(232c) Resonance-Enhanced Hydrocarbon Oxidation Via Programmable Catalysis

The oxidation of small organic molecules over metal catalysts is at the heart of many sustainable technologies, where precious metal catalysts like Group VIII metals are typically the most active catalysts. Given their relatively high costs, it is essential to the realization of applications like fuel cells, to replace precious metal catalysts or greatly reduce their use. Taking the electro-oxidation of formic acid as a model reaction, we investigate the kinetics of this chemistry and its implications for catalyst design. Under potentiostatic conditions, Pt is typically found to be the most active catalyst, sitting at the top of the so-called Sabatier volcano. However, the limit of static catalyst performance defined by the Sabatier principle has motivated a new approach to programmable catalyst design, whereby catalysts oscillate with time between varying energetic states at sufficiently high resonant frequencies to overcome the Sabatier ‘volcano peak’. In this work, we experimentally demonstrate the concept of dynamic catalytic resonance via the electro-catalytic oxidation of formic acid in water on a Pt working electrode within a semi-continuous multi-phase flow reactor. Steady-state electro-oxidation of formic acid at 0.6 V (NHE) exhibited a maximum turnover frequency (TOF) of CO2 formation of ~1.0 s-1 at room temperature. However, oscillation of the electrodynamic potential between 0.8 V and open circuit potential via a square waveform at varying frequency (10-3 < f < 103 Hz) increased the optimal TOF to ~20 s-1 at 100 Hz. The rate increase in formic acid electro-oxidation via catalytic resonance of more than an order of magnitude (20x) above potentiostatic conditions was interpreted to occur by non-faradaic formic acid dehydration to surface-bound carbon monoxide at low potentials, followed by surface oxidation and desorption to carbon dioxide at high potentials