RESUMEN
To realize economically feasible electrochemical CO2 conversion, achieving a high partial current density for value-added products is particularly vital. However, acceleration of the hydrogen evolution reaction due to cathode flooding in a high-current-density region makes this challenging. Herein, we find that partially ligand-derived Ag nanoparticles (Ag-NPs) could prevent electrolyte flooding while maintaining catalytic activity for CO2 electroreduction. This results in a high Faradaic efficiency for CO (>90%) and high partial current density (298.39 mA cmâ2), even under harsh stability test conditions (3.4 V). The suppressed splitting/detachment of Ag particles, due to the lipid ligand, enhance the uniform hydrophobicity retention of the Ag-NP electrode at high cathodic overpotentials and prevent flooding and current fluctuations. The mass transfer of gaseous CO2 is maintained in the catalytic region of several hundred nanometers, with the smooth formation of a triple phase boundary, which facilitate the occurrence of CO2RR instead of HER. We analyze catalyst degradation and cathode flooding during CO2 electrolysis through identical-location transmission electron microscopy and operando synchrotron-based X-ray computed tomography. This study develops an efficient strategy for designing active and durable electrocatalysts for CO2 electrolysis.
RESUMEN
In the operation of a direct methanol fuel cell, the modification by chloride ions on the surface of a Pt cathode can facilitate the extraordinary increase of power performance and long-term stability. Analyzing the results of cyclic voltammograms and electrochemical impedance spectroscopy, the positive shift of Pt oxidation onset potential and the depression of oxidation current are observed, which results from the role of chloride as surface inhibitor. In addition, O(2) temperature-programmed desorption and X-ray photoelectron spectroscopy also reveal that the suppression of Pt surface oxide can be best understood in terms of lower binding of oxygen species by the alteration of electronic state of Pt atoms. Such a reduced surface oxide formation not only provides more efficient proton adsorption sites with high selectivity but also decreases the mixed potential by crossover methanol, resulting in higher performance and stability even under high voltage long-term operation.
RESUMEN
The use of a ribbon-shaped Pt electrode gives rise to edge effects of the interfacial potential, as is predicted from the potential theory in the form of the corresponding reaction-migration equation. They are studied in the bistable region of formic acid oxidation. Essentially, the edges tend to be more passive than the bulk of the electrode, which also causes a passivation (activation) transition to originate from the edges (center) of the ribbon. The experimental results are in agreement with simulations of the reaction-migration system.
