Preparation,Modification And Catalytic Performance Of CdS Composite Photocatalytic Materials For Hydrogen Production

Since 1970s,Japanese scholars Honda and Fujima have used titanium dioxide to convert photocatalytic water into H₂and O₂.Semiconductor photocatalyst technology has been widely used in photocatalytic decomposition of aquatic hydrogen.However,traditional semiconductors such as titanium dioxide can absorb less than 4%of the total sunlight,which greatly limits its application in photocatalytic water decomposition technology.Therefore,the research and development of catalysts for visible light response is one of the means to solve this problem.Metal sulfide materials have become the most promising candidates because of their ability to utilize visible light,better photocatalytic performance,and lower cost.Among them,CdS,as a narrow band gap sulfide semiconductor,has a good response to visible light,and the valence band position satisfies the conditions for semiconductor decomposition of hydrogen production,so it exhibits excellent photocatalytic hydrogen production performance under visible light irradiation.However,the application of CdS is still limited because it has the disadvantages of common sulfides:severe photocorrosion,high recombination of photogenerated electron and hole pairs.Photocorrosion can be effectively improved by adding a sacrificial agent during photocatalysis;Meanwhile,for photocomposite electron and hole recombination,many methods such as dye photosensitization,loadeded cocatalyst,and constructing heterojunction were employed.Therefore,this paper mainly focuses on improving the photo-corrosion and photo-generated electron-hole recombination:1.RB-NH-HA@CdS photocatalyst prepared by dialysis and hydrothermal method.Compared with pure CdS and RB-NH₂@CdS,RB-NH-HA@CdS exhibits significantly enhanced photocatalytic activity under visible light irradiation.This may be due to wettability of CdS directly modified by the introduction of the fluorescent polymer dye component RB-NH-HA.The contact angle test and the fluorescence test show that RB-NH-HA has the dual promotion of hydrophilicity and optical properties,which can promote the transfer and separation of photoinduced carriers,and can generate ground state and excited state electrons in the photosensitization process.In this case,more transport paths are provided for the migration of photogenerated carriers,thereby improving the separation efficiency of photogenerated electrons and holes.2.Preparation of CdS NRS@NiSilicate composites by one-step solvothermal method.A series of characterizations such as SEM,XRD and TEM characterization proved that CdS NRS@Ni Silicate composite photocatalysts was successfully prepared,and the improvement of the composite materials may be attributed to the loading of Ni Silicate as a cocatalyst,which promoted better separation of photogenerated electrons and holes.Meanwhile,Ni Silicate as a protective layer,effectively inhibits the photo-corrosion of CdS,thereby improving the photocatalytic decomposition of hydrogen production efficiency.3.AgVO₃/CdS（x%）composite photocatalyst was prepared by precipitation method.The AgVO₃/CdS（x%）composite photocatalyst was characterized by a series of such as SEM,TEM,BET and XRD.The photocatalytic hydrogen production performance of AgVO₃/CdS（3%）sample was the best when the loading amount of AgVO₃was 3%,and the photocatalytic stability was also improved.This may be attributed to the increase of specific surface area of photocatalyst after loading AgVO₃.It provides more active sites for photocatalysts.At the same time,the construction of p-n heterojunction improves the separation efficiency of photogenerated electrons and holes,so that the photocatalyst has higher photocatalytic activity for hydrogen production.