COF to facilitate charge separation and migration, thus promoting photocatalytic H2O2 generation. This vinyl group-bearing COF photocatalyst demonstrates a H2O2 production rate of 84.5 µmol h−1 (per 10 mg), which is ten times higher than its analogue without vinyl functionating and superior to most reported COF photocatalysts. Both experimental and theoretical studies have provided deep insights into the origin of the improved photocatalytic performance. Such findings may facilitate the rational design and modification of organic semiconductors for photocatalytic applications.

Published in: "Angewandte Chemie International Edition".

Interfacial Engineering for Oriented Crystal Growth toward Dendrite‐Free Zn Anode for Aqueous Zinc Metal Battery

2024-03-16T13:07:56+00:00March 16th, 2024|Categories: Publications|Tags: |

Zn deposition with a surface-preferred (002) crystal plane has attracted extensive attention due to its inhibited dendrite growth and side reactions. However, the nucleation and growth of the Zn(002) crystal plane are closely related to the interfacial properties. Herein, oriented growth of Zn(002) crystal plane is realized on Ag-modified surface that is directly visualized by in situ atomic force microscopy. A solid solution HCP-Zn (~1.10 at.% solubility of Ag, 30 °C) is formed on the Ag coated Zn foil (Zn@Ag) and possesses the same crystal structure as Zn to reduce its nucleation barrier caused by their lattice mismatch. It merits oriented Zn deposition and corrosion-resistant surface, and presents long cycling stability in symmetric cells and full cells coupled with V2O5 cathode. This work provides insights into interfacial regulation of Zn anodes for high-performance aqueous zinc metal batteries.

Published in: "Angewandte Chemie International Edition".

How to Deal with Charge in the Ranking of Lewis Acidity: Critical Evaluation of an Extensive Set of Cationic Lewis Acids

2024-03-15T13:08:11+00:00March 15th, 2024|Categories: Publications|

The quantification of Lewis acidity is of fundamental and applied importance in chemistry. However, if neutral and charged Lewis acids are compared, a coherent ranking has been elusive, and severe uncertainties were accepted. With this study, we present a systematic computational analysis of Lewis base affinities of 784 mono-, di- and tricationic Lewis acids and their comparison with 149 representative neutral Lewis acids. Evaluating vacuum fluoride ion affinities (FIA) reveals a charge-caused clustering that prohibits any meaningful ranking. Instead, solvation-corrected FIAsolv is identified as a metric that overcomes charge sensitivity in a balanced manner, allowing for a coherent evaluation of Lewis acidity across varying charge states. Analyzing the impact of molecular volume on solvation-induced FIA damping provides rationales for fundamental trends and guidelines for the choice or design of neutral and cationic Lewis acids in the condensed phase. Exploring alternative scales, explicit counteranion effects, and selected experimental case studies reaffirms the advantages of solvation-corrected FIAsolv as the most versatile and practical approach for the quantitative ranking of general (thermodynamic) Lewis acidity.

Published in: "Angewandte Chemie International Edition".

Heterodyne‐Detected Sum‐Frequency Generation Vibrational Spectroscopy Reveals Aqueous Molecular Structure at the Suspended Graphene/Water Interface

2024-03-15T13:08:09+00:00March 15th, 2024|Categories: Publications|Tags: , |

Graphene, a transparent two-dimensional conductive material, has brought extensive new perspectives and prospects to various aqueous technological systems, such as desalination membranes, chemical sensors, energy storage, and energy conversion devices. Yet, the molecular-level details of graphene in contact with aqueous electrolytes, such as water orientation and hydrogen bond structure, remain elusive or controversial. Here, we employ surface-specific heterodyne-detection sum-frequency generation (HD-SFG) vibrational spectroscopy to re-examine the water molecular structure at a freely suspended graphene/water interface. We compare the response from the air/graphene/water system to that from the air/water interface. Our results indicate that the χ(2)yyz spectrum recorded from the air/graphene/water system arises from the topmost 1-2 water layers in contact with the graphene, with the graphene itself not generating a significant SFG response. Compared to the air/water interface response, the presence of monolayer graphene weakly affects the interfacial water. Graphene weakly affects the dangling O-H group, lowering its frequency through its interaction with the graphene sheet, and has a small effect on the hydrogen-bonded O-H group. Molecular dynamics simulations confirm our experimental observation. Our work provides molecular insight into the interfacial structure at a suspended graphene/water interface, relevant to various technological applications of graphene.

Published in: "Angewandte Chemie International Edition".

Self‐Adaptive Aromatic Cation–π Driven Dimensional Polymorphism in Supramolecular Polymers for the Photocatalytic Oxidation and Separation of Aromatic/Cyclic Aliphatic Compounds

2024-03-15T13:08:07+00:00March 15th, 2024|Categories: Publications|

The phenomenon of polymorphism is ubiquitous in nature, the controlled manipulation of which not only increases our ontological understanding of nature but also facilitates the conceptualization and realization of novel functional materials. However, achieving targeted polymorphism in supramolecular assemblies (SAs) remains a formidable challenge, largely because of the constraints inherent in controlling the specific binding motifs of noncovalent interactions. Herein, we propose self-adaptive aromatic cation–π binding motifs to construct polymorphic SAs in both the solid and solution states. Using distinct discrete cation–π–cation and long-range cation–π binding motifs enables control of the self-assembly directionality of a C2h-symmetric bifunctional monomer, resulting in the successful formation of both two-dimensional and three-dimensional crystalline SAs (2D-CSA and 3D-CSA). The differences in the molecular packing of 3D-CSA compared with that of 2D-CSA significantly improve the charge separation and carrier mobility, leading to enhanced photocatalytic activity for the aerobic oxidation of thioanisole to methyl phenyl sulfoxide (yield of 99% vs 57%). 2D-CSA, which has a vertical extended structure with favorable stronger interaction with toluene though face-to-face cation–π interactions than methylcyclohexane, shows higher toluene/methylcyclohexane separation efficiency than 3D-CSA (96.9% for 2D-CSA vs 56.3% for 3D-CSA).

Published in: "Angewandte Chemie International Edition".

Large Organic Polar Molecules Tailored Electrode Interfaces for Stable Lithium Metal Battery

2024-03-15T13:08:05+00:00March 15th, 2024|Categories: Publications|Tags: |

Lithium (Li) metal batteries (LMBs) are deemed as ones of the most promising energy storage devices for next electrification applications. However, the uneven Li electroplating process caused by the diffusion-limited Li+ transportation at the Li metal surface inherently promotes the formation of dendritic morphology and instable Li interphase, while the sluggish Li+ transfer kinetic can also cause lithiation-induced stress on the cathode materials suffering from serious structural stability. Herein, a novel electrolyte designing strategy is proposed to accelerate the Li+ transfer by introducing a trace of large organic polar molecules of lithium phytate (LP) without significantly altering the electrolyte structure. The LP molecules can afford a competitive solvent attraction mechanism against the solvated Li+, enhancing both the bulk and interfacial Li+ transfer kinetic, and creating better anode/cathode interfaces to suppress the side reactions, resulting in much improved cycling efficiency of LMBs. Using LP-based electrolyte, the performance of LMB pouch cell with a practical capacity of ~1.5 Ah can be improved greatly. This strategy opens up a novel electrolyte designing route for reliable LMBs.

Published in: "Angewandte Chemie International Edition".

Dynamic‐bond‐mediated Chain Reptation Enhances Energy Dissipation of Elastomers

2024-03-13T13:08:09+00:00March 13th, 2024|Categories: Publications|Tags: |

Vibrations with various frequencies in daily life and industry can cause health hazards and fatigue failure of critical structures, which requires the development of elastomers with high energy dissipation at desired frequencies. Current strategies relying on tuning characteristic relaxation time of polymer chains are mostly qualitative empirical methods, and it is difficult to precisely control damping performances. Here, we report a general strategy for constructing dynamic crosslinked polymer fluid gels that provide controllable ultrahigh energy dissipation. This is realized by dynamic-bond-mediated chain reptation of polymer fluids in a crosslinked network, where the characteristic time of chain reptation is dominated by the presence of well-defined dissociation time of dynamic bonds and almost independent of their molar mass. Using prototypical supramolecular polydimethylsiloxane elastomers, we demonstrate that dynamic crosslinked polymer fluid gels exhibit a controllable ultrahigh damping performance at desired frequencies (10^-2 ~ 10^2 Hz), exceeding that of typical state-of-the-art silicone damping materials. Their shock absorption is over 300% higher than that of commercial silicone rubber under the same impact force.

Published in: "Angewandte Chemie International Edition".

Solvation‐tailored PVDF‐based Solid‐state Electrolyte for High‐voltage Lithium Metal Batteries

2024-03-13T13:08:06+00:00March 13th, 2024|Categories: Publications|

Poly(vinylidene fluoride) (PVDF)-based polymer electro-lytes are attracting increasing attention for high-voltage solid-state lithium metal batteries because of their high room temperature ionic conductivity, adequate mechanical strength and good thermal stability. However, the presence of highly reactive residual solvents, such as N, N-dimethylformamide (DMF), severely jeopardizes the long-term cycling stability. Herein, we propose a solvation-tailoring strategy to confine residual solvent molecules by introducing low-cost 3 Å zeolite molecular sieves as fillers. The strong interaction between DMF and the molecular sieve weakens the ability of DMF to participate in the solvation of Li+, leading to more anions being involved in solvation. Benefiting from the tailored anion-rich coordination environment, the interfacial side reactions with the lithium anode and high-voltage NCM811 cathode are effectively suppressed. As a result, the solid-state Li||Li symmetrical cells demonstrates ultra-stable cycling over 5100 h at 0.1 mA cm−2, and the Li||NCM811 full cells achieve excellent cycling stability for more than 1130 and 250 cycles under the charging cut-off voltages of 4.3 V and 4.5 V, respectively. Our work is an innovative exploration to address the negative effects of residual DMF in PVDF-based solid-state electrolytes and highlights the importance of modulating the solvation structures in solid-state polymer electrolytes.

Published in: "Angewandte Chemie International Edition".

Photoluminescence Quenching of Hydrophobic Ag29 Nanoclusters Caused by Molecular Decoupling during Aqueous Phase Transfer and EmissionRecovery through Supramolecular Recoupling

2024-03-12T13:10:22+00:00March 12th, 2024|Categories: Publications|

This work presents the phase transfer of hydrophobic clusters into the aqueous phase with maintained emission intensities via the supramolecular recoupling of emissive Ag29 nanoclusters with atomic precision. Abstract Exploiting emissive hydrophobic nanoclusters for hydrophilic applications remains a challenge because of photoluminescence (PL) quenching during phase transfer. In addition, the mechanism underlying PL quenching remains unclear. In this study, the PL-quenching mechanism was examined by analyzing the atomically precise structures and optical properties of a surface-engineered Ag29 nanocluster with an all-around-carboxyl-functionalized surface. Specifically, phase-transfer-triggered PL quenching was justified as molecular decoupling, which directed an unfixed cluster surface and weakened the radiative transition. Furthermore, emission recovery of the quenched nanoclusters was accomplished by using a supramolecular recoupling approach through the glutathione-addition-induced aggregation of cluster molecules, wherein the restriction of intracluster motion and intercluster rotation strengthened the radiative transition of the clusters. The results of this work offer a new perspective on structure-emission correlations for atomically precise nanoclusters and hopefully provide insight into the fabrication of highly emissive cluster-based nanomaterials for downstream hydrophilic applications.

Published in: "Angewandte Chemie International Edition".

Empowering Site‐Specific Bioconjugations In Vitro and In Vivo: Advances in Sortase Engineering and Sortase‐Mediated Ligation

2024-03-12T13:10:21+00:00March 12th, 2024|Categories: Publications|

Sortase-mediated ligation (SML) is extensively employed in site-specific bioconjugations. This review presents an overview of recent advancements in sortase engineering and the resulting innovative in vitro and in vivo SML applications. Moreover, we explore the potential future impact of integrating SML with cutting-edge techniques, such as click chemistry, unnatural amino acid incorporation, and CRISPR-Cas9, for interdisciplinary research. Abstract Sortase-mediated ligation (SML) has emerged as a powerful and versatile methodology for site-specific protein conjugation, functionalization/labeling, immobilization, and design of biohybrid molecules and systems. However, the broader application of SML faces several challenges, such as limited activity and stability, dependence on calcium ions, and reversible reactions caused by nucleophilic side-products. Over the past decade, protein engineering campaigns and particularly directed evolution, have been extensively employed to overcome sortase limitations, thereby expanding the potential application of SML in multiple directions, including therapeutics, biorthogonal chemistry, biomaterials, and biosensors. This review provides an overview of achieved advancements in sortase engineering and highlights recent progress in utilizing SML in combination with other state-of-the-art chemical and biological methodologies. The aim is to encourage scientists to employ sortases in their conjugation experiments.

Published in: "Angewandte Chemie International Edition".

Unlocking Four‐electron Conversion in Tellurium Cathodes for Advanced Magnesium‐based Dual‐ion Batteries

2024-03-12T13:10:18+00:00March 12th, 2024|Categories: Publications|Tags: |

Magnesium (Mg) batteries hold promise as a large-scale energy storage solution, but their progress has been hindered by the lack of high-performance cathodes. Here, we address this challenge by unlocking the reversible four-electron Te0/Te4+ conversion in elemental Te, enabling the demonstration of superior Mg//Te dual-ion batteries. Specifically, the classic magnesium aluminum chloride complex (MACC) electrolyte is tailored by introducing Mg bis(trifluoromethanesulfonyl)imide (Mg(TFSI)2), which initiates the Te0/Te4+ conversion with two distinct charge-storage steps. Te cathode undergoes Te/TeCl4 conversion involving Cl– as charge carriers, during which a tellurium subchloride phase is presented as an intermediate. Significantly, the Te cathode achieves a high specific capacity of 543 mAh gTe–1 and an outstanding energy density of 850 Wh kgTe–1, outperforming most of the previously reported cathodes. Our electrolyte analysis indicates that the addition of Mg(TFSI)2 reduces the overall ion-molecule interaction and mitigates the strength of ion-solvent aggregation within the MACC electrolyte, which implies the facilized Cl– dissociation from the electrolyte. Besides, Mg(TFSI)2 is verified as an essential buffer to mitigate the corrosion and passivation of Mg anodes caused by the consumption of the electrolyte MgCl2 in Mg//Te dual-ion cells. These findings provide crucial insights into the development of advanced Mg-based dual-ion batteries.

Published in: "Angewandte Chemie International Edition".

Catalytic Mechanism of Fatty Acid Photodecarboxylase: on the Detection and Stability of the Initial Carbonyloxy Radical Intermediate

2024-03-12T13:10:16+00:00March 12th, 2024|Categories: Publications|

In fatty acid photodecarboxylase (FAP), light-induced formation of the primary radical product RCOO● from fatty acid RCOO– occurs in 300 ps, upon which CO2 is released quasi-immediately. Based on the hypothesis that aliphatic RCOO● (spectroscopically uncharacterized because unstable) absorbs in the red similarly to aromatic carbonyloxy radicals such as 2,6‑dichlorobenzoyloxy radical (DCB●), much longer-lived linear RCOO● has been suggested recently. We performed quantum chemical reaction pathway and spectral calculations. These calculations are in line with the experimental DCB● decarboxylation dynamics and spectral properties and show that in contrast to DCB●, aliphatic RCOO● radicals a) decarboxylate with a very low energetic barrier and on the timescale of a few ps and b) exhibit little red absorption. A time-resolved infrared spectroscopy experiment confirms very rapid,

Published in: "Angewandte Chemie International Edition".

Dynamic Molecular Interphases Regulated by Trace Dual Electrolyte Additives for Ultralong‐Lifespan and Dendrite‐Free Zinc Metal Anode

2024-03-12T13:10:11+00:00March 12th, 2024|Categories: Publications|

Metallic zinc is a promising anode material for rechargeable aqueous multivalent metal-ion batteries due to its high capacity and low cost. However, the practical use is always beset by severe dendrite growth and parasitic side reactions occurring at anode/electrolyte interface. Here we demonstrate that dynamic molecular interphases caused by trace dual electrolyte additives of D-mannose and sodium lignosulfonate for ultralong-lifespan and dendrite-free zinc anode. Triggered by plating and stripping electric fields, the D-mannose and lignosulfonate species are alternately and reversibly (de-)adsorbed on Zn metal, respectively, to accelerate Zn2+ transportation for uniform Zn nucleation and deposition and inhibit side reactions for high coulombic efficiency. As a result, Zn anode in such dual-additive electrolyte exhibits highly reversible and dendrite-free Zn stripping/plating behaviors for >6400 hours at 1 mA cm−2, which enables long-term cycling stability of Zn||ZnxMnO2 full cell for more than 2000 cycles.

Published in: "Angewandte Chemie International Edition".

Electrochemical CO2 Activation and Valorization on Metallic Copper and Carbon‐Embedded N‐Coordinated Single Metal MNC Catalysts

2024-03-12T13:10:04+00:00March 12th, 2024|Categories: Publications|Tags: |

The electrochemical reductive valorization of CO2, referred to as the CO2RR, is an emerging approach for the conversion of CO2-containing feeds into valuable carbonaceous fuels and chemicals, with potential contributions to carbon capture and use (CCU) for reducing greenhouse gas emissions. Copper surfaces and graphene-embedded, N-coordinated single metal atom (MNC) catalysts exhibit distinctive reactivity, attracting attention as efficient electrocatalysts for CO2RR. This review offers a comparative analysis of CO2RR on copper surfaces and MNC catalysts, highlighting their unique characteristics in terms of CO2 activation, C1/C2(+) product formation, and the competing hydrogen evolution pathway. The assessment underscores the significance of understanding structure-activity relationships to optimize catalyst design for efficient and selective CO2RR. Examining detailed reaction mechanisms and structure-selectivity patterns, the analysis explores recent insights into changes in the chemical catalyst states, atomic motif rearrangements, and fractal agglomeration, providing essential kinetic information from advanced in/ex-situ microscopy/spectroscopy techniques. At the end, this review addresses future challenges and solutions related to today’s disconnect between our current molecular understanding of structure-activity-selectivity relations in CO2RR and the relevant factors controlling the performance of CO2 electrolyzers over longer times, at larger electrode sizes, and at higher current densities.

Published in: "Angewandte Chemie International Edition".

CO‐Induced Dimer Decay Responsible for Gem‐Dicarbonyl Formation on a Model Single‐Atom Catalyst

2024-03-08T13:08:20+00:00March 8th, 2024|Categories: Publications|

Time-lapse scanning tunneling microscopy movies are combined with theoretical computations to study CO adsorption on a model Rh1/Fe3O4(001) catalyst under ultrahigh vacuum conditions. Direct CO adsorption at Rh1 sites results in monocarbonyl species. Rh1−(CO)2 gem dicarbonyl species are observed, but from only via the CO-induced break-up of Rh2 dimer species. Abstract The ability to coordinate multiple reactants at the same active site is important for the wide-spread applicability of single-atom catalysis. Model catalysts are ideal to investigate the link between active site geometry and reactant binding, because the structure of single-crystal surfaces can be precisely determined, the adsorbates imaged by scanning tunneling microscopy (STM), and direct comparisons made to density functional theory. In this study, we follow the evolution of Rh1 adatoms and minority Rh2 dimers on Fe3O4(001) during exposure to CO using time-lapse STM at room temperature. CO adsorption at Rh1 sites results exclusively in stable Rh1CO monocarbonyls, because the Rh atom adapts its coordination to create a stable pseudo-square planar environment. Rh1(CO)2 gem-dicarbonyl species are also observed, but these form exclusively through the breakup of Rh2 dimers via an unstable Rh2(CO)3 intermediate. Overall, our results illustrate how minority species invisible to area-averaging spectra can play an important role in catalytic systems, and show that the decomposition of dimers or small clusters can be an avenue to produce reactive, metastable configurations in single-atom catalysis.

Published in: "Angewandte Chemie International Edition".

Fabrication of Self‐Expanding Metal–Organic Cages Using a Ring‐Openable Ligand

2024-03-08T13:08:19+00:00March 8th, 2024|Categories: Publications|

Metal–organic cages (MOCs), which are formed via coordination-driven assembly, are being extensively developed for various applications owing to the utility of their accessible molecular-sized cavity. While MOC structures are uniquely and precisely predetermined by the metal coordination number and ligand configuration, tailoring MOCs to further modulate the size, shape, and chemical environment of the cavities has become intensively studied for a more efficient and adaptive molecular binding. Herein, we report self-expanding MOCs that exhibit remarkable structural variations in cage size and flexibility while maintaining their topology. A cyclic ligand with an oligomeric chain tethering the two benzene rings of stilbene was designed and mixed with RhII ions to obtain the parent MOCs. These MOCs were successfully transformed into expanded MOCs via the selective cleavage of the double bond in stilbene. The expanded MOCs could effectively trap multidentate N-donor molecules in their enlarged cavity, in contrast to the original MOCs with a narrow cavity. As the direct synthesis of expanded MOCs is impractical because of the entropically disfavored structures, self-expansion using ring-openable ligands is a promising approach that allows precision engineering and the production of functional MOCs that would otherwise be inaccessible.

Published in: "Angewandte Chemie International Edition".

An n‐Type Conjugated Polymer with Low Crystallinity for High‐Performance Organic Thermoelectrics

2024-03-08T13:08:17+00:00March 8th, 2024|Categories: Publications|

Conjugated polymers (CPs) with low molecular packing order are promising candidates for application in organic thermoelectrics (OTEs), particularly in flexible devices, because the disordered structures can effectively accommodate dopants and ensure robust resistance to bending. On the other hand, n-doped CPs usually exhibit inferior thermoelectric performance, restricting the development of high-performance thermoelectric generators. Herein, we report an n-type CP (ThDPP-CNBTz) by alternating two acceptor units of thiophene-flanked diketopyrrolopyrrole and cyano-functionalized benzothiadiazole. ThDPP-CNBTz shows a low-lying LUMO level below -4.20 eV and features low crystallinity, enabling the attainment of high doping efficiency. Moreover, the dual-acceptor molecular design enhances polaron delocalization, thereby improving the thermoelectric performance of the polymer. After n-doping, ThDPP-CNBTz exhibits an electrical conductivity (s) of 50.6 S cm-1 and a power factor (PF) of 126.8 μW m-1 K-2, which ranks among the highest reported for solution-processed n-type CPs to date. Additionally, solution-processed flexible OTE device employing doped ThDPP-CNBTz achieves a PF of 70 μW m-1 K-2. Meanwhile, the flexible OTE devices present remarkable resistance to bending strain, with marginal change in σ after 600 bending cycles. The findings presented in this work will advance the development of n-type CPs for OTE devices, with a particular focus on flexible properties.

Published in: "Angewandte Chemie International Edition".

Accessing Mg‐Ion Storage in V2PS10 via Combined Cationic‐Anionic Redox with Selective Bond Cleavage

2024-03-07T13:08:04+00:00March 7th, 2024|Categories: Publications|Tags: |

Magnesium batteries attract interest as alternative energy-storage devices because of elemental abundance and potential for high energy density. Development is limited by the absence of suitable cathodes, associated with poor diffusion kinetics resulting from strong interactions between Mg2+ and the host structure. V2PS10 is reported as a positive electrode material for rechargeable magnesium batteries. Cyclable capacity of 100 mAh g-1 is achieved with fast Mg2+ diffusion of 7.2[[EQUATION]]10-11-4[[EQUATION]]10-14 cm2s-1. The fast insertion mechanism results from combined cationic redox on the V site and anionic redox on the (S2)2- site; enabled by reversible cleavage of S–S bonds, identified by X-ray photoelectron and X-ray absorption spectroscopy. Detailed structural characterisation with maximum entropy method analysis, supported by density functional theory calculations and projected density of states analysis, reveals that the sulphur species involved in anion redox are not connected to the transition metal centres, spatially separating the two redox processes. This facilitates fast and reversible Mg insertion in which the nature of the redox process depends on the cation insertion site, creating a synergy between the occupancy of specific Mg sites and the location of the electrons transferred.

Published in: "Angewandte Chemie International Edition".

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