(20c) Electrochemical Control over Reaction Kinetics Using Rationally Designed Redox-Switchable Catalysts

Authors: 
Tian, W., Massachusetts Institute of Technology
Mao, X., Massachusetts Institute of Technology
Wu, J., MIT
Rutledge, G. C., Massachusetts Institute of Technology
Hatton, T. A., Massachusetts Institute of Technology

The ability to exert control over an entity or a process is arguably the ultimate demonstration of our understanding of that process, and enables the full exploitation of its potential. Chemists are starting to incorporate control elements into catalyst design, enabling new strategies for the modulation of reaction kinetics using external stimuli. Here we introduce a new strategy to control reaction kinetics, both in batch and flow systems, using electrochemically responsive heterogeneous catalysis (ERHC), which relies on the use of a hybrid system composed of an electron-conducting porous network conformally coated with a redox-switchable catalyst. ERHC is the first type of catalysis control strategy that combines all the following desired characteristics: continuous variation of reaction rates as a function of the magnitude of external stimulus, easy integration into fixed-bed flow reactors, and precise spatial and temporal control of the catalyst activity. Previously reported stimuli-responsive catalytic systems are usually limited to on/off bimodal control and cannot be used easily in a fixed bed reactor due to significant morphological/structural changes during activation/deactivation. Additionally, these catalytic systems often use chemical or thermal stimuli (e.g., pH, solvent composition, temperature), precise variation of which over location and time is difficult to achieve (especially in a flow system) and is further hampered by mass diffusion or heat dissipation. In this talk, first, I will demonstrate rational design and facile fabrication of several ERHC systems with different morphologies, micro-/nano-structures and chemical compositions. Second, I will evaluate the ERHC performances of these different catalytic systems in batch systems, using a range of important reactions. Furthermore, I will demonstrate highly flexible control over reactant concentrations as a function of both location and time, using ERHC-integrated flow reactors. This study introduces a new paradigm for the design of stimuli-responsive catalytic systems. The ERHC concept could open the door to intriguing novel applications in controlled catalysis, chemical synthesis, and reaction engineering.