Omar Abdelrahman University of Massachusetts Amherst
It is a truth universally acknowledged that faster catalysts enable the more efficient transformation of molecules to useful products and enhance the sustainable utilization of natural resources. However, the limit of static catalyst performance defined by the Sabatier principle has motivated a new approach to dynamic 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, the concept of dynamic catalytic resonance was experimentally demonstrated 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 via a square waveform at varying frequency (10-3 < f < 103 Hz) increased the optimal TOF to ~5 s-1 at 0.5 Hz. An even higher TOF of ~20 s-1 was observed at a resonant frequency of 100 Hz for a square waveform oscillating between zero and 0.8 V. 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.
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