物理化学学报 >> 2023, Vol. 39 >> Issue (6): 2210003.doi: 10.3866/PKU.WHXB202210003

所属专题: S型光催化剂

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多面体状Cu2O修饰片状BiOI的S型异质结构筑及光催化水蒸气中CO2转化性能研究

王吉超1,3,*(), 乔秀1, 史维娜2,*(), 贺景1, 陈军1, 张万庆1   

  1. 1 河南科技学院化学化工学院, 河南 新乡 453003
    2 新乡学院化学与材料工程学院, 河南 新乡 453003
    3 郑州大学化学学院, 郑州 450000
  • 收稿日期:2022-10-05 录用日期:2022-11-14 发布日期:2022-11-17
  • 通讯作者: 王吉超,史维娜 E-mail:wangjichao@hist.edu.cn;shiweina516@163.com

S-Scheme Heterojunction of Cu2O Polytope-Modified BiOI Sheet for Efficient Visible-Light-Driven CO2 Conversion under Water Vapor

Ji-Chao Wang1,3,*(), Xiu Qiao1, Weina Shi2,*(), Jing He1, Jun Chen1, Wanqing Zhang1   

  1. 1 College of Chemistry and Chemical Engineering, Henan Institute of Science and Technology, Xinxiang 453003, Henan Province, China
    2 School of Chemistry and Materials Engineering, Xinxiang University, Xinxiang 453003, Henan Province, China
    3 School of Chemistry, Zhengzhou University, Zhengzhou 450000, China
  • Received:2022-10-05 Accepted:2022-11-14 Published:2022-11-17
  • Contact: Ji-Chao Wang, Weina Shi E-mail:wangjichao@hist.edu.cn;shiweina516@163.com

摘要:

过量的CO2排放引起了一系列的环境问题。利用光催化技术将CO2转为高附加值化合物不仅可以减小碳排放也可以缓解能源短缺。其中高效光催化剂开发是光催化技术的关键之一。纳米结构调控和异质结构筑是两种有效地提升材料光催化CO2转化活性的方法。特别是,由还原型和氧化型催化剂组成的新型S型传导异质结,其在两组分之间不同的费米能级作用下,实现高效的光生载流子的分离。S型的电荷传导不仅可以有效的抑制光生载流子的复合,同时,聚集了大量具有较强催化氧化和还原能力的光生空穴与电子。Cu2O和BiOI材料作为典型的还原型和氧化型催化剂,因其都具有良好的可见光吸收能力和适合的能带结构,可以应用于还原CO2和氧化H2O的耦合反应。我们利用电沉积的方法,在FTO导电玻璃基底表面构筑了多面体Cu2O/片状BiOI的复合材料。我们利用粉末X射线衍射(XRD),X射线光电子能谱(XPS),紫外线光电子能谱(UPS),场发射扫描电镜(SEM)和场发射投射电镜(TEM)技术对材料结构、形貌和组成进行了系统的探索和解析。13C/18O同位素标记实验证实,该复合材料可以实现可见光(波长 > 400 nm)驱动下水蒸气气氛中CO2的快速转化。最优样品BiOI/Cu2O-1500在光照11 h后,反应产物CO,CH4,H2和O2的产量可以分别达到53.03,30.75,8.49和82.73 μmol∙m−2。在8次循环实验中,催化产物产量有小幅下降,但其主要产物CO,CH4和O2的产量仍然可以分别达到27.38,34.08和75.52 μmol∙m−2。循环前后使用催化剂的XRD和XPS结果表明,该复合材料具有良好的结构稳定性。催化实验结果表明,BiOI/Cu2O异质结的形成提升了催化剂的光催化性能关键之一。固体漫反射光谱(DRS)和XPS测试结果表明异质结的能带结构为交错型,进一步利用UPS技术探索材料费米能级,进而确定异质结内内建电场方向。根据原位XPS测试结果证实,BiOI/Cu2O异质结内光生电子采用S型模式分离传输。由此可见,S型异质结可以高效的分离和利用光生载流子。此外,我们通过原位红外(in situ FTIR)技术在催化剂表面发现了HCO3,CO32−,HCOO和•CH3等活性物质并推测其催化机理。该研究为S型载流子传输模式的探索提供了实验结果,同时为高效还原CO2光催化剂提供了一定的借鉴。

关键词: S型, 光催化剂, CO2还原, BiOI/Cu2O, 片状

Abstract:

Excessive CO2 emissions have led to serious environmental problems. The photocatalytic reduction of CO2 to value-added chemicals is a promising strategy to reduce carbon emissions and alleviate the energy crisis simultaneously. Photocatalysts is crucial in the reduction process. Nanostructure engineering and heterojunction construction have been identified as prospective approaches to develop efficient photocatalysts for CO2 reduction. Step-scheme (S-scheme) heterojunctions are novel systems composed of a reduction catalyst and an oxidation catalyst. In these systems, the charge separation at the interface between the two catalysts could be enhanced by an internal electric field directed from the reduction photocatalyst to the oxidation photocatalyst on account of their matched Fermi levels (Ef). The S-scheme transfer mode can not only efficaciously inhibit the recombination of photoinduced carriers but also accumulate electrons and holes with greater redox potential. Cu2O and BiOI materials, as typical reduction and oxidation catalysts, are endowed with efficient visible-light absorption and favorable band position for catalyzing the coupling reaction of CO2 reduction and H2O oxidation. In this study, a series of S-scheme catalysts consisting of polyhedral Cu2O-modified BiOI flakes were synthesized onto a fluorine-doped tin oxide substrate via the electrodeposition method. The structure, morphology, and surface composition of the as-obtained samples were then studied using X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) measurements. 13C/18O isotope tracer experiments indicated that the BiOI/Cu2O composite achieved CO2 conversion with water vapor under visible-light irradiation (λ > 400 nm). The CO, CH4, H2, and O2 yields of the optimal BiOI/Cu2O-1500 catalyst reached 53.03, 30.75, 8.49, and 82.73 μmol∙m−2, respectively, after 11 h of visible-light illumination. The photocatalytic activity of BiOI/Cu2O-1500 slightly decreased at the eighth cycling, but its CO, CH4, and O2 yields still reached 27.38, 34.08, and 75.52 μmol∙m−2, respectively. The XPS and XRD results confirmed the excellent cycling stability of the catalysts, and analysis using the XPS core-level (CL) alignment method revealed that a staggered band structure was formed in the BiOI/Cu2O heterojunction. The direction of the built-in electric field in the heterojunction was determined using UPS measurements, and the S-scheme mechanism of charge transfer was verified via the in situ XPS results. In addition, the production of HCO3, CO32−, HCOO, and •CH3 species during CO2 reduction was confirmed using in situ diffuse reflectance Fourier transform spectrometry, and a possible mechanism of CO2 conversion under water vapor was proposed. Benefiting from its S-scheme BiOI/Cu2O heterojunction, the prepared catalyst showed improved photoinduced charge separation, and its photogenerated carriers with strong redox ability were preserved, thereby leading to enhanced photocatalytic performance.

Key words: S-scheme, Photocatalyst, CO2 reduction, BiOI/Cu2O, Sheet