Accelerating Electrocatalysis on 2D Working Electrodes with a Backside Gate

Heterogeneous catalysis is well-known to be sensitive to electron accumulation or depletion on surfaces, but electron density is usually controlled by chemical doping (e.g., promoters) in the case of thermocatalysis, or electrochemical potential in the case of electrocatalysis. The recent advent of ultrathin two dimensional (2D) catalysts prepared either by exfoliation or thin film growth methods opens up a third approach — the transverse field effect, so central to silicon CMOS technology—to modulate the carrier density in a catalyst or electrocatalyst. In this approach the 2D catalyst material is deposited on top of a metal/dielectric stack (the “gate”) to make a capacitor; application of a voltage between the catalyst and the metal causes positive or negative charge to accumulate in the catalyst, depending on the sign of the voltage. This charge in turn tunes the reactivity of active sites, accelerating rates of reaction on the catalyst top surface. This talk will describe some early results for outer-sphere and inner-sphere electrochemical reactions at 2D working electrodes with a backside gate electrode. In particular, we show that a backgate voltage can significantly lower the required overpotential for H₂ evolution at 10 mA/cm² at MoS₂ electrodes. In general, 2D working electrodes with a backside gate provide a novel platform for fundamental investigations in electrochemistry.