Electro-tuned catalysts: voltage-controlled activity selection of bimetallic exsolution particles

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Bimetallic catalysts offer tunable properties for various chemical reactions.
• Exsolution of active nanoparticles from oxide supports is a promising strategy for catalyst design.
• Understanding the electrochemical control of exsolved catalyst activity is crucial for optimizing performance.

Purpose of the Study:

• To investigate the electrochemical influence on the activity states of bimetallic Ni-Fe catalysts exsolved from Nd_0.6Ca_0.4Fe_0.97Ni_0.03O_3- (NCFNi).
• To explore the reversible switching of catalytic activity using electrochemical polarization.
• To elucidate the mechanisms behind the observed activity differences between Ni and Fe exsolutions.

Main Methods:

• Fabrication of thin film mixed conducting model electrodes using NCFNi perovskite oxide.
• Electrochemical polarization under humid hydrogen atmosphere to control oxygen chemical potential.
• In situ near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) to monitor surface chemical changes.

Main Results:

• Selective exsolution of Ni nanoparticles from the NCFNi perovskite lattice was achieved via electrochemical control.
• Reversible switching between three distinct activity states (bimetallic Ni-Fe, pure Ni, inactive oxides) was demonstrated.
• Differences in switching behavior compared to Fe exsolutions were attributed to kinetic interplay and slow oxygen transport through nickel oxide at the interface.

Conclusions:

• Electrochemical polarization is an effective method for controlling the activity of exsolved bimetallic Ni-Fe catalysts.
• The study provides insights into the role of oxygen transport kinetics in catalyst switching behavior.
• This work opens avenues for designing electrochemically switchable catalysts for various applications.