MoS_(2)/g-C_(3)N_(4)S型异质结的构建及光催化性能研究

S-type Heterojunction of MOS_(2)/g-C_(3)N_(4):Construction and Photocatalysis

制备高效稳定的光催化剂对于光催化技术的发展至关重要。本研究采用超声辅助沉积加低温煅烧的方法制备了2H相MoS_(2)/g-C_(3)N_(4)S型异质结光催化剂(MGCD),并综合考察了材料的相结构、微观形貌、光吸收性能、X射线光电子能谱、电化学交流阻抗和光电流等对光催化性能的影响。结果表明:经过超声辅助沉积-煅烧处理,MoS_(2)微米球发生破碎分散结合在g-C_(3)N_(4)纳米片层表面上并形成异质结。可见光下5%MGCD(添加5%MoS_(2))对罗丹明B(RhB)在20 min时的降解率达到了99%,且样品重复使用5次后对RhB的降解率仍能达到95.2%,表现出良好的光催化性能及稳定性。从内建电场形成的角度进一步分析表明,异质结中MoS_(2)与g-C_(3)N_(4)间耦合形成的内建电场引起的能带弯曲可以有效引导载流子的定向迁移,并促进光生载流子的分离,从而提高了光催化反应效率。异质结光催化剂的自由基捕获实验表明:O_(2)^(–)和·OH在催化降解RhB中是主要的活性物种,h^(+)的贡献次之。

Preparation of highly efficient and stable photocatalysts is crucial for the development of photocatalysis technology.In this study,the method of ultrasonic-assisted deposition and low-temperature calcination was used to prepare MoS_(2)/g-C_(3)N_(4)S-type heterojunction photocatalyst(MGCD).Effects of the phase structure,micro-morphology,optical absorption performance,X-ray photoelectron spectroscopy,electrochemical AC impedance,and photocurrent of the materials on the photocatalytic activity were comprehensively investigated.The results show that,after ultrasonic-assisted deposition-calcination treatment,MoS_(2)microspheres were broken,dispersed and combined on the surface of g-C_(3)N_(4)nanosheets,and formed a kind of heterojunction.Under visible light,the degradation rate of 5%MGCD(with 5%MoS_(2)addition)for Rhodamine B(RhB)reached 99%in 20 min,and still reach 95.2%when the sample was reused for 5 times,showing good photocatalytic performance and stability.Further analysis from the point of view of the formation of built-in electric field shows that the band bending caused by built-in electric field,coupled with MoS_(2)and g-C_(3)N_(4)in heterojunction,can effectively guide the directional migration of carriers,which can efficiently promote the separation of photogenerated carriers,thus improving the efficiency of photocatalytic reaction.Free radical capture experiment of heterojunction photocatalyst reveals that O_(2)^(–)and·OH are the main active species in the catalytic degradation of RhB,followed by H+.