Recent Advances in Cadmium Sulfide-Based Photocatalysts for Photocatalytic Hydrogen Evolution

High-efficiency photocatalytic hydrogen evolution(PHE)relies on the development of inexpensive,stable,and efficient photocatalysts.Cadmium sulfide(CdS),as a typical binary metal sulfide,has attracted considerable research attention due to its negative conduction band position,narrow band gap for visible-light response,and strong driving force for PHE.However,the construction of CdSbased photocatalysts and the PHE rate still require improvement for practical applications.In this review,recent advances in CdS-based photocatalysts for PHE via water splitting are systematically summarized.First,the semiconductor properties of CdS,including the crystal and band structures,are briefly introduced.Afterward,the fundamental mechanisms of PHE using semiconductor photocatalysts via water splitting are discussed.Subsequently,the photoactivity of bare CdS with different morphologies and structures,CdS with cocatalyst loading,and CdS-based heterojunction photocatalysts are reviewed and discussed in detail.Finally,the challenges and prospects for exploring advanced CdS-based photocatalysts are provided.

Influence of thermal ageing on high-field polarisation characteristics and conductivity behaviour of submarine polymeric cables insulation

Diagnosing insulation intrinsic ageing is essential for preventing insulation failure of submarine cables,and in case of failure,helping in any decision about maintenance actions.In this study,a novel aged cable diagnosis approach based on high-voltage frequency domain spectroscopy(HV-FDS)with broader frequency width is proposed to analyse the high-field polarisation characteristics and conductivity behaviour of 500 kV submarine polymeric cables insulation,aiming to support the evaluation of overall insulation ageing.The measurement principle of HV-FDS and relaxation mechanism are stated,and then focus is on studying the extent of change of polarisation and conduction properties of submarine cables insulation as a function of ageing stress and time.Moreover,the high-field polarisation characteristics and conductivity behaviour are discussed in-depth based on the carrier transport and trap properties.Finally,the novel diagnostic indicator based on the high-field characteristics is extracted to quantify the thermal ageing state of submarine cables insulation.Results show that the high-field polarisation characteristics and conductivity behaviour seem to become sensitive diagnostic quantities if measured at reasonably high voltage,which are able to reveal mechanisms associated with thermo-oxidative ageing as that generated in the testing procedure considered in this paper.Sensitivity is considerably higher than that experienced in typical dielectric spectroscopy approaches.

High-voltage frequency domain spectroscopy analysis of a thermally aged XLPE submarine cable under continuous and cyclic voltage based on carrier transport and polarisation characteristics

In order to ensure the safe operation of submarine cables,it is of great significance to analyse the insulation state of submarine cables from the perspectives of microstructure,carrier transport characteristics and macroscopic dielectric properties.In this study,based on the high-voltage frequency domain spectroscopy(HV-FDS)measurement system,HV-FDS experiments of fresh and thermally aged submarine cables were carried out under continuous(0.5,2,4 and 10 kV)and cyclic(2-10-2 kV)applied alternating voltages.Then,combining the changes of the microstructure structure of cross-linked poly-ethylene(XLPE)insulation,the aggregate structure deterioration model of XLPE was proposed to discuss the physical mechanism of HV-FDS characteristics of submarine cables under different voltages and insulation states.Results show that the HV-FDS characteristics of submarine cables have significant voltage dependence under contin-uous voltage excitation.The HV-FDS of submarine cables show memory characteristics under cyclic voltage excitation.Compared with the fresh submarine cable,the thermally aged submarine cable shows more significant voltage dependence and memory charac-teristics of HV-FDS.The memory characteristics of HV-FDS are mainly determined by the carriers transport and the interfacial polarisation caused by the accumulation of polar particles at the electrode/dielectric interface.This study covers the correlation mecha-nism among the microstructure,carrier transport and macroscopic HV-FDS properties of submarine cable insulation,which lays a foundation for further research and condition evaluation of submarine cables.