构筑Bi纳米粒子负载BiOCl纳米片欧姆结用于光催化CO_(2)还原

Construction of Bi Nanoparticles Loaded BiOCl Nanosheets Ohmic Junction for Photocatalytic CO_(2) Reduction

煤炭、石油和天然气等能源的不断增长消耗,不仅导致不可再生能源逐渐枯竭,还使大气中的CO_(2)浓度显著上升,引发严重的能源危机和气候问题。因此,我们必须开发清洁、可持续的能源转换技术,以应对不断增长的能源需求和日益严重的环境危机。受到自然界光合作用的启发,光催化CO_(2)转化利用太阳能驱动,可以将CO_(2)和水转化为高附加值的化学品。经过多年的发展,人工光合作用已被认为是一种绿色、经济、可持续的方法,有望助力实现国家的碳中和发展目标。然而,现有的光催化剂存在着载流子分离效率低和活性位点不足的问题,从而导致CO_(2)光还原效率较低。为了应对这些科学问题,研究人员发现将金属纳米粒子负载到半导体材料上形成欧姆结,可以产生内建电场,有助于光生电子和空穴的分离。因此,本研究通过溶剂热法在BiOCl纳米片表面负载Bi纳米粒子,构建了Bi/BiOCl欧姆结光催化剂。通过X射线衍射(XRD)、X射线光电子能谱(XPS)和透射电子显微镜(TEM)分析了光催化剂的成分和微观结构。利用紫外-可见漫反射光谱(UV-Vis DRS)研究了催化剂的光吸收性能。通过瞬态光电流响应测试、电化学阻抗谱(EIS)和电子自旋共振谱(ESR)研究了光生电子和空穴的分离能力。由于Bi纳米粒子与BiOCl的功函数不同,二者形成的欧姆结具有优异的电荷转移特性,可以显著提高光生载流子的利用效率。此外,Bi纳米粒子还可以作为助催化剂,促进惰性CO_(2)分子的活化。光催化测试结果显示,经过300 W氙灯照射4 h后,具有最佳活性的复合材料(Bi/BiOCl-2)将CO_(2)还原为CO(34.31μmol·g^(-1))和CH_(4)(1.57μmol·g^(-1))的速率分别是BiOCl纳米片的2.55倍和4.76倍。同位素示踪实验证实,产物是CO_(2)和水分子经过光催化反应得到的。此外,根据原位傅里叶变换红外光谱(in situ FTIR)结果,发现在CO_(2)还原过程中形成了^(*)CHO、^(*)CH_(3)O、b-CO_(3)^(2-)、m-CO_(3)^(2-)、HCO_(3)^(-)、HCOOH、^(*)COOH和HCOO^(-)等中间体,并进一步提出了可能的光催化CO_(2)还原机制。经过25 h的CO_(2)光还,原反应后,CO和CH_(4)产量持续增加,同时结合XRD、XPS和TEM结果表明,制备的Bi/BiOCl-2材料具有良好的结构稳定性。这项研究为高效CO_(2)光还原催化剂的构建提供了有益的参考。

The continuous increase in the consumption of coal,oil,and natural gas has not only led to the depletion of unsustainable energy sources,but has also caused excessive CO_(2)emissions,thus resulting in serious energy crises and climate issues.In such a scenario,it is imperative to explore clean and sustainable energy conversion technologies to address the escalating energy demands and environmental crises.Photocatalytic CO_(2)conversion,inspired by natural photosynthesis,utilizes solar energy to convert CO_(2)and water into valuable chemicals.After decades of development,artificial photosynthesis has emerged as a green,cost-effective,and sustainable approach to achieving carbon neutrality.However,the challenges of low carrier separation efficiency and insufficient active sites in photocatalysts remain significant hurdles in achieving high-performance CO_(2)photoreduction.To address this challenge,the integration of metal nanoparticles with semiconductors to create an Ohmic junction can enhance electron-hole migration by the assist of interfacial electric field(IEF).In this study,an Ohmic junction photocatalyst is constructed by in situ formation of Bi nanoparticles on the surface of BiOCI nanosheets through a solvothermal process.The composition and morphology of the photocatalysts were analyzed using X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and transmission electron microscopy(TEM).UV-Vis diffuse reflectance spectroscopy(UV-Vis DRS)was employed to assess the light absorption performance of the photocatalyst.Transient photocurrent response,electrochemical impedance spectroscopy(EIS),and electron spin resonance(ESR)were utilized to evaluate the efficiency of electron-hole transfer.The distinct work function difference between Bi nanoparticles and BiOCI nanosheets leads to favorable charge transfer characteristics within the formed Ohmic junction,significantly improving the utilization efficiency of photogenerated carriers.Besides,the Bi nanoparticles serve as co-catalysts,enhancing the activation of inert CO_2.As a result,the optimized Bi/BiOCI composite(Bi/BiOCI-2)exhibits enhanced generation rates of CO(34.31μmol·g^(-1))and CH4(1.57μmol g^(-1))during 4-h of irradiation,which is 2.55 and4.76 times compared to pristine BiOCI nanosheets,respectively.Isotope tracer experiments suggest that the obtained carbon-based products are generated through CO_(2)photoreduction in the presence of water molecule under irradiation.Moreover,in situ Fourier-transform infrared spectroscopy(in situ FTIR)results indicate the formation of^(*)CHO,^(*)CH_(3)O,bCO_(3)^(2-),m-CO_(3)^(2-),HCO_(3)^(-),HCOOH,^(*)COOH,and HCOO^(-)species during the CO_(2)reduction process and a possible mechanism for CO_(2)photoreduction into CO and CH_(4)is proposed based on these findings.After 25-h of CO_(2)photoreduction reaction,the yields of CO and CH_(4)continue to increase.Furthermore,the stability of the prepared material is confirmed by XRD pattern,XPS analysis,and TEM image.These outcomes underscore an effective strategy for constructing advanced photocatalysts tailored for high-performance solar-driven CO_(2)reduction.