Large oriented electric
fields spontaneously arise at all solid–liquid
interfaces via the exchange of ions and/or electrons with the solution.
Although intrinsic electric fields are known to play an important
role in molecular and biological catalysis, the role of spontaneous
polarization in heterogeneous thermocatalysis remains unclear because
the catalysts employed are typically disconnected from an external
circuit, which makes 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. We employ liquid-phase ethylene hydrogenation on a Pt/C
catalyst as a thermochemical probe reaction and observe that the rate
of this nonpolar hydrogenation reaction is significantly influenced
by spontaneous electric fields generated by both interfacial proton
transfer in water and interfacial electron transfer from organometallic
redox buffers in a polar aprotic
ortho
-difluorobenzene
solvent. Across these vastly disparate reaction media, we observe
quantitatively similar scaling of ethylene hydrogenation rates with
the Pt open-circuit electrochemical potential (
E
OCP
). These results isolate the role of interfacial electrostatic
effects from medium-specific chemical interactions and establish that
spontaneous interfacial electric fields play a critical role in liquid-phase
heterogeneous catalysis. Consequently,
E
OCP
—a generally overlooked parameter in heterogeneous catalysis—warrants
consideration in mechanistic studies of thermochemical reactions at
solid–liquid interfaces, alongside chemical factors such as
temperature, reactant activities, and catalyst structure. Indeed,
this work establishes the experimental and conceptual foundation for
harnessing electric fields to both elucidate surface chemistry and
manipulate preparative thermochemical catalysis.