手性分子及内建磁场对光催化剂中光电子自旋极化、自旋输运和制氢行为的影响

Solar-driven photo-catalytic hydrogen production is an ideal strategy for solving worldwide energy crisis. In order to enhance the transfer efficiency of electrons, it is necessary to reduce their energy loss caused by lattice scattering and electron-electron interaction in photo-catalyst. This project focuses on how to take advantages of spin transporting to enhance electron transfer efficiency for dye-sensitized photo-catalytic hydrogen generation. Chiral molecules and magnetic unit will be assembled on the surface of photo-catalyst. Due to CISS (Chiral Induced Spin Selectivity) effect of chiral molecules, photo-electrons will be spin polarized and then migrate into photo-catalysts to form spin polarized currents. The spin polarizing mechanism and spin injection process will be investigated in detail to understand how to modify chiral molecules layers to improve their spin polarizing efficiency for photo-electrons. Meanwhile, intrinsic magnetic field of photo-catalysts will be adjusted by regulating the composition, size, and structure of magnetic unit as well as their position on photo-catalysts. By systematically investigating the influence of intrinsic magnetic field on the spin transporting behavior and proton reduction efficiency of photo-electrons, we will reveal the regularity and close relationships between the intrinsic magnetic field, photo-electrons spin transporting, and hydrogen production efficiency of photo-catalysts, and propose feasible way to enhance spin transporting and hydrogen evolution efficiency of photo-catalysts by regulating their magnetic unit. The potential results will provide useful information for designing high efficient photo-catalyst from the view of decreasing energy loss of electrons transporting by making intrinsic merit of spin transporting.

太阳能光催化分解水制氢是解决能源问题的理想途径之一。为了提高光电子在制氢光催化剂中的传输效率，需要设法降低晶格散射等造成的电子能量及态密度损失。项目研究以染料敏化体系为研究对象，探索如何利用自旋传输的优点来提高光电子的传输效率。首先，借助手性分子对光电子自旋态的选择过滤作用，给光催化剂注入自旋极化光电流，阐明其中的极化机理和电子注入过程，通过优化手性分子层，提高自旋极化及注入的效率。在此基础上，给催化剂构筑不同的磁性单元来调节内建磁场，详细研究内建磁场变化对光电子自旋输运效率和催化剂制氢行为的影响，总结并掌握其中的变化规律，结合电磁学理论分析，阐明“内建磁场-光电子自旋输运效率-催化剂产氢活性”之间的作用规律及内在机理。进而，通过调控催化剂内建磁场来提高光电流的自旋输运效率，借助自旋传输低散射的优点，降低光生电荷传输的阻力和能量损失，提高催化剂的产氢活性，为设计合成高效的光催化剂提供参考。

太阳能光催化分解水制氢是解决能源问题的理想途径之一。本项目的研究，在手性分子和手性界面诱导调控载流子输运/手性传感/太阳能-氢能光电催化的交叉耦合领域取得了进展，探索了如何通过手性分子和手性结构层的CISS效应及催化剂的内建磁场来调节光电子的输运效率、降低光生电荷传输的阻力和能量损失、抑制光电催化副产物的生成、提高光电催化材料的产氢活性，为设计合成高效的光催化剂提供了参考。研究主要取得了三项进展。研究进展一，是实现了手性单元(手性分子层或由金属氧化物组成的无机手性结构层)和磁性单元与光电催化材料的耦合：通过合理的组分选择与微纳结构设计，在超顺磁性光电催化材料上有效耦合了手性分子、手性金属氧化物结构层、磁性单元，总结并阐明了该类光催化制氢复合材料的设计思想和制备规律。研究进展二，是探索并阐明了手性单元的CISS效应对超顺磁性光电催化材料中载流子输运的作用规律及作用机理，通过手性界面的调控，实现了对光电制氢体系中过氧化物副产物形成过程的调节。研究表明，由于手性分子及手性金属氧化物结构层的螺旋电场对载流子的自旋极化作用（CISS效应），使得超顺磁性光电催化阳极上载流子的自旋极化率得到提高，生成三线态O2分子的反应截面积增大，抑制了单线态副产物H2O2的生成(体系副产物H2O2的生成率可降低90%)，光阳极析氧过电位可降低630mV，体系的水分解效率可提高8倍，氢能的生产效率得到有效提高；还通过研究，说明了血红蛋白分子层在水分解阳极析氧反应中发挥了allosteric effect以及CISS效应的双重作用，使超顺磁性光电催化材料的催化产氢效率提高了近2倍。研究进展三，是探讨了磁性单元的引入对光电催化材料中载流子输运行为的影响规律和作用机理，通过引入NiO/Ni活性位点，提高了光电子在碳传输介质中的输运效率，使可见光催化产氢效率提高了62倍；还探索并证明了促进光电子在手性荧光蛋白与磁性微纳米材料表面之间迁移的关键是手性荧光蛋白在磁性微纳米材料表面的构象变化。