摘要
Weak redox ability and severe charge recombination pose significant obstacles to the advancement of CO_(2)photoreduction.To tackle this challenge and enhance the CO_(2)photoconversion efficiency,fabricating well-matched S-scheme heterostructure and establishing a robust built-in electric field emerge as pivotal strategies.In pursuit of this goal,a core-shell structured CuInS_(2)@CoS_(2)S-scheme heterojunction was meticulously engineered through a two-step molten salt method.This approach over the CuInS_(2)-based composites produced an internal electric field owing to the disparity be-tween the Fermi levels of CoS_(2)and CuInS_(2)at their interface.Consequently,the electric field facili-tated the directed migration of charges and the proficient separation of photoinduced carriers.The resulting CuInS_(2)@CoS_(2)heterostructure exhibited remarkable CO_(2)photoreduction performance,which was 21.7 and 26.5 times that of pure CuInS_(2)and CoS_(2),respectively.The S-scheme heterojunc-tion photogenerated charge transfer mechanism was validated through a series of rigorous anal-yses,including in situ irradiation X-ray photoelectron spectroscopy,work function calculations,and differential charge density examinations.Furthermore,in situ infrared spectroscopy and density functional theory calculations corroborated the fact that the CuInS_(2)@CoS_(2)heterojunction substan-tially lowered the formation energy of*COOH and*CO.This study demonstrates the application potential of S-scheme heterojunctions fabricated via the molten salt method in the realm of ad-dressing carbon-related environmental issues.
利用太阳能将CO_(2)和H_(2)O转化为CO,CH4和CH3OH等碳基燃料是一种清洁和可持续技术.然而,较弱的氧化还原能力和严重的电荷重组阻碍了CO_(2)光还原技术的实际应用.为应对该挑战,多组分体系的构建是提高光催化性能的最有效途径之一.近年来,S型异质结受到研究人员的广泛关注,为复合体系的光催化剂提供了新的发展方向.S型异质结通常由具有更负的导带(CB)电位的还原型半导体(RP)和具有更正的价带(VB)电位的氧化型半导体(OP)组成.在S型异质结中,强内建电场的存在驱动电子和空穴分别在RP的CB和OP的VB上积累.这种积累克服了II型异质结氧化还原能力弱的缺点,并且有效改善了单个半导体电子-空穴对快速复合和光吸收范围有限的问题.因此,构建匹配良好的S型异质结构和建立强大的内建电场是提高CO_(2)光转换效率的重要策略.本文通过两步熔盐法设计合成了核壳结构的CuInS_(2)@CoS_(2)(CIS-CS)S型异质结光催化剂.熔盐法不仅有利于高结晶CuInS_(2)的形成,使CuInS_(2)与CoS_(2)充分接触,实现电子高效转移,还可以为光催化CO_(2)还原提供更多的比表面积和活性位点合成的CuInS_(2)@CoS_(2)异质结构表现出较好的CO_(2)光还原性能,光照2 h下CO的产率为239μmol g^(-1)h^(-1),分别是纯CuInS_(2)和CoS_(2)的21.7倍和26.5倍.X射线粉末衍射、扫描电镜、透射电镜和氮气等温吸附脱附曲线等表征测试证明了CuInS_(2)@CoS_(2)复合材料的结构特征.采用光电化学测试、光致发光光谱和时间分辨光致发光光谱研究了催化剂的载流子分离和重组行为.原位光照X射线光电子能谱和功函数计算证明了异质结符合S型电荷转移机制,开尔文探针力显微镜证明了异质结具有更大的内建电场强度.在黑暗条件下,由于CoS_(2)和CuInS_(2)在界面上的费米能级存在差异,当两种材料复合时,电子会自发地从CoS_(2)迁移到CuInS_(2),直到费米能级达到平衡,从而在复合材料的界面处产生了强内建电场.在光照下,电子由CuInS_(2)转移到CoS_(2),内建电场的存在诱导了电荷的定向迁移使得光生载流子能够有效分离,从而提高了CuInS_(2)@CoS_(2)异质结的光催化活性.此外,原位光照傅里叶变换红外光谱研究了光催化CO_(2)还原反应的中间体,并进一步通过密度泛函理论计算证实了CuInS_(2)@CoS_(2)异质结降低了*COOH和*CO的形成能.综上,通过两步熔融盐法成功合成了CuInS_(2)@CoS_(2)(CIS-CS)S型异质结光催化剂.S型异质结构的形成有效增强了材料的内建电场,并促进光生载流子的高效分离和转移,从而获得了优异的光催化CO_(2)还原为CO的性能.本文为通过熔盐方法设计合成S型异质结光催化剂提供了参考.
基金
国家自然科学基金(22366018,5236005,22272034)
江西省自然科学基金重点项目(20232ACB203022,20224ACB213010)
江西双千人才培养计划(jxsq2023201086,jxsq2023102141,jxsq2023102142,jxsq2023102143)
江西理工大学清江拔尖人才计划(JXUSTQJBJ2020005)
江西省自然科学基金(20224BAB203018)
江西省研究生创新专项基金项目(YC2022-S659).
