Phase-engineering modulation of Mn-based oxide cathode for constructing super-stable sodium storage

The Mn-based oxide cathode with enriched crystal phase structure and component diversity can provide the excellent chemistry structure for Na-ion batteries.Nevertheless,the broad application prospect is obstructed by the sluggish Na^(+)kinetics and the phase transitions upon cycling.Herein,we establish the thermodynamically stable phase diagram of various Mn-based oxide composites precisely controlled by sodium content tailoring strategy coupling with co-doping and solid-state reaction.The chemical environment of the P2/P'3 and P2/P3 biphasic composites indicate that the charge compensation mechanism stems from the cooperative contribution of anions and cations.Benefiting from the no phase transition to scavenge the structure strain,P2/P'3 electrode can deliver long cycling stability(capacity retention of 73.8%after 1000 cycles at 10 C)and outstanding rate properties(the discharge capacity of 84.08 mA h g^(-1)at 20 C)than P2/P3 electrode.Furthermore,the DFT calculation demonstrates that the introducing novel P'3 phase can significantly regulate the Na^(+)reaction dynamics and modify the local electron configuration of Mn.The effective phase engineering can provide a reference for designing other high-performance electrode materials for Na-ion batteries.

Microstructure and magnetic properties of FePt/MgO multilayers deposited by RF magnetron sputtering

FePt （50 nm） and [FePt（a nm）/MgO（b nm）5/glass （a=1, 2, 3; b=1, 2, 3） films were prepared by radio frequency （RF） magnetron sputtering technique, and then were annealed at 600℃ for 30 min. The effect of MgO layer thickness on the structures and magnetic properties of the FePt/MgO multilayers was investigated. The coercivities and inter-grain interactions of the FePt/MgO films were decreased, yet the degree of （001） texturing drastically increased with the increase in MgO layer thickness when the FePt layer thickness was fixed. Thus, the FePt/MgO films with appropriate coercivities, high perpendicular anisotropy, and weak intergrain interactions were obtained by controlling the MgO layer thickness. Overall, these results indicate that the FePt/MgO nanostructured films are promising candidates for future high-density perpendicular recording media.

Interfacial engineering of the layered oxide cathode materials for sodium-ion battery

The layered metal oxides are reviewed as the hopeful cathode materials for high-performance sodium-ion batteries(SIBs)due to their large theoretical capacity,favorable two-dimensional(2D)ion diffusion channel,and simple manipuility.However,their cycling stability,rate capability,and thermal stability are still significantly concerned and highlighted before further practical application.The chemical,mechanical and electrochemical stability of the cathode–electrolyte interfaces upon cycling is of great significance.Herein,the unique structural and electrochemical properties of the layered oxide cathode materials for SIB are reviewed.The mechanism of bulk/surface degradation induced by oxygen evolution,phase transition,microcrack,and electrolyte decomposition is thoroughly understood.Furthermore,the interfacial engineering to construct stable interface through various effective methods is fully discussed.The future outlook and challenges for interfacial engineering in this filed are also summarized.This review should shed light on the rational design and construct of robust interface for applications of superior layered oxide cathodes in SIB and may suggest future research directions.

Cobalt-iron oxide/black phosphorus nanosheet heterostructure:Electrosynthesis and performance of(photo-)electrocatalytic oxygen evolution

Highly active,stable,and cut-price(photo-)electrocatalysts are desired to overwhelm high energy barriers for anodic oxygen evolution reaction processes.Herein,a heterostructure of cobalt-iron oxide/black phosphorus nanosheets is in-situ synthesized via a facile and novel three-electrode electrolysis method.Bulky black phosphorus is exfoliated into its nanosheets at the cathode while the CoFe oxide is derived directly from the metal wire anode during the electrolysis process.This heterostructure exhibits excellent electrocatalytic oxygen evolution reaction(OER)performance,and the overpotential at 10 mA·cm^(−2)is 51 mV lower than that of the commercial RuO_(2)catalyst.Its superior OER performance stems from the favorable adsorption behavior and an enlarged electrochemical active surface area of the catalyst.To reveal the origin of excellent OER performance from the point of adsorption strength of OH*,methanol oxidation reaction(MOR)test is applied under the identified OER operating conditions.Further introduction of light illumination enhances the OER activity of this heterostructure.The overpotential drops down to 280 mV,benefiting from pronounced photochemical response of black phosphorus nanosheets and iron oxide inside the heterostructure.This work develops a new electrochemical method to construct high performance and light-sensitive heterostructures from black phosphorus nanosheets for the OER.

Revealing component synergy of Ni‒Fe/black phosphorous composites synthesized by self-designed electrochemical method for enhancing photoelectrocatalytic oxygen evolution reaction

Developing high-activity and low-cost catalysts is the key to eliminate the limitation of sluggish anodic oxygen evolution reaction(OER)during electrocatalytic overall water splitting.Herein,Ni‒Fe/black phosphorous(BP)composites are synthesized using a simple three-electrode system,where exfoliation of bulky BP and synthesis of NiFe composites are simultaneously achieved.Under light illumination,the optimized Ni‒Fe/BP composite exhibits excellent photoelectrocatalytic OER performance(e.g.,the overpotential is 58 mV lower than a commercial RuO_(2) electrocatalyst at a current density of 10 mA·cm^(-2)).The electron transfer on this composite is proved to follow a Ni‒BP‒Fe pathway.The electronic structure of this Ni‒Fe/BP composite is effectively regulated,leading to optimized adsorption strength of the intermediate OH*and improved intrinsic activity for the OER.Together with active sites on the support,this Ni‒Fe/BP composite possesses abundant electrochemical active sites and a bug surface area for the OER.The introduction of light further accelerates the electrocatalytic OER.This work provides a novel and facile method to synthesize high-performance metal/BP composites as well as the approaches to reveal their OER mechanisms.

Bifunctional functionalized two-dimensional transition metal borides for fast reaction redox kinetics in lithium-sulfur batteries

Lithium-sulfur(Li-S)batteries are regarded as one of the most promising next-generation energy storage systems due to their high theoretical specific energy density and low cost.However,serious shuttle effect and sluggish lithium polysulfides(LiPSs)redox kinetics severely impede the practical application of Li-S batteries.Employing polar sulfur hosts is an effective strategy to alleviate the above problems.Herein,the potential of two-dimensional(2D)Ti_(2)B-based sulfur hosts for Li-S batteries was comprehensively explored using first-principles calculations.The results show that functional groups of Ti_(2)B can significantly modulate its structural properties,thus affecting its interaction with sulfurcontaining species.Among S,Se,F,Cl,and Br elements,Ti_(2)B terminated with S and Se atoms possess stronger adsorption capability towards soluble Li_(2)S_(8),Li_(2)S_(6),and Li_(2)S_(4),obviously stronger than organic electrolytes,which indicates that they can completely suppress the shuttle effect.Besides,Ti_(2)BS_(2)and Ti_(2)BSe_(2)can powerfully expedite the electrochemical conversion of LiPSs.Moreover,the decomposition energy barrier of Li_(2)S and diffusion energy barrier of single Li ion on them are also fairly low,manifesting their excellent catalytic performance towards the oxidation of Li_(2)S.Finally,Ti_(2)BS_(2)and Ti_(2)BSe_(2)always keep metallic conductivity during the whole charge/discharge process.Taking all this into account,Ti_(2)BS_(2)and Ti_(2)BSe_(2)are proposed as promising bifunctional sulfur hosts for Li-S batteries.Our results suggest that increasing the proportion of S and Se groups during the synthesis of Ti_(2)B monolayers is greatly helpful for obtaining high-performance Li-S batteries.Besides,our work not only reveals the huge potential of 2D transition metal borides in Li-S batteries,but also provides insightful guidance for the design and screening of new efficient sulfur cathodes.

Ni2P Nanosheets:A High Catalytic Activity Platform for Electrochemical Detection of Acetaminophen

Main observation and conclusion Accurate determination of acetaminophen concentration is essential for studying the metabolic status of acetaminophen in clinical practice.In this study,nickel phosphide was used for electrochemical detection of acetaminophen for the first time.