Cobalt Oxide-Silica Core-Shell Nanotubes for Photodriven CO2 Reduction by H2O

该项目的主要挑战是开发和研究空间分离的，垂直排列的钴氧化物-二氧化硅核壳纳米管的宏观阵列的电荷传输和催化转化，用于光驱动的水还原二氧化碳。目标是优化光催化性能，以在分离产物的情况下关闭光合循环。在这种分层结构中，水氧化催化在氧化钴表面上进行，而二氧化碳还原发生在通过质子可渗透的氧阻挡二氧化硅层与氧化钴纳米管分离的异双核光催化单元处。分子线嵌入在硅膜内，以允许半反应之间的电子通信。我们将研究光催化体系的电子和质子输运性质。以下示波器在电化学和物理学评价中发挥重要作用：i）稳定质子通量通过几纳米薄（无定形，致密相）二氧化硅层，ii）分子线介导的穿过二氧化硅膜的可见光敏化电荷流，iii）从发色团通过二氧化硅嵌入的分子线到氧化钴催化剂的空穴注入过程的电荷转移动力学，和iv）通过实现二氧化碳还原异双核电荷转移发色团的弛豫和电子转移动力学。我们将特别强调在光催化循环的不同位点（即二氧化碳还原位点，光吸收剂，二氧化硅膜，分子线，水氧化位点）的竞争过程的分支比的识别，这将指导催化剂的设计改进。在产品分离下关闭纳米级的光合循环是一项基本的科学挑战，这是一种最大限度地减少副反应和交叉反应以及其他效率降低过程的方法。这对于光合作用在适当大规模上的可扩展性至关重要，这将对可再生太阳能燃料发电产生影响。

The key challenge of this project is to develop and investigate charge transport and catalytic transformations of a macroscale array of spatially separated, vertically arranged cobalt oxide-silica core-shell nanotubes for photodriven carbon dioxide reduction by water. The goal is the optimization of the photocatalytic performance for closing the photosynthetic cycle under separation of the products. In this hierarchical construct, water oxidation catalysis proceeds on the cobalt oxide surface while carbon dioxide reduction takes place at a heterobinuclear photocatalytic unit separated from the cobalt oxide nanotube by the proton permeable, oxygen blocking silica layer. Molecular wires are embedded within the silican membrane in order to allow electronic communication between the half reactions. We will study the electron and proton transport properties of the photocatalytic system. The following scopes play important roles in the electrochemical and photophysical evaluation: i) steady proton flux through a few nanometer thin (amorphous, dense phase) silica layer, ii) molecular wire mediated visible light sensitized charge flow across the silica membrane, iii) charge transfer dynamics of the hole injection process from a chromophore through the silica embedded molecular wire to the cobalt oxide catalyst, and iv) relaxation and electron transfer dynamics by implementing carbon dioxide reducing heterobinuclear charge transfer chromophores. We will place special emphasis on the identification of branching ratios of the competing processes at the different sites of the photocatalytic cycle (i.e. carbon dioxide reduction site, light absorber, silica membrane, molecular wires, water oxidation site) that will guide catalyst design improvement. Closing the photosynthetic cycle on the nanoscale under product separation is a fundamental scientific challenge, which is an approach that minimizes side and cross reactions and other efficiency degrading processes. This is essential for scalability of photosynthesis on an appropriately large scale that will have an impact on renewable solar fuels generation.