Reactive Intermediates Research Articles

Advanced Zeolite-based Catalysts for CO2 Hydrogenation to Targeted High-Value Chemicals and Fuels.

The excessive use of fossil fuels has resulted in elevated CO2 emissions in the atmosphere, significantly impacting the climate and global environment. The catalytic conversion of CO2 into high-value chemicals has been recognized as a promising strategy to mitigate CO2 emissions. Light olefins, aromatics, and alcohols, etc. are widely used high-value chemicals as fuels and chemical synthesis intermediates. To enhance the catalytic efficiency and selectivity for producing these chemicals, various catalysts have been developed. Among them, zeolite-based catalysts have garnered significant attention due to their unique microporous structure, shape-selective catalysis capability, high thermal stability, and tunable acidity. This article focuses on the distinctive structural characteristics of zeolites and their notable representative applications, with particular emphasis on the impact of zeolite structural properties on catalytic performance and reaction mechanism. Additionally, we discuss the current challenges of fabricating highly efficient zeolite-based catalysts and future development prospects in improving the catalytic performance and industrial-scale applications. We propose rational and strategic insights to pave the way for the efficient utilization of CO₂ as a valuable resource.

Transient pulsed discharge preparation of graphene aerogel supports asymmetric Cu cluster catalysts promote CO2 electroreduction

Designing asymmetrical structures is an effective strategy to optimize metallic catalysts for electrochemical carbon dioxide reduction reactions. Herein, we demonstrate a transient pulsed discharge method for instantaneously constructing graphene-aerogel supports asymmetric copper nanocluster catalysts. This process induces the convergence of copper atoms decomposed by copper chloride onto graphene originating from the intense current pulse and high temperature. The catalysts exhibit asymmetrical atomic and electronic structures due to lattice distortion and oxygen doping of copper clusters. In carbon dioxide reduction reaction, the selectivity and activity for ethanol production are enhanced by the asymmetric structure and abundance of active sites on catalysts, achieving a Faradaic efficiency of 75.3% for ethanol and 90.5% for multicarbon products at −1.1 V vs. reversible hydrogen electrode. Moreover, the strong interactions between copper nanoclusters and graphene-aerogel support confer notable long-term stability. We elucidate the key reaction intermediates and mechanisms on Cu4O-Cu/C2O1 moieties through in situ testing and density functional theory calculations. This study provides an innovative approach to balancing activity and stability in asymmetric-structure catalysts for energy conversion.

Conformational dynamics of a multienzyme complex in anaerobic carbon fixation.

In the ancient microbial Wood-Ljungdahl pathway, carbon dioxide (CO2) is fixed in a multistep process that ends with acetyl-coenzyme A (acetyl-CoA) synthesis at the bifunctional carbon monoxide dehydrogenase/acetyl-CoA synthase complex (CODH/ACS). In this work, we present structural snapshots of the CODH/ACS from the gas-converting acetogen Clostridium autoethanogenum, characterizing the molecular choreography of the overall reaction, including electron transfer to the CODH for CO2 reduction, methyl transfer from the corrinoid iron-sulfur protein (CoFeSP) partner to the ACS active site, and acetyl-CoA production. Unlike CODH, the multidomain ACS undergoes large conformational changes to form an internal connection to the CODH active site, accommodate the CoFeSP for methyl transfer, and protect the reaction intermediates. Altogether, the structures allow us to draw a detailed reaction mechanism of this enzyme, which is crucial for CO2 fixation in anaerobic organisms.

Designing Supported Nanoparticles via Synergistic Ex-Solution and Phosphorization for Tailored Active Site Generation.

Supported nanoparticles incorporating catalytically attractive nonmetal elements have gained significant attention as a promising strategy for enhancing catalytic activity in various industrial applications. This study presents an innovative one-pot synthesis method for fabricating hybrid catalysts, which simultaneously modifies surface properties through the precipitation of nanoparticles with the concurrent incorporation of nonmetal elements. The underlying concept is to synchronize the temperature required for particle formation with that of nonmetal incorporation by adjusting the oxygen chemical potential of the host oxide. As a case study, Ir- and Ru-doped WO3 are selected as the starting material, with phosphorus (P) as the representative nonmetal for surface functionalization. Notably, the hybrid catalyst, composed of amorphous (Ir,Ru)Px particles dispersed on P-rich WO2.9 sheets, is synthesized through a single heat treatment at 500°C, avoiding undesirable sintering of the host material. When used as a hydrogen evolution catalyst, this material exhibits outstanding mass activity, durability, compared to state-of-the-art Pt/C catalysts. Density functional theory calculations further reveal that the superior performance of the hybrid catalysts attributes to improved water dissociation and favorable adsorption and desorption of key reaction intermediates. This novel synthesis strategy offers considerable potential for advancing diverse areas of heterogeneous catalysis.

Secondary Coordination Effects of Adjacent Metal Center in Metal-Nitrogen-Carbon Improve Scaling Relation of Oxygen Electrocatalysis.

Heterogenous single-atom catalysts (SACs) are reminiscent of homogeneous catalysts because of the similarity of structural motif of active sites, showing the potential of using the advantage of homogeneous catalysts to tackle challenges in hetereogenous catalysis. In heterogeneous oxygen electrocatalysis, the homogeneity of adsorption patterns of reaction intermediates leads to scaling relationships that limit their activities. In contrast, homogeneous catalysts can circumvent such limits by selectively altering the adsorption of intermediates through secondary coordination effects (SCEs). This inspired us to explore potential SCEs in metal-nitrogen-carbon (M-N-C), a promising type of oxygen evolution electrocatalyst. We introduced SCEs with a neighboring metal site that can modulate the adsorption strengths of oxygen-containing intermediates. First-principles calculations show that the second site in the heteronuclear duo four-nitrogen-coordinated metal center can induce SCEs that selectively stabilize the OOH intermediate but with minor effects on the OH intermediate and, thereby, disrupt the scaling relation between oxygen species and eventually increase the catalytic activity in oxygen evolution reactions. Additionally, the activity of oxygen reduction reaction of selected M-N-C is also enhanced by such SCE. Our computational work underscored the critical role SCEs can have in shaping activities of SACs, particularly in favorably altering scaling relationships, and demonstrated its potential to address catalytic challenges in heterogeneous catalysis.

Electrochemically Driven Selective Olefin Epoxidation by Cobalt-TAML Catalyst.

Epoxides are versatile chemical intermediates that are used in the manufacture of diversified industrial products. For decades, thermochemical conversion has long been employed as the primary synthetic route. However, it has several drawbacks, such as harsh and explosive operating conditions, as well as a significant greenhouse gas emissions problem. In this study, we propose an alternative electrocatalytic epoxidation reaction, using [CoIII(TAML)]- (TAML = tetraamido macrocyclic ligand) as a molecular catalyst. Under ambient conditions, the catalyst selectively epoxidized olefin substrates using water as the oxygen atom source, affording an efficient catalytic epoxidation of olefins with a broad substrate scope. Notably, [CoIII(TAML)]- achieved >60% Faradaic efficiency (FE) with >90% selectivity for cyclohexene epoxidation, which other heterogeneous electrocatalysts have never attained. Electrokinetic studies shed further light on the detailed mechanism of olefin epoxidation, which involved a rate-limiting proton-coupled electron transfer process, forming reactive cobalt oxygen active species embedded in 2e-oxidized TAML. Operando voltammetry-electrospray ionization mass spectrometry (VESI-MS) and electron paramagnetic resonance (EPR) analyses were utilized to identify a cobalt oxygen active intermediate during an electrocatalytic epoxidation by [CoIII(TAML)]-. Our findings offer a new possibility for sustainable chemical feedstock production using electrochemical methods.

Self-assembled Gap-Rich PdMn Nanofibers with High Mass/Electron Transport Highways for Electrocatalytic Reforming of Waste Plastics.

Innovating nanocatalysts with both high intrinsic catalytic activity and high selectivity is crucial for multi-electron reactions, however, their low mass/electron transport at industrial-level currents is often overlooked, which usually leads to low comprehensive performance at the device level. Herein, a Cl-/O2 etching-assisted self-assembly strategy is reported for synthesizing a self-assembled gap-rich PdMn nanofibers with high mass/electron transport highway for greatly enhancing the electrocatalytic reforming of waste plastics at industrial-level currents. The self-assembled PdMn nanofiber shows excellent catalytic activity in upcycling waste plastics into glycolic acid, with a high current density of 223 mA cm-2@0.75 V (vs RHE), high selectivity (95.6%), and Faraday efficiency (94.3%) to glycolic acid in a flow electrolyzer. Density functional theory calculation, X-ray absorption spectroscopy combined with in situ electrochemical Fourier transform infrared spectroscopy reveals that the introduction of highly oxophilic Mn induces a downshift of the d-band center of Pd, which optimizes the adsorption energy of the reaction intermediates on PdMn surface, thereby facilitating the desorption of glycolic acid as a high-value product. Computational fluid dynamics simulations confirm that the gap-rich nanofiber structure is conducive for mass transfer to deliver an industrial-level current.

Molecular Mechanism for the Unprecedented Metal-Independent Hydroxyl Radical Production from Thioureas and H2O2.

The most well-known hydroxyl radical (•OH)-generating system is the classic iron-mediated Fenton reaction. Thiourea has been considered as an efficient •OH scavenger and is frequently used to study the role of •OH in various biochemical and medical research studies. Here we found that the highly reactive •OH can be produced from thiourea and H2O2 through a metal-independent pathway, as measured by electron spin resonance (ESR) secondary radical spin-trapping and fluorescent methods. The major reaction intermediates from thiourea/H2O2 were identified as formamidinesulfenic acid and formamidinesulfinic acid, with urea and sulfate as the major final products. Taken together, the underlying molecular mechanism for the unprecedented •OH production from thiourea/H2O2 was proposed: thiourea is initially attacked by H2O2 to produce the transient intermediates formamidinesulfenic acid and then formamidinesulfinic acid, which further react with H2O2 to produce their corresponding hydroperoxyl intermediates, which can decompose homolytically to generate •OH and the final products. Analogous •OH production and oxidative DNA damage were also observed with other thiourea derivatives and H2O2. This is the first report on metal-independent •OH production from the well-known •OH scavenging thioureas and H2O2, which may have important biochemical, environmental, and medical implications for future study of thiourea compounds.

Boosting OER Performance of NiFe‐MOFs via Heterostructure Engineering: Promoted Phase Transformation and Self‐optimized Dynamic Interface Electron Structure

AbstractHow to manipulate heterostructure engineering to achieve high‐efficiency oxygen evolution reaction (OER) remains a significant challenge. Herein, a promising OER heterostructure electrocatalyst with IrNi nanoalloys (≈3.29 ± 0.12 nm) anchored on NiFe‐MOFs (IrNi@NiFe‐MOFs), exhibiting promoted phase transformation and self‐optimized dynamic interface electronic structure, via a one‐step hydrothermal method is designed and developed. Specifically, IrNi@NiFe‐MOFs displays excellent OER performance with a low overpotential of 228 mV at 10 mA cm−2, a small Tafel slope of 37.6 mV dec−1, and robust stability at 10 and 100 mA cm−2. Experimental and theoretical calculations identify the actual active sites as IrNi@NiFeOOH and further reveal that the dynamic structure evolution and self‐optimized dynamic interface electron structure, promoted by heterostructure engineering, boost its OER catalytic performance. Moreover, IrNi@NiFeOOH heterostructure displays strong interface electron interactions and a unique self‐optimized dynamic interface electron structure, resulting in better charge redistribution and adaptive bonding (Ir─O─Ni/Fe bonds). This structure therefore plays a critical role in promoting electron transfer, facilitating the dynamic evolution of reaction intermediates, and reducing the energy barrier of the potential‐determining step, thereby boosting the OER performance. These findings provide new insights into the development of MOF‐based electrocatalysts via heterostructure engineering.

Recent Advances in Transition Metal Chalcogenides Electrocatalysts for Oxygen Evolution Reaction in Water Splitting

Rapid industrial growth has overexploited fossil fuels, making hydrogen energy a crucial research area for its high energy and zero carbon emissions. Water electrolysis is a promising method as it is greenhouse gas-free and energy-efficient. However, OER, a slow multi-electron transfer process, is the limiting step. Thus, developing efficient, low-cost, abundant electrocatalysts is vital for large-scale water electrolysis. In this paper, the application and progress of transition metal chalcogenides (TMCs) as catalysts for the oxygen evolution reaction in recent years are comprehensively reviewed. The key findings highlight the catalytic mechanism and performance of TMCs synthesized using single or multiple transition metals. Notably, modifications through recombination, heterogeneous interface engineering, vacancy, and atom doping are found to effectively regulate the electronic structure of metal chalcogenides, increasing the number of active centers and reducing the adsorption energy of reaction intermediates and energy barriers in OER. The paper further discusses the shortcomings and challenges of TMCs as OER catalysts, including low electrical conductivity, limited active sites, and insufficient stability under harsh conditions. Finally, potential research directions for developing new TMC catalysts with enhanced efficiency and stability are proposed.

Regulating Peripheral Nitrogen Dopants in Single-Atom Catalysts to Enhance Propane Dehydrogenation.

For single-atom catalysts (SACs), the dopants situated near the metal site have demonstrated a significant impact on the catalytic properties. However, the effect of dopants situated further away from the metal centers and their working mechanisms remain to be elucidated. Herein, we conduct density functional theory-driven studies on regulating the peripheral nitrogen dopants in graphene-based SACs, with a particular focus on Ir1 SAC, for propane dehydrogenation (PDH). It is found that increasing the distance between the N dopant and the Ir1 site results in a different energy change for the reaction process compared to the dense doping models with only first and second-shell N species. The proposed stochastic doping models demonstrate statistically that increasing the N dopant in farther shells not only enhances the activity of Ir1 but also maintains a high selectivity for propene, which is verified by experimental tests. The modulation of the d-band center of Ir1 by stochastic N dopants effectively modifies the binding strength of reaction intermediates, thereby enabling the optimization of the potential energy surface of PDH. These results deepen the understanding of dopant states around metal sites and provide an important implication for the doping engineering in heterogeneous catalysis.

Toward Scalable Synthesis of Mo2C/MoNi4 Heterojunction Catalysts on Ni Mesh via Laser Radiation for Efficient H2 Production in Alkaline Electrolysis

AbstractThe alkaline electrolysis is the dominant production method for hydrogen since non‐noble Ni metals can be used as catalysts. The low activity of the commercial nickel mesh (NM) electrodes remains a considerable obstacle to reducing energy consumption for water splitting. Conducting surface modification on commercial NM is a promising tactic to improve the hydrog enevolution reaction (HER) intrinsic activity of NM catalysts. Herein, Mo2C/MoNi4 heterojunction coating on the NM substrate via a laser Radiation strategy is designed. The results indicate that the Mo2C8.5/MoNi4/NM delivers an extremely low overpotential to trigger HER (η10 = 49.5 mV) processes and maintains a stable overpotential for 100 h in alkaline media. The experimental and theoretical calculations reveal that the downshifted d‐band center of Ni in MoNi4 caused by two‐phase heterojunction can regulate the free energy of reactive intermediates adsorption & desorption, thereby accelerating the entire HER process. This work will open up an avenue for developing highly efficient Ni‐based heterostructured electrocatalysts for commercial HER electrode application.

Achieving Near Infrared Photodegradation by the Synergistic Effect of Z-Scheme Heterojunction and Antenna of Rare Earth Single Atoms.

Near-infrared light response catalysts have received great attention in renewable solar energy conversion, energy production, and environmental purification. Here, near-infrared photodegradation is successfully achieved in rare earth single atom anchored NaYF4@g-C3N4 heterojunctions by the synergistic effect of Z-scheme heterojunction and antenna of rare earth single atoms. The UV-vis light emitted by Tm3+ can not only be directly absorbed by g-C3N4 to generate electron-hole pairs, realizing efficient energy transfer, but also be absorbed by NaYF4 substrate, and generating photo-generated electrons at its impurity level, transferring the active charge to the valence band of g-C3N4, forming a Z-scheme heterojunction and further improving the photocatalytic efficiency. Importantly, Tm single atoms has multiple functions such as acting as charge transfer channels to facilitate charge transfer, regulating the critical distance of energy transfer, and prolonging electron-hole pair lifetime. Under NIR light, it exhibited remarkable performance in degrading antibiotics (the removal rate of TC reached 91% for 6 h) while maintaining excellent stability. The LC-MS/MS technology is used to reveal the reaction intermediates, active species, and reaction pathways, and the complex mechanism of photodegradation is further proposed. This study provides experimental and theoretical support for designing and synthesizing catalysts with near-infrared light response characteristics.

Synthesize and characterization of a novel sol–gel-driven Bi2O3 semiconductor: complete degradation and fast photocatalytic activity for paracetamol

Abstract The pollutants are getting released fluently as a waste from the pharmaceutical pollutants leading to the decrease in quality of water. The widespread occurrence of pharmaceutical pollutants poses a serious threat to the environment and human health. Besides, today carbon dioxide emissions and other forms of pollution appear to be a critical global issue. In this study, Bi2O3 catalyst has been prepared via co-precipitation (CP) and a facile sol–gel (SG) methods used as photocatalyst for the degradation of paracetamol (PAR) under different light sources. The preparation method has significant effect on the optical and structural properties of the catalysts. The tetragonal phase of Bi2O3, the presence of more surface OH groups and lower band gap energy remarkably improved the sun-light-driven photoactivity of PAR. The photocatalysts have been characterized by some structural and morphological analysis techniques and optical analysis techniques. In addition, zeta potential (ZP) measurements were performed to explain the impact of the initial pH of solution on photocatalytic degradation. Identification of PAR and the reaction intermediates was determined using Liquid Chromatography-Mass/Mass Spectrometry (LC-MS/MS) technique. Higher photocatalytic activity was obtained with the Bi2O3-SG (1:2) catalyst at pH 5 compared to the activity of Bi2O3-CP. Moreover, Bi2O3-SG (1:2) achieved the highest photocatalytic activity at pH 3. The photocatalytic activity was enhanced, and the time required for 100% degradation of PAR was reduced from 60 min to 30 min and 15 min under UVB irradiation and directly sun light irradiation, respectively. The highest reaction rate (0.086 (min−1)) were obtained in 15 min with the Bi2O3-SG (1:2) catalyst. The results showed TOC removal could be achieved in 60 min 99.19 and 88.97% for Bi2O3-SG and Bi2O3-CP, respectively. In general, sol–gel-driven Bi2O3 as a flower and needle-like morphology, can reveal excellent opportunities in the photocatalytic technology. Graphical Abstract

Advances in the catalytic promiscuity of nitrilases

As important biocatalysts, nitrilases can efficiently convert nitrile groups into acids and ammonia in a mild and eco-friendly manner, being widely used in the synthesis of important pharmaceutical intermediates. Early studies reported that nitrilases only had the hydrolysis activity of catalyzing the formation of corresponding carboxylic acid products from nitriles, showing catalytic specificity. However, recent studies have shown that some nitrilases exhibit the hydration activity for catalyzing the formation of amides from nitriles, showing catalytic promiscuity. The catalytic promiscuity of nitrilases has dual effects. On the one hand, the presence of amide by-products increases the difficulties and costs of subsequent separation and purification of carboxylic acid products. On the other hand, however, if the catalytic reaction pathways of nitrilases can be precisely regulated to reshape enzyme functions, the reactions catalyzed by nitrilases can be broadened to provide new ideas for the biosynthesis of high-value amides, which is crucial for the development of artificial enzymes and biocatalysis. This review summarized the research progress in the catalytic promiscuity of nitrilases and discussed the key regulatory factors that may affect the catalytic promiscuity of nitrilases from the evolutionary origin, catalytic domains, and catalytic mechanisms, hoping to provide reference and inspiration for the application of nitrilases in biocatalysis.

Structural investigations of benzoyl fluoride and the benzoacyl cation of low-melting compounds and reactive intermediates.

Acyl fluorides and acyl cations represent typical reactive intermediates in organic reactions, such as Friedel-Crafts acylation. However, the comparatively stable phenyl-substituted compounds have not been fully characterized yet, offering a promising backbone. Attempts to isolate the benzoacylium cation have only been carried out starting from the acyl chloride with weaker chloride-based Lewis acids. Therefore, only adducts of 1,4-stabilized acyl cations could be obtained. Due to the low melting point of benzoyl fluoride, together with its volitality and sensitivity toward hydrolysis, the structures of the acyl fluoride and its acylium cation have not been determined. Herein, we report the first crystal structure of benzoyl fluoride, C7H5FO or PhCOF (monoclinic P21/n, Z = 8) and the benzoacylium undecafluorodiarsenate, C7H5O+·As2F11- or [PhCO]+[As2F11]- (monoclinic P21/n, Z = 4). The compounds were characterized by low-temperature vibrational spectroscopy and single-crystal X-ray analysis, and are discussed together with quantum chemical calculations. In addition, their specific π-interactions were elucidated.

Intrinsic Mechanical Effects on the Activation of Carbon Catalysts.

The mechanical effects on carbon-based metal-free catalysts (C-MFCs) have rarely been explored, despite the global interest in C-MFCs as substitutes for noble metal catalysts. Stress is ubiquitous, whereas its dedicated study is severely restricted due to its frequent entanglement with other structural variables, such as dopants, defects, and interfaces in catalysis. Herein, we report a proof-of-concept study by establishing a platform to continuously apply strain to a highly oriented pyrolytic graphite (HOPG) lamina, simultaneously collecting electrochemical signals. Notably, we establish, for the first time, the correlation between the surface strain of graphitic carbon and its activation effect on the oxygen reduction reaction (ORR). Our results indicate that while in-plane and edge carbon sites in HOPG could not be further activated by applying tensile strain, a strong and repeatable dependence of catalytic activity on tensile strain was observed when the structure incorporated in-plane defects, leading to a significant ∼35.0% improvement in ORR current density with the application of ∼0.6% tensile strain. Density functional theory (DFT) simulations reveal that appropriate strain on specific defects can optimize the adsorption of reaction intermediates, and the Stone-Wales defect on graphene is correlated with the observed mechanical effect. This work elucidates fundamental principles of strain effects on the catalytic activity of graphitic carbon toward ORR and may lay the groundwork for the development of carbon-based mechano-electrocatalysis.

Mechanism, Performance, and Application of g-C3N5-Coupled TiO2 as an S-Scheme Heterojunction Photocatalyst for the Abatement of Gaseous Benzene.

In this research, S-scheme heterojunction photocatalysts are prepared through the hybridization of nitrogen-rich g-C3N5 with TiO2 (coded as TCN5-(x): x as the weight ratio of TiO2:g-C3N5). The photocatalytic potential of TCN5-(x) is evaluated against benzene (1-5 ppm) across varying humidity levels using a dynamic flow packed-bed photocatalytic reactor. Among the prepared composites, TCN5-(10) exhibits the highest synergy between g-C3N5 and TiO2 at "x" ratio of 10%, showing superior best benzene degradation performance (e.g., 93.9% removal efficiency, specific clean air delivery rate of 1126.9 L g-1 h-1, kinetic reaction rate of 46.1 nmol mg-1 min-1, quantum yield of 6.0 × 10-4 molec. photon-1, and space-time yield of 1.2 × 10-4 molec. photon-1 mg-1). The formation of an S-scheme heterojunction with a built-in internal electric field is supported by both theoretical (through the density functional theory calculations) and photoelectrochemical bases (e.g., improvement in the band potential and electrochemistry along with surface characteristics (e.g., reactive sites and charge migrations at the interface)). The results of the in situ DRIFTS analysis confirm that the oxidation of benzene molecules is accompanied by many reaction intermediates (e.g., phenolate, maleate, acetate, and methylene). The outcomes of this work will help us pursue the development of a state-of-the-art photocatalytic system for air quality management.

Densely populated macrocyclic dicobalt sites in ladder polymers for low-overpotential oxygen reduction catalysis

Dual-atom catalysts featuring synergetic dinuclear active sites, have the potential of breaking the linear scaling relationship of the well-established single-atom catalysts for oxygen reduction reaction; however, the design of dual-atom catalysts with rationalized local microenvironment for high activity and selectivity remains a great challenge. Here we design a bisalphen ladder polymer with well-defined densely populated binuclear cobalt sites on Ketjenblack substrates. The strong electron coupling effect between the fully-conjugated ladder structure and carbon substrates enhances the electron transfer between the cobalt center and oxygen intermediates, inducing the low-to-high spin transition for the 3d electron of Co(II). In situ techniques and theoretical calculations reveal the dynamic evolution of Co2N4O2 active sites and reaction intermediates. In alkaline conditions, the catalyst exhibits impressive oxygen reduction reaction activity featuring an onset potential of 1.10 V and a half-wave potential of 1.00 V, insignificant decay after 30,000 cycles, pushing the overpotential boundaries of ORR electrocatalysis to a low level. This work provides a platform for designing efficient dual-atom catalysts with well-defined coordination and electronic structures in energy conversion technologies.

Atomically Dispersed Ta-O-Co Sites Capable of Mitigating Side Reaction Occurrence for Stable Lithium-Oxygen Batteries.

The side reactions accompanying the charging and discharging process, as well as the difficulty in decomposing the discharge product lithium peroxide, have been important issues in the research field of lithium-oxygen batteries for a long time. Here, single atom Ta supported by Co3O4 hollow sphere was designed and synthesized as a cathode catalyst. The single atom Ta forms an electron transport channel through the Ta-O-Co structure to stabilize octahedral Co sites, forming strong adsorption with reaction intermediates and ultimately forming a film-like lithium peroxide that is highly dispersed. More importantly, the formation of the Ta-O-Co structure can reduce the vacancy formation energy on the catalyst surface, accelerate oxygen activation and conversion into superoxide anions, promote the rapid conversion of strong oxidizing intermediate lithium superoxide into lithium peroxide, avoid the oxidation of lithium superoxide to the electrode and electrolyte, reduce the occurrence of side reactions, and mitigate the production of byproduct lithium carbonate. The overpotential of the battery is reduced significantly, and the reversibility and cycling stability of the battery are improved. This study provides a practical and feasible direction for mitigating the side reaction and improving the performance of the battery.