Collaborative Research: SusChEM: Engineering Charge Transport through Directed Orientation of Transition Metal Dichalcogenide Catalysts

点击翻译按钮获取中文摘要

The project will investigate new materials and catalyst structures for the efficient photocatalysis and photoelectrocatalysis of chemical reactions of importance for the production of clean energy from the sun and other renewable or sustainable resources. The research will also have applicability to a number of technologies of importance to the Nation's economic competitiveness and resource utilization, including energy storage, photovoltaics, and optoelectronics. In addition, educational and outreach activities will be incorporated, including both graduate and undergraduate student training, a K-12 workshop on interactive photocatalytic energy conversion, and summer research opportunities for high-school students. The project investigates the transition metal dichalcogenide (TMDC) catalyst tungsten disulfide (WS2) for the electrocatalytic hydrogen evolution reaction and the photocatalytic reduction of water to produce hydrogen as a renewable component of fuels and chemicals. Specifically, a unique edge-on orientation of the nanoscale WS2 catalyst particles with respect to their supporting charge transfer material will be investigated to achieve dramatically higher reaction rates than obtainable with conventional flat particle oriented catalysts. The dichalcogenides are known to be active due to the high catalytic activity of their edge sites when supported on a semiconductor, metal, or carbon material. Maximization of performance in these applications requires rapid charge transfer across the TMDC/support interface. However, for the typical orientations of TMDCs in most electro- and photocatalysts, the interfacial charge transfer is especially slow, since it must occur across the inert TMDC basal plane. The research will test the hypothesis that the rates of charge transfer across the WS2-support interface will be increased by an edge-on orientation of the WS2 layers due to interfacial bonding, and that this rate can be tuned by controlling the edge termination of the WS2 layers. The study will build upon the investigators' preliminary results showing promising photocatalytic activity of WS2 nanotube-arrays, in which the WS2 layers are in an edge-on orientation. These WS2 nanotubes will be used as a platform to design and synthesize novel Janus-type photoelectrodes and photocatalyst particles containing tailored interfaces. To gain fundamental understanding of these interfaces and guide their design, the investigators have prepared model systems consisting of WS2 single-crystals in either a basal plane or edge-on orientation. They will create WS2-semiconductor, metal or carbon interfaces by depositing these materials on top of the model WS2 systems and will measure the influence of WS2 orientation, defects, and edge termination on charge transfer and recombination rates at the interface. They will also perform measurements and modeling to understand these rates in terms of underlying factors including interfacial bonding and separation distance, interfacial dangling bonds and their electronic energies, and step changes in electrical potential energy and local electric field at the interface.