Synthesis And Photocatalytic Performance Of Transition Metal Doped Manganese-Cadmium-Sulfur Solid Solution

The consumption of fossil energy will cause serious environmental pollution,so the search for cleaner alternative energy sources has attracted great attention.Because hydrogen energy is non-polluting and solar energy is inexhaustible,the production of hydrogen through photocatalysis is becoming a promising and attractive way to provide renewable energy carriers.In addition,since Ti O₂ semiconductors were first used for water decomposition in1972,many semiconductors have been developed for photocatalytic hydrogen production,such as metal oxides,metal sulfides,and nitrogen oxides.Among them,metal sulfides have attracted attention in the past few decades due to their suitable electronic band gap,energy band position,abundant active sites,and high photocatalytic activity.However,its photocatalytic activity is still limited by the rapid recombination of photogenerated electron-hole pairs,so there is an urgent need to prepare low-cost,high-performance photocatalysts.By ion-doping the metal sulfide nanocatalyst,the donor energy level higher than the original valence band or the acceptor energy level lower than the original conduction band can be generated in the forbidden band,so that the photocatalyst reacts to visible light.The doped ions in the photocatalyst not only help to absorb visible light,but also suppress the recombination of photogenerated carriers by trapping electrons or holes,thereby improving the efficiency of photocatalytic hydrogen evolution.This paper mainly studied the influence of Ni and Cu doping on the morphology and properties of Mn_0.5Cd_0.5S.（1）A rod-shaped Ni-doped Mn_0.5Cd_0.5S solid solution（Ni-MCS）was synthesized by colloidal chemical method.Doping Ni did not change the morphology of Mn_0.5Cd_0.5S solid solution.When the Ni doping content was 4%,the photocatalytic hydrogen evolution performance of Ni-MCS will be as high as 12.8 mmol·g^-1·h^-1,which was 6.4 times higher than that of Mn Cd S monomer,and Ni-MCS showed good photocatalysis stability.The high photocatalytic activity of Ni-MCS can be attributed to the following reasons:On the one hand,doped Ni²⁺played a key role in narrowing the band gap and reducing the recombination rate of photo-generated carriers,which can significantly improve the catalyst activity and Stability;on the other hand,when doped with Ni²⁺,the length of Mn_0.5Cd_0.5S nanorods was significantly shortened,which can effectively shorten the time for photogenerated electrons to reach the active site surface,reduce the recombination rate of photogenerated electrons and holes,and improve the photocatalytic hydrogen production activity.（2）High-crystallinity hexagonal cone-shaped Cu-doped Mn_0.5Cd_0.5S solid solution（Cu-MCS）was prepared by colloidal hot injection method.Cu doping changed the morphology of Mn Cd S solid solution,and significantly affected its optical properties.Adding copper to Mn Cd S could adjust the conduction band potential to a more negative direction,which was beneficial to water decomposition.The hydrogen evolution rate of Cu-MCS（5%）solid solution under visible light irradiation reached 14.8 mmol·g^-1·h^-1,which was about 7.4of the monomer Mn_0.5Cd_0.5S solid solution(1.99 mmol·g^-1·h^-1)Times.The photocatalytic hydrogen evolution performance of Cu-MCS has been significantly improved,mainly due tothe rapid separation and transfer of photo-generated charge carriers,and the increased light absorption capacity in the visible range.