Arcudi Francesca, Đorđević Luka, Nagasing Benjamin, Stupp Samuel I, Weiss Emily A
Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.
Center for Bio-Inspired Energy Science, Northwestern University, Chicago, Illinois 60611, United States.
J Am Chem Soc. 2021 Nov 3;143(43):18131-18138. doi: 10.1021/jacs.1c06961. Epub 2021 Oct 19.
Climate change and global energy demands motivate the search for sustainable transformations of carbon dioxide (CO) to storable liquid fuels. Photocatalysis is a pathway for direct conversion of CO to CO, one step within light-powered reaction networks that could, if efficient enough, transform the solar energy conversion landscape. To date, the best performing photocatalytic CO reduction systems operate in nonaqueous solvents, but technologically viable solar fuels networks will likely operate in water. Here we demonstrate catalytic photoreduction of CO to CO in pure water at pH 6-7 with an unprecedented combination of performance parameters: turnover number (TON(CO)) = 72,484-84,101, quantum yield (QY) = 0.96-3.39%, and selectivity () > 99%, using CuInS colloidal quantum dots (QDs) as photosensitizers and a Co-porphyrin catalyst. At higher catalyst concentration, the system reaches QY = 3.53-5.23%. The performance of the QD-driven system greatly exceeds that of the benchmark aqueous system (926 turnovers with a quantum yield of 0.81% and selectivity of 82%), due primarily to (i) electrostatic attraction of the QD to the catalyst, which promotes fast multielectron delivery and colocalization of protons, CO, and catalyst at the source of photoelectrons, and (ii) termination of the QD's ligand shell with free amines, which capture CO as carbamic acid that serves as a reservoir for CO, effectively increasing its solubility in water, and lowers the onset potential for catalytic CO reduction by the Co-porphyrin. The breakthrough efficiency achieved in this work represents a nonincremental step in the realization of reaction networks for direct solar-to-fuel conversion.
气候变化和全球能源需求推动了对二氧化碳（CO₂）向可储存液体燃料进行可持续转化的探索。光催化是将CO₂直接转化为CO的一条途径，是光驱动反应网络中的一步，如果效率足够高，可能会改变太阳能转化的格局。迄今为止，性能最佳的光催化CO₂还原系统在非水溶剂中运行，但技术上可行的太阳能燃料网络可能会在水中运行。在此，我们展示了在pH值为6 - 7的纯水中，使用铜铟硫胶体量子点（QDs）作为光敏剂和钴卟啉催化剂，将CO₂催化光还原为CO，其性能参数组合前所未有的优异：周转数（TON(CO)） = 72,484 - 84,101，量子产率（QY） = 0.96 - 3.39%，选择性（ɸ）> 99%。在较高的催化剂浓度下，该系统的量子产率达到3.53 - 5.23%。量子点驱动系统的性能大大超过了基准水相系统（926次周转，量子产率为0.81%，选择性为82%），这主要归因于：（i）量子点与催化剂之间的静电吸引，促进了快速多电子传递以及质子、CO₂和催化剂在光电子源处的共定位；（ii）用游离胺终止量子点的配体壳，游离胺将CO₂捕获为氨基甲酸，作为CO₂的储存库，有效提高了其在水中的溶解度，并降低了钴卟啉催化CO₂还原的起始电位。这项工作所实现的突破性效率代表了直接太阳能到燃料转化反应网络实现过程中的一个非渐进性步骤。
