Temporal Programming of Interfacial States Reveals a Hidden Formate Pathway from CO2 Reduction on Palladium
Year: 2026
Type: preprint
Abstract: Controlling electrocatalytic selectivity requires not only tuning catalyst composition but also controlling the interfacial states that emerge during operation. Here, using bulk Pd as a model system for electrochemical CO 2 reduction reaction (CO 2 RR), we show that poor steady-state formate production emerges from time-dependent evolution of the electrochemical interface. Pd initially exhibits appreciable formate activity but rapidly accumulates strongly bound CO and evolves toward a CO-rich, formate-inactive state. Although substantial sorbed H persists during this evolution, its oxidation shifts to increasingly positive potentials with increasing CO coverage, indicating reduced electrochemical accessibility and reactivity of H at the CO-covered interface. Density functional theory shows that CO-rich configurations are thermodynamically favored under cathodic conditions, while increasing CO coverage destabilizes early intermediates of both the formate and CO pathways. Dynamic potential modulation temporally separates surface-state preparation from catalytic turnover: anodic excursions remove accumulated CO, and subsequent cathodic polarization repeatedly accesses a CO-depleted state that is not thermodynamically favored at the reaction potential. This strategy produces an approximately 230-fold enhancement in formate partial current density relative to static operation. Within this dynamically accessible low-CO regime, formate activity further correlates with sorbed-H availability. These results reveal a hierarchical interfacial control in which CO coverage gates pathway accessibility while hydrogen availability modulates formate activity, demonstrating how temporal control can access catalytic states and reaction pathways hidden under steady-state operation.
Source: ChemRxiv
Institutions: The University of Texas at Austin, Texas Materials Institute
Language: English
Field: Energy
Domain: Physical Sciences
Open Access status: green
Funder: National Institutes of Health
OpenAlex ID: W7211875385