棒状金属有机框架结构PCN-222(Cu)/TiO2复合材料的制备及其高效光催化CO2还原性能

Rod-Shaped Metal Organic Framework Structured PCN-222(Cu)/TiO2 Composites for Efficient Photocatalytic CO2 Reduction

受环境污染和能源短缺的双重压迫,光催化CO2还原技术引起了人们的广泛关注。低成本光催化材料的开发对于实现有效的太阳能-燃料转换至关重要。TiO2作为光催化剂在光催化CO2还原中被广泛采用。然而,较宽的禁带宽度和光生载流子的复合限制了它的进一步应用。在这项工作中,我们使用棒状PCN-222(Cu)/TiO2复合材料作为光催化剂,使用简单的水热法报告了二氧化碳的光化学还原。经过对PCN-222(Cu)/TiO2进行一系列X射线衍射(XRD),扫描电子显微镜(SEM),紫外-可见漫反射光谱(DRS),傅里叶变换红外光谱(FT-IR),光电化学(PEC)和光致发光光谱(PL)等表征结果证明成功制备了该复合材料。SEM证实,TiO2颗粒均匀分布在棒状PCN-222(Cu)/TiO2的表面上。XRD结果表明,成功制备了具有良好晶体结构的PCN-222(Cu)和PCN-222(Cu)/TiO2复合光催化剂。DRS显示制备的PCN-222(Cu)/TiO2复合材料在可见光区域出现金属卟啉的特征吸收峰。PL和瞬态光电流响应和电化学阻抗谱(EIS)进一步证实了棒状PCN-222(Cu)/TiO2具有更好的电子-空穴对分离效率。通过控制PCN-222(Cu)和TiO2的质量比,经CO2还原性能测试表明,10%PCN-222(Cu)/TiO2复合材料具有最佳的催化活性。在氙灯照射下,棒状PCN-222(Cu)/TiO2表现出比TiO2纳米颗粒更好的光催化CO2活性,这归因于电荷传输和较好的电子-空穴分离能力。10%PCN-222(Cu)/TiO2复合材料的催化效率最高,产率分别为13.24μmol·g-1·h-1 CO和1.73μmol·g-1·h-1CH4。此外,经过三个循环的测试,PCN-222(Cu)/TiO2光催化剂的催化活性基本保持不变,在连续8小时光照下,催化剂的还原产率持续增加,表明PCN-222(Cu)/TiO2复合材料具有好的稳定性。禁带宽度和Mote-Schottky(M-S)曲线结果表明,PCN-222(Cu)的LUMO位比TiO2的导带(CB)更负,因此提出了PCN-222(Cu)/TiO2复合材料可能的光催化反应机理。该研究为金属有机骨架和氧化物半导体复合材料光催化体系提供了新的策略。

The photocatalytic reduction of CO2 has attracted considerable attention owing to the dual suppression of environmental pollution and energy shortage.The technology uses solar energy to convert carbon dioxide into hydrocarbon fuel,which is of great significance for achieving the carbon cycle.The development of low-cost photocatalytic materials is critical to achieving efficient solar energy to fuels conversion.One of the most commonly employed photocatalysts is TiO2.However,it suffers from broad band gap as well as the recombination of photo-excited holes and electron.Hence,in this work,we report the photochemical reduction of CO2 using rodlike PCN-222(Cu)/TiO2 composites as photocatalyst through a simple hydrothermal method,in which TiO2 nanoparticles are anchored at the interface of the SiC rod PCN-222(Cu).Multiple characterization techniques were used to analyze the structure,morphology,and properties of the PCN-222(Cu)/TiO2 composite.A series of characterizations including X-ray diffraction(XRD),scanning electron microscopy(SEM),diffuse reflectance spectroscopy(DRS),Fourier-transform infrared spectroscopy,photo-electrochemical,and photoluminescence(PL)confirm the successful preparation of PCN-222(Cu)/TiO2 composites.SEM reveals that the TiO2 nanoparticles are uniformly distributed on the surface of the rod-shaped PCN-222(Cu)/TiO2.XRD results show that PCN-222(Cu)and PCN-222(Cu)/TiO2 composite photocatalysts with good crystal structure were successfully synthesized.According to the DRS results,the prepared PCN-222(Cu)/TiO2 composite samples exhibit characteristic absorption peaks of metalloporphyrins in the visible region.PL spectroscopy,transient photocurrent response and electrochemical impedance spectroscopy further confirm that the rod-like PCN-222(Cu)/TiO2 samples have high electron-hole pair separation efficiency.By controlling the mass ratio of PCN-222(Cu)and TiO2,the photocatalytic CO2 reduction performance test shows that the 10%PCN-222(Cu)/TiO2 composite achieves optimal catalytic performance,yielding 13.24μmol·g-1·h-1 CO and 1.73μmol·g-1·h-1 CH4,respectively.All the rod-like PCN-222(Cu)/TiO2 composites exhibit better photocatalytic CO2 activity than that of TiO2 nanoparticles or PCN-222(Cu)under the illumination of xenon lamps,which is attributed to charge transport and electron-hole separation capabilities.After three test cycles,the catalytic activity of PCN-222(Cu)/TiO2 photocatalyst was virtually unchanged.The reduction yield of the catalyst increased for 8 h under continuous illumination,indicating that PCN-222(Cu)/TiO2 composites have acceptable stability.The estimation of the band gap curve and the Mote-Schottky curve test show that the lowest unoccupied molecular orbital position of PCN-222(Cu)is more negative than the TiO2 of the conduction band;hence,a possible photocatalytic reaction mechanism of the PCN-222(Cu)/TiO2 composite is proposed.This study provides a new strategy for the integration of metal-organic frameworks and oxide semiconductors to construct efficient photocatalytic systems.