摘要
CO_(2)的过量排放造成了全球生态系统的失衡,如温室效应、海洋酸化和极端天气频发等.CO_(2)作为一种储量丰富且可循环利用的碳一资源,利用光催化技术将其催化转化为包括一氧化碳和甲烷在内的碳氢燃料,为上述问题提供了一个很有前景的解决方案.纳米片作为典型的二维材料,其厚度一般低至100 nm.此外,二维材料具有较大的比表面积、可调谐的端基官能团、出色的光学性能以及较好的导电性和柔韧性,在光催化领域受到了广泛关注.在半导体材料中,钛酸镧(La_(2)Ti_(2)O_(7))具有优良的氧化还原能力和良好的稳定性和耐久性,但与其他半导体类似,La_(2)Ti_(2)O_(7)的宽带隙性质决定了其只能利用波长较短的光,这极大地限制了其对太阳光的利用.为了增强光吸收能力,降低光生载流子的复合,本文通过溶剂热法在La_(2)Ti_(2)O_(7)纳米片上负载薄层Ti_(3)C_(2)MXene纳米片,设计制备了二维/二维(2D/2D)La_(2)Ti_(2)O_(7)/Ti_(3)C_(2)Mxene肖特基异质结复合材料,并用于增强光催化CO_(2)还原性能.研究发现,当Ti_(3)C_(2)MXene的负载量为3 wt%时,CO和CH4的产率是物理混合的La_(2)Ti_(2)O_(7)和Ti_(3)C_(2)MXene的4.6倍和11.4倍.飞秒瞬态吸收光谱和X射线光电子能谱结果表明,La_(2)Ti_(2)O_(7)/Ti_(3)C_(2)Mxene较好的光催化CO_(2)还原反应性能归因于高效电荷载流子迁移率和两组分接触界面之间形成了肖特基异质结的协同作用.原位红外漫反射光谱观察到的反应中间产物、紫外光电子能谱计算得到的功函数和原子层级的密度泛函理论计算得到的吉布斯自由能和差分电荷密度揭示了该体系光催化CO_(2)还原的机理、光催化反应的路径和产物选择性的由来.相比于单独的La_(2)Ti_(2)O_(7)和物理混合的La_(2)Ti_(2)O_(7)和Ti_(3)C_(2)MXene,2D/2D La_(2)Ti_(2)O_(7)/Ti_(3)C_(2)Mxene肖特基异质结复合材料表现出增强的光催化CO_(2)还原性能.引入Ti_(3)C_(2)MXene形成平面间2D/2D的异质结结构可作为电荷转移通道并促进电荷的快速分离,形成的肖特基结能够有效地抑制光生电子的回流,同时降低了光催化CO_(2)还原的反应势垒,最终促进了光催化CO_(2)还原过程.综上,本文详细阐述了肖特基异质结构中光催化性能增强的机理机制,并为设计和制造用于转化和利用二氧化碳的光催化剂及其探究光催化转化机理提供借鉴.
Ascribing to incremental fossil fuels emissions,the utilization and conversion of CO_(2)and development of renewable energy is globally essential and significative.Ultrathin 2D/2D heterojunctions with fast photo-generated electrons transmission channels illustrate a better strategy to improve photocatalytic activity.Herein,combing La_(2)Ti_(2)O_(7)with metallic few-layered Ti_(3)C_(2)MXene to construct inter-plane 2D/2D heterojunction was in situ self-assembled through solvothermal method.Benefiting from the advantages including stability,conductivity,abundant active sites and formation of Schottky junctions,as expected,the ultrathin 2D/2D La_(2)Ti_(2)O_(7)/Ti_(3)C_(2)MXene nanosheets presented much improved photocatalytic ability for CO_(2)reduction to CO and CH4,which is about 4.6 and 11.4 times higher than that of mechanical mixed La_(2)Ti_(2)O_(7)and Ti_(3)C_(2)MXene.fs-TAS and XPS provided direct evidence that the prominence of La_(2)Ti_(2)O_(7)/Ti_(3)C_(2)MXene in photocatalytic CO_(2)reduction reaction over other opponents should be attributed to the synergetic effect of efficient charge carrier mobility and formed 2D/2D Schottky heterojunction interfacial contact between La_(2)Ti_(2)O_(7)and Ti_(3)C_(2)MXene.Intermediates revealed by in-situ DRIFTS and corresponding atomic-level DFT calculations confirmed the mechanism,pathways and selectivity for photocatalytic CO_(2)conversion.This work expanded promising prospects arouses new impetus for deepening the prehension of the mechanism of photocatalytic CO_(2)reduction,designing and fabrication of Schottky heterojunctions for application in conversion and utilization of CO_(2).
作者
王可
程淼
王楠
张千一
刘懿
梁俊威
管杰
刘茂昌
周建成
李乃旭
Ke Wang;Miao Cheng;Nan Wang;Qianyi Zhang;Yi Liu;Junwei Liang;Jie Guan;Maochang Liu;Jiancheng Zhou;Naixu Li(School of Chemistry and Chemical Engineering,Southeast University,Nanjing 211189,Jiangsu,China;School of Physics,Southeast University,Nanjing 211189,Jiangsu,China;International Research Center for Renewable Energy,State Key Laboratory of Multiphase Flow in Power Engineering,Xi'an Jiaotong University,Xi'an 710049,Shaanxi,China;Institute of Chemical Industry of Forest Products of the Chinese Academy of Forestry Sciences,Jiangsu Key Laboratory for Biomass Energy and Material,Nanjing 210042,Jiangsu,China)
基金
国家自然科学基金(21576050,21227801)
中央高校基本科研业务费项目(3207045403,3207042107D,3207042108D)
江苏省生物质能源与材料重点实验室开放基金资助项目(JSBEM202001)
江苏高校优势学科建设工程资助项目(PAPD)
东南大学“仲英青年学者”
江苏省研究生科研实践创新计划(SJCX20_0014,SJCX20_0015).
