Modulating charge separation and transfer for high-performance photoelectrodes via built-in electric field

Constructing a built-in electric field has emerged as a key strategy for enhancing charge separation and transfer,thereby improving photoelectrochemical performance.Recently,considerable efforts have been devoted to this endeavor.This review systematically summarizes the impact of built-in electric fields on enhancing charge separation and transfer mechanisms,focusing on the modulation of built-in electric fields in terms of depth and orderliness.First,mechanisms and tuning strategies for built-in electric fields are explored.Then,the state-of-the-art works regarding built-in electric fields for modulating charge separation and transfer are summarized and categorized according to surface and interface depth.Finally,current strategies for constructing bulk built-in electric fields in photoelectrodes are explored,and insights into future developments for enhancing charge separation and transfer in high-performance photoelectrochemical applications are provided.

VSe_(2)/V_(2)C heterocatalyst with built-in electric field for efficient lithium-sulfur batteries:Remedies polysulfide shuttle and conversion kinetics

Lithium sulfur(Li-S)battery is a kind of burgeoning energy storage system with high energy density.However,the electrolyte-soluble intermediate lithium polysulfides(Li PSs)undergo notorious shuttle effect,which seriously hinders the commercialization of Li-S batteries.Herein,a unique VSe_(2)/V_(2)C heterostructure with local built-in electric field was rationally engineered from V_(2)C parent via a facile thermal selenization process.It exquisitely synergizes the strong affinity of V_(2)C with the effective electrocatalytic activity of VSe_(2).More importantly,the local built-in electric field at the heterointerface can sufficiently promote the electron/ion transport ability and eventually boost the conversion kinetics of sulfur species.The Li-S battery equipped with VSe_(2)/V_(2)C-CNTs-PP separator achieved an outstanding initial specific capacity of 1439.1 m A h g^(-1)with a high capacity retention of 73%after 100 cycles at0.1 C.More impressively,a wonderful capacity of 571.6 mA h g^(-1)was effectively maintained after 600cycles at 2 C with a capacity decay rate of 0.07%.Even under a sulfur loading of 4.8 mg cm^(-2),areal capacity still can be up to 5.6 m A h cm^(-2).In-situ Raman tests explicitly illustrate the effectiveness of VSe_(2)/V_(2)C-CNTs modifier in restricting Li PSs shuttle.Combined with density functional theory calculations,the underlying mechanism of VSe_(2)/V_(2)C heterostructure for remedying Li PSs shuttling and conversion kinetics was deciphered.The strategy of constructing VSe_(2)/V_(2)C heterocatalyst in this work proposes a universal protocol to design metal selenide-based separator modifier for Li-S battery.Besides,it opens an efficient avenue for the separator engineering of Li-S batteries.

Built-in electric field induced S-scheme g-C_(3)N_(4)homojunction for efficient photocatalytic hydrogen evolution:Interfacial engineering and morphology control

S-scheme possesses superior redox capabilities compared with the II-scheme,providing an effective method to solve the innate defects of g-C_(3)N_(4)(CN).In this study,S-doped g-C_(3)N_(4)/g-C_(3)N_(4)(SCN-tm/CN)S-scheme homojunction was constructed by rationally integrating morphology control with interfacial engineering to enhance the photocatalytic hydrogen evolution performance.In-situ Kelvin probe force microscopy(KPFM)confirms the transport of photo-generated electrons from CN to SCN.Density functional theory(DFT)calculations reveal that the generation of a built-in electric field between SCN and CN enables the carrier separation to be more efficient and effective.Femtosecond transient absorption spectrum(fs-TAS)indicates prolonged lifetimes of SCN-tm/CN_(3)(τ1:9.7,τ2:110,andτ3:1343.5 ps)in comparison to those of CN(τ1:4.86,τ2:55.2,andτ3:927 ps),signifying that the construction of homojunction promotes the separation and transport of electron hole pairs,thus favoring the photocatalytic process.Under visible light irradiation,the optimized SCN-tm/CN_(3)exhibits excellent photocatalytic activity with the hydrogen evolution rate of 5407.3μmol·g^(−1)·h^(−1),which is 20.4 times higher than that of CN(265.7μmol·g^(−1)·h^(−1)).Moreover,the homojunction also displays an apparent quantum efficiency of 26.8%at 435 nm as well as ultra-long and ultra-stable cycle ability.This work offers a new strategy to construct highly efficient photocatalysts based on the metal-free conjugated polymeric CN for realizing solar energy conversion.

华能沁北电厂600MW超临界机组热控系统调试与改进

介绍了华能沁北电厂国产超临界600MW机组热控系统设计与调试情况,对存在的问题进行了改进,改进后系统工作正常,效果较好。

第一台出口海外国产600MW超临界锅炉技术特点分析

东方锅炉厂生产的DG1827/25.4-Ⅱ4型锅炉是我国出口海外的第一台600 MW锅炉,安装在土耳其宗古尔达克省EREN电厂,这是我国超临界火力发电机组首次海外中标,与其它国产600 MW机组配套锅炉相比,在设计方面存在许多独到之处,并有很多技术特点值得分析研究。文中着重分析了锅炉在蒸汽参数选择、变压运行设计、螺旋管圈水冷壁、内置式汽水分离器及燃烧系统方面的技术特点。

A carbon-rich g-C_(3)N_(4) with promoted charge separation for highly efficient photocatalytic degradation of amoxicillin

A novel carbon-rich g-C_(3)N_(4) nanosheets with large surface area was prepared by facile thermal polymerization method using urea and 1,3,5-cyclohexanetriol.Plenty of carbon-rich functional groups were introduced into the surface layers of g-C_(3)N_(4),which constructed the built-in electric field(BIEF)and resulted in improved charge separation;therefore,the carbon-rich g-C_(3)N_(4) displayed superior photocatalytic activity for amoxicillin degradation under solar light.The contaminant degradation mechanism was proposed based on radical quenching experiments,intermediates analysis and density functional theory(DFT)calculation.Moreover,the reusing experiments showed the high stability of the material,and the amoxicillin degradation under various water matrix parameters indicated its high applicability on pollutants treatment,all of which demonstrated its high engineering application potentials.

CsPbI nanorods as the interfacial layer for high-performance,all-solution-processed self-powered photodetectors

Heterojunction is regarded as a crucial step toward realizing high-performance devices,particularly,forming gradient energy band between heterojunctions benefits self-powered photodetectors.Therefore,in this paper,the synthesis of CsPbI3 nanorods(NRs)and its application as the interfacial layer in high-performance,all-solution-processed self-powered photodetectors are presented.For the bilayer photodetector ITO/ZnO(100 nm)/PbS-TBAI(150 nm)/Au,a responsivity of 3.6 A/W with a specific detectivity of 9.8×10^(12)Jones was obtained under 0.1 mW/cm^(2)white light illumination at zero bias(i.e.in self-powered mode).Meanwhile,the photocurrent was enhanced to an On/Off current ratio of 105 at zero bias with an open circuit voltage of 0.53 V for trilayer photodetector ITO/ZnO(100 nm)/PbSTBAI(150 nm)/CsPbI3(250 nm)/Au,in which the CsPbI3 NRs layer works as the interfacial layer.As a result,a specific detectivity of 4.5×10^(13)Jones with a responsivity of 11.12 A/W was obtained under0.1 mW/cm^(2) white light illumination,as well as the rising/decaying time of 0.57 s/0.41 s with excellent stability and reproducibility upto four weeks in air.The enhanced-performance is ascribed to the mismatch bandgap between PbS-TBAI/CsPbI_(3)interface,which can suppress the carrier recombination and provide efficient transport passages for charge carriers.Thus,it provides a feasible and efficient method for high-performance photodetectors.

Insights into the photocatalytic mechanism of the C4N/MoS2 heterostructure: A first-principle study

Constructing heterostructures by combining COFs and TMD is a new strategy to design efficient photocatalysts for CO2 reduction reaction(CO2RR) due to their good stability,tunable band gaps and efficient charge separation.Based on the synthesis of completely novel C4N-COF in our previous re ported work,a new C4N/MoS2 heterostructure was constructed and then the related structural,electronic and optical properties were also studied using first principle calculations.The interlayer coupling effect and charge transfer between the C4N and MoS2 layer are systematically illuminated.The reduced band gap of the C4N/MoS2 heterostructure is beneficial to absorb more visible light.For the formation of type-Ⅱ band alignment,a built-in electric field appears which separates the photogene rated electrons and holes into different layers efficiently and produces redox active sites.The band alignment of the heterostructure ensures its photocatalytic activities of the whole CO2 reduction reaction.Furthermore,the charge density difference and charge carrier mobility confirm the existence of the built-in electric field at the interface of the C4N/MoS2 heterostructure directly.Finally,the high optical absorption indicates it is an efficient visible light harvesting photocatalyst.Therefore,this wo rk could provide strong insights into the internal mechanism and high photocatalytic activity of the C4N/MoS2 heterostructure and offer guiding of designing and synthesizing COF/TMD heterostructure photocatalysts.