Surface coverage control for dramatic enhancement of thermal CO oxidation by precise potential tuning of metal supported catalysts

Abstract

Chemical heterogeneous catalysis maximizes performance by controlling the interactions between the catalyst and the substrates. Steady-state catalytic rates depend on the heat of adsorption and the resultant coverage of adsorbates, which in turn reflects the electronic structure of the heterogeneous catalyst surfaces. This study aims to free the surface from high coverage of a kind of substance by externally controlling the electrochemical potential of the catalysts for improved thermal-catalytic rates. We employed aqueous CO oxidation at 295 K as a model reaction, where strong binding of chemisorbed CO (CO*) to the metal surfaces and its high coverage led to inhibition of O₂ accessing the surface site. Based on the establishment of coverage–potential–performance correlation, our potential-controlling experiments used an electrochemical configuration to identify the appropriate potentials of Pt/C catalysts that can drastically enhance the CO₂ formation rate through the thermal reaction pathway. An anodic potential was applied to suppress the high coverage of chemisorbed CO; consequently, the catalytic testing recorded a 5-fold increase in thermal CO₂ formation compared to the open-circuit counterpart with a faradaic efficiency (FE) of over 400%. In situ infrared spectroscopy corroborates the potential–coverage correlation, where the suppression of high CO* coverage due to pinning the catalyst potential triggered the enhancement of thermal-catalytic contribution to CO₂ formation. Our extended study employing other metal catalysts also exhibited FEs exceeding unity. This work establishes a universal methodology of electrochemical tools for thermal catalysis to precisely tune the electrochemical potential of solids and achieve green and innovative reactions.