Bulk preparation of free-standing single-iron-atom catalysts directly as the air electrodes for high-performance zinc-air batteries

The keen interest in fuel cells and metal-air batteries stimulates a great deal of research on the development of a cost-efficient and high-performance catalyst as an alternative to traditional Pt to boost the sluggish oxygen reduction reaction(ORR)at the cathode.Herein,we report a facile and scalable strategy for the large-scale preparation of a free-standing and flexible porous atomically dispersed Fe-N-doped carbon microtube(FeSAC/PCMT)sponge.Benefiting from its unique structure that greatly facilitates the catalytic kinetics,mass transport,and electron transfer,our FeSAC/PCMT electrode exhibits excellent performance with an ORR potential of 0.942 V at^(-3) mA cm^(-2).When the FeSAC/PCMT sponge was directly used as an oxygen electrode for liquid-state and flexible solid-state zinc-air batteries,high peak power densities of 183.1 and 58.0 mW cm^(-2) were respectively achieved,better than its powdery counterpart and commercial Pt/C catalyst.Experimental and theoretical investigation results demonstrate that such ultrahigh ORR performance can be attributed to atomically dispersed Fe-N_(5) species in FeSAC/PCMT.This study presents a cost-effective and scalable strategy for the fabrication of highly efficient and flexible oxygen electrodes,provides a significant new insight into the catalytic mechanisms,and helps to realize significant advances in energy devices.

Optimizing groundwater recharge plan in North China Plain to repair shallow groundwater depression zone, China

The North China Plain is one of the main grain producing areas in China. However, overexploitation has long been unsustainable since the water supply is mainly from groundwater. Since 2014,the South-to-North Water Diversion Project's central route has been charted to the integrated management of water supply and over-exploitation, which has alleviated the problem to a certain extent. Although the Ministry of Water Resources has made many efforts on groundwater recharge since 2018 most of which have been successful, the recharge has not yet been sufficiently focused on the repair of shallow groundwater depression zones. It still needs further optimization. This paper discusses this particular issue,proposes optimized recharge plan and provides the following recommendations:(1) Seven priority target areas are selected for groundwater recharge in alluvial and proluvial fans in the piedmont plain, and the storage capacity is estimated to be 181.00×10~8 m~3;(2) A recharge of 31.18×10~8 m~3/a is required by 2035 to achieve the repair target;(3) It is proposed to increase the recharge of Hutuo River, Dasha River and Tanghe River to 19.00×10~8 m~3/a and to rehabilitate Gaoliqing-Ningbailong Depression Zone;increase the recharge of Fuyang River, Zhanghe River and Anyang River to 7.05×10~8 m~3/a and rehabilitate Handan Feixiang-Guangping Depression Zone;increase the recharge of Luanhe River by 0.56×10~8 m~3/a and restore Tanghai Depression Zone and Luanan-Leting Depression Zone;moderately reduce the amount of water recharged to North Canal and Yongding River to prevent excessive rebound of groundwater;(4) Recharge through well is implemented on a pilot basis in areas of severe urban ground subsidence and coastal saltwater intrusion;(5) An early warning mechanism for groundwater quality risks in recharge areas is established to ensure the safety. The numerical groundwater flow model also proves reasonable groundwater level restoration in the depression zones by 2035.

不同城市道路工况下重型商用车侧风气动特性研究

依托动网格技术,并采用局部节点位移方式,研究城市道路方案分别为重型商用车经过位于其背风侧的单个建筑物、经过位于其迎风侧的单个建筑物和连续经过位于其迎风侧的2个建筑物3种情况下的瞬态气动特性。方案中网格节点位移速度即重型商用车行驶速度定为15 ms,侧风速度为10 m/s。结果显示,建筑物对重型商用车瞬态气动特性的影响较为明显,行驶过程中侧向力系数与横摆力矩系数在1 s内变化值达到5.0之多,相应的侧向力和横摆力矩变化值约为12 kN和30 kN·m,变化率峰值可达-12kN·s^-1和35 kN·m·s^-1,并且方向在行驶过程中发生改变。

A peroxidase-like single-atom Fe-N_(5)active site for effective killing human lung adenocarcinoma cells

Single-atom catalyst(SAC)is one of the newest catalysts,and attracts people’s wide attention in cancer therapy based on their characteristics of maximum specific catalytic activity and high stability.We designed and synthesized a Fe-N decorated graphene nanosheet(Fe-N5/GN SAC)with the coordination number of five.Through enzymology and theoretical calculations,the Fe-N5/GN SAC has outstanding intrinsic peroxidase-like catalytic activity due to single-atom Fe site with five-N-coordination structure.We explored its potential on lung cancer therapy,and found that it could kill human lung adenocarcinoma cells(A549)by decomposing hydrogen peroxide(H_(2)O_(2))into toxic reactive oxygen species(ROS)under acidic microenvironment in threedimensional(3D)lung cancer cell model.Our study demonstrates a promising application of SAC with highly efficient single-atom catalytic sites for cancer treatment.

Three-dimensional interconnected graphene network-based high-performance air electrode for rechargeable zinc‒air batteries

Although zinc-air batteries(ZABs)are regarded as one of the most prospective energy storage devices,their practical application has been restricted by poor air electrode performance.Herein,we developed a free-standing air electrode that is fabricated on the basis of a multifunctional three-dimensional interconnected graphene network.Specifically,a three-dimensional interconnected graphene network with fast mass and electron transport ability,prepared by catalyzing growth of graphene foam on nickel foam and then filling reduced graphene oxide into the pores of graphene foam,is used to anchor iron phthalocyanine molecules with atomic Fe-N_(4)sites for boosting the oxygen reduction during discharging and nanosized FeNi hydroxides for accelerating the oxygen evolution during charging.As a result,the obtained air electrode exhibited an ultra-small electrocatalytic overpotential of 0.603 V for oxygen reactions,a high peak power density of 220.2mWcm^(-2),and a small and stable charge-discharge voltage gap of 0.70 V at 10mA cm^(-2)after 1136 cycles.Furthermore,in situ Raman spectroscopy together with theoretical calculations confirmed that phase transformation of FeNi hydroxides takes place fromα-Ni(OH)_(x)toβ-Ni(OH)_(x)toγ-Ni^((3+δ)+)OOH for the oxygen evolution reaction and Ni is the active center while Fe enhances the activity of Ni active sites.

Recent advances in carbon-supported non-precious metal singleatom catalysts for energy conversion electrocatalysis

Non-precious metal single-atom catalysts(NPM-SACs)with unique electronic structures and coordination environments have gained much attention in electrocatalysis owing to their low cost,high atomic utilization,and high performance.NPM-SACs on carbon support(NPM-SACs/CS)are promising because of the carbon substrate with a large surface area,excellent electrical conductivity,and high chemical stability.This review provides an overview of recent developments in NPM-SACs/CS for the electrocatalytic field.First,the state-of-the-art synthesis methods and advanced characterization techniques of NPM-SACs/CS are discussed in detail.Then,the structural adjustment strategy of NPM-SACs/CS for optimizing electrocatalytic performance is introduced concisely.Furthermore,we provide a comprehensive summary of recent advances in developing NPM-SACs/CS for important electrochemical reactions,including carbon dioxide reduction reaction,hydrogen evolution reaction,oxygen evolution reaction,oxygen reduction reaction,and nitrogen reduction reaction.In the end,the existing challenges and future opportunities of NPM-SACs/CS in the electrocatalytic field are highlighted.

Single-Atom Ce-N_(4)-C-(OH)_(2)Nanozyme-Catalyzed Cascade Reaction to Alleviate Hyperglycemia

The enzyme-mimicking catalytic activity of single-atom nanozymes has been widely used in tumor treatment.However,research on alleviating metabolic diseases,such as hyperglycemia,has not been reported.Herein,we found that the single-atom Ce-N_(4)-C-(OH)_(2)(SACe-N_(4)-C-(OH)_(2))nanozyme promoted glucose absorption in lysosomes,resulting in increased reactive oxygen species production in HepG2 cells.Furthermore,the SACe-N_(4)-C-(OH)_(2)nanozyme initiated a cascade reaction involving superoxide dismutase-,oxidase-,catalase-,and peroxidase-like activity to overcome the limitations associated with the substrate and produce•OH,thus improving glucose intolerance and insulin resistance by increasing the phosphorylation of protein kinase B and glycogen synthase kinase 3β,and the expression of glycogen synthase,promoting glycogen synthesis to improve glucose intolerance and insulin resistance in high-fat diet-induced hyperglycemic mice.Altogether,these results demonstrated that the novel nanozyme SACeN_(4)-C-(OH)_(2)alleviated the effects of hyperglycemia without evident toxicity,demonstrating its excellent clinical application potential.

Boosting the activity of Fe–N_x moieties in Fe–N–C electrocatalysts via phosphorus doping for oxygen reduction reaction

The Fe–N–C material is a promising non-noblemetal electrocatalyst for oxygen reduction reaction(ORR).Further improvement on the ORR activity is highly desired in order to replace Pt/C in acidic media.Herein,we developed a new-type of single-atom Fe–N–C electrocatalyst,in which Fe–Nxactive sites were modified by P atoms.The half-wave potential of the optimized material reached 0.858 V,which is 23 mV higher than that of the pristine one in a 0.1 mol L-1 HClO4 solution.Density functional theory(DFT)calculations revealed that P-doping can reduce the thermodynamic overpotential of the rate determining step and consequently improve the ORR activity.

Research Progress of Nanomaterials-Based Sensors for Food Safety

With the improvement of people’s requirements for food quality,food safety has become the focus of society.More and more researchers continue to develop specific and convenient biochemical sensors for the detection of certain components in food,which also imposes higher requirements for the structure and performance of nanomaterials.Biochemical sensors based on carbon nanotubes,metal nanowires,nanofibers,metal-organic framework(MOF)compounds and other functional composite materials have the advantages of high sensitivity,great detection speed and reliable results,and have been continuously developed and widely used in medical,environmental and food safety fields.This paper reviews the progress of research on the application of the sensors based on the above functional nanomaterials in food detection in recent years,demonstrates the advantages brought by the functional composite materials,and discusses the challenges faced by the functional nanomaterials in the field of food safety testing,to provide an effective reference for developing functional composite material sensors for food safety testing.