Reaction Kinetics Research Articles

Large-Eddy Simulation Study of Flow and Combustion Dynamics in a Full-Scale Hydrogen-Air Rotating Detonation Combustor-Stator Integrated System

Abstract A first-of-its-kind large-eddy simulation (LES) study is conducted to numerically investigate the combustion dynamics as well as aero-thermal phenomena in a full-scale non-premixed hydrogen-air rotating detonation engine (RDE) integrated with nozzle guide vanes (NGV) acting as the turbine stator. The LES framework incorporates hydrogen-air detailed chemical kinetics and adaptive mesh refinement. A comparative analysis is carried out for two operating conditions with different fuel/air mass flow rates but global equivalence ratio of unity. The LES model is validated against experimental data with respect to detonation wave speed/height, wave dynamics, and axial static pressure distribution. Numerical results indicate significant deflagrative combustion occurring in the fill region near the inner wall due to formation of recirculation zones in the injection near-field driven by the backward facing step. The leading detonation wave is found to be trailed by an azimuthal reflected-shock combustion wave, which consumes unburned vitiated reactants that leak through the main detonation wave. The detonation wave characteristics do not change appreciably with the presence of NGV. The exit flow is found to be nearly fully subsonic and supersonic for the low and high mass flux conditions, respectively. The presence of NGV renders the flow more axial, and significantly impacts the exit Mach number and total pressure. The low mass flux operating point, despite exhibiting more deflagrative losses within the combustor, yields overall lower pressure drop from plenum to exhaust, mainly attributed to lower pressure drop across the injectors.

Effect of direct water injection on knock suppressing mechanism in a high compression ratio gasoline engine

ABSTRACT A low capacity, boosted gasoline engine is an effective approach to enhancing fuel economy. However, knock combustion poses significant limitations to the practical development of these engines. This study investigated the chemical kinetics and macroscopic properties of engines equipped with direct water injection (DWI) at high compression ratios (CRs) to address knock issues. The results indicated that the generation and consumption pathways of OH and CH2O remain unaffected by water injection. Although water exhibited an opposing effect on the sensitive reactions of OH and CH2O, the production reaction rates of OH and CH2O decrease with water injection. Knock index values at each monitoring point approached zero when the water injection quality exceeds 30%. Additionally, knock suppression effectiveness improved with the advancement of water injection timing. The simulation results indicated that the knock index at high CR decreased from 13.61 to 0.27 when the water/fuel ratio exceeded 30%. The indicated specific fuel consumption decreased by 29.3%, and indicated power increased by 41.8% compared to the original engine. Although NOx and CO emissions increased because of the high CR, the water injection coupled with the compression ratio strategy limited the increase in emissions. These findings indicated that DWI coupled with high CR was advantageous to enhancing fuel economy and reducing emissions in low capacity gasoline engines.

Spatiotemporal Nitric Oxide Modulation via Electrochemical Platform to Profile Tumor Cell Response.

Nitric oxide (NO) is a gaseous molecule intricately implicated in oncologic processes, encompassing the modulation of angiogenesis and instigating apoptosis. Investigation of the antitumor effects of NO is currently underway, necessitating a detailed understanding of its cellular-level reactions. Regulating the behavior of radical NO species has been a significant challenge, primarily due to its instability in aqueous environments by rapid O2-induced degradation. In this study, we devised an electrochemical platform to investigate the cellular responses to reactive gaseous molecules. Our designed platform precisely controlled the NO flux and diffusion rates of NO to tumor cells. COMSOL Multiphysics calculations based on diffusion and reaction kinetics were conducted to simulate the behavior of electrochemically generated NO. We discerned that the effective distance, NO flux, and electrolysis duration are pivotal factors governing cellular response by NO.

An experimental and modeling study on pyrolysis reaction kinetics of oxygenated biofuel blended with aviation kerosene RP-3

Blending the renewable oxygenated biofuels with conventional fossil fuels is one of the feasible approaches to achieve carbon-neutral in the aviation industry, while there is very limited research available on the fundamental reaction characteristics of blended fuels. The primary objective of the present study is to conduct experimental investigations on the pyrolysis and oxidative pyrolysis reaction kinetics of oxygenated biofuels blended with China aviation kerosene RP-3 and establish a kinetic model. Pyrolysis experiments were conducted in a flow reactor at atmospheric pressure and temperature of 1130 K for blended fuels (methyl butanoate blended with RP-3, and n-butanol with RP-3) to examine fuel reactivity and formation of critical intermediates. The introduction of alternative oxygenated biofuel to the conventional hydrocarbon fuel RP-3 leads to the generation of CO during the pyrolysis reactions, as well as the reduced formation of olefin products. Notably, the CO yield from pyrolysis reactions of the blended fuel is increasing almost linearly with the concentrations of added oxygenated biofuels. A Two-Step Reaction Scheme (TSRS) modeling approach was extended for describing the reaction kinetics of oxygenated biofuels. TSRS models for methyl butanoate and n-butanol were constructed and merged with the HyChem model of RP-3 to complete the blended fuel model. Results show that the blended model predicts well the evolution of key intermediates with time, demonstrating the applicability of the model based on the two-stage characteristics of high-temperature reaction kinetics for describing the pyrolysis reactions of oxygenated fuels and hydrocarbon fuels.

Spatiotemporal Nitric Oxide Modulation via Electrochemical Platform to Profile Tumor Cell Response

Nitric oxide (NO) is a gaseous molecule intricately implicated in oncologic processes, encompassing the modulation of angiogenesis and instigating apoptosis. Investigation of the antitumor effects of NO is currently underway, necessitating a detailed understanding of its cellular‐level reactions. Regulating the behavior of radical NO species has been a significant challenge, primarily due to its instability in aqueous environments by rapid O2‐induced degradation. In this study, we devised an electrochemical platform to investigate the cellular responses to reactive gaseous molecules. Our designed platform precisely controlled the NO flux and diffusion rates of NO to tumor cells. COMSOL Multiphysics calculations based on diffusion and reaction kinetics were conducted to simulate the behavior of electrochemically generated NO. We discerned that the effective distance, NO flux, and electrolysis duration are pivotal factors governing cellular response by NO.

Improving the electrocatalytic activity of the copper (II) metal-organic framework by functionalized imidazolate linker and functionalized carbon nanoparticles for detection of acyclovir

With the aim of expansion of nanocomposite materials in electrochemical sensors, the use of nanostructures as the electrode modifier has been shown to improves the kinetics of the electron transfer reactions and consequently increases the sensitivity of the sensors. So, in this study, a new electrochemical sensor was fabricated by using the nanocomposite of copper (II) metal–organic framework with functionalized imidazolate linker [Cu3(BTC)2-2-MIM] and cationic functionalized carbon nanoparticles (CFCNPs) at the glassy carbon electrode (GCE); Cu3(BTC)2-2-MIM/CFCNPs/GCE. The as prepared nanocomposite; Cu3(BTC)2-2-MIM/CFCNPs was characterized using various instrumental techniques. To identify the capabilities and electrocatalytic activity of the synthesized nanocomposite in analytical chemistry, it was used as an electrochemical modifier along with suitable electrochemical techniques. In this regard, the prepared modified electrode; Cu3(BTC)2-2-MIM/CFCNPs/GCE was utilized to the electrooxidation and determination of the acyclovir (ACR) in NaOH solution. Under optimal experimental conditions, the Cu3(BTC)2-2-MIM/CFCNPs/GCE showed low detection limit (0.24 µM) over the concentration ranges of 2.49–84.28 μM of ACR. On the other hand, the present sensor has robust stability, good reproducibility, high selectivity and sensitivity (5.907 µAµM−1 cm−2) in electrodetermination of ACR. Also, the diffusion coefficient of ACR (DACR = 9.25 × 10−6 cm2 s−1), the transfer coefficient (α = 0.34) and catalytic rate constant (kcat = 10.1 × 105 cm3 mol−1 s−1) of ACR electrooxidation reaction were estimated at the surface of modified electrode in NaOH solution. Finally, the Cu3(BTC)2-2-MIM/CFCNPs/GCE was applied as a promising and low-cost sensor for determination of the ACR in actual pharmaceutical formulations and biological samples.

Modulation of interface electric field over CoMoP-CoMoP2 heterostructure for high-efficiency oxygen evolution reaction

The construction of a heterostructure can significantly enhance the intrinsic activity of the electrocatalysts. In this study, a simple electrospinning combined with post-treatment strategy is successively employed to fabricate novel CoMoP-CoMoP2 heterostructure nanofibers. Experimental results and density functional theory (DFT) calculations demonstrate that the formation of CoMoP-CoMoP2 heterointerface can optimize the kinetics of the oxygen evolution reaction (OER) and enhance the intrinsic catalytic activity. As anticipated, the resulting CoMoP-CoMoP2 electrocatalyst displays outstanding OER performance (184 mV @ 10 mA cm−2, and 302 mV @100 mA cm−2) as well as excellent stability in 1 M KOH. Moreover, the OER test results of CoMoP-CoMoP2 with varying CoMoP and CoMoP2 contents indicate that CoMoP-CoMoP2-1 (with a mass ratio of approximately 1.01/10.1) exhibits the highest OER activity. Utilized as the overall water splitting electrocatalyst, CoMoP-CoMoP2-1 demonstrates exceptional durability and outperforms Pt/C||RuO2 electrolyzer, achieving a current density of 10 mA cm−2 and a battery voltage of only 1.53 V during continuous operation for 260 h. These findings suggest the practical application potential of this material, confirming the promising nature of bimetallic phosphide-bimetallic phosphide heterostructure electrocatalysts.

Thermal vapor sulfurization of Ti3C2TX MXene to TiS2/carbon nanosheet cathode for long-life and high-loading all-solid-state lithium batteries

Stable and fast operation of all-solid-state lithium batteries (ASSBs) depends on durable and sufficient interfacial contacts between electrode components, especially when the loading and content of electrode active materials are high. Here, we propose promoting ionic/electronic transportations and contacts in sulfide electrolyte-based ASSBs by using TiS2/carbon nanosheets (TiS2/C-s) with large area-to-thickness aspect ratios as the cathode, which are prepared by simple thermal vapor sulfurization of exfoliated Ti3C2Tx MXene. The elastic 2D structure of the TiS2/C-s material can substantially improve interfacial contact with the solid electrolyte, minimize the diffusion distance of lithium ions, and buffer volume/stress changes during cycling, thereby ensuring the electro-chemo-mechanical stability and fast reaction kinetics of electrodes. Consequently, a 50 wt% TiS2/C-s cathode without any conductive carbon additives demonstrates a high discharge capacity (295 mAh g−1), long-term cyclic stability (94.7 and 74.7 % capacity retention after 250 cycles at 0.1 mA cm−2 and after 2300 cycles at 1 mA cm−2, respectively), and decent rate capability (126.0 mAh g−1 at 3 mA cm−2). Moreover, stable cycling with a high areal capacity (5.95 mAh cm−2) can also be achieved.

Electrospun carbon nanofibers loaded with sulfur vacancy CoS2 as separator coating to accelerate sulfur conversion in Lithium-Sulfur batteries

Lithium–sulfur batteries (LSBs) have been sought after by researchers owing to their high energy density; however, the inevitable capacity decay and slow reaction kinetics have hindered their advancement. Here, we prepare a Prussian blue analog, Co3[Co(CN)6]2 and synthesize carbon nanofibers/S vacancy CoS2−x (CNFs/CoS2−x) as electrocatalysts for separator coating via electrospinning, carbonization, sulfurization, and hydrogen reduction. CNFs/CoS2−x exhibits excellent electrocatalytic activity, wherein S vacancies induce the partial oxidation of Co2+ to Co3+ in CoS2 and CNFs provide long-range electron transport pathways. Various electrochemical tests, such as Tafel, ion diffusion coefficient, Li2S precipitation, and Li2S6 symmetric cells, further confirm the enhanced electrocatalytic activity. The LSBs with CNFs/CoS2−x modified separator delivers an initial discharge capacity of 1056.7 mAh g−1 at 0.2C, maintaining 840.8 mAh g−1 after 100 cycles at 0.2C. When S loading is increased to 4.42 mg cm−2, the battery retains a discharge capacity of 687.9 mAh g−1 (3.04 mAh cm−2) after 70 cycles at 0.1C. Our work can provide a reference for synthesizing anion-vacancy materials and designing anion-vacancy electrocatalytic composites for LSBs.

Stochastic bipedal dual-DNA walkers for fast and sensitive detection of apurinic/apyrimidinic endonuclease1 and inhibitor screening

DNA walkers have emerged as a powerful tool in various biosensors, enabling the detection of low-abundance analytes with their precise programmability and efficient signal amplification capacity. However, many existing approaches are hampered by limited reaction kinetics. Herein, we designed a stochastic bipedal dual-DNA walkers (SBDW) that can traverse at high speed on AuNP-based three-dimensional (3D) tracks powered by Exo III. The SBDW exhibited superior reaction kinetics and are up to least 2.25 times faster than traditional DNA walkers, reaching a plateau within 40 min. This advancement allows for rapid and highly sensitive fluorescence detection of a significant base excision repair enzyme of APE1 with a detection limit of 0.001 U/mL. In comparison to traditional DNA walkers, this platform enables highly sensitive and specific APE1 assays in cell lysate and facilitates rapid and accurate screening of APE1 inhibitors. Given its rapid, sensitive, specific, and reliable analysis features, the strategy shows great promise in drug discovery and clinical diagnosis.

Biofuel processing in a closed-loop geothermal system

Closed-loop geothermal systems (CLGS) provide a renewable heat source for district heating and electricity production. However, high capital costs can be a barrier to these applications. This study finds that the high pressures (>8MPa) and temperatures (>240°C) attained by working fluid inside the loop present additional opportunities: driving supercritical reactions that produce biodiesel from fatty acids. A new design for a subsurface geothermal reactor is proposed, enabling biofuel processing underground without the need for conventional processing equipment (pump, heater, reactors, and heat exchangers) or fossil fuel as energy source. To analyze the feasibility of this approach and its environmental and economic effects, a computational model that incorporates the simultaneous effects of flow dynamics, heat transfer, and reaction kinetics is developed. The application of CLGS is concluded to reduce the CO2 intensity of the resulting biodiesel by up to 33%. A geothermal-driven biofuel reactor could yield up to 95% fatty acid methyl esters. Additional sensible heat carried by the products can be redirected to electricity generation or district heating. The relevant requirements and optimal operating conditions for this approach to biofuel synthesis are identified. A technoeconomic analysis shows CLGS-based biofuel production cost can be comparable to natural gas-based production (∼840 $/ton). It also indicates return-on-investment after five years and highlights the most suitable locations that combine proximity to appropriate feedstocks and subsurface conditions. Integrated biodiesel production and energy extraction provides an alternative route to harnessing geothermal energy.

Eco-friendly plant extract-assisted fabrication of CeO2@CH@Ag nanocomposite: A heterogeneous catalyst for organic pollutant remediation

This study explores the synthesis and application of a novel cerium oxide-chitosan-silver (CeO2@CH@Ag) nanocomposite as an efficient catalyst for the reduction of organic pollutants, including methyl orange (MO), congo red (CR), and 4-nitroaniline (4-NA). The nanocomposite was synthesized via a co-precipitation method, followed by in-situ deposition of silver nanoparticles on its surface. Comprehensive characterization techniques, including FTIR, XRD, FESEM, EDX, XPS and nitrogen sorption measurements, confirmed the successful incorporation of CeO₂ and silver within the chitosan matrix. The CeO2@CH@Ag nanocatalyst exhibited a high surface area of 58.081 m2/g, exhibiting remarkable catalytic activity, facilitating rapid reduction of the organic pollutants within 6 min using sodium borohydride as a reducing agent. Kinetic studies revealed pseudo-first-order reaction kinetics, with rate constants of 1.09, 0.38, and 0.58 min⁻1 for MO, CR, and 4-NA, respectively. The proposed mechanism involves the adsorption of dye molecules onto the catalyst's porous surface, followed by electron transfer from the reducing agent to the dye, facilitated by the redox properties of CeO2 and silver. The CeO2@CH@Ag nanocatalyst demonstrates the promising potential for efficient wastewater treatment and remediation of organic pollutants.

Investigation of NO emissions and chemical reaction kinetics of ammonia/methane flames under dual-fuel co-combustion mode at elevated air temperature conditions

Utilising ammonia, which is one of the most promising carbon-free fuels, comes with the challenge of stable combustion due to its low reactivity. Therefore, advanced strategies are needed, including blending ammonia with highly reactive fuels or implementing innovative combustion techniques. For this reason, the present study proposes an ammonia-methane dual-fuel co-firing combustion mode. The second focus is to analyse the effect of preheating the main swirl air on NO emissions and examine the chemical kinetic reactions. Experimentally, chemiluminescence imaging was conducted to analyse OH* and NH2* emissions to evaluate the flame structure and reaction zones. Numerically, simulations were performed using a chemical multi-reactor network model to examine kinetics. By comparing the fully premixed combustion to the dual-flame co-burning mode, the NO emissions decreased by 80% in the latter case at T = 473K and ϕ = 0.6. The NH3 reaction pathway analysis shows a significantly higher percentage reduction of NO and NH2 reactions in dual flame mode compared to premixed flames. Preheating the main air impacts NO reactions in the dual flame mode, allowing for lower NO emissions.

Porous heterojunction CoSe2–MoSe2 nanosheet arrays for electrocatalytic oxygen evolution

Oxygen evolution reaction (OER) is an important half-reaction of many actual processes, which has the slow kinetics of four-electron process. Interface engineering as an effective method can accelerate the slow kinetics of oxygen evolution reaction. In this paper, CoSe2–MoSe2 porous nanosheet arrays with heterostructures were synthesized on carbon cloth by ion exchange and vapor phase selenization using Co-MOF as template. Due to the porous two-dimensional structure, the electron diffusion path is shortened and the self-supporting electrode has excellent conductivity. When catalyzing OER in 1 M KOH solution, the CoSe2–MoSe2 delivers an overpotential of 278 mV at 10 mA cmm2, and Tafel slope of 61.2 mV dec−1, making catalytic activity a better result than commercial RuO2. In addition, the decay of the catalytic activity is negligible after 24 h of continuous electrolysis. This work provides a method for the design of porous bimetallic selenide self-supporting oxygen evolution electrocatalysts.

Enhancing proton-coupled electron transfer drives efficient methanogenesis in anaerobic digestion

The enhancement of electron or proton transfer between syntrophic microbes has been widely recognised as a means for improving methane generation. However, the uncoupled supplementation of electrons and protons in multiphase anaerobic environment hinders the balanced uptake of electrons and protons in the cytoplasm of methanogens, limiting methanogenesis efficiency. Herein, the cooperative effect of a proton-conductive material (PM) and an electron-conductive material (EM) in enhancing proton-coupled electron transfer (PCET) and driving efficient methanogenesis in anaerobic digestion was investigated. The cooperation of the PM and EM significantly increased methane production and the maximum methane generation rate by 78.9 % and 103.5 %, respectively, indicating enhanced methanogenesis efficiency. Analysis of the physicochemical properties, biochemical components, and microbial dynamics revealed that the cooperation of the PM and EM improved the metabolism of syntrophic microbes, which was critically dependent on electron and proton transfer. This enhancement was primarily due to the improvement in PCET, as mainly supported by hydrogen/deuterium kinetic isotope effect measurements, multi-omics integration analyses and reaction thermodynamics and kinetics analyses. Our findings suggest that the PCET enhancement stimulated efficient membrane-bound enzymatic reactions related to electron-driven proton translocation and facilitated electron and proton supply for CO2 reduction to realise highly efficient methane generation. These findings are expected to provide a new insight into effective electron and proton coupling transfer for methanogenic metabolism in multiphase anaerobic environments.

A comparative thermodynamic assessment of microwave-assisted and conventional pyrolysis of biomass in poly-generation systems using coupled numerical and process simulations

Biomass is a unique renewable carbon resource that can be flexibly converted into biofuels, chemicals, and biomaterials using pyrolysis technology. Microwave-assisted pyrolysis (MAP) has gained increasing attention due to its faster and more uniform heating characteristics compared to conventional pyrolysis (CP). However, thermodynamic assessments of biomass MAP-based systems that consider detailed pyrolytic product information are lacking. This study simulated biomass-derived poly-generation systems employing MAP with microwave absorbers (MAP-S) and CP with solid heat carriers (CP-S). The proposed systems included pretreatment, pyrolysis, bio-oil rectification, hydrodeoxygenation, and combined cycle power units, producing biofuels, chemicals, and electricity. To obtain operating information that aligns more closely with engineering reality, pilot-scale numerical models integrating reaction kinetics and transport processes were established for the MAP and CP reactors. These models were validated against lab-scale experimental results after scaling down the models’ geometrical sizes. The results of product yields and energy consumption from numerical simulations were used to support the process simulation. Simulation results showed that the energy efficiency and net power generation efficiency of MAP-S were 59.37 % and 17.78 %, respectively, lower than the 67.19 % and 18.22 % of CP-S. In CP-S, the exergy of materials primarily moved towards the chemicals production units with an exergy efficiency (ηex) of 60.0 %, whereas in MAP-S, more exergy flowed towards the power generation units with a lower ηex of 58.46 %. Notably, the exergy destruction rate (Exd) for CP-S was 3.91 MW, higher than the 3.65 MW for MAP-S. Moreover, the CP-S achieves a higher carbon utilization efficiency at 42.32 %, compared to 35.03 % for the MAP-S. For the pyrolysis units, although the CP unit experienced higher heat losses (0.31 MW) compared to the MAP unit (0.1 MW), the ηex for the CP unit was higher due to a lower Exd. Additionally, CP-S consumed more hydrogen in the hydrodeoxygenation units, whereas MAP-S might achieve self-supply of hydrogen by adjusting operation conditions and technology processes.

Evaluation of reaction kinetics for chemoselective hydrogenation of citral for intensification of citral intermediates using copper-based catalysts

ABSTRACT Citral intermediates’ formation kinetics is studied using non-noble metal catalyst (Cu/SiO2) to evaluate catalyst performance characteristics via chemoselective hydrogenation of citral. The catalyst is synthesised by the precipitation method and characterised using XRD, FESEM and BET surface area analyser. Hydrogenation experiments are carried out using an Autoclave reactor in the temperature range of 80–120°C, pressure range of 10–50 bar and for catalyst loadings of 0.5, 1 and 1.5 g. The intermediates product distribution comprises aldehyde and alcohol formation such as citronellal, nerol and citronellol formation. The performance of the Cu/SiO2 catalyst is evaluated using the parameters such as citral conversion, citronellol selectivity and yield as 96.96%, 95.30% and 92.30%, respectively under optimal conditions of 50 bar, 120°C and 1 g catalyst for the reaction time of 100 min. The absence of internal and external mass transfer limitations is verified using the Carberry number and Weisz-Prater modulus criterion. The intrinsic kinetics of the gas–liquid phase hydrogenation of citral is determined using the Langmuir–Hinshelwood-Hougen-Watson (LHHW) model for citral intermediates formation. The reaction kinetic parameters show that citronellol formation favours by the nerol route compared to citronellal conversion. HIGHLIGHT Citral conversion to its intermediate chemicals using a non-noble metal catalyst (Cu/SiO2) Intrinsic kinetics evaluation using the LHHW model for citral hydrogenation Evaluation of performance parameters for citral hydrogenation to its intermediates Improved conversion of unsaturated alcohol (nerol) and aldehyde to saturated alcohol (citronellol)

The design of chemisorption and catalysis synergistic defender for efficient room temperature sodium-sulfur batteries

Room temperature sodium-sulfur (RT-Na/S) batteries are a promising candidate for large-scale energy storage systems owing to their low manufacturing cost and high energy density. However, the severe shuttle effects and sluggish reaction kinetics hinder their practical application. Here, a Fe3Se4 nanoparticle anchored three-dimensional nitrogen-doped porous carbon nanosheet was designed as a functional defender to inhibit the shuttle effect and achieve high sulfur utilization. The porous carbon nanosheet builds a fast platform for electron and ion transport and acts as a limiting barrier for polysulfide dissolution and shuttling. Additionally, Fe3Se4 nanoparticles are incorporated to enhance the chemical anchoring and catalytic activity of polysulfides. The ex-situ characterization revealed that the Fe sites can feed electrons to polysulfides, thus facilitating the conversion of long-chain polysulfides to Na2S, resulting in high sulfur availability (323 mAh/g at 2 A/g) and long-term cycle life (72 % capacity retention at 1 A/g for 500 cycles).

Freestanding molybdenum carbide nanowires electrode for high specific capacity and superior rate performance Li–CO2 batteries

Li–CO2 batteries have attracted wide attention owing to unique CO2 capture ability and potential power source for Mars exploration. However, the practical application of Li–CO2 batteries are severely restricted by the sluggish reaction kinetics of 4–electron Li2CO3 as discharged products. Herein, we design efficient freestanding Mo2C nanowires electrode following low electron Li2C2O4–product route to achieve high–performance Li–CO2 batteries. More importantly, we propose a regulation and evolution mechanism of discharge products Li2C2O4 and Li2CO3 on Mo2C cathode in Li–CO2 battery with different discharge depths. Based on reasonable regulation of discharge products, Li–CO2 batteries with the Mo2C nanowires exhibit excellent electrochemical performance with an ultra–low overpotential 0.35 V at 0.05 mA cm–2 and a cycle life of 165 cycles below charge potential of 3.8 V. The Mo2C nanowires electrode also delivers high discharge capacity of 8.47 mAh cm–2 and superior rate capability compared to a conventional Mo2C cathode reported. Moreover, the superior flexibility and stability of the binder–free Mo2C nanowires electrode under different deformations assists in the development of wearable Li–CO2 batteries with safety and sustainability.

Enhancing aqueous zinc-ion energy storage performance with ion-mediating carbon quantum dots-modified separators regulating zinc deposition behavior

Aqueous zinc-ion batteries (AZIBs) hold promising applications owing to their safety, cost-effectiveness, and competitive capacity. However, issues such as zinc dendritic formation and side reactions severely impede their practical viability. Utilizing carbon quantum dots (CQDs) to modify cheap, tenacious, and highly hydrophilic filter paper (FP) as separator effectively improves the electrochemical performance of zinc ion energy storage systems. The structured arrangement of CQDs redistributes zinc ion transport and induces uniform zinc icon deposition, thereby improving zinc ion reaction kinetics. Moreover, the rich functional groups on the surface of CQDs readily form hydrogen bonds with active H2O, further inhibiting corrosion reactions. With the assistance of CQDs, the FP-CQDs separator maintains high ionic conductivity and a high zinc-ion transference number, ensuring dendrite-free and corrosion-resistant operation with high coulombic efficiency and a prolonged lifespan of 1200 h at 1 mA cm−2. Zn//AC hybrid capacitors incorporating FP-CQDs separator demonstrate superior capacity retention compared to those using FP separator alone, with a high capacity retention after 600 cycles at 1 A/g, while Zn//V2O5 full batteries also exhibit excellent cycling stability. Given these findings, this study presents a new composite separator for advanced aqueous zinc-ion energy storage systems.