内电场增强S型异质结N-C_(3)N_(4)/BiOCl_(x)I_(1−x)的制备及其光催化性能

Preparation of S-type heterojunction N-C_(3)N_(4)/BiOCl_(x)I_(1−x) with internal electric field and enhanced photocatalytic properties

采用一步水热法使固溶体BiOCl_(x)I_(1−x)静电自组装在N掺杂的氮化碳(N-C_(3)N_(4))表面,制备了NC_(3)N_(4)/BiOCl_(x)I_(1−x)S型异质结。通过XRD、XPS、SEM、TEM、FTIR、UV-Vis等技术对样品的晶型、形貌、结构、元素组成、表面官能团、光学性质等进行了表征,并考察了N-C_(3)N_(4)/BiOCl_(x)I_(1−x)光催化氧化有机污染物与还原Cr(VI)的活性。结果表明,N-C_(3)N_(4)/BiOCl_(x)I_(1−x)具有强的光吸收,在N-C_(3)N_(4)与BiOCl_(x)I_(1−x)界面处形成的内电场抑制了电子-空穴对的复合。在可见光照射下,20%N-BiOCl0.5I0.5呈现出优异的光催化活性,2.5 h内苯酚的降解率达到98.53%;1 h内Cr(VI)的还原率达到99.11%。20%N-BiOCl0.5I0.5在5次循环后表现出良好的稳定性。3 h内20%N-BiOCl0.5I0.5可见光降解苯酚的总有机碳(TOC)去除率为80.21%。结合捕获实验、ESR、DFT计算等表明,N-C_(3)N_(4)/BiOCl_(x)I_(1−x)活性归因于S型异质结的形成、N-C_(3)N_(4)和BiOCl_(x)I_(1−x)之间的内部电场及能带弯曲和库仑力的存在,加速了光生载流子的空间分离和有序电子流。

N doped carbon nitride(N-C_(3)N_(4))/BiOCl_(x)I_(1−x)S-type heterojunctions were prepared by a facile one-step hydrothermal method.The crystal form,morphology,structure,elemental composition,surface functional groups and optical properties of the samples were characterized by XRD,XPS,SEM,TEM,FTIR and UV-Vis.The photocatalytic activity of N-C_(3)N_(4)/BiOCl_(x)I_(1−x)oxidation of organic pollutants and reduction of Cr(VI)was investigated.The results show that N-C_(3)N_(4)/BiOCl_(x)I_(1−x)sample exhibits the effective enhancement in light absorption.The charge carriers were generated by the transfer of the photoinduced electron from N-C_(3)N_(4)to BiOCl_(x)I_(1−x)across the interface under irradiation,which inhibited the recombination of electron-hole pairs.Under visible light irradiation,20%NBiOCl0.5I0.5 exhibited high activity,the degradation rate of phenol reached 98.53%with 2.5 h of visible light irradiation.Meanwhile,the reduction rate of Cr(VI)of 20%N-BiOCl0.5I0.5 reached to 99.11%with 1 h of visible light irradiation.20%N-BiOCl0.5I0.5 showed good stability after five cycles.The total organic carbon(TOC)removal rate of degradation phenol by 20%N-BiOCl0.5I0.5 within 3 h was 80.21%.Combined with capture experiment,ESR and DFT calculation,the improvement activity of N-C_(3)N_(4)/BiOCl_(x)I_(1−x)was attributed to the formation of S-type heterojunction,the internal electric field based on different Fermi levels between N-C_(3)N_(4)and BiOCl_(x)I_(1−x),as well as band bending and Coulomb force,which together accelerated spatial separation of photogenerated carriers and orderly electron flow.