Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
J Am Chem Soc. 2017 Jul 5;139(26):8931-8938. doi: 10.1021/jacs.7b03134. Epub 2017 Jun 22.
Photosensitization of molecular catalysts to reduce CO to CO is a sustainable route to storable solar fuels. Crucial to the sensitization process is highly efficient transfer of redox equivalents from sensitizer to catalyst; in systems with molecular sensitizers, this transfer is often slow because it is gated by diffusion-limited collisions between sensitizer and catalyst. This article describes the photosensitization of a meso-tetraphenylporphyrin iron(III) chloride (FeTPP) catalyst by colloidal, heavy metal-free CuInS/ZnS quantum dots (QDs) to reduce CO to CO using 450 nm light. The sensitization efficiency (turnover number per absorbed unit of photon energy) of the QD system is a factor of 18 greater than that of an analogous system with a fac-tris(2-phenylpyridine)iridium sensitizer. This high efficiency originates in ultrafast electron transfer between the QD and FeTPP, enabled by formation of QD/FeTPP complexes. Optical spectroscopy reveals that the electron-transfer processes primarily responsible for the first two sensitization steps (FeTPP → FeTPP, and FeTPP → FeTPP) both occur in <200 fs.
分子催化剂将 CO 光还原为 CO2 是一种可持续的太阳能燃料存储途径。敏化过程的关键是有效地将氧化还原当量从敏化剂转移到催化剂；在具有分子敏化剂的系统中，由于敏化剂和催化剂之间扩散限制的碰撞，这种转移通常很慢。本文描述了胶体、无重金属的 CuInS/ZnS 量子点（QD）对 FeTPP 催化剂的敏化作用，使用 450nm 光将 CO 光还原为 CO2。QD 体系的敏化效率（每吸收单位光子能量的周转数）比具有 fac-tris(2-苯基吡啶)铱敏化剂的类似体系高 18 倍。这种高效率源于 QD 和 FeTPP 之间超快的电子转移，这是由 QD/FeTPP 配合物的形成所实现的。光光谱学表明，前两个敏化步骤（FeTPP → FeTPP 和 FeTPP → FeTPP）的主要电子转移过程都发生在 <200fs 内。
