Preparation And Investigation Of Nickel Foam Loaded CdS Composite Catalyst For Its Photocatalytic Performance

With the continuous development of economy and society,more and more people focus on hydrogen energy owing to the energy crisis.As a clean renewable energy,hydrogen energy is expected to replace traditional carbon-based fuels due to its advantages of non-toxicity,high energy density and abundant reserves,and it is also called the"green gold"of the 21st century.However,the traditional electrolysis technology for hydrogen production has the disadvantages of high energy consumption and serious pollution.The photocatalytic water splitting directly makes use of solar energy,which has the advantages of low cost,high efficiency and environmental friendliness,and it has become a research hotspot.The key to hydrogen industrialization is to a design low-cost,efficient and stable catalyst for hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）.Cadmium sulfide is characterized by narrow band gap,good light absorption capacity and energy band alignment for reduction of H⁺to H₂,which makes it outstanding among the photoelectric catalysts.But the pristine CdS is not an effective photocatalyst due to the recombination of the photogenerated electron-hole pair.To improve the intrinsic electric conductivity and optimize the photoelectrocatalytic activity,it is crucial to investigate the influence of the morphological and constituent changes of the photoelectrode on the photoelectrocatalytic activity.In the paper,we attempt to design a structure of 1D CdS nanorod array wraped with hierarchical Mo_xNi_yS nanosheets on nickle foam（CdS@Mo_xNi_yS-NF）.The microstructure of photoelectrode was optimized by adjusting the feeding ratio,and thus leading to the improved photocatalytic performance.Firstly,CdS-NF was prepared by hydrothermal method.Hexagonal columnar cadmium sulfide was grown on three-dimensional porous nickel foam,which was beneficial to expose photochemical active sites.Secondly,CdS@Mo_xNi_yS-NF was prepared by simple hydrothermal method and solvothermal synthesis method,using ammonium molybdate tetrahydrate as molybdenum source and thiourea as sulfur source.The microstructure of photoelectrode was optimized by adjusting the feeding ratio.Herein,CdS@Mo_xNi_yS-NF composite is characterized by a core-shell structure,which constructed an suitable energy band alignment conducive to photogenerated electron-hole pair separation for HER.Among them,S/Mo=1/3 sample had the lowest hydrogen evolution overpotential under light condition,reaching71.5 m V.Its light response capability△I was 0.111 m A·cm^-2,which was1.98 times of the one-yuan sample.And its optical stability had been improved significantly.Additionally,using cobalt acetate tetrahydrate as cobalt source,CdS@CoO-NF binary composite OER catalyst was prepared by hydrothermal and solvothermal method.CoO was introduced to act as the active site of OER.The microstructure,optical performance and photoelectrochemical performance of the photocathodes were tested,and the corresponding suitable energy band models were constructed.The mechanism of the enhanced photoelectrocatalytic activity for composite catalysts was analyzed,respectively.The enhanced photocatalytic activity of the as prepared catalysts derived of thire improved the specific surface area of electrochemical activity of the electrode and suitable band alignments towards either HER or OER.And the oxygen evolution overpotential of CdS@CoO（0.25 mmol）-NF under light condition was 354.0 m V,which was the lowest.