Wavelength-sensitive photocatalytic H2 evolution from H2S splitting over g-C3N4 with S,N-codoped carbon dots as the photosensitizer

Photocatalytic splitting of hydrogen sulfide(H2S) for hydrogen evolution is a promising method to solve the energy and environmental issues.In this work,S,N-codoped carbon dots(S,N-CDs)/graphitic carbon nitride(g-C3N4) nanosheet is synthesized by hydrothermal method as an efficient photocatalyst for the decomposition of H2S.In addition to the characterization of the morphology and structure,chemical state,optical and electrochemical performances of S,N-CDs/g-C3N4,hydrogen evolution tests show that the activity of g-C3N4 is improved by introducing S,N-CDs,and the enhancement depends strongly on the wavelength of incident light.The photocatalytic hydrogen production rate of S,N-CDs/g-C3N4 composite reaches 832 μmol g-1h-1, which is 38 times to that of g-C3N4 under irradiation at 460 nm.Density functional theory calculations and electron paramagnetic resonance as well as photoluminescence technologies have altogether authenticated that the unique wavelength-dependent photosensitization of S,N-CDs on g-C3N4;meanwhile,a good match between the energy level of S,N-CDs and g-C3N4 is pivotal for the effective photocatalytic activity.Our work has unveiled the detailed mechanism of the photocatalytic activity enhancement in S,N-CDs/g-C3N4 composite and showed its potential in photocatalytic splitting of H2S for hydrogen evolution.

Modelling charge transport and electro-optical characteristics of quantum dot light-emitting diodes

Quantum dot light-emitting diodes(QD-LEDs)are considered as competitive candidate for next-generation displays or lightings.Recent advances in the synthesis of core/shell quantum dots(QDs)and tailoring procedures for achieving their high quantum yield have facilitated the emergence of high-performance QD-LEDs.Meanwhile,the charge-carrier dynamics in QD-LED devices,which constitutes the remaining core research area for further improvement of QD-LEDs,is,however,poorly understood yet.Here,we propose a charge transport model in which the charge-carrier dynamics in QD-LEDs are comprehensively described by computer simulations.The charge-carrier injection is modelled by the carrier-capturing process,while the effect of electric fields at their interfaces is considered.The simulated electro-optical characteristics of QD-LEDs,such as the luminance,current density and external quantum efficiency(EQE)curves with varying voltages,show excellent agreement with experiments.Therefore,our computational method proposed here provides a useful means for designing and optimising high-performance QD-LED devices.