Synergistic Electrocatalysis and Spatial Nanoconfinement to Accelerate Sulfur Conversion Kinetics in Aqueous Zn-S Battery.

Aqueous zinc batteries based on the conversion-type sulfur cathodes are promising in energy storage system due to the high theoretical energy density, low cost, and good safety. However, the multi-electron solid-state intermediate conversion reaction of sulfur cathodes generally possess sluggish kinetics, which leads to lower discharge voltage and inefficient sulfur utilization, thus suppressing the practical energy density. Herein, sulfur nanoparticles derived from metal-organic frameworks confined in-situ within electrospun fibers derived sulfur and nitrogen co-doped carbon nanofibers (S@S,N-CNF) composite, which possesses yolk-shell S@C nanostructure, is fabricated through successive sulfidation, pyrolysis, and sulfide oxidation processes, and served as a high-performance cathode material for Zn-S battery. The S and N dopants on carbon can collectively catalyse sulfur reduction reaction (SRR) by lowering energy barrier and accelerating kinetics to increase discharge voltage and specific capacity. Meanwhile, the yolk-shell S@C structure with spatially confined S nanoparticle yolks is beneficial to improve charge transfer and lower activation energy, thus further expediting SRR kinetics. Furthermore, extensive density functional theory (DFT) calculations reveal that S and N dual-doping can thermodynamically and dynamically reduce the energy barrier of rate-determining step (i.e., the transformation of *ZnS4 into *ZnS2) for the overall SRR, thereby significantly accelerating SRR kinetics.

Studying the Conversion Mechanism to Broaden Cathode Options in Aqueous Zinc-Ion Batteries.

Aqueous Zn-ion batteries (ZIBs) are regarded as alternatives to Li-ion batteries benefiting from both improved safety and environmental impact. The widespread application of ZIBs, however, is compromised by the lack of high-performance cathodes. Currently, only the intercalation mechanism is widely reported in aqueous ZIBs, which significantly limits cathode options. Beyond Zn-ion intercalation, we comprehensively study the conversion mechanism for Zn2+ storage and its diffusion pathway in a CuI cathode, indicating that CuI occurs a direct conversion reaction without Zn2+ intercalation due to the high energy barrier for Zn2+ intercalation and migration. Importantly, this direct conversion reaction mechanism can be readily generalized to other high-capacity cathodes, such as Cu2 S (336.7 mA h g-1 ) and Cu2 O (374.5 mA h g-1 ), indicating its practical universality. Our work enriches the Zn-ion storage mechanism and significantly broadens the cathode horizons towards next-generation ZIBs.

Revealing the Magnesium-Storage Mechanism in Mesoporous Bismuth via Spectroscopy and Ab-Initio Simulations.

We present mesoporous bismuth nanosheets as a model to study the charge-storage mechanism of Mg/Bi systems in magnesium-ion batteries (MIBs). Using a systematic spectroscopy investigation of combined synchrotron-based operando X-ray diffraction, near-edge X-ray absorption fine structure and Raman, we demonstrate a reversible two-step alloying reaction mechanism Bi↔MgBi↔Mg3 Bi2 . Ab-initio simulation methods disclose the formation of a MgBi intermediate and confirm its high electronic conductivity. This intermediate serves as a buffer for the significant volume expansion (204 %) and acts to regulate Mg storage kinetics. The mesoporous bismuth nanosheets, as an ideal material for the investigation of the Mg charge-storage mechanism, effectively alleviate volume expansion and enable significant electrochemical performance in a lithium-free electrolyte. These findings will benefit mechanistic understandings and advance material designs for MIBs.

Ultrathin Titanate Nanosheets/Graphene Films Derived from Confined Transformation for Excellent Na/K Ion Storage.

Confined transformation of assembled two-dimensional MXene (titanium carbide) and reduced graphene oxide (rGO) nanosheets was employed to prepare the free-standing films of the integrated ultrathin sodium titanate (NTO)/potassium titanate (KTO) nanosheets sandwiched between graphene layers. The ultrathin Ti-based nanosheets reduce the diffusion distance while rGO layers enhance conductivity. Incorporation of graphene into the titanate films produced efficient binder-free anodes for ion storage. The resulting flexible NTO/rGO and KTO/rGO electrodes exhibited excellent rate performances and long cycling stability characterized by reversible capacities of 72 mA h g-1 at 5 A g-1 after 10000 cycles and 75 mA h g-1 after 700 cycles at 2 A g-1 for sodium and potassium ion batteries, respectively. These results demonstrate the superiority of the unique sandwich-type electrodes.

Engineering High-Energy Interfacial Structures for High-Performance Oxygen-Involving Electrocatalysis.

Engineering high-energy interfacial structures for high-performance electrocatalysis is achieved by chemical coupling of active CoO nanoclusters and high-index facet Mn3 O4 nano-octahedrons (hi-Mn3 O4 ). A thorough characterization, including synchrotron-based near edge X-ray absorption fine structure, reveals that strong interactions between both components promote the formation of high-energy interfacial Mn-O-Co species and high oxidation state CoO, from which electrons are drawn by MnIII -O present in hi-Mn3 O4 . The CoO/hi-Mn3 O4 demonstrates an excellent catalytic performance over the conventional metal oxide-based electrocatalysts, which is reflected by 1.2 times higher oxygen evolution reaction (OER) activity than that of Ru/C and a comparable oxygen reduction reaction (ORR) activity to that of Pt/C as well as a better stability than that of Ru/C (95 % vs. 81 % retained OER activity) and Pt/C (92 % vs. 78 % retained ORR activity after 10 h running) in alkaline electrolyte.

Regulate transportation of ions and polysulfides in all-solid-state Li-S batteries using ordered-MOF composite solid electrolyte.

A dilemma arises when striving to balance the maximum desired ion conductivity and minimize the undesired lithium polysulfide shuttling effect for all-solid-state lithium-sulfur batteries (ASSLSBs). Here, we introduce a strategy of using ordered MIL-125-NH2 as fillers for poly(ethylene oxide)-based electrolytes to simultaneously regulate the transportation of lithium ions and polysulfides. When compared to electrolytes lacking metal-organic frameworks (MOFs) and those containing disordered MOFs, the electrolyte featuring an ordered-MOF structure, denoted as three-dimensional (3D) MPPL composite solid electrolyte (CSE), exhibits the highest ion conductivity of 8.3 × 10-4 siemens per centimeter at 60°C. As a result, pouch-type ASSLSBs with 3D MPPL CSE maintains stable cycling for 400 cycles at 0.5 C at 60°C, showcasing the successful implementation of this strategy in simultaneously regulating ion and polysulfide transport. This approach opens up alternative avenues to achieve high-performance ASSLSBs with exceptional energy density.

Single-Atom-Based Nanoenzyme in Tissue Repair.

Since the discovery of ferromagnetic nanoparticles Fe3O4 that exhibit enzyme-like activity in 2007, the research on nanoenzymes has made significant progress. With the in-depth study of various nanoenzymes and the rapid development of related nanotechnology, nanoenzymes have emerged as a promising alternative to natural enzymes. Within nanozymes, there is a category of metal-based single-atom nanozymes that has been rapidly developed due to low cast, convenient preparation, long storage, less immunogenicity, and especially higher efficiency. More importantly, single-atom nanozymes possess the capacity to scavenge reactive oxygen species through various mechanisms, which is beneficial in the tissue repair process. Herein, this paper systemically highlights the types of metal single-atom nanozymes, their catalytic mechanisms, and their recent applications in tissue repair. The existing challenges are identified and the prospects of future research on nanozymes composed of metallic nanomaterials are proposed. We hope this review will illuminate the potential of single-atom nanozymes in tissue repair, encouraging their sequential clinical translation.

Emission Reduction from a Light-Duty Diesel Vehicle over Two Driving Cycles through Dynamic Correction Calibration.

The potential of a method of transient control of model-based engine charge control (MCCT) is investigated to minimize nitrogen oxide (NOx) emissions of a light-duty diesel vehicle over two driving cycles, the worldwide harmonized light-duty test cycle (WLTC) and real driving emission (RDE) cycle. The MCCT function was switched on by calibrating factor maps corrected for several parameters. In addition, the relationship between electronic control unit signals and nitrogen oxide (NOx) emissions was analyzed under the WLTC and RDE. The engine-out and tail-pipe NOx emissions in the WLTC and RDE could achieve varying degrees of reduction with MCCT.

High Compression Ratio Active Pre-chamber Single-Cylinder Gasoline Engine with 50% Gross Indicated Thermal Efficiency.

Active pre-chamber turbulent jet ignition with a high compression ratio has been demonstrated to be an effective method for significantly enhancing engine thermal efficiency. A dual modification of the combustion chamber and the pre-chamber was performed on an AVL 5400 single-cylinder Miller engine to achieve stable ultra-lean burn at a high compression ratio, and a breakthrough of 51.10% gross indicated thermal efficiency was achieved at the compression ratio of 16.4 and λ = 2.236. Spark ignition and pre-chamber turbulent jet ignition exhibit significant performance diversities under lean burn conditions. Pre-chamber turbulent jet ignition is able to significantly expand the lean burn limit of spark ignition to λ = 2.7 (CoVIMEP < 5%) at only the expense of an increased HC emission, while apparently reducing fuel consumption and nitrogen oxide emissions. With an increase in the compression ratio from 13.6 to16.4, spark ignition and pre-chamber turbulent jet ignition exhibit contradictory performance laws. The engine performance of a spark ignition engine decreases significantly as the compression ratio increases, whereas a pre-chamber jet ignition engine can still operate reliably at a high compression ratio with ultra-lean combustion. Within the scope of the test, the performance of the pre-chamber jet ignition engine is enhanced by a greater compression ratio. This improvement is primarily attributable to the reduction of heat transfer loss and exhaust energy loss under ultra-lean combustion, as determined by an analysis of the structure of power losses.

CoFe nanoalloys encapsulated in nitrogen-doped carbon for efficient nitrite electroreduction to ammonia.

Electrochemical nitrite (NO2-) reduction to ammonia (NH3) can not only remove harmful NO2- in wastewater, but also produce valuable NH3. Herein, a CoFe nanoalloy encapsulated in nitrogen-doped carbon (CoFe-NC) electrocatalyst was fabricated for nitrite reduction, which achieved a high NH3 Faraday efficiency of 94.5%, and a large NH3 yield of 4050.6 µg h-1 cm-2 in a neutral electrolyte.

Study on Control Strategies on NOX Emissions to Meet Real Driving Emissions.

The aim of this study was to fulfill the NOx emissions standards for a light-duty diesel vehicle under real driving emissions (RDE) testing conditions by implementing various control strategies. In this study, RDE tests were performed by adjusting the air mass quantity and postinjection quantity in order to analyze engine-out and tail-pipe nitrogen oxides (NOx) emissions for different phases of RDE. The results showed that reducing in air mass quantity enabled the engine to operate in higher exhaust gas recirculation (EGR) rate regions, resulting in a 32.5% reduction in engine-out NOx emissions and an 80.4% decrease in tail-pipe NOx emissions. Increasing the postinjection quantity primarily enhanced the NOx conversion efficiency for the urban phase by 7.5%, leading to a 22.6% reduction in tail-pipe NOx emissions. By employing both strategies, vehicles can comfortably meet the CN6b emission regulations by a substantial margin.

Atomic Engineering Catalyzed MnO2 Electrolysis Kinetics for a Hybrid Aqueous Battery with High Power and Energy Density.

Research interest and achievements in zinc aqueous batteries, such as alkaline Zn//Mn, Zn//Ni/Co, Zn-air batteries, and near-neutral Zn-ion and hybrid ion batteries, have surged throughout the world due to their features of low-cost and high-safety. However, practical application of Zn-based secondary batteries is plagued by restrictive energy and power densities in which an inadequate output plateau voltage and sluggish kinetics are mutually accountable. Here, a novel paradigm high-rate and high-voltage Zn-Mn hybrid aqueous battery (HAB) is constructed with an expanded electrochemical stability window over 3.4 V that is affordable. As a proof of concept, catalyzed MnO2 /Mn2+ electrolysis kinetics is demonstrated in the HAB via facile introduction of Ni2+ into the electrolyte. Various techniques are employed, including in situ synchrotron X-ray powder diffraction, ex situ X-ray absorption fine structure, and electron energy loss spectroscopy, to reveal the reversible charge-storage mechanism and the origin of the boosted rate-capability. Density functional theory (DFT) calculations reveal enhanced active electron states and charge delocalization after introducing strongly electronegative Ni. Simulations of the reaction pathways confirm the enhanced catalyzed electrolysis kinetics by the facilitated charge transfer at the active O sites around Ni dopants. These findings significantly advance aqueous batteries a step closer toward practical low-cost application.

Roadmap for advanced aqueous batteries: From design of materials to applications.

Safety concerns about organic media-based batteries are the key public arguments against their widespread usage. Aqueous batteries (ABs), based on water which is environmentally benign, provide a promising alternative for safe, cost-effective, and scalable energy storage, with high power density and tolerance against mishandling. Research interests and achievements in ABs have surged globally in the past 5 years. However, their large-scale application is plagued by the limited output voltage and inadequate energy density. We present the challenges in AB fundamental research, focusing on the design of advanced materials and practical applications of whole devices. Potential interactions of the challenges in different AB systems are established. A critical appraisal of recent advances in ABs is presented for addressing the key issues, with special emphasis on the connection between advanced materials and emerging electrochemistry. Last, we provide a roadmap starting with material design and ending with the commercialization of next-generation reliable ABs.

Graphitic Carbon Nitride (g-C3 N4 )-Derived N-Rich Graphene with Tuneable Interlayer Distance as a High-Rate Anode for Sodium-Ion Batteries.

Heteroatom-doped carbon materials with expanded interlayer distance have been widely studied as anodes for sodium-ion batteries (SIBs). However, it remains unexplored to further enlarge the interlayer spacing and reveal the influence of heteroatom doping on carbon nanostructures for developing more efficient SIB anode materials. Here, a series of N-rich few-layer graphene (N-FLG) with tuneable interlayer distance ranging from 0.45 to 0.51 nm is successfully synthesized by annealing graphitic carbon nitride (g-C3 N4 ) under zinc catalysis and selected temperature (T = 700, 800, and 900 °C). More significantly, the correlation between N dopants and interlayer distance of resultant N-FLG-T highlights the effect of pyrrolic N on the enlargement of graphene interlayer spacing, due to its stronger electrostatic repulsion. As a consequence, N-FLG-800 achieves the optimal properties in terms of interlayer spacing, nitrogen configuration and electronic conductivity. When used as an anode for SIBs, N-FLG-800 shows remarkable Na+ storage performance with ultrahigh rate capability (56.6 mAh g-1 at 40 A g-1 ) and excellent long-term stability (211.3 mAh g-1 at 0.5 A g-1 after 2000 cycles), demonstrating the effectiveness of material design.

The Application of Hollow Structured Anodes for Sodium-Ion Batteries: From Simple to Complex Systems.

Hollow structures exhibit fascinating and important properties for energy-related applications, such as lithium-ion batteries, supercapacitors, and electrocatalysts. Sodium-ion batteries, as analogs of lithium-ion batteries, are considered as promising devices for large-scale electrical energy storage. Inspired by applications of hollow structures as anodes for lithium-ion batteries, the application of these structures in sodium-ion batteries has attracted great attention in recent years. However, due to the difference in lithium and sodium-ion batteries, there are several issues that need to be addressed toward rational design of hollow structured sodium anodes. Herein, this research news article presents the recent developments in the synthesis of hollow structured anodes for sodium-ion batteries. The main strategies for rational design of materials for sodium-ion batteries are presented to provide an overview and perspectives for the future developments of this research area.

1D Sub-Nanotubes with Anatase/Bronze TiO2 Nanocrystal Wall for High-Rate and Long-Life Sodium-Ion Batteries.

The development of 1D nanostructures with enhanced material properties has been an attractive endeavor for applications in energy and environmental fields, but it remains a major research challenge. Herein, this work demonstrates a simple, gel-derived method to synthesize uniform 1D elongated sub-nanotubes with an anatase/bronze TiO2 nanocrystal wall (TiO2 SNTs). The transformation mechanism of TiO2 SNTs is studied by various ex situ characterization techniques. The resulting 1D nanostructures exhibit, synchronously, a high aspect ratio, open tubular interior, and anatase/bronze nanocrystal TiO2 wall. This results in excellent properties of electron/ion transport and reaction kinetics. Consequently, as an anode material for sodium-ion batteries (SIBs), the TiO2 SNTs display an ultrastable long-life cycling stability with a capacity of 107 mAh g-1 at 16 C after 4000 cycles and a high-rate capacity of 94 mAh g-1 at 32 C. This a high-rate and long-life performance is superior to any report on pure TiO2 for SIBs. This work provides new fundamental information for the design and fabrication of inorganic structures for energy and environmental applications.

Na2 Ti3 O7 @N-Doped Carbon Hollow Spheres for Sodium-Ion Batteries with Excellent Rate Performance.

Uniform Na2 Ti3 O7 hollow spheres assembled from N-doped carbon-coated ultrathin nanosheets are synthesized. A unique multilayer structure of nanosheets is presumed to significantly reduce energy consumption during the diffusion process of sodium ions, while the carbon-coated structure can increase the overall conductivity. The as-prepared sample used as an anode in sodium-ion batteries exhibits the best rate performance ever reported for Na2 Ti3 O7 , delivering more than 60 mAh g-1 after 1000 continuous cycles at the high rate of 50 C, which was achieved due to its unique structure.

Ultra-small nanoparticles of MgTi2O5 embedded in carbon rods with superior rate performance for sodium ion batteries.

Confinement of ultra-small MgTi2O5 nanoparticles in carbon is demonstrated to be an efficient method for fabricating long cycle-life anode material for sodium ion batteries. Superior rate and excellent cyclic capabilities as well as high Coulombic efficiency of the MgTi2O5-C nanocomposite, obtained from pyrolysis of a single molecule precursor, are shown.