Increasing Iridium Oxide Activity for the Oxygen Evolution Reaction with Hafnium Modification

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Developing efficient electrocatalysts for the oxygen evolution reaction (OER) is crucial for energy conversion devices.
• Iridium oxide (IrO2) is the benchmark OER catalyst but is expensive and scarce.
• There is a need for affordable, highly active, and stable OER electrocatalysts.

Purpose of the Study:

• To synthesize and implement a novel hafnium-modified iridium oxide (IrHfO) electrocatalyst for the oxygen evolution reaction (OER).
• To evaluate the activity and stability of the IrHfO catalyst in both alkaline and acidic conditions.
• To elucidate the mechanism behind the enhanced OER activity using spectroscopic and computational methods.

Main Methods:

• Synthesis of hafnium-modified iridium oxide (IrHfO) electrocatalyst.
• Electrochemical testing in alkaline (pH=11) and acidic (pH=1) media.
• Operando surface-enhanced Raman spectroscopy (SERS) and Density Functional Theory (DFT) calculations.

Main Results:

• The IrHfO electrocatalyst exhibited ten times higher activity in alkaline and four times higher activity in acidic conditions compared to IrO2.
• The highest intrinsic mass activity of IrHfO in acid was 6950 A gIrOx-1 at an overpotential of 0.3 V.
• SERS and DFT studies identified Ir-O species as active sites and revealed that Hf modification enhances OER activity by altering electronic states and lowering energy barriers.

Conclusions:

• Hafnium modification of iridium oxide significantly boosts OER performance in both acidic and alkaline environments.
• The IrHfO catalyst presents a promising, cost-effective alternative to pure IrO2 for energy conversion applications.
• Understanding the active sites and reaction mechanisms is key to designing advanced electrocatalysts.