Platinum Graphene Catalytic Condenser for Millisecond Programmable Metal Surfaces

Accelerating catalytic chemistry and tuning surface reactions requires precise control of the electron density of metal atoms. In this work, nanoclusters of platinum were supported on a graphene sheet within a catalytic condenser device that facilitated electron or hole accumulation in the platinum active sites with negative or positive applied potential, respectively. The catalytic condenser was fabricated by depositing on top of a p-type Si wafer an amorphous HfO2 dielectric (70 nm), on which was placed the active layer of 2-4 nm platinum nanoclusters on graphene. Potential of +/-6 V applied to the Pt/graphene layer relative to the silicon electrode moved electrons into or out of the active sites of Pt, attaining charge densities more than 1% of an electron or hole per surface Pt atom. At a level of charge condensation of +/-10% of an electron per surface atom, the binding energy of carbon monoxide to a Pt(111) surface was computed via density functional theory to change 24 kJ/mol (0.25 eV), which was consistent with the range of carbon monoxide binding energies determined from temperature programmed desorption (ΔBE,CO of 20±1 kJ/mol or 0.19 eV) and equilibrium surface coverage measurements (ΔBE,CO of 14±1 kJ/mol or 0.14 eV). Impedance spectroscopy indicated that Pt/graphene condensers with potentials oscillating at 3,000 Hz exhibited negligible loss in capacitance and charge accumulation, enabling programmable surface conditions at amplitudes and frequencies necessary to achieve catalytic resonance.