SnO_(2) quantum dots modified N-doped carbon as high-performance anode for lithium ion batteries by enhanced pseudocapacitance

SnO_(2) is considered to be a promising candidate as anode material for lithium ion batteries,due to its high theoretical specific capacity(1494 mAh·g^(-1)).Nevertheless,SnO_(2)-based anodes suffer from poor electronic conductivity and serious volume variation(300%)during lithiation/delithiation process,leading to fast capacity fading.To solve these problems,SnO_(2) quantum dots modified N-doped carbon spheres(SnO_(2) QDs@N-C)are fabricated by facile hydrolysis process of SnCl2,accompanied with the polymerization of polypyrrole(PPy),followed by a calcination method.When used as anodes for lithium ion batteries,SnO_(2) QDs@N-C exhibits high discharge capacity,superior rate properties as well as good cyclability.The carbon matrix completely encapsulates the SnO_(2) quantum dots,preventing the aggregation and volume change during cycling.Furthermore,the high N content produces abundant defects in carbon matrix.It is worth noting that SnO_(2) QDs@N-C shows excellent capacitive contribution properties,which may be due to the ultra-small size of SnO_(2) and high conductivity of the carbon matrix.

Fabrication of N-CQDs@W_(18)O_(49) heterojunction with enhanced charge separation and photocatalytic performance under full-spectrum ligh irradiation

Increasing the charge separation and the utilization efficiency of sunlight are essential factors in a photocatalytic process.In this study,we prepared crystalline N-CQDs@W_(18) O_(49) heterostructures,through the in situ growth of W_(18) O_(49) nanocrystals on nitrogen-doped carbon quantum dots(N-CQDs).N-CQDs@W_(18) O_(49) nanocomposites showed high activity in the photodegradation of ciprofloxacin(CIP)and methyl orange(MO).The photodegradation activity of the optimized N-CQDs@W_(18) O_(49)-5 sample was four times higher than that of W_(18) O_(49) under ultraviolet-visible(UV–vis) light irradiation.The photodegradation activity of N-CQDs@W_(18) O_(49)-5 sample was two times higher than that of W_(18) O_(49) under near-infrared(NIR) light irradiation.The enhanced photosensitivity of the nanocomposites was attributed to the promotion of charge separation by N-CQDs and the local surface plasmon resonance(LSPR) effect of W_(18) O_(49) under NIR light irradiation.This work provides a promising approach for designing and manufacturing photocatalysts with full-spectral responsiveness and improved charge separation.