Construction Of Novel In₂S₃-based Composite Photocatalysts And Their Performance For Purifing Water Environment

Photocatalytic technology has opened up a broad road for effective achievement of pollution control and energy production.Indium sulfide（In₂S₃）has exhibited the enormous space of development in photocatalysis owing to the intense visible light response range,suitable energy band position,low toxicity.However,the photocatalytic activity of In₂S₃alone is still unsatisfactory due to the rapid recombination of carriers.In this paper,to address this pitfall,two novel In₂S₃-based composite photocatalysts were prepared through constructing heterostructures and used for the first time in water environment purification.While the external conditions of reaction were optimized,the mechanism of photocatalytic activity enhancement was systematically and thoroughly elaborated under the dual support of characterization and test results.（1）Novel In₂S₃/bismuth molybdate（Bi₂Mo O₆）composite photocatalysts were synthesized via hydrothermal and solvothermal method using Bi₂Mo O₆and In₂S₃as substrates,and applied for rhodamine B（Rh B）degradation.Hydrothermal method was the optimal synthesis route according to the preliminary test results of photocatalytic performance.Obviously,all the In₂S₃/Bi₂Mo O₆composites demonstrated more splendid activity for Rh B（p H=7,10 mg/L）degradation than pure In₂S₃and Bi₂Mo O₆at low catalyst dose（0.2 g/L）.Among them,the degradation efficiency of the optimal product IB-2,whose composite molar ratio between In₂S₃and Bi₂Mo O₆was 30:1,was 88.2%,and its efficiency remained at a high level after 4 cycles.The reinforced photocatalytic activity was ascribed to the formation of Type-II heterojunction,which not only significantly enhanced the ability to absorb pollutants and collect visible light,but also mightily drove the migration of spatial charges,thus induced the generation of superoxide radicals（·O₂^-）on the conduction band of Bi₂Mo O₆and the accumulation of holes（h⁺）on the valence band of In₂S₃.The synergetic degradation of·O₂^-and h⁺improved the catalytic performance.（2）A series of novel In₂S₃/MIL-53（Fe）photocatalysts with Type-II heterojunction were successfully constructed by hydrothermal method using iron-based MOFs MIL-53（Fe）as the substrate.The characterization and experimental results testified that the emergence of this Type-II heterostructure remarkably accelerated the transfer of spatial charges,which induced the accumulation of electrons（e^-）and the production of·O₂^-on the conduction band of MIL-53（Fe）.The synergetic reduction of e^-and·O₂^-maximized the removal performance of hexavalent chromium（Cr（VI））.Especially,the product IM-2 with a composite mass ratio of 20:1 of In₂S₃and MIL-53（Fe）displayed the highest degradation efficiency（97.04%）and the fastest degradation velocity(k=0.1428 min^-1)under the optimal reaction external conditions,where its k value was nearly 26 and 4 times stronger than that of MIL-53（Fe）and In₂S₃,respectively.More importantly,the removal effect remained high after 4 cycles.Moreover,the excellent visible light absorption and the increased reaction sites was also conductive to the soar of performance.