Organic Conjugated Trimers with Donor–Acceptor–Donor Structures for Photocatalytic Hydrogen Generation Application

Organic donor–acceptor–donor (D–A–D) polymers or small molecules are widely investigated in organic solar cells due to their broad light absorption, narrow band gap, excellent charge mobility, and exciton seperation at the interface. However, studies of conjugated small molecules with D–A–D molecule structures as photocatalytically active materials are still rare. In this study, an unprecedented demonstration that photocatalytic activity can in fact be affected by tuning the D and A is given. Especially, the EBE trimer, comprising 3,4-ethylenedioxythiophene (E) and benzothiadiazole (B) units, exhibits the best photophysical, chemical, and photocatalytic properties compared to other D–A–D combinations of D and A. Detailed kinetic studies show that all trimers in organic solution present relatively long-lived and highly emissive photogenerated singlet excitons (τ = 4–13 ns; ϕ_em = 0.5–0.9) as judged by photoluminescence and transient absorption measurements, while in specific cases formation of long-lived triplet states can be identified. Organic microparticles of the trimers are efficiently formed in aqueous solution by nanoprecipitation, and rapid photoinduced electron release/injection to the solvent is evidenced spectroscopically. The results indicate that organic small molecule structures with D–A–D structures pave a new pathway for photocatalytic solar-to-chemical energy conversion of novel small organic molecules.     

Molecular Evolution of Acceptor–Donor–Acceptor-type Conjugated Oligomer Nanoparticles for Efficient Photothermal Antimicrobial Therapy

Infectious diseases (such as wound infections) caused by pathogenic microorganisms can lead to serious consequences and even threaten life. The emergence of drug-resistant bacteria has severely prevented the validity of traditional antibiotics. Therefore, developing novel antimicrobial strategies without drug-resistant holds great promise for maximizing efficacy and minimizing the risk of drug-resistance of resistant bacterial infections. Herein, near-infrared (NIR)-absorbing A–D–A type conjugated oligomers with a tunable backbone are designed and synthesized for regulating their photothermal conversion. After being assembled into nanoparticles, the conjugated oligomer CP-F8P nanoparticles (NPs) containing a strong electron-donating component show the strongest photothermal conversion efficiency of 81.6%. The low concentration of CP-F8P NPs receive over 99% of antimicrobial efficiency against Amp^r E. coli, S. aureus, and C. albicans upon NIR irradiation, and the phototherapy treatment of CP-F8P NPs can effectively promote wound healing in diabetic mice with good biocompatibility. This work provides ideas for the design of efficient NIR-activated antimicrobial reagents against drug-resistant microbial infections.     

Intramolecular Donor–Acceptor Design in Porous Organic Framework for Liquid Fuels Adsorption Desulfurization

A porous organic framework containing well-defined donor–acceptor units, named donor–acceptor porous organic framework (D–A-POF), is successfully synthesized. The localized electric field gradient at the pore surface induced by the intramolecular donor–acceptor (D–A) interactions endows D–A-POF with excellent desulfurization capabilities. D–A-POF exhibits high adsorption capacity of 3-methylthiophene (12.26 mmol g⁻¹, 392.32 mg S g⁻¹) and 1-benzothiophene (793.65 mg g⁻¹, 189.25 mg S g⁻¹) with impressive adsorption selectivity. Density functional theory calculations provide compelling evidence of the preferential selective adsorption of aromatic thiophene sulfides in D–A-POF. In fixed-bed breakthrough experiments, D–A-POF demonstrates its ability to selectively capture thiophene sulfides from model gasoline, resulting in fuel with sulfide content below 10 ppb. The high stability and high desulfurization efficiency of D–A-POF make it promising as a new porous adsorbent for ultra-depth adsorption desulfurization.     

Architecting Freestanding Sulfur Cathodes for Superior Room-Temperature Na–S Batteries

Room-temperature sodium–sulfur (RT Na–S) batteries have attracted extensive attention because of their low cost and high specific energy. RT Na–S batteries, however, usually suffer from sluggish reaction kinetics, low reversible capacity, and short lifespans. Herein, it is shown that chain-mail catalysts, consisting of porous nitrogen doped carbon nanofibers (PCNFs) encapsulating Co nanoparticles (Co@PCNFs), can activate sulfur via electron engineering. The chain-mail catalysts Co@PCNFs with a micrograde hierarchical structure as a freestanding sulfur cathode (Co@PCNFs/S) can provide space for high mass loading of sulfur and polysulfides. The electrons can rapidly transfer from chain-mail catalysts to sulfur and polysulfides during discharge–charge processes, therefore boosting its conversion kinetics. As a result, this freestanding Co@PCNFs/S cathode achieves a high sulfur loading of 2.1 ± 0.2 mg cm⁻², delivering a high reversible capacity of 398 mA h g⁻¹ at 0.5 C (1 C = 1675 mA g⁻¹) over 600 cycles and superior rate capability of an average capacity of 240 mA h g⁻¹ at 5 C. Experimental results, combined with density functional theory calculations, demonstrate that the Co@PCNFs/S can efficiently improve the conversion kinetics between the polysulfides and Na₂S via transferring electrons from Co to them, thereby realizing efficient sulfur redox reactions.     

Donor–Acceptor–Donor Modular Small Organic Molecules Based on the Naphthalene Diimide Acceptor Unit for Solution-Processable Photovoltaic Devices

Two novel solution-processable small organic molecules, 4,9-bis(4-(diphenylamino)phenyl)-2,7-dioctylbenzo[3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone (S6) and 4,9-bis(benzo[b]thiophen-2-yl)-2,7-dioctylbenzo[3,8]phenanthroline-1,3,6,8 (2H,7H)-tetraone (S7), have been successfully designed, synthesized, characterized, and applied in solution-processable photovoltaic devices. S6 and S7 contain a common electron-accepting moiety, naphthalene diimide (NDI), with different electron-donating moieties, triphenylamine (S6) and benzothiophene (S7), and are based on a donor–acceptor–donor structure. S7 was isolated as black, rod-shaped crystals. Its triclinic structure was determined by single crystal x-ray diffraction (XRD): space group \(P\bar{1}\) , Z = 2, a = 9.434(5) Å, b = 14.460(7) Å, c = 15.359(8) Å, α = 67.256(9) degrees, β = 80.356(11) degrees, γ = 76.618(10) degrees, at 150 Kelvin (K), R = 0.073. Ultraviolet–visible absorption spectra revealed that use of triphenylamine donor functionality with the NDI acceptor unit resulted in an enhanced intramolecular charge transfer (ICT) transition and reduction of the optical band gap compared with the benzothiophene analogue. Solution-processable inverted bulk heterojunction devices with the structure indium tin oxide/zinc oxide (30 nm)/active layer/molybdenum trioxide (10 nm)/silver (100 nm) were fabricated with S6 and S7 as donors and (6,6)-phenyl C₇₀-butyric acid methyl ester (PC₇₀BM) as acceptor. Power conversion efficiencies of 0.22% for S6/PC₇₀BM and 0.10% for S7/PC₇₀BM were achieved for the preliminary photovoltaic devices under simulated AM 1.5 illumination (100 mW cm^?2). This paper reports donor–acceptor–donor modular small organic molecules, with NDI as central accepting unit, that have been screened for use in solution-processable inverted photovoltaic devices.     

Glassy Metal–Organic-Framework-Based Quasi-Solid-State Electrolyte for High-Performance Lithium-Metal Batteries

Enhancing ionic conductivity of quasi-solid-state electrolytes (QSSEs) is one of the top priorities, while conventional metal–organic frameworks (MOFs) severely impede ion migration due to their abundant grain boundaries. Herein, ZIF-4 glass, a subset of MOFs, is reported as QSSEs (LGZ) for lithium-metal batteries. With lean Li content (0.12 wt%) and solvent amount (19.4 wt%), LGZ can achieve a remarkable ion conductivity of 1.61 × 10⁻⁴ S cm⁻¹ at 30 °C, higher than those of crystalline ZIF-4-based QSSEs (LCZ, 8.21 × 10⁻⁵ S cm⁻¹) and the reported QSSEs containing high Li contents (0.32–5.4 wt%) and huge plasticizer (30–70 wt%). Even at −56.6 °C, LGZ can still deliver a conductivity of 5.96 × 10⁻⁶ S cm⁻¹ (vs 4.51 × 10⁻⁷ S cm⁻¹ for LCZ). Owing to the grain boundary-free and isotropic properties of glassy ZIF-4, the facilitated ion conduction enables a homogeneous ion flux, suppressing Li dendrites. When paired with LiFePO₄ cathode, LGZ cell demonstrates a prominent cycling capacity of 101 mAh g⁻¹ for 500 cycles at 1 C with the near-utility retention, outperforming LCZ (30.7 mAh g⁻¹) and the explored MOF-/covalent–organic frameworks (COF)-based QSSEs. Hence, MOF glasses will be a potential platform for practical quasi-solid-state batteries in the future.     

An Iridium (III) Complex Bearing a Donor–Acceptor–Donor Type Ligand for NIR-Triggered Dual Phototherapy

Iridium(III) complexes are an important group of photosensitizers for photodynamic therapy (PDT). This work constructs a donor–acceptor–donor structure-based iridium(III) complex (IrDAD) with high reactive oxygen species (ROS) generation efficiency, negligible dark toxicity, and synergistic PDT and photothermal therapy (PTT) effect under near-infrared (NIR) stimulation. This complex self-assembles into metallosupramolecular aggregates with a unique aggregation-induced PDT behavior. Compared with conventional iridium(III) photosensitizers, IrDAD not only achieves NIR light deep tissue penetration but also shows highly efficient ROS and heat generation with ROS quantum yield of 14.6% and photothermal conversion efficiency of 27.5%. After conjugation with polyethylene glycol (PEG), IrDAD is formulated to a nanoparticulate system (IrDAD-NPs) with good solubility. In cancer phototherapy, IrDAD-NPs preferentially accumulate in tumor area and display a significant tumor inhibition in vivo, with 96% reduction in tumor volume, and even tumor elimination.     

Molecular-level Designed Polymer Electrolyte for High-Voltage Lithium–Metal Solid-State Batteries

In solid polymer electrolytes (SPEs) based Li–metal batteries, the inhomogeneous migration of dual-ion in the cell results in large concentration polarization and reduces interfacial stability during cycling. A special molecular-level designed polymer electrolyte (MDPE) is proposed by embedding a special functional group (4-vinylbenzotrifluoride) in the polycarbonate base. In MDPE, the polymer matrix obtained by copolymerization of vinylidene carbonate and 4-vinylbenzotrifluoride is coupled with the anion of lithium-salt by hydrogen bonding and the “σ-hole” effect of the C F bond. This intermolecular interaction limits the migration of the anion and increases the ionic transfer number of MDPE (t_Li⁺ = 0.76). The mechanisms of the enhanced t_Li⁺ of MDPE are profoundly understood by conducting first-principles density functional theory calculation. Furthermore, MDPE has an electrochemical stability window (4.9 V) and excellent electrochemical stability with Li–metal due to the CO group and trifluoromethylbenzene (ph-CF₃) of the polymer matrix. Benefited from these merits, LiNi_0.8Co_0.1Mn_0.1O₂-based solid-state cells with the MDPE as both the electrolyte host and electrode binder exhibit good rate and cycling performance. This study demonstrates that polymer electrolytes designed at the molecular level can provide a broader platform for the high-performance design needs of lithium batteries.     

Water-Soluble Cross-Linking Functional Binder for Low-Cost and High-Performance Lithium–Sulfur Batteries

Binders play an important role in battery systems. The lithium–sulfur (Li–S) batteries have poor cycling performance owing to large volume alteration of sulfur and shuttle effect. Herein, a novel water-soluble functional binder (named GN-BA) is prepared by the cross-linking effect between gelatin and boric acid. The excellent binder can effectively maintain the integrated electrode stable, buffer the volume changes, prevent active materials exfoliation from current collectors, and anchor polysulfides by chemical bonding. Sulfur electrodes in this binder also exhibit a loosely stacked porous structure, which is advantageous to the electrolyte permeation and fast ion diffusion. X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, and density functional theory calculations further verified that the binder can anchor polysulfides by forming B O Li, C O Li, and C N Li chemical bonds. At 0.5 C, a high initial capacity of 980 mA h g⁻¹ can be obtained, which is higher than those sulfur cathodes with traditional poly(vinylidene fluoride) binder. When the sulfur loading is up to 5.0 mg cm⁻², a high areal specific capacity of 5.7 mA h cm⁻² and excellent cycling stability are achieved. This study proposes an economical and environmentally friendly strategy for the construction of advanced binders and promotes the practical application of high-energy Li–S batteries.     

Morphology Associated Positive Correlation between Carrier Mobility and Carrier Density in Highly Doped Donor–Acceptor Conjugated Polymers

Molecular doping in conjugated polymers (CPs) has recently received intensive attention for its potential to achieve high electrical conductivity in organic thermoelectric materials. In particular, it affects not only the carrier density n but also the carrier mobility µ because high degree of molecular doping changes the morphological properties. Herein, the effect of molecular doping in CP thin films on the pathways and mechanisms of charge transport is investigated, which govern the µ-n relationship. Two representative donor–acceptor type CPs with similar µ but different molecular assembly in an undoped state, that is poly[2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole-alt-5,5-(2,5-di(thien-2-yl)thieno[3,2-b]thiophene)] (DPPDTT) and indacenodithiophene-co-benzothiadiazole (IDTBT), are prepared. Heavy doping with iron chloride (FeCl₃) induced DPPDTT with highly crystalline edge-on orientation to increase its µ up to 19.6 cm² V⁻¹ s⁻¹, whereas IDTBT with irregular intermolecular stacking showed little change in µ. It is revealed that this different µ-n relationship is highly attributed to the initial molecular ordering of CP films. The charge transport mechanism also becomes significantly different: both coherent and incoherent transports are observed in the doped DPPDTT, whereas incoherent transport is only found in the doped IDTBT. This study suggests guidelines for enhancing charge transport of CPs under doping in terms of structural disorder.     

Rational Design of Multifunctional Integrated Host Configuration with Lithiophilicity-Sulfiphilicity toward High-Performance Li–S Full Batteries

High-energy-density Li–S batteries are considered one of the next-generation energy storage systems, but the uncontrolled Li-dendrite growth in Li metal anodes and the shuttling of polysulfides in S cathode severely impede the commercial development of Li–S batteries. Herein, a conductive composite architecture that is made up of bio-derived N-doped porous carbon fiber bundles (N-PCFs) with co-imbedded cobalt and niobium carbide nanoparticles is employed as a multifunctional integrated host for simultaneously addressing the challenges in both Li anodes and S cathodes. The implantation of Co and NbC nanoparticles bestows the N-PCFs matrix with synergistically enhanced degree of graphitization, electrical conductivity, hierarchical porosity, and surface polarization. Theoretical calculations and experimental results show that NbC with specific lithiophilic and sulfiphilic features can synchronously regulate the Li and S electrochemistry by realizing homogeneous lithium deposition with suppressed Li-dendrite growth and exerting catalytic effects for promoting the polysulfide conversion together with fast Li₂S nucleation. Hence, the assembled Li–S full batteries exhibit a superb rate capability (704 mAh g⁻¹ at 5 C) and cycling life (≈82.3% capacity retention after 500 cycles) at a sulfur loading over 3.0 mg cm⁻², as well as high reversible areal capacity (>6.0 mAh cm⁻²) even at a higher sulfur loading of 6.7 mg cm⁻².     

A New Nonlinear Optically Active Donor–Acceptor-Type Conjugated Polymer: Synthesis and Electrochemical and Optical Characterization

A new donor–acceptor-type poly[3-{5-[3,4-didodecyloxy-5-(1,3,4-oxadiazol- 2-yl)thiophen-2-yl]-1,3,4-oxadiazol-2-yl}-9-dodecyl-9H-carbazole] (P) has been synthesized through multistep reactions. The new polymer P exhibited good thermal stability and film-forming behavior. The electrochemical band gap is estimated to be 2.15 eV. The polymer emits intense green fluorescence in the solid state. Third-order nonlinear optical (NLO) studies showed that the strong absorptive nonlinearity observed for the polymer is of the optical limiting type, which is due to an “effective” three-photon absorption (3PA) process. This 3PA process can have potential applications in photonic devices. The studies revealed that the new polymer P is a promising material for development of efficient optoelectronic devices.     

Universal Design Rules for Flory–Huggins Polymer Photonic Vapor Sensors

Multilayered photonic sensors that rely on polymer-solvent Flory–Huggins interactions are drawing increasing interest owing to their broad-band selectivity, even among mixtures, without the need for chemical targeting. Moreover, these sensors provide simple colorimetric responses, and easy, quick fabrication both on laboratory and industrial scales. However, complex optical responses and slow response times are limiting their development. In this work, the behavior of different photonic sensor architectures is analyzed to speed up response time and define a strategy to simplify their spectral behavior. To this end, the effect of interfaces, materials order, and thickness on the diffusion kinetics of a single reference analyte in the multilayered sensors is studied to design the optimal structure.     

Precise Engineering of Octahedron-Induced Subcrystalline CoMoO4 Cathode Catalyst for High-Performance Li–Air Batteries

Lithium–air batteries (LABs) have attracted intense interest due to their ultrahigh energy density. However, the performance of LABs has to depend on modified electrolytes, gas selective film and Li anode protection. In this study, firstly it is reported that Mo-O octahedron induced subcrystalline scheelite CoMoO₄ catalyst achieves a high performance LABs performance based only on the high catalytic activity in air. The subcrystalline CoMoO₄ catalyst obtains a specific capacity of 12 000 mAh g⁻¹, and ultralong cycle stability over 270 cycles at 1000 mA g⁻¹ in ambient air. This study demonstrates an ultrastable crystal structure and surface conditions of the CoMoO₄ catalyst toward a corrosive environment and complex air-involved reactions. A theoretical calculation further reveals that the polyhedral framework in the scheelite CoMoO₄ can provide a highly stable catalytic surface for the OER/ORR reactions, furthermore, its repulsive nature toward H₂O and CO₂ can efficiently avoid side reactions and slow the corrosion of the Li anode in air. Moreover, the induced octahedron enhances the adsorption energies to O₂ and LiO₂, and accelerates the catalytic reactions in air. The present study provides a conceptual breakthrough to find highly active cathode catalysts for LABs.     

Harvesting Air and Light Energy via “All-in-One” Polymer Cathodes for High-Capacity,Self-Chargeable,and Multimode-Switching Zinc Batteries

Aqueous rechargeable Zinc (Zn)–polymer batteries are promising alternatives to prevalent Li-ion cells in terms of cost, safety, and rate capability but they suffer from limited specific capacity in addition to poor environmental adaptability. Herein, air and light are successfully utilized from external environments in single near-neutral two-electrode Zn batteries to enable remarkably improved electrochemical performance, fast self-charging, and switchable multimode-operation from Zn–polymer to Zn–air cells. This system is enabled by a well-designed polyaniline-nanorod-array based “all-in-one” cathode combining reversible redox capability, oxygen reduction activity, and photothermal-responsiveness. The initiative design allows perfect integration of multiple energy harvesting from ambient “air” and light, energy conversion, and storage in one single cathode. Thus, it can act as an efficient light-assisted electrically-rechargeable Zn–polymer cell featuring the highest specific capacity of 430.0 mAh g⁻¹ among all existing polymer cathodes. Without external power sources, it can be self-charged to deliver a high discharging capacity of 363.1 mAh g⁻¹ by concurrently harvesting chemical energy from air and light energy for only 20 min. It can also switch to a light-responsive Zn–air battery mode to surmount the output capacity limit of Zn–polymer battery mode for continued electricity supply.     

Asymmetric Sandwich Janus Structure for High-Performance Textile-Based Thermo–Hydroelectric Generators Toward Human Health Monitoring

Textile-based generators that can convert low-grade energy from the human body or environment into sustainable electricity have generated immense scientific interest in self-powered wearable applications. However, their low power density and environmental suitability have extremely restricted their portable applications in complex and mutable environments. Herein, an asymmetric sandwich structure between molybdenum disulfide (MoS₂)-carbonized silks (MCs) and MoS₂/MXene–Cottons (MMCs) to construct efficient thermo–hydroelectric generators (THEGs) that synergistically harvest heat-moisture energy to generate considerable electricity is rationally designed. Notably, the large surface area of MoS₂/MXene van der Waals heterojunctions (vdWhs) enables efficient charge collection, and the vertical MoS₂ nanosheet arrays supply abundant nanochannels for a highly efficient hydration effect, generating an output power density of 32.26 µW cm⁻² after wetting with deionized water. Combined with the sensitive temperature recognition ability with a Seebeck coefficient of 23.5 µV K⁻¹, the application possibilities of these prepared THEGs in the mutual conversion of fingertip temperature/language, and the monitoring of the human physiological state is foresee.     

Dynamical SEI Reinforced by Open-Architecture MOF Film with Stereoscopic Lithiophilic Sites for High-Performance Lithium–Metal Batteries

A vulnerable solid–electrolyte interphase (SEI) layer cannot retard Li dendrite growth, electrolyte consumption, and anode volumetric expansion, which seriously hinders the development of high-safety Li-metal batteries (LMBs). Herein, a dynamical SEI reinforced by an open-architecture metal–organic framework (OA-MOF) film characterized by elastic expansion and contraction of the volume of stereoscopic lithiophilic sites, is designed. The self-adjustment distribution of lithiophilic sites on vertically grown Cu₂(BDC)₂ nanosheets enables the homogenization of Li-ion flux, smart control of Li mass transport, and compaction of Li deposition. The trapped N, N-dimethylformamide molecules in the open framework structure are favorable for the better wetting and dissolution effect of Li-ions accessing to Cu₂(BDC)₂. Combining these advantages, the featured OA-MOF/Cu@Li anode enables a high coulombic efficiency and low voltage hysteresis in Li||Cu cells even at an ultrahigh current density of 15 mA cm⁻².     

Poly(2,5-Dihydroxy-1,4-Benzoquinonyl Sulfide) As an Efficient Cathode for High-Performance Aqueous Zinc–Organic Batteries

Aqueous rechargeable zinc-ion batteries (ZIBs) have attracted considerable attention as a promising candidate for low-cost and high-safety electrochemical energy storage. However, the advancement of ZIBs is strongly hindered by the sluggish ionic diffusion and structural instability of inorganic metal oxide cathode materials during the Zn²⁺ insertion/extraction. To address these issues, a new organic host material, poly(2,5-dihydroxy-1,4-benzoquinonyl sulfide) (PDBS), has been designed and applied for zinc ion storage due to its elastic structural factors (tunable space and soft lattice). The aqueous Zn-organic batteries based on the PDBS cathode show outstanding cycling stability and rate capability. The coordination moieties (O and S) display the strong electron donor character during the discharging process and can act as the coordination arms to host Zn²⁺. Also, under the electrochemical environment, the malleable polymer structure of PDBS permits the rotation and bending of polymer chains to facilitate the insertion/extraction of Zn²⁺, manifesting the superiority and uniqueness of organic electrode materials in the polyvalent cation storage. Finally, quasi-solid-state batteries based on aqueous gel electrolyte demonstrate highly stable capacity under different bending conditions.     

Electronic Metal-Support Interactions in Atomically Dispersed Fe(III)-VO2 Nanoribbons for High-Performance Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries have attracted wide attention as high-energy-density energy storage devices, but their practical applications are hindered by the severe shuttle effect and sluggish kinetics of lithium polysulfides (LiPSs). To address these challenges, polar mediators are employed to chemisorb and catalyze LiPSs, but most of them suffer from low electronic conductivity and poor catalytic activity. Here, a novel strategy is reported to enhance both properties by dispersing Fe(III) atoms in VO₂ nanoribbons(Fe-VO₂), creating electronic metal-support interactions (EMSI) that modulate the electronic structure and charge transfer of VO₂. Theoretical calculations reveal that EMSI lowers the energy barrier for the decomposition of Li₂S from 1.60 to 1.32 eV and increases the electronic conductivity of VO₂. Fe doping reduces the Li-ions diffusion barrier from 1.42 eV in VO₂ to 0.99 eV in Fe-VO₂. The Fe-VO₂ catalyst shows strong adsorption and fast converstion of LiPSs, resulting in high energy density and long cycling life of Li-S batteries. The cathode with Fe-VO₂ maintains a higher capacity retention of 67% after 500 cycles at 1 C, compared with 52.4% and 53.6% for the carbon black based cathode and VO₂  based cathode, respectively. This work demonstrates the potential of EMSI for designing efficient catalysts for Li–S batteries and provides new insights into the electronic structure engineering of polar mediators.     

Toward an Understanding of Bimetallic MXene Solid-Solution in Binder-Free Electrocatalyst Cathode for Advanced Li–CO2 Batteries

Li–CO₂ batteries have received extensive attention due to their high energy storage capacity and utilization of CO₂ resources. Herein, bimetallic MXene solid-solution TiVC is prepared and combined with highly conductive graphene for the construction of binder-free electrocatalyst cathodes for Li–CO₂ batteries. Considering the electronic structure, the unique synergy effect between Ti and V in TiVC enhances the interfacial chemical bonding ability, facilitates sufficient exposure of active sites and promotes catalytic interfacial structural reformation, thereby promoting the reversible formation and decomposition of the chemically inert discharge product Li₂CO₃. Meanwhile, the abundant pores and excellent electron transfer ability of graphene aerogel are conducive to the gas diffusion and ion transport, thus reducing the mass and charge transfer resistance. As a result, the assembled Li–CO₂ battery presents an excellent discharge capacity of 27 880 mAh g⁻¹ with a stable discharge plateau of 2.77 V and low overpotential of 1.5 V based on the TiVC-graphene aerogel electrocatalytic cathode. The density functional theory calculations are further performed to deeply reveal the unique electronic structure information between Ti and V in the solid-solution TiVC. This study provides inspiration for exploring more bimetallic MXene solid solutions and developing advanced cathode catalysts for flexible Li–CO₂ batteries.