2D/2D S-scheme heterojunction with a covalent organic framework and g-C_(3)N_(4) nanosheets for highly efficient photocatalytic H2 evolution

The fabrication of S-scheme heterojunctions with fast charge transfer and good interface contacts,such as intermolecularπ–πinteractions,is a promising approach to improve photocatalytic performance.A unique two-dimensional/two-dimensional(2D/2D)S-scheme heterojunction containing TpPa-1-COF/g-C_(3)N_(4) nanosheets(denoted as TPCNNS)was developed.The established maximum interfacial interaction between TpPa-1-COF NS and g-C_(3)N_(4) NS may result in aπ–πconjugated heterointerface.Furthermore,the difference in the work functions of TpPa-1-COF and g-C_(3)N_(4) results in a large Fermi level gap,leading to upward/downward band edge bending.The spontaneous interfacial charge transfer from g-C_(3)N_(4) to TpPa-1-COF at theπ–πconjugated interface area results in the presence of a built-in electric field,according to the charge density difference analysis based on density functional theory calculations.Such an enhanced built-in electric field can efficiently drive directional charge migration via the S-scheme mechanism,which enhances charge separation and utilization.Thus,an approximately 2.8 and 5.6 times increase in the photocatalytic hydrogen evolution rate was recorded in TPCNNS-2(1153μmol g^(-1) h^(-1))compared to pristine TpPa-1-COF and g-C_(3)N_(4) NS,respectively,under visible light irradiation.Overall,this work opens new avenues in the fabrication of 2D/2Dπ–πconjugated S-scheme heterojunction photocatalysts with highly efficient hydrogen evolution performance.

SiOx/C-Ag nanosheets derived from Zintl phase CaSi_(2) via a facile redox reaction for high performance lithium storage

As one of the high-capacity anodes in lithium-ion batteries(LIBs),silicon oxide(SiOx)has attracted wide attention due to its high theoretical capacity,low cost,and proper working voltage.However,the huge volume change and the intrinsic poor conductivity of SiOx still hinder the practical applications.How to address the issues is the focus of current research.In this work,firstly,hydrogen passivated Si nanosheets(Si6H6)were prepared from Zintl phase CaSi2,then,two-dimensional Ag nanoparticle modified SiOVC nanocomposite was prepared via a facile complex redox reaction between SieH6 and AgN03-aniline complexing agent.In this design,aniline was served as carbon sources,and Si6H6could be transformed to SiOx by AgN03 in mild solution condition.The obtained Ag modified SiOVC(SiOx/C-Ag)electrode exhibited high specific capacity(550 mAh·g^(-1)at 0.6 A·g^(-1)),superior rate,and cycling performance when served as anode for LIBs.

Z-scheme CdS/WO_(3)on a carbon cloth enabling effective hydrogen evolution

Photocatalytic water splitting for hydrogen(H2)generation is a potential strategy to solve the problem of energy crisis and environmental deterioration.However,powder-like photocatalysts are difficult to recycle,and the agglomeration of particles would affect the photocatalytic activity.Herein,a direct Z-scheme CdS/WO_(3)composite photocatalyst was fabricated based on carbon cloth through a two-step process.With the support of carbon cloth,photocatalysts tend to grow uniformly for further applications.The experimental results showed that the H2 yield of adding one piece of CdS/WO_(3)composite material was 17.28μmol/h,which was 5.5 times as compared to that of pure CdS-loaded carbon cloth material.A cycle experiment was conducted to verify the stability of the asprepared material and the result demonstrated that the H2 generation performance of CdS/WO_(3)decreased slightly after 3 cycles.This work provides new ideas for the development of recyclable photocatalysts and has a positive significance for practical applications.