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(527c) Harnessing Spontaneous Electric Fields to Direct Thermochemical Catalysis

Surendranath, Y., Massachusetts Institute of Technology
While it is known that intrinsic electric fields play an important role in molecular and biological catalysis, their role in heterogeneous thermochemical systems remains unclear because the catalysts employed are typically disconnected from an external circuit (thus making it difficult to monitor or control the degree of electrical polarization of the surface). Here, we address this knowledge gap by developing general methods for wirelessly monitoring and controlling spontaneous electrical polarization at conductive catalysts dispersed in liquid media. By combining electrochemical and spectroscopic measurements, we demonstrate that proton and electron transfer from solution controllably, spontaneously, and wirelessly polarize Pt surfaces during thermochemical catalysis. Next, we rigorously show that the rates for ethylene hydrogenation using Pt-based catalysts are significantly influenced by spontaneous electric fields generated by both interfacial proton transfer in water and interfacial electron transfer from organometallic redox buffers aprotic solvents. We combine mechanistic experiments with transition state theory to elucidate the rigorous thermodynamic and molecular origin of this electrostatic phenomenology, and conclude that spontaneous polarization plays an essential role in non-faradaic reactivity at solid–liquid interfaces. This work shows that spontaneous interfacial electric fields should be considered alongside temperature, reactant activities, and catalyst structure as critical parameters to understand liquid-phase heterogeneous catalysis.