Engineering the Electronic Interaction between Atomically Dispersed Fe and RuO2 Attaining High Catalytic Activity and Durability Catalyst for Li-O2 Battery

Upcycling Spent Cathodes from Li-Ion Batteries into a High-Entropy Alloy Catalyst with Reverse Electron Transfer for Li-O2 Batteries

Traditional recovery of valuable metals from spent ternary lithium-ion batteries concentrates on complicated pyrometallurgy and hydrometallurgy routes. Direct reutilization of these valuable used metals to catalyze Li-O2 batteries is highly appealing yet remains a significant challenge. Here, we report a general synthesis of ultrafine αNiCoMn (α = Pt, Ir, Ru) high-entropy alloy (HEA) nanoparticles anchored on a nitrogen-doped carbon (N-C) support through a facile one-step Joule heating, which serves as a high-efficiency catalyst for Li-O2 batteries. Solution alloying of recycled NiCoMn with Pt group metals facilitates catalytic efficiency through 3d-5d electronic interactions and the high-entropy assembly effect. Both experimental and calculation results reveal that, driven by rapid, nonequilibrium thermal shock, electron transfer defies conventional expectations, where the electrons are inclined to transfer from the higher electronegative Pt to the surrounding NiCoMn atoms. This interesting reverse local charge redistribution and orbital hybridization endow Pt with an elevated d-band center and an optimized electronic structure. The induced high-entropy coordination effects further generate highly active catalysis surfaces, favoring the adsorption of LiO2 intermediates and facilitating rapid decomposition kinetics of nanoscale Li2O2 products. These advantages endow Pt HEA@N-C with superior bifunctional catalytic activity, achieving an ultralow polarization of 0.27 V and a significantly enhanced cycling life of 240 cycles. We anticipate that this work will provide further insights into upcycling spent valuable metals for constructing efficient HEA electrocatalysts.

Electron Itinerancy Mediated by Oxygen Vacancies Breaks the Inert Electron Chain to Boost Lithium-Oxygen Batteries Electrocatalysis

The synergistic effect of dopants and oxygen vacancies (Vo) in metal oxides is crucial for enhancing the adsorption and electron transfer processes in lithium-oxygen (Li-O2) batteries; however, the underlying mechanisms remain unclear. Herein, Ru single-atom-modified TiO2 nanorod array (Ru1-TiO2- x) electrocatalysts with abundant Vo were fabricated, serving as an efficient catalyst for Li-O2 batteries. Experimental and theoretical investigations have demonstrated that Vo functions as an "electron pump", facilitating electron itinerant behavior, while Ru1 serves as an "electron buffer" to further activate the [Ru-O-Ti] electronic chain. This synergistic interplay endows Li-O2 batteries with a highly active and stable bidirectional self-regulating capability during the process of circulation, exhibiting an ultra-low charge polarization (0.42V) and exceptional cycling stability (1680 h). Vo and Ru1 synergistically modulate the d-band center at the Ti site to establish an adaptively tunable Ru-Ti dual-active site. This adjustment effectively balances the binding strength with the interface oxygen intermediate (*O), thereby significantly reducing the activation barrier. The Hamiltonian layout further revealed the crucial role of remote orbital coupling in maintaining the structural stability. This study not only provides profound insights into Vo-dependent electron transfer kinetics but also proposes new strategies and theoretical guidance for the activation of inert materials.

A Self-Catalysis System Coupled with Redox Mediator Effect for Ultra-Long Cycle Life Li-O2 Batteries

The sluggish kinetics of Li-O2 batteries significantly limit their performance. To address this issue, the insulating characteristics of the discharge product Li2O2 and the reactivity of highly active superoxide species are examined. Herein, organic metal salts with weak electrolyte properties are utilized as bifunctional additives. The ionized metal ions can be reduced and doped Li2O2 through in situ electrochemical implantation, thereby altering its insulating properties. Additionally, organic metal salts function as redox mediators (RMs), stabilizing the intermediate LiO2 and facilitating its further disproportionation to Li2O2, as well as enhancing the decomposition reaction during charging, which are further proven by the in situ X-ray absorption spectroscopy and UV-vis spectroscopy. Notably, Li-O2 batteries incorporating Mn(acac)3 demonstrate an ultra-low overpotential of 0.43 V and sustain 250 long cycles at 1000 mA g-1. Furthermore, when combined with the optimized cathode, a remarkable cycle stability of 3850 cycles at 1000 mA g-1 is achieved. These findings offer novel insights into the design of advanced Li-O2 battery systems and the enhancement of their performance.

Construction of an Oxygen-Vacancy-Rich CeO2@CoO Heterojunction toward High-Performance Lithium-Oxygen Batteries

Lithium-oxygen (Li-O2) batteries theoretically possess an exceptional energy density comparable to gasoline (up to 3500 W h kg-1), but in practical applications, the discharge products are difficult to effectively decompose, which leads to clogging of the cathode, resulting in severe polarization, limited actual capacity, and shortened battery life for Li-O2 batteries. Herein, we construct a highly active and stable catalyst with d-f electronic orbit coupling as a redox center by anchoring CeO2 onto CoO, simultaneously, oxygen vacancy (Ov) and CeO2 coactivated CoO. By leveraging the effects of interface engineering and defect engineering on the electronic structure of the catalyst, the adsorption energy for LiO2 can be adjusted to an ideal range. This not only avoids surface passivation caused by excessively strong binding energy but also overcomes the issue of sluggish Li2O2 decomposition efficiency due to excessively weak binding energy. Bracingly, the CeO2/CoO-based Li-O2 batteries exhibit an ultralow charge-discharge polarization, and Li2O2 was successfully induced to nucleate uniformly in nanoflower-like shapes, which could promote the reversible decomposition of the discharge products during the charging process and thereby enhance the electrochemical performance of Li-O2 batteries. Therefore, the CeO2@CoO/CC cathode exhibited an ultralow overpotential of 0.57 V and achieved a high discharge capacity of 19,850 mA h g-1. This work provides an important reference for designing the structure of cathode catalysts for Li-O2 batteries and regulating the growth paths and morphologies of discharge products.

Anti-Self-Discharge Capability of Zn-Halogen Batteries Through an Entrapment-Adsorption-Catalysis Strategy Built Upon Separator

Aqueous Zn-halogen batteries (Zn-I2/Br2) suffer from grievous self-discharge behavior, resulting in irreversible loss of active cathode material and severe corrosion of zinc anode, which ultimately leads to rapid battery failure. Herein, an entrapment-adsorption-catalysis strategy is reported, leveraging Zn─Mn atom pairs-modified glass fiber separator (designated as ZnMn-NC/GF), to effectively mitigate the self-discharge phenomenon. The in situ Raman and UV experiments, along with theoretical calculations, confirmed the single-atom Mn sites are responsible for polyiodides adsorption, while Zn─Mn atom pairs facilitated the conversion of reaction intermediates. As a result, the utilization rate of cathode active species is enhanced through this ZnMn-NC/GF separator. The fully charged Zn-I2 battery assembled with ZnMn-NC/GF maintained a Coulombic efficiency (CE) of 90.1% after being left for 120 h, as well as a capacity retention rate of 95.3% after 30000 cycles at a current density of 5 A g-1. Additionally, the Zn-Br2 battery designed with ZnMn-NC/GF separator can withstand more serious self-discharge problems of bromine species, with an average discharge voltage platform of 1.75 V at 0.5 A g-1. The self-discharge problem of aqueous Zn-halogen batteries is significantly suppressed by this entrapment-adsorption-catalysis strategy, which can serve as a crucial reference for the advancement of high-performance aqueous Zn-halogen batteries.

Harnessing 4f Electron Itinerancy for Integrated Dual-Band Redox Systems Boosts Lithium-Oxygen Batteries Electrocatalysis

In-depth comprehension and manipulation of band occupation at metal centers are crucial for facilitating effective adsorption and electron transfer in lithium-oxygen battery (LOB) reactions. Rare earth elements play a unique role in band hybridization due to their deep orbitals and strong localization of 4 f electrons. Herein, we anchor single Ce atoms onto CoO, constructing a highly active and stable catalyst with d-f a dual-band redox center. It is discovered that the itinerant behavior of 4 f electrons introduces an enhanced spin-orbit coupling effect, which facilitates ideal σ/π bonding and flexible adsorption between the Ce/Co active sites and *O. Simultaneously, the injection of localized Ce 4 f electrons strengthens the orbital bonding capacity of Co-O, effectively inhibits the dissolution of Co sites and improves the structural stability of the cathode material. Bracingly, the Ce1/CoO-based LOB exhibits an ultra-low charge-discharge polarization (0.46 V) and stable cyclic performance (1088 hours). This work breaks through the traditional limitations in catalyst activity and stability, providing new strategies and theoretical insights for developing high-performance LOBs powered by rare-earth elements.

Strong Metal-Support Interactions in Heterogeneous Oxygen Electrocatalysis

Molecular oxygen redox electrocatalysis involves oxygen reduction and evolution as core reactions in various energy conversion and environmental technology fields. Strong metal-support interactions (SMSIs) based nanomaterials are regarded as desirable and state-of-the-art heterogeneous electrocatalysts due to their exceptional physicochemical properties. Over the past decades, considerable advancements in theory and experiment have been achieved in related studies, especially in modulating the electronic structure and geometrical configuration of SMSIs to enable activity, selectivity, and stability. In this focuses on the concept of SMSI, explore their various manifestations and mechanisms of action, and summarizes recent advances in SMSIs for efficient energy conversion in oxygen redox electrocatalysis applications. Additionally, the correlation between the physicochemical properties of different metals and supports is systematically elucidated, and the potential mechanisms of the structure-activity relationships between SMSIs and catalytic performance are outlined through theoretical models. Finally, the obstacles confronting this burgeoning field are comprehensively concluded, targeted recommendations and coping strategies are proposed, and future research perspectives are outlined.

Self-supported Ru-Fe-Ox nanospheres as efficient electrocatalyst to boost overall water-splitting in acid and alkaline media

Developing electrocatalysts with high activity and durability for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in both acidic and alkaline electrolytes remains challenging. In this study, we synthesize a self-supported ruthenium-iron oxide on carbon cloth (Ru-Fe-Ox/CC) using solvothermal methods followed by air calcination. The morphology of the nanoparticle exposes numerous active sites vital for electrocatalysis. Additionally, the strong electronic interaction between Ru and Fe enhances electrocatalytic kinetics optimization. The porous structure of the carbon cloth matrix facilitates mass transport, improving electrolyte penetration and bubble release. Consequently, Ru-Fe-Ox/CC demonstrates excellent catalytic performance, achieving low overpotentials of 32 mV and 28 mV for HER and 216 mV and 228 mV for OER in acidic and alkaline electrolytes, respectively. Notably, only 1.48 V and 1.46 V are required to reach 10 mA cm-2 for efficient water-splitting in both mediums, exhibiting remarkable stability. This research offers insights into designing versatile, highly efficient catalysts suitable for varied pH conditions.

Oxygen-bridged W-Pd atomic pairs enable H2O2 activation for sensitive immunoassays

Regulating the performance of peroxidase (POD)-like nanozymes is a prerequisite for achieving highly sensitive and accurate immunoassays. Inspired by natural enzyme catalysis, we design a highly active and selective nanozyme by loading atomically dispersed tungsten (W) sites on Pd metallene (W-O-Pdene) to construct an artificial three-dimensional (3D) catalytic center. The 3D asymmetric W-O-Pd atomic pairs can effectively stretch the O-O bonds in H2O2 and further promote the desorption of H2O to enhance POD-like activity. Moreover, the W-O-Pd sites with unique spatial structures demonstrate satisfactory specificity for H2O2 activation, effectively preventing the interference of dissolved oxygen. Accordingly, the highly active and specific W-O-Pdene nanozymes are utilized for sensitive and accurate prostate-specific antigen (PSA) immunoassay with a low detection limit of 1.92 pg mL-1, superior to commercial enzyme-linked immunosorbent assay.

Unleashing the potential of Li-O2 batteries with electronic modulation and lattice strain in pre-lithiated electrocatalysts

Efficient catalysts are indispensable for overcoming the sluggish reaction kinetics and high overpotentials inherent in Li-O2 batteries. However, the lack of precise control over catalyst structures at the atomic level and limited understanding of the underlying catalytic mechanisms pose significant challenges to advancing catalyst technology. In this study, we propose the concept of precisely controlled pre-lithiated electrocatalysts, drawing inspiration from lithium electrochemistry. Our results demonstrate that Li+ intercalation induces lattice strain in RuO2 and modulates its electronic structure. These modifications promote electron transfer between catalysts and reaction intermediates, optimizing the adsorption behavior of Li-O intermediates. As a result, Li-O2 batteries employing Li0.52RuO2 exhibit ultrahigh energy efficiency, long lifespan, high discharge capacity, and excellent rate performance. This research offers valuable insights for the design and optimization of efficient electrocatalysts at the atomic level, paving the way for further advancements in Li-O2 battery technology.

Methacrylated Wood Flour-Reinforced Gelatin-Based Gel Polymer as Green Electrolytes for Li-O2 Batteries

With its very high theoretical energy density, the Li-O2 battery could be considered a valid candidate for future advanced energy storage solutions. However, the challenges hindering the practical application of this technology are many, as for example electrolyte degradation under the action of superoxide radicals produced upon cycling. In that frame, a gel polymer electrolyte was developed starting from waste-derived components: gelatin from cold water fish skin, waste from the fishing industry, and wood flour waste from the wood industry. Both were methacrylated and then easily cross-linked through a one-pot ultraviolet (UV)-initiated free radical polymerization, directly in the presence of the liquid electrolyte (0.5 M LiTFSI in DMSO). The wood flour works as cross-linking points, reinforcing the mechanical properties of the obtained gel polymer electrolyte, but it also increases Li-ion transport properties with an ionic conductivity of 3.3 mS cm-1 and a transference number of 0.65 at room temperature. The Li-O2 cells assembled with this green gel polymer electrolyte were able to perform 180 cycles at 0.1 mA cm-2, at a fixed capacity of 0.2 mAh cm-2, under a constant O2 flow. Cathodes post-mortem analysis confirmed that this electrolyte was able to slow down solvent degradation, but it also revealed that the higher reversibility of the cells could be explained by the formation of Li2O2 in the amorphous phase for a higher number of cycles compared to a purely gelatin-based electrolyte.

Modulating the d-Band Center of RuO2 via Ni Incorporation for Efficient and Durable Li-O2 batteries

Rechargeable Li-O2 batteries (LOBs) are considered as one of the most promising candidates for new-generation energy storage devices. One of major impediments is the poor cycle stability derived from the sluggish reaction kinetics of unreliable cathode catalysts, hindering the commercial application of LOBs. Therefore, the rational design of efficient and durable catalysts is critical for LOBs. Optimizing surface electron structure via the negative shift of the d-band center offers a reasonable descriptor for enhancing the electrocatalytic activity. In this study, the construction of Ni-incorporating RuO2 porous nanospheres is proposed as the cathode catalyst to demonstrate the hypothesis. Density functional theory calculations reveal that the introduction of Ni atoms can effectively modulate the surface electron structure of RuO2 and the adsorption capacities of oxygen-containing intermediates, accelerating charge transfer between them and optimizing the growth pathway of discharge products. Resultantly, the LOBs exhibit a large discharge specific capacity of 19658 mA h g-1 at 200 mA g-1 and extraordinary cycle life of 791 cycles. This study confers the concept of d-band center modulation for efficient and durable cathode catalysts of LOBs.

Constructing Built-In Electric Field in NiCo2O4-CeO2 Heterostructures to Regulate Li2O2 Formation Routes at High Current Densities

Developing catalysts with suitable adsorption energy for oxygen-containing intermediates and elucidating their internal structure-performance relationships are essential for the commercialization of Li-O2 batteries (LOBs), especially under high current densities. Herein, NiCo2O4-CeO2 heterostructure with a spontaneous built-in electric field (BIEF) is designed and utilized as a cathode catalyst for LOBs at high current density. The driving mechanism of electron pumping/accumulation at heterointerface is studied via experiments and density functional theory (DFT) calculations, elucidating the growth mechanism of discharge products. The results show that BIEF induced by work function difference optimizes the affinity for LiO2 and promotes the formation of nano-flocculent Li2O2, thus improving LOBs performance at high current density. Specifically, NiCo2O4-CeO2 cathode exhibits a large discharge capacity (9546 mAh g-1 at 4000 mA g-1) and high stability (>430 cycles at 4000 mA g-1), which are better than the majority of previously reported metal-based catalysts. This work provides a new method for tuning the nucleation and decomposition of Li2O2 and inspires the design of ideal catalysts for LOBs to operate at high current density.

Tuning the Electronic Property of Reconstructed Atomic Ni-CuO Cluster Supported on N/O-C for Electrocatalytic Oxygen Evolution

Electrochemical activation usually accompanies in situ atom rearrangement forming new catalytic sites with higher activity due to reconstructed atomic clusters or amorphous phases with abundant dangling bonds, vacancies, and defects. By harnessing the pre-catalytic process of reconstruction, a multilevel structure of CuNi alloy nanoparticles encapsulated in N-doped carbon (CuNi nanoalloy@N/C) transforms into a highly active compound of Ni-doped CuO nanocluster supported on (N/O-C) co-doped C. Both the exposure of accessible active sites and the activity of individual active sites are greatly improved after the pre-catalytic reconstruction. Manipulating the Cu/Ni ratios of CuNi nanoalloy@N/C can tailor the electronic property and d-band center of the high-active compound, which greatly optimizes the energetics of oxygen evolution reaction (OER) intermediates. This interplay among Cu, Ni, C, N, and O modifies the interface, triggers the active sites, and regulates the work functions, thereby realizing a synergistic boost in OER.

First Principles Study of the Structure-Performance Relation of Pristine Wn+1Cn and Oxygen-Functionalized Wn+1CnO2 MXenes as Cathode Catalysts for Li-O2 Batteries

Li-O2 batteries are considered a highly promising energy storage solution. However, their practical implementation is hindered by the sluggish kinetics of the oxygen reduction (ORR) and oxygen evolution (OER) reactions at cathodes during discharging and charging, respectively. In this work, we investigated the catalytic performance of Wn+1Cn and Wn+1CnO2 MXenes (n = 1, 2, and 3) as cathodes for Li-O2 batteries using first principles calculations. Both Wn+1Cn and Wn+1CnO2 MXenes show high conductivity, and their conductivity is further enhanced with increasing atomic layers, as reflected by the elevated density of states at the Fermi level. The oxygen functionalization can change the electronic properties of WC MXenes from the electrophilic W surface of Wn+1Cn to the nucleophilic O surface of Wn+1CnO2, which is beneficial for the activation of the Li-O bond, and thus promotes the Li+ deintercalation during the charge-discharge process. On both Wn+1Cn and Wn+1CnO2, the rate-determining step (RDS) of ORR is the formation of the (Li2O)2* product, while the RDS of OER is the LiO2* decomposition. The overpotentials of ORR and OER are positively linearly correlated with the adsorption energy of the RDS LixO2* intermediates. By lowering the energy band center, the oxygen functionalization and increasing atomic layers can effectively reduce the adsorption strength of the LixO2* intermediates, thereby reducing the ORR and OER overpotentials. The W4C3O2 MXene shows immense potential as a cathode catalyst for Li-O2 batteries due to its outstanding conductivity and super-low ORR, OER, and total overpotentials (0.25, 0.38, and 0.63 V).

Constructing Symmetry-Mismatched RuxFe3-xO4 Heterointerface-Supported Ru Clusters for Efficient Hydrogen Evolution and Oxidation Reactions

Ru-related catalysts have shown excellent performance for the hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR); however, a deep understanding of Ru-active sites on a nanoscale heterogeneous support for hydrogen catalysis is still lacking. Herein, a click chemistry strategy is proposed to design Ru cluster-decorated nanometer RuxFe3-xO4 heterointerfaces (Ru/RuxFe3-xO4) as highly effective bifunctional hydrogen catalysts. It is found that introducing Ru into nanometric Fe3O4 species breaks the symmetry configuration and optimizes the active site in Ru/RuxFe3-xO4 for HER and HOR. As expected, the catalyst displays prominent alkaline HER and HOR performance with mass activity much higher than that of commercial Pt/C as well as robust stability during catalysis because of the strong interaction between the Ru cluster and the RuxFe3-xO4 support, and the optimized adsorption intermediate (Had and OHad). This work sheds light on a promsing approach to improving the electrocatalysis performance of catalysts by the breaking of atomic dimension symmetry.

New Reaction Pathway of Superoxide Disproportionation Induced by a Soluble Catalyst in Li-O2 Batteries

Aprotic Li-O2 battery has attracted considerable interest for high theoretical energy density, however the disproportionation of the intermediate of superoxide (O2 - ) during discharge and charge leads to slow reaction kinetics and large voltage hysteresis. Herein, the chemically stable ruthenium tris(bipyridine) (RB) cations are employed as a soluble catalyst to alternate the pathway of O2 - disproportionation and its kinetics in both the discharge and charge processes. RB captures O2 - dimer and promotes their intramolecular charge transfer, and it decreases the energy barrier of the disproportionation reaction from 7.70 to 0.70 kcal mol-1 . This facilitates the discharge and charge processes and simultaneously mitigates O2 - and singlet oxygen related side reactions. These endow the Li-O2 battery with reduced discharge/charge voltage gap of 0.72 V and prolonged lifespan for over 230 cycles when coupled with RuO2 catalyst. This work highlights the vital role of superoxide disproportionation for Li-O2 battery.