Crystal plane induced in-situ electrochemical activation of manganese-based cathode enable long-term aqueous zinc-ion batteries

Rapid capacity decay and sluggish reaction kinetics are major barriers hindering the applications of manganese-based cathode materials for aqueous zinc-ion batteries.Herein,the effects of crystal plane on the in-situ transformation behavior and electrochemical performance of manganese-based cathode is discussed.A comprehensive discussion manifests that the exposed(100)crystal plane is beneficial to the phase transformation from tunnel-structured MnO_(2) to layer-structured ZnMn_(3)O_(7)·3H_(2)O,which plays a critical role for the high reactivity,high capacity,fast diffusion kinetics and long cycling stability.Additionally,a two-stage zinc storage mechanism can be demonstrated,involving continuous activation reaction and phase transition reaction.As expected,it exhibits a high capacity of 275 mAh g^(-1)at 100 mA g^(-1),a superior durability over 1000 cycles and good rate capability.This study may open new windows toward developing advanced cathodes for ZIBs,and facilitate the applications of ZIBs in large-scale energy storage system.

Regulation of Active Oxygen Species by Grain Boundaries to Optimize Reaction Paths toward Aerobic Oxidations

Aerobic oxidation by using molecular oxygen(O_(2))as the oxidant is highly attractive,in which activating O_(2)to reactive oxygen species(ROS)is a prerequisite.Although some progress has been achieved in regulating ROS by heterogeneous catalysts,the strategies to efficiently control ROS in aerobic oxidation are still urgently desired.Herein,grain boundaries(GBs)in metal oxides are discovered to be able to facilely regulate ROS.Impressively,MoO_(3)nanocrystals with high density of GBs(MoO_(3)-600)deliver a mass activity of 83 mmol g^(-1)h^(-1)in aerobic oxidation of benzyl alcohol,7 and 8 times as high as that of MoO_(3)nanoparticles without GBs and Pt/C,respectively.In addition,the selectivity of benzoic acid is 100%during whole reaction process over MoO_(3)-600.Mechanistic studies reveal that the oxygen atoms at GBs in MoO_(3)-600 are highly active to form·OH radicals with the generation of oxygen vacancies,while the oxygen vacancies are replenished by O_(2).The reaction path directly contributes to the excellent catalytic performance.

皖北新元古代张渠组灰岩地球化学数理统计分析

地球化学在沉积学研究中发挥了重要作用。本研究以灵璧石国家地质公园新元古代张渠组灰岩为研究对象,在系统采样的基础上测试了其岩石地球化学组成,并进行了数理统计分析。结果表明,张渠组上下部灰岩中元素组成存在差异,主体表现出高的Ca含量,但其他元素含量相对较低,这种差异可能与其沉积环境变化有关。基于数理统计分析(相关性、聚类及因子分析),10种元素被划分为3类:代表陆相的Al-K-Ti-Fe、代表海相的Ca-P和代表其他的Mg-Mn-Zr-Ni。在此基础上,构建出了用于探讨陆源、海相特征及陆海相对贡献的Al/Fe、Ca/P和Al/P比值,并被应用于张渠组沉积环境分析,发现张渠组上下部的海相环境无明显差异,但陆源贡献上变化显著。

Au atoms doped in Ti_(3)C_(2)T_(x)MXene:Benefiting recovery of oxygen vacancies towards photocatalytic aerobic oxidation

Photocatalytic aerobic oxidation by using oxygen molecules(O_(2))as green and low-cost oxidants is of great attraction,where the introduction of irradiation has been proved as an efficient strategy to lower reaction temperature as well as promote catalytic performance.Moreover,the oxygen vacancies(OVs)of catalyst are highly active sites to adsorb and activate O_(2)during photocatalytic aerobic oxidation.However,OVs are easily blocked by oxygen atoms from active oxygen species during the catalytic process,leading to the deactivation of catalysis.Herein,a promising catalyst toward photocatalytic aerobic oxidation was successfully developed by recovering the OVs through doping Au atoms into Ti_(3)C_(2)T_(x)MXene(Au/Ti_(3)C_(2)T_(x)).Impressively,Au/Ti_(3)C_(2)T_(x)exhibited remarkable activity under full-spectrum irradiation towards photooxidation of methyl phenyl sulfide(MPS)and methylene blue(MB),attaining a conversion of>90%at room temperature.Moreover,Au/Ti_(3)C_(2)T_(x)also manifested remarkable stability by maintaining>95%initial activity after 10 successive reaction rounds.Further mechanistic studies indicated that the OVs of Au/Ti_(3)C_(2)T_(x)served as the active centers to efficiently adsorb and activate O_(2).More importantly,the doped Au atoms of Au/Ti_(3)C_(2)T_(x)were conducive to the recovery of OVs during photocatalytic process from the results of theoretical and experimental aspects.The recovered OVs of Au/Ti_(3)C_(2)T_(x)continuously and efficiently activated O_(2),directly contributing to the remarkable catalytic activity and stability.

Simultaneous regulation of cations and anions in an electrolyte for high-capacity, high-stability aqueous zinc–vanadium batteries

Safe,inexpensive aqueous zinc-ion batteries(AZIBs)are regarded as promising energy storage devices.However,they still face issues,including dissolution and collapse of the cathode as well as H_(2)evolution and the growth of Zn dendrites on the Zn anode.Herein,we simultaneously regulate the cations and anions in the electrolyte for high-capacity,high-stability aqueous zinc–vanadium(Zn–V)batteries based on a bimetallic cation-doped Na_(0.33)K_(0.1)V_(2)O_(5)·nH_(2)O cathode.We demonstrate that Na^(+) cations suppress cathode dissolution and restrain Zn dendrite growth on the anode via an electrostatic shield effect.We also illustrate that ClO_(4)^(-) anions participate in energy storage at the cathode and are reduced to Cl^(-),generating a protective layer on the Zn anode surface and providing a stable interface to decrease Zn dendrites and H_(2)evolution during long-term cycling.When Na^(+) and ClO_(4)^(-) are introduced into an aqueous ZnSO_(4) electrolyte,a Zn/Zn symmetric cell shows durable and reversible Zn stripping/plating for 1500 h at a current density of 1 mA cm^(-2) and with an area capacity of 1 mAh cm^(-2).Zn/Na_(0.33)K_(0.1)V_(2)O_(5)·nH_(2)O full batteries exhibit a high capacity of 600 mAh g^(-1)at 0.1 A g^(-1) and long-term cycling performance for 5000 cycles,with a capacity of 200 mAh g^(-1) at 20 Ag^(-1).

Large-scale synthesis of metal nanosheets as highly active catalysts: Combining accumulative roll-bonding and etching process

Metal nanosheets with ultrathin layer of metal atoms represent relatively high specific surface area and fast electronic transmission[1–2].Besides,metal nanosheets are considered to expose abundant active sites,thereby exhibiting significant advantages[3].As a result,metal nanosheets have attracted widespread attention in the field of catalysis[4–8],energy storage[9–10],environmental protection[11],and sensing[12]in recent years.For example,amorphous Ir nanosheets were found to be effectively applied to oxygen evolution reaction(OER)under acidic media with a high mass activity of 221.8 A·g^(–1)[4].