Non-redox doping boosts oxygen evolution electrocatalysis on hematite

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• The oxygen evolution reaction (OER) is crucial for water electrolysis and renewable fuel production.
• Hematite (α-Fe2O3) is an abundant and inexpensive material with theoretical OER potential but exhibits poor activity.
• Current OER catalysts often rely on cobalt or nickel, driving research into alternatives.

Purpose of the Study:

• To investigate the effect of doping hematite with redox (Ni) and non-redox (Zn) active species to improve OER performance.
• To understand the mechanism behind the enhanced catalytic activity in doped hematite.
• To explore novel strategies for optimizing oxide catalysts for water splitting.

Main Methods:

• Synthesis and characterization of Ni-doped and Zn-doped hematite.
• Electrochemical testing of OER activity in alkaline media.
• Mechanistic studies to elucidate the role of dopants in the OER pathway.

Main Results:

• Zn-doped hematite demonstrates significantly higher OER activity than Ni-doped hematite and pristine hematite.
• Zn-doped hematite achieves state-of-the-art performance (10 mA cm⁻² at 350 mV overpotential at pH 13).
• Doping with Zn alters the OER mechanism, promoting a faster two-site reaction pathway.

Conclusions:

• Non-redox active Zn doping is a superior strategy for enhancing hematite's OER performance compared to redox active Ni doping.
• The enhanced activity of Zn-doped hematite is attributed to a modified reaction pathway involving adjacent metal centers.
• This study presents a new approach for optimizing oxide catalysts, particularly iron oxides, for efficient water electrolysis.