Operando studies of Mn oxide based electrocatalysts for the oxygen evolution reaction

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Photosystem II (PS II) inspires Mn oxide electrocatalysts for oxygen evolution reaction (OER).
• Industrial OER catalysis differs fundamentally from biological water splitting.
• Developing artificial Mn-based OER catalysts requires mechanistic understanding and industrial practicality assessment.

Purpose of the Study:

• Highlight challenges in operando investigation methods for OER electrocatalysts.
• Provide insights into Mn-based OER catalyst mechanisms using advanced techniques.
• Review recent in situ and operando studies on Mn oxide OER catalysts.

Main Methods:

• Utilized in situ and operando spectroscopic methods, including Raman spectroscopy and absorption techniques.
• Employed operando X-ray spectroelectrochemistry (SEC) in both hard and soft X-ray regimes.
• Discussed technical challenges specific to each method and Mn oxide systems.

Main Results:

• Identified common challenges in operando methods for OER catalyst studies.
• Highlighted Mn oxidation states between III and IV in active catalysts.
• Observed layered birnessite phases in highly active Mn-based OER systems.

Conclusions:

• Despite technical and system-specific challenges, Mn oxide OER catalysts show promise.
• Structural disorder is a key feature in active Mn-based OER catalysts.
• Layered birnessite phases and specific Mn oxidation states correlate with significant OER activity.