Research On The Construction Of Zn_0.5Cd_0.5S Based Heterostructures On The Photocatalytic Performance

The environmental pollution and energy shortage caused by industrial development are significant obstacles that cannot be ignored in the process of sustainable development.Photocatalytic technology which can convert solar energy into chemical energy is an appropriate technology to satisfy the sustainable development and carbon neutrality strategy.The core of photocatalytic technology lies in seeking efficient and stable photocatalysts.Zn_xCd_1-xS,a ternary transition metal sulfide,widely used in various applications of photocatalytic technology due to its excellent surface properties,adjustable band structure,and inherent optical properties.However,Zn_xCd_1-xS also has undeniable defects,such as easy aggregation of particles,insufficient stability,and severe recombination of photogenerated charge carriers.Developing appropriate performance improvement strategies is a key step in ensuring efficient and stable photocatalytic performance.The Zn_0.5Cd_0.5S was chosen as the target material in this article,and achieved rapid electron hole pair separation by constructing a heterostructure between Zn_0.5Cd_0.5S and other photocatalytic materials,thus increasing the photocatalytic activity.The successful construction of heterogeneous structures were demonstrated XRD,SEM,TEM and XPS.The photocatalytic performance and stability were evaluated through photocatalytic hydrogen evolution,degradation of organic pollutants,reduction of heavy metal chromium ions（Cr（VI））,and H₂O₂production etc.Finally,the mechanism of their photocatalytic action was explained.The main tasks are as follows:（1）Zn_0.5Cd_0.5S nanospheres were grown on the surface of Sn₃O₄nanosheets to construct Zn_0.5Cd_0.5S/Sn₃O₄（ZCS/SO）heterostructures by using hydrothermal method and in-situ growth method.The ZCS/SO heterostructure had made significant progress in photocatalytic hydrogen evolution and organic pollutant degradation compared to the Zn_0.5Cd_0.5S.ZCS/SO-10 owned the highest H₂production rate(7.19 mmol·g^-1·h^-1),and degraded 91%of tetracycline hydrochloride（TCH）under visible light in 60 minutes,where the catalytic degradation rate of 0.0484 min^-1was242 times and 1.9 times of the those of Sn₃O₄(0.0002 min^-1)and Zn_0.5Cd_0.5S(0.0249 min^-1).The construction of heterostructures not only optimized the specific surface area,hydrophilicity and photoresponse ability of ZCS/SO,but also accelerated the migrating and separating of photogenerated charges,which were the main reasons of the improvement the photocatalytic efficiency.Finally,the mechanism of photocatalytic reaction was discussed.（2）The Zn_0.5Cd_0.5S/Bi₄V₂O₁₁（ZCS/BVO）heterostructure was creatively synthesized by two-step hydrothermal method by loading Zn_0.5Cd_0.5S nanospheres on the surface of Bi₄V₂O₁₁nanoflowers.The successful preparation of the heterostructures with close contact was demonstrated by testing such as XRD,SEM,TEM,XPS,etc.The photocatalytic degradation of TCH and Cr（VI）reduction experiments had demonstrated that the composite structure had superior photocatalytic performance compared those of Zn_0.5Cd_0.5S and Bi₄V₂O₁₁.The ZCS/BVO-10 sample owned the most excellent performance,and degraded 80.3%of TCH in 48minutes.The degradation rate was 2.19 and 3.20 times higher than the those of Zn_0.5Cd_0.5S and Bi₄V₂O₁₁,respectively.Moreover,the photocatalytic reduce Cr（VI）of ZCS/BVO-10 reached86.7%in 60 min,which was 1.38 and 9.96 times higher than those of Zn_0.5Cd_0.5S and Bi₄V₂O₁₁.The construction of ZCS/BVO heterostructure not only provided more active site for reaction on the material surface,but also allowed the fast flow of photogenerated carriers through the close interface,which accelerated the separation of photogenerated electron hole pairs,and improved the photocatalytic activity.（3）Firstly,bulk BN was synthesized by recrystallization and calcination methods,and peeled off under ultrasonic conditions.Zn_0.5Cd_0.5S nanospheres were in-situ grown on BN nanosheets using hydrothermal method to form Zn_0.5Cd_0.5S/BN（ZCS/BN）heterostructures.The successful construction was demonstrated through microscopic characterization methods such as XRD,SEM,TEM,XPS,etc.The ZCS/BN exhibited significant performance in photocatalytic reduction of Cr（VI）and H₂O₂production.ZCS/BN-5 photocatalytic reduced 97.5%of Cr（VI）at 60 min,with a reaction rate constant of 0.0418 min^-1,which was 3.14 and 209 times higher than those of Zn_0.5Cd_0.5S and BN.The composite ZCS/BN-10 exhibited the best photocatalytic H₂O₂production performance under visible light,with the concentration of 791.28μmol·L^-1（μM）after 60 min.The H₂O₂production rate was 1987.19μmol·g^-1·h^-1,which is 2.24 times than that of Zn_0.5Cd_0.5S.The excellent photocatalytic performance might account for the electrostatic interaction of negatively charged BN to photogenerated holes in the VB of Zn_0.5Cd_0.5S,which promoted the transferring of photogenerated holes to BN through the contact interface,and improved the separation of photogenerated electron hole pairs.At the same time,the heterostructure enabled the composite to have a larger specific surface area and enhanced light absorption ability.At the end,the possible reaction mechanism of the photocatalytic process was provided.