Programmable rate enhancement over catalytic condensers and transistors

Abstract

Programmable catalysis, the rapid oscillation of catalysts between weakly and strongly binding energetic states, could dramatically accelerate reaction rates. Catalytically active, ultrathin films incorporated into a condenser or transistor device architecture can leverage external electric fields to manipulate the electron density and binding energy of active sites. Therefore, catalytic rates can be controlled in situ with simply an applied voltage. Catalytic condensers consisting of platinum nanoclusters on ultrathin graphene and carbon supports on hafnia achieved Pt-13CO binding energy variations of 1.5 kJ/mol per volt. The optimization and incorporation of high-k dielectric alumina-titania nanolaminate increased the modulation to 7 kJ/mol per volt. The limited quantum capacitance of the graphene and carbon underlayers enabled charge carriers to congregate in the active Pt metal centers and affect the CO adsorption strength. Moving from graphene to carbon enabled reproducible film deposition and the scale-up of device area from 1 to 46 cm2. Various p-type materials active for the oxygen evolution reaction were deposited via atomic layer deposition, characterized, and integrated into catalytic field-effect transistors. An automated test station was developed to expedite and standardize electronic measurements. Although the metal oxides showed orders of magnitude changes in resistivity with annealing, none of the p-type films showed gate-modulable conductivity, likely due to Fermi level pinning. Ultrathin, n-type zinc oxide or indium tin oxide transistors on strontium titanate or hafnia dielectrics showed promise as next-generation catalytic devices.