Year: 2026
Type: preprint
Abstract: Heterogeneous catalysts are usually optimized under static feed conditions, forcing a compromise between reactant adsorption, surface reaction, and site regeneration. For CO oxidation on Pt, this compromise is especially severe because CO binds strongly and suppresses O2 activation. Here we show that externally imposed square-wave modulation of the CO pressure can break this static limitation on Pt(111). Using synchronized infrared reflection absorption spectroscopy and mass spectrometry under constant O2 background, we directly resolve the coupled evolution of CO∗ coverage and CO2 production during each forcing cycle. CO introduction produces an initial CO2 burst followed by CO poisoning, whereas CO removal generates a second CO2 burst as vacant sites reopen O2 dissociation pathways. A Langmuir–Hinshelwood microkinetic model reproduces these transients and identifies the optimum forcing window as a balance between CO replenishment, CO desorption, and O2 activation on regenerated sites. Model-guided experimentation indicates the most favorable regimes of forcing frequency and duty cycle. At 475 K and PO2 = 5 × 10−5 mbar, the strongest tested protocol (approximately 0.3 s CO-on and 0.7 s CO-off) gives an approximately threefold larger time-averaged normalized m/z = 44 signal than continuous CO exposure at the same temperature, O2 pressure, and peak CO pressure. These results provide direct experimental evidence that reactant forcing can access productive non-steady-state surface coverages unavailable under static operation, establishing a mechanistic framework for programmable catalytic rate enhancement.
Source: ChemRxiv
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7215109642