Structure-dependent spin-polarized electron transport in twin-crystal Cu1-xEuxO semiconductors.

In this work, Eu-doped twin copper oxide (twin Cu1-xEuxO) was synthesized using the gas-liquid phase chemical deposition method in combination with high-temperature oxidation. The incorporation of Eu3+ ions was affected by their diffusivity and the related charge trapping mechanisms. The twin Cu1-xEuxO configuration exhibited significant room-temperature ferromagnetism. From our analysis, it was demonstrated that as the Eu3+ doping concentration increased, the saturation magnetization first increased and then gradually decreased, reaching a peak at 0.82 at%. A p-type to an n-type semiconducting transition was also recorded as the doping concentration increased. A significant anomalous Hall effect characterized by a maximum anomalous Hall coefficient of 1.65, and a maximum Hall conductivity mobility of 16.50 Ohm-1 cm-1 and 250.59 cm2 v-1 s-1, respectively, were derived for the twin Cu1-xEuxO, doped with 0.82 at% at room temperature. First-principles computational simulations were also conducted to elucidate the underlying mechanisms of the magnetic properties, the p-type to n-type transition, and the interplay between the spin-polarized states associated with 4f and carriers. In twin Cu1-xEuxO, the anomalous Hall effect originated from the contribution of the edge-to-jump scattering mechanism. The latter can be significantly enhanced by doping with Eu atoms, which yields the manifestation of the oblique scattering mechanism. Our work paves the way for the development of twin Cu1-xEuxO material structures, which emerge as an ideal candidate for future spintronic applications.

Regulating the Spin State Configuration in Bimetallic Phosphorus Trisulfides for Promoting Sulfur Redox Kinetics.

Lithium-sulfur (Li-S) batteries suffer from sluggish kinetics due to the poor conductivity of sulfur cathodes and polysulfide shutting. Current studies on sulfur redox catalysis mainly focus on the adsorption and catalytic conversion of lithium polysulfides but ignore the modulation of the electronic structure of the catalysts which involves spin-related charge transfer and orbital interactions. In this work, bimetallic phosphorus trisulfides embedded in Prussian blue analogue-derived nitrogen-doped hollow carbon nanocubes (FeCoPS3/NCs) were elaborately synthesized as a host to reveal the relationship between the catalytic activity and the spin state configuration for Li-S batteries. Orbital spin splitting in FeCoPS3 drives the electronic structure transition from low-spin to high-spin states, generating more unpaired electrons on the 3d orbit. Specifically, the nondegenerate orbitals involved in the high-spin configuration of FeCoPS3 result in the upshift of energy levels, generating more active electronic states. Such tailored electronic structure increases the charge transfer, influences the d-band center, and further modifies the adsorption energy with lithium polysulfides and the potential reaction pathways. Consequently, the cell with FeCoPS3/NC host exhibits an ultralow capacity decay of 0.037% per cycle over 1000 cycles. This study proposed a general strategy for sculpting geometric configurations to enable spin and orbital topology regulation in Li-S battery catalysts.

Anions Regulation Engineering Enables a Highly Reversible and Dendrite-Free Nickel-Metal Anode with Ultrahigh Capacities.

The development of safe and high-energy metal anodes represents a crucial research direction. Here, the achievement of highly reversible, dendrite-free transition metal anodes with ultrahigh capacities by regulating aqueous electrolytes is reported. Using nickel (Ni) as a model, theoretical and experimental evidence demonstrating the beneficial role of chloride ions in inhibiting and disrupting the nickel hydroxide passivation layer on the Ni electrode is provided. As a result, Ni anodes with an ultrahigh areal capacity of 1000 mAh cm-2 (volumetric capacity of ≈6000 mAh cm-3 ), and a Coulombic efficiency of 99.4% on a carbon substrate, surpassing the state-of-the-art metal electrodes by approximately two orders of magnitude, are realized. Furthermore, as a proof-of-concept, a series of full cells based on the Ni anode is developed. The designed Ni-MnO2 full battery exhibits a long lifespan of 2000 cycles, while the Ni-PbO2 full battery achieves a high areal capacity of 200 mAh cm-2 . The findings of this study are important for enlightening a new arena toward the advancement of dendrite-free Ni-metal anodes with ultrahigh capacities and long cycle life for various energy-storage devices.

Modulation of p- and n-Type Transitions in Co3- x Nix O4 Nanoparticles for Enhanced Supercapacitor Electrochemical Performance.

The efficient storage of electrons and the type of conduction in semiconductor materials are important factors in determining their electrochemical performance. However, the interaction between these two factors is often overlooked by researchers. In this study, the effects of Ni doping at Co3- x Nix O4 nanoparticles on the electronic storage form of the material and resulting changes in the conduction p/n-type are reported. Theoretical calculations demonstrate that n-type conduction with high effective mass of electrons contributes significantly to the redox reaction of electrode materials and is beneficial for improving electrochemical performance. The specific capacitance of Co3- x Nix O4 (x = 0.67) electrode material is 10 times larger than that of Co3 O4 due to enhanced orbital hybridization caused by Ni atom doping. The findings provide new directions for exploring the mechanism of conductive type conversion of materials and offer insights beyond the traditional approach of considering doping content alone.

Aqueous Zinc-Chlorine Battery Modulated by a MnO2 Redox Adsorbent.

Aqueous zinc-chlorine battery with high discharge voltage and attractive theoretical energy density is expected to become an important technology for large-scale energy storage. However, the practical application of Zn-Cl2 batteries has been restricted due to the Cl2 cathode with sluggish kinetics and low Coulombic efficiency (CE). Here, an aqueous Zn-Cl2 battery using an inexpensive and effective MnO2 redox adsorbent (referred to Zn-Cl2 @MnO2 battery) to modulate the electrochemical performance of the Cl2 cathode is developed. Density functional theory calculations reveal that the existence of the intermediate state Clads free radical catalyzed by MnO2 on the Cl2 cathode contributes to the charge storage capacity, which is the key to modulate the electrode and improve the electrochemical performance. Further analysis of the Cl2 cathode kinetics discloses the adsorption and catalytic roles of the MnO2 redox adsorbent. The Zn-Cl2 @MnO2 battery displays an enhanced discharge voltage of 2.0 V at a current density of 2.5 mA cm-2 , and stable 1000 cycles with an average CE of 91.6%, much superior to the conventional Zn-Cl2 battery with an average CE of only 66.8%. The regulation strategy to the Cl2 cathode provides opportunities for the future development of aqueous Zn-Cl2 batteries.

Constructing robust heterostructured interface for anode-free zinc batteries with ultrahigh capacities.

The development of Zn-free anodes to inhibit Zn dendrite formation and modulate high-capacity Zn batteries is highly applauded yet very challenging. Here, we design a robust two-dimensional antimony/antimony-zinc alloy heterostructured interface to regulate Zn plating. Benefiting from the stronger adsorption and homogeneous electric field distribution of the Sb/Sb2Zn3-heterostructured interface in Zn plating, the Zn anode enables an ultrahigh areal capacity of 200 mAh cm-2 with an overpotential of 112 mV and a Coulombic efficiency of 98.5%. An anode-free Zn-Br2 battery using the Sb/Sb2Zn3-heterostructured interface@Cu anode shows an attractive energy density of 274 Wh kg-1 with a practical pouch cell energy density of 62 Wh kg-1. The scaled-up Zn-Br2 battery in a capacity of 500 mAh exhibits over 400 stable cycles. Further, the Zn-Br2 battery module in an energy of 9 Wh (6 V, 1.5 Ah) is integrated with a photovoltaic panel to demonstrate the practical renewable energy storage capabilities. Our superior anode-free Zn batteries enabled by the heterostructured interface enlighten an arena towards large-scale energy storage applications.

High-Capacity Zinc Anode with 96 % Utilization Rate Enabled by Solvation Structure Design.

Aqueous zinc-ion batteries (AZBs) show promises for large-scale energy storage. However, the zinc utilization rate (ZUR) is generally low due to side reactions in the aqueous electrolyte caused by the active water molecules. Here, we design a novel solvation structure in the electrolyte by introduction of sulfolane (SL). Theoretical calculations, molecular dynamics simulations and experimental tests show that SL remodels the primary solvation shell of Zn2+ , which significantly reduces the side reactions of Zn anode and achieves high ZUR under large capacities. Specifically, the symmetric and asymmetric cells could achieve a maximum of ∼96 % ZUR at an areal capacity of 24 mAh cm-2 . In a ZUR of ∼67 %, the developed Zn-V2 O5 full cell can be stably cycled for 500 cycles with an energy density of 180 Wh kg-1 and Zn-AC capacitor is stable for 5000 cycles. This electrolyte structural engineering strategy provides new insight into achieving high ZUR of Zn anodes for high performance AZBs.

Proton-Trapping Agent for Mitigating Hydrogen Evolution Corrosion of Zn for an Electrolytic MnO2/Zn Battery.

A rechargeable aqueous electrolytic MnO2/Zn battery (EMZB) based on a reversible Mn2+/MnO2 two-electron redox reaction in an acidic electrolyte is very attractive for large-scale energy storage due to its high output voltage, large gravimetric capacity, and low cost. However, severe hydrogen evolution corrosion (HEC) of the Zn anode in an acidic electrolyte limits its application. Here, a proton-trapping agent (PTA) is introduced in the electrolyte to improve the electrochemical performance of the EMZB. Experimental results and theoretical calculations demonstrate that HEC of the Zn electrode can be effectively mitigated through high binding energy between the protons and PTA. The optimized EMZB regulated by a PTA of acetate (EMZB-20% Ac) delivers a high discharge voltage of 1.91 V and over 400 stable cycles at 1 C, which is more than 5 times the cycle life of the battery without PTA. EMZB-20% Ac also shows a Coulombic efficiency of 90.7% at a high areal capacity of 8 mAh cm-2 and an energy retention of 83.6% after 1000 cycles at 5 C with an areal capacity of 1 mAh cm-2. This work provides a promising electrolyte regulation strategy for the design and application of a high-performance EMZB and other energy storage systems.

Descriptor-Driven Computational Design of Bifunctional Double-Atom Hydrogen Evolution and Oxidation Reaction Electrocatalysts for Rechargeable Hydrogen Gas Batteries.

Rechargeable hydrogen gas batteries (RHGBs) have been attracting much attention as promising all-climate large-scale energy storage devices, which calls for low-cost and high-activity hydrogen evolution/oxidation reaction (HER/HOR) bifunctional electrocatalysts to replace the costly platinum-based catalysts. Based on density functional theory (DFT) computations, herein we report an effective descriptor-driven design principle to govern the HER/HOR electrocatalytic activity of double-atom catalysts (DACs) for RHGBs. We systematically investigate the d-band center variation of DACs and their correlations with HER/HOR free energies. We construct activity maps with the d-band center of DACs as a descriptor, which demonstrate that high HER/HOR electrocatalytic activity can be achieved with an appropriate d-band center of DACs. This work not only broadens the applicability of d-band center theory to the prediction of bifunctional HER/HOR electrocatalysts but also paves the way to fast screening and design of efficient and low-cost DACs to promote practical applications of RHGBs.

Theory-Driven Design of a Cationic Accelerator for High-Performance Electrolytic MnO2 -Zn Batteries.

Aqueous electrolytic MnO2 -Zn batteries are considered as one of the most promising energy-storage devices for their cost effectiveness, high output voltage, and safety, but their electrochemical performance is limited by the sluggish kinetics of cathodic MnO2 /Mn2+ and anodic Zn/Zn2+ reactions. To overcome this critical challenge, herein, a cationic accelerator (CA) strategy is proposed based on the prediction of first-principles calculations. Poly(vinylpyrrolidone) is utilized as a model to testify the rational design of the CA strategy. It manifests that the CA effectively facilitates rapid cations migration in electrolyte and adequate charge transfer at electrode-electrolyte interface, benefiting the deposition/dissolution processes of both Mn2+ and Zn2+ cations to simultaneously improve kinetics of cathodic MnO2 /Mn2+ and anodic Zn/Zn2+ reactions. The resulting MnO2 -Zn battery regulated by CA exhibits large reversible capacities of 455 mAh g-1 and 3.64 mAh cm-2 at 20 C, as well as a long lifespan of 2000 cycles with energy density retention of 90%, achieving one of the best overall performances in the electrolytic MnO2 -Zn batteries. This comprehensive work integrating theoretical prediction with experimental studies provides opportunities to the development of high-performance energy-storage devices.

Nucleophilic Interfacial Layer Enables Stable Zn Anodes for Aqueous Zn Batteries.

Aqueous Zn batteries are emerging as promising energy storage devices. However, severe dendrite growth and side reactions of Zn anodes restrict their further development. Herein, we develop a nucleophilic interfacial layer (NIL) on Zn to achieve a highly stable Zn anode for rechargeable Zn batteries. The NIL in a composition of zinc acetate acetamide is homogeneous, compact, and Zn2+-conductive, rendering dendrite-free Zn deposition, which is observed by in situ optical microscopy. Benefiting from the advantages of NIL, the Zn||Zn symmetric cells show a low overpotential of 0.12 V at a high current density of 40 mA/cm2, enhanced Coulombic efficiency up to 99.9%, and extended lifespan over 2600 cycles. The Zn||Ti asymmetric cells exhibit a high areal capacity of 5 mAh/cm2. Moreover, the NIL functionalized Zn anode enables stable cycling of both anode-free Zn||Cl2 cells and zinc-ion capacitors, providing opportunities for the development of high-performance energy storage devices.

Boosting Electrolytic MnO2-Zn Batteries by a Bromine Mediator.

An aqueous electrolytic MnO2-Zn battery with eye-catching Mn2+/MnO2 cathode chemistry has been attracting immense interest for next-generation energy storage devices due to its irreplaceable advantages. However, the limited MnO2 conductivity restricts its long service life at high areal capacities. Here, we report a high-performance electrolytic MnO2-Zn battery via a bromine redox mediator, to enhance its electrochemical performance. The MnO2/Br2-Zn battery displays a high discharge voltage of 1.98 V with a capacity of ∼5.8 mAh cm-2. It also shows an excellent rate performance of 20 C with a long-term stability of over 600 cycles. Furthermore, the scaled-up MnO2/Br2-Zn battery with a capacity of ∼950 mAh exhibits a stable 100 cycles with a practical cell energy density of ∼32.4 Wh kg-1 and an attractively low energy cost of below 15 US$ kWh-1. The design approach can be generalized to other electrodes and battery systems, thus opening up new possibilities for large-scale energy storage.

Synthesis of ZnO nanosheet arrays with exposed (100) facets for gas sensing applications.

ZnO nanosheet (NS) arrays have been synthesized by a facile ultrathin liquid layer electrodeposition method. The ion concentration and electrode potential play important roles in the formation of ZnO NS arrays. Studies on the structural information indicate that the NSs are exposed with (100) facets. The results of Raman and PL spectra indicate that there existed a large amount of oxygen vacancies in the NSs. The gas sensing performances of the ZnO NS arrays are investigated: the ZnO NS arrays exhibited high gas selectivity and quick response/recovery for detecting NO2 at a low working temperature. High binding energies between NO2 molecules and exposed ZnO(100) facets lead to large surface reconstructions, which is responsible for the intrinsic NO2 sensing properties. In addition, the highly exposed surface and a large amount of oxygen vacancies existing in the NSs also make a great contribution to the gas sensing performance.