Enhancing oxygen evolution reaction performance via Zn/Fe co-doping in a Co₃O₄ nanostructure: mechanistic insights...

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• The oxygen evolution reaction (OER) is crucial for energy conversion technologies.
• Cobalt oxide (Co3O4) is a promising OER electrocatalyst but requires performance enhancement.
• Bimetallic doping offers a strategy to improve electrocatalyst kinetics and stability.

Purpose of the Study:

• To synthesize and evaluate Zn/Fe co-doped Co3O4 nanostructures (ZnFe-Co3O4) for enhanced OER performance.
• To elucidate the doping mechanism and active species involved in the OER process.
• To provide insights into rational catalyst design for improved electrocatalytic activity.

Main Methods:

• Synthesis of Zn/Fe co-doped Co3O4 nanostructures.
• Electrochemical characterization including overpotential, Tafel slope, and durability testing.
• X-ray photoelectron spectroscopy (XPS) for site occupancy analysis.
• Theoretical calculations and *in situ* Raman spectroscopy to determine reaction mechanisms.

Main Results:

• ZnFe-Co3O4 exhibits a low overpotential (255 mV at 10 mA cm-2) and Tafel slope (54 mV dec-1).
• The catalyst demonstrates excellent long-term durability (120 hours at 100 mA cm-2).
• XPS confirms Zn at octahedral Co3+ sites and Fe at tetrahedral Co2+ sites.
• *In situ* Raman spectroscopy reveals the formation of active FeOOH/CoOOH species via surface reconstruction.

Conclusions:

• Zn/Fe co-doping significantly enhances the OER performance of Co3O4 in alkaline media.
• Synergistic effects of Zn and Fe stabilize the Co3O4 structure and promote active species generation.
• The enhanced activity follows the lattice oxygen mechanism (LOM), driven by surface reconstruction and active (oxy)hydroxide formation.