Electrical Junction at the Substrate-Fe₃O₄ Nanoparticle Interface Governs Oxygen Evolution Reaction Activity.

Area of Science:

• Electrochemistry
• Materials Science
• Nanotechnology

Background:

• The oxygen evolution reaction (OER) is crucial for energy conversion, converting electrical energy to chemical energy.
• Efficient OER devices rely on nanoparticle catalysts and suitable substrates, with interfacial properties being key performance determinants.
• Understanding charge transport through substrate-catalyst junctions is essential for optimizing electrocatalyst performance.

Purpose of the Study:

• To investigate the impact of substrate work function on the performance of Fe3O4 nanoparticle electrocatalysts for OER.
• To elucidate the relationship between junction type (Ohmic vs. Schottky) and OER efficiency.
• To demonstrate a strategy for tuning interfacial properties to enhance electrocatalytic activity.

Main Methods:

• Fabrication of Fe3O4 nanoparticle-based electrodes on substrates with varying work functions (Cu, Ni, glassy carbon, Pt, Au).
• Electrochemical characterization including overpotential and Tafel slope measurements to assess OER performance.
• Introduction of a Ni2P buffer layer to modify the substrate-catalyst interface and evaluate its effect.

Main Results:

• Fe3O4 nanoparticles on low work function substrates (Cu, Ni) formed Ohmic junctions, exhibiting significantly lower overpotentials and Tafel slopes compared to those on high work function materials (GC, Pt, Au) forming Schottky junctions.
• The introduction of a Ni2P buffer layer successfully transformed the Schottky junction between GC and Fe3O4 into an Ohmic junction, leading to improved OER performance.
• Work function matching at the substrate-catalyst interface is a critical factor in determining the efficiency of the oxygen evolution reaction.

Conclusions:

• Interfacial energy matching is paramount for designing efficient electrocatalysts for the oxygen evolution reaction.
• Ohmic junctions facilitate superior charge transfer, leading to enhanced OER performance compared to Schottky junctions.
• Interfacial engineering, including the use of buffer layers, offers a viable strategy to optimize nanoparticle-based electrocatalytic devices for water electrolysis.