Characterizing nano-scale electrocatalysis during partial oxidation of methane

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Engineering

Background:

• In situ electrochemical analysis is crucial for characterizing solid oxide electrochemical cells (SOCs) under operating conditions.
• Previous methods faced limitations due to ill-defined microstructures, hindering nano-scale characterization of three-phase boundaries.
• Understanding anode behavior is key to optimizing SOC performance.

Purpose of the Study:

• To introduce a novel in situ electrochemical analysis technique for SOCs.
• To investigate the oscillatory behavior of a porous Ni-yttria-stabilized zirconia (YSZ) anode during methane partial oxidation.
• To elucidate the role of microstructural features, particularly three-phase boundaries, in anode performance.

Main Methods:

• Combined solid electrolyte potentiometry (SEP) and electrochemical impedance spectroscopy (EIS).
• In situ characterization of a Ni-YSZ anode under partial oxidation of methane at 800°C and ambient pressure.
• Analysis of oscillatory behavior in impedance and electrode potential.

Main Results:

• The novel combined SEP and impedance method successfully characterized SOCs with well-defined microstructures.
• Observed oscillatory behavior in the Ni-YSZ anode, linked to cyclic oxidation and reduction of nickel.
• In situ surface characterization indicated nickel oxidation primarily at two-phase boundaries, while three-phase boundaries remained metallic.

Conclusions:

• The developed in situ electrochemical analysis provides unprecedented insight into SOC anode behavior.
• The study clarifies the redox dynamics at different interfaces within the anode during operation.
• Findings contribute to a better understanding of three-phase boundary stability and function in SOCs.