掌性鈣鈦礦奈米晶體進行光催化二氧化碳還原反應之探討

Abstract

鹵化鈣鈦礦由於具備優異的光電性質，在光學元件的應用上獲得相當不錯的成就，在催化領域中，藉由自旋極化電子的導入，除了能有效分離電荷外，也能抑制電荷複合以提升催化表現。本篇研究透過結合掌性分子及鈣鈦礦材料製備出具有2D/3D混合結構的掌性鈣鈦礦奈米晶體，並利用其作為能形成自旋極化電子的光觸媒材料，以提高光催化二氧化碳還原反應表現。首先進行CsPbBr3 奈米片（NPLs）及掌性分子鹽類MBA:Br的合成，並進行光學及結構分析。將CsPbBr3 NPLs利用MBA:Br修飾後，透過粉末X光繞射、吸收及光致發光光譜確認其結構及光學性質，再透過圓二色及圓偏振螢光光譜確認MBA:Br成功接上CsPbBr3 NPLs。由於自旋極化電子的產生， 2D/3D混合結構的掌性鈣鈦礦奈米晶體能有效提升催化表現，以反應主產物一氧化碳（CO）而言，產率自14.8 μmol g-1分別提升至39.2及26.8 μmol g-1，掌性鈣鈦礦材料在外加磁場（0.3T）的幫助下，CO產率更是分別提升到75.3及48.2 μmol g-1。另外藉由透過磁性圓二色光譜及時間解析螢光光譜探討磁場對於反應機制的影響，證實外加磁場能有效增強自旋極化及延長載流子生命週期並提升催化表現。Halide perovskites have achieved considerable success in the application of optical devices due to their excellent optoelectronic properties. In the field of catalysis, the introduction of spin-polarized electrons not only effectively separates charges but also inhibits charge recombination to enhance catalytic performance. In this study, photocatalyst with spin-polarized electrons prepared by combining chiral molecules with halide perovskites, which forms chiral perovskite nanocrystal with 2D/3D mixed structure, is capable to enhance the performance of photocatalytic CO2 reduction reaction(CO2RR)CsPbBr3 nanoplates(NPLs) and chiral molecular salt MBA:Br are synthesized and their characterizations are analyzed. After modifying CsPbBr3 NPLs with MBA:Br, the structures and optical properties are confirmed by powder X-ray diffraction, absorption and photoluminescence spectra. The successful bonding of MBA:Br to CsPbBr3 NPLs is further confirmed by circular dichroism and circularly polarized luminescence spectra. The improvement of CO2RR efficiency is attributed to the spin-polarized electrons generated from chiral perovskite nanocrystals. The CO yield increases from 14.9 μmol g-1 to 39.2 μmol g-1 and 26.8 μmol g-1, respectively and further increases to 75.3 μmol g-1 and 48.2 μmol g-1 while an external magnetic field(0.3T) is applied. Moreover, the reaction mechanism under magnetic field(0.3T) was investigated by magnetic circular dichroism and time-resolved photoluminescence spectra, which indicates the enhanced performance is attributed to the better spin-polarization and longer carrier lifetime.