Electric-field-assisted proton coupling enhanced oxygen evolution reaction

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• The oxygen evolution reaction (OER) is crucial for water splitting but challenging to regulate due to its complex four-electron process.
• Manganese-based catalysts, inspired by photosystem II, are promising for OER, yet controlling proton-electron coupling remains difficult.
• Conventional chemical methods struggle to fine-tune the intricate steps involved in OER.

Purpose of the Study:

• To investigate alpha-manganese dioxide (α-MnO2) as a model system for understanding and controlling proton coupling in OER.
• To explore the use of an external electric field as a novel method to enhance OER efficiency in situ.
• To demonstrate a practical approach for high-efficiency electrocatalysis using manganese-based materials.

Main Methods:

• Investigated α-MnO2 with MnIV-O-MnIII-HxO motifs to model proton coupling dynamics.
• Utilized a single-nanowire α-MnO2 device to apply gate voltage and study its effect on OER.
• Developed and tested a proof-of-principle external electric field-assisted flow cell for water splitting.

Main Results:

• Pre-equilibrium proton-coupled redox transition in α-MnO2 was identified as a key factor for adjustable OER energy profiles.
• Gate voltage applied to the α-MnO2 nanowire device increased OER current density by fourfold at 1.7 V vs. RHE.
• The electric field-assisted flow cell showed a 34% increase in current density and a 44.7 mW/cm² rise in net output power.

Conclusions:

• External electric fields can effectively enhance proton coupling for OER in manganese-based catalysts.
• Proton-incorporated redox transitions play a critical role in electrocatalytic OER efficiency.
• This work presents a practical and efficient strategy for advancing water splitting technologies.