Boron modulating electronic structure of FeN4C to initiate high-efficiency oxygen reduction reaction and high-performance zinc-air battery

The biggest challenge is to develop a low cost and readily available catalyst to replace expensive commercial Pt/C for efficient electrochemical oxygen reduction reaction(ORR).In this research,closo-[B_(12)H_(12)]^(2−)and 1,10-phenanthroline-iron complexes were introduced into the porous metal-organic framework by impregnation method,and further annealing treatment achieved the successful anchoring of single-atom-Fe in B-doped CN Matrix(FeN4CB).The ORR activity of FeN4CB is comparable to the widely used commercial 20 wt%Pt/C.Where the half-wave potential(E_(1/2))in alkaline medium up to 0.84 V,and even in the face of challenging ORR in acidic medium,the E_(1/2)of ORR driven by FeN4CB is still as high as 0.81 V.When FeN4CB was used as air cathode,the open circuit voltage of Zn-air battery reaches 1.435 V,and the power density and specific capacity are as high as 177 mW cm^(−2)and 800 mAh g_(Zn)^(−1)(theoretical value:820 mAh g_(Zn)^(−1)),respectively.The dazzling point of FeN4CB also appears in the high ORR stability,whether in alkaline or acidic media,E_(1/2)and limiting current density are still close to the initial value after 5000 times cycles.After continuously running the charge-discharge test for 220 h,the charge voltage and discharge voltage of the rechargeable zinc-air battery with FeN4CB as the air cathode maintained the initial state.Density functional theory calculations reveals that introducing B atom to Fe–N4–C can adjust the electronic structure to easily break O=O bond and significantly reduce the energy barrier of the rate-determining step resulting in an improved ORR activity.

Advances of the functionalized carbon nitrides for electrocatalysis

Over the past few decades,the design and development of carbon materials have occurred at a rapid pace.In particular,these porous graphene-like carbon nitride materials have received considerable attention due to their superior structures and performances in the energy transformation field.In this review,nitrogenated holey two-dimensional graphene and polymeric carbon nitride will be discussed in depth.The structural properties,synthetic methods,and applications including electrocatalytic reactions,such as hydrogen evolution reaction,oxygen reduction reaction,oxygen evolution reaction,and nitrogen reduction reaction,will be presented in detail.Finally,we will present the outlooks on the current obstacles to the development of carbon nitride materials.This comprehensive understanding will help guide and motivate researchers to develop and modify carbon nitride materials with better properties in the future.

In-situ formation of cobalt phosphide nanoparticles confined in three-dimensional porous carbon for high-performing zinc-air battery and water splitting

The rational design of efficient and stable carbon-based electrocatalysts for oxygen reduction and oxygen evolution reactions is crucial for improving energy density and long-term stability of rechargeable zinc-air batteries(ZABs).Herein,a general and controllable synthesis method was developed to prepare three-dimensional(3D)porous carbon composites embedded with diverse metal phosphide nanocrystallites by interfacial coordination of transition metal ions with phytic acid-doped polyaniline networks and subsequent pyrolysis.Phytic acid as the dopant of polyaniline provides favorable anchoring sites for metal ions owing to the coordination interaction.Specifically,adjusting the concentration of adsorbed cobalt ions can achieve the phase regulation of transition metal phosphides.Thus,with abundant cobalt phosphide nanoparticles and nitrogen-and phosphorus-doping sites,the obtained carbon-based electrocatalysts exhibited efficient electrocatalytic activities toward oxygen reduction and evolution reactions.Consequently,the fabricated ZABs exhibited a high energy density,high power density of 368 mW cm^(-2),and good cycling/mechanical stability,which could power water splitting for integrated device fabrication with high gas yields.

Degradation and its fast recovery in a-IGZO thin-film transistors under negative gate bias stress

A new type of degradation phenomena featured with increased subthreshold swing and threshold voltage after negative gate bias stress(NBS)is observed for amorphous InGaZnO(a-IGZO)thin-film transistors(TFTs),which can recover in a short time.After comparing with the degradation phenomena under negative bias illumination stress(NBIS),positive bias stress(PBS),and positive bias illumination stress(PBIS),degradation mechanisms under NBS is proposed to be the generation of singly charged oxygen vacancies(V_(o)^(+))in addition to the commonly reported doubly charged oxygen vacancies(V_(o)^(2+)).Furthermore,the NBS degradation phenomena can only be observed when the transfer curves after NBS are measured from the negative gate bias to the positive gate bias direction due to the fast recovery of V_(o)^(+)under positive gate bias.The proposed degradation mechanisms are verified by TCAD simulation.

Degradation mechanisms for polycrystalline silicon thin-film transistors with a grain boundary in the channel under negative gate bias stress

The negative gate bias stress(NBS)reliability of n-type polycrystalline silicon(poly-Si)thin-film transistors(TFTs)with a distinct defective grain boundary(GB)in the channel is investigated.Results show that conventional NBS degradation with negative shift of the transfer curves is absent.The on-state current is decreased,but the subthreshold characteristics are not affected.The gate bias dependence of the drain leakage current at V_(ds)of 5.0 V is suppressed,whereas the drain leakage current at V_(ds)of 0.1 V exhibits obvious gate bias dependence.As confirmed via TCAD simulation,the corresponding mechanisms are proposed to be trap state generation in the GB region,positive-charge local formation in the gate oxide near the source and drain,and trap state introduction in the gate oxide.

A systematic study of light dependency of persistentphotoconductivity in a-InGaZnO thin-film transistors

Persistent photoconductivity(PPC)effect and its light-intensity dependence of both enhancement and depletion(E-/D-)mode amorphous InGaZnO(a-IGZO)thin-film transistors(TFTs)are systematically investigated.Density of oxygen vacancy(V O)defects of E-mode TFTs is relatively small,in which formation of the photo-induced metastable defects is thermally activated,and the activation energy(E a)decreases continuously with increasing light-intensity.Density of V O defects of D-mode TFTs is much larger,in which the formation of photo-induced metastable defects is found to be spontaneous instead of thermally activated.Furthermore,for the first time it is found that a threshold dose of light-exposure is required to form fully developed photo-induced metastable defects.Under low light-exposure below the threshold,only a low PPC barrier is formed and the PPC recovery is fast.With increasing the light-exposure to the threshold,the lattice relaxation of metal cations adjacent to the doubly ionized oxygen vacancies(V O^2+)is fully developed,and the PPC barrier increases to∼0.25 eV,which remains basically unchanged under higher light-exposure.Based on the density of V O defects in the channel and the condition of light illumination,a unified model of formation of photo-induced metastable defects in a-IGZO TFTs is proposed to explain the experimental observations.

Electrospun Flexible Nanofibres for Batteries:Design and Application

Flexible and free-standing electrospun nanofibres have been used as electrode materials in electrochemical energy storage systems due to their versatile properties,such as mechanical stability,superb electrical conductivity,and high functionality.In energy storage systems such as metal-ion,metal-air,and metal-sulphur batteries,electrospun nanofibres are vital for constructing flexible electrodes and substantially enhancing their electrochemical properties.The need for flexible batteries has increased with increasing demand for new products such as wearable and flexible devices,including smartwatches and flexible displays.Conventional batteries have several semirigid to rigid components that limit their expansion in the flexible device market.The creation of flexible and wearable batteries with greater mechanical flexibility,higher energy,and substantial power density is critical in meeting the demand for these new electronic items.The implementation of carbon and carbon-derived composites into flexible electrodes is required to realize this goal.It is essential to understand recent advances and the comprehensive foundation behind the synthesis and assembly of various flexible electrospun nanofibres.The design of nanofibres,including those comprising carbon,N-doped carbon,hierarchical,porous carbon,and metal/metal oxide carbon composites,will be explored.We will highlight the merits of electrospun carbon flexible electrodes by describing porosity,surface area,binder-free and free-standing electrode construction,cycling stability,and performance rate.Significant scientific progress has been achieved and logistical challenges have been met in promoting secondary battery usage;therefore,this review of flexible electrode materials will advance this easily used and sought-after technology.The challenges and prospects involved in the timely development of carbon nanofibre composite flexible electrodes and batteries will be addressed.

In-situ deposition of Pd/Pd_(4)S heterostructure on hollow carbon spheres as efficient electrocatalysts for rechargeable Li-O_(2)batteries

The sluggish kinetics of oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)have always restricted the development of lithium oxygen batteries(LOBs).Herein,hollow carbon spheres loaded with Pd/Pd_(4)S heterostructure(Pd/Pd_(4)S@HCS)were successfully prepared via the in-situ deposition to improve the electrocatalytic activities for both ORR and OER in LOBs.With the welldispersed Pd/Pd_(4)S nanoparticles,the hierarchical composite with large specific surface area offers favorable transport channels for ions,electron and oxygen.Especially,the Pd/Pd_(4)S nanoparticles could exhibit excellent electrochemical performance for ORR and OER due to their intrinsic catalytic property and interfacial effect from the heterostructure.Therefore,the LOBs with Pd/Pd_(4)S@HCS as cathode catalyst show improved specific capacities,good rate ability and stable cycling performance.

Fe_(2)O_(3)-decorated boron/nitrogen-co-doped carbon nanosheets as an electrochemical sensing platform for ultrasensitive determination of paraquat in natural water

Boron/nitrogen-co-doped carbon(BCN)nanosheets decorated with Fe_(2)O_(3) nanocrystals(Fe_(2)O_(3)–BCN)were cast on a glassy carbon electrode(GCE)and applied as an electrochemical sensor to effectively detect paraquat(PQ),a toxic herbicide,in aqueous environments.A linear experiment performed using square wave voltammetry(SWV)under optimized experimental conditions produced a decent linear relationship and a low detection limit(LOD)of 2.74 nmol/L(S/N=3).Repeatability,reproducibility,stability,and interference experiments confirmed that the Fe_(2)O_(3)–BCN/GCE system exhibited decent electrochemical sensing performance for PQ molecules.Notably,the designed sensor showed high selectivity and a decent linear relationship with PQ concentration in natural water samples.To the best of our knowledge,this is the first study on the preparation of Fe_(2)O_(3)–BCN nanosheets for PQ detection.The proposed sensor can be employed as an effective alternative tool for distinguishing and processing PQ.

Finite element analysis of temperature distribution of polycrystalline silicon thin film transistors under self-heating stress

The temperature distribution of typical n-type polycrystalline silicon thin film transistors under selfheating(SH)stress is studied by finite element analysis.From both steady-state and transient thermal simulation,the influence of device power density,substrate material,and channel width on device temperature distribution is analyzed.This study is helpful to understand the mechanism of SH degradation,and to effectively alleviate the SH effect in device operation.