Driving Adsorbate Evolution via Oxygenated Surface Species Modulation for Ammonia Electrooxidation

Area of Science:

• Electrochemistry
• Materials Science
• Sustainable Chemistry

Background:

• Electrochemical ammonia oxidation (eAOR) to dinitrogen is key for sustainable nitrogen cycles and hydrogen generation.
• Conventional catalysts like Pt and Pt-Ir alloys exhibit sluggish kinetics and poor stability in eAOR.
• Understanding reaction mechanisms, including *NHx dehydrogenation and proton-coupled electron transfer, is crucial.

Purpose of the Study:

• To develop a novel catalyst that enhances the kinetics and stability of the electrochemical ammonia oxidation reaction (eAOR) to dinitrogen.
• To investigate the role of oxygenated co-adsorbates in steering the adsorbate-evolution pathway for improved eAOR performance.
• To establish an adsorbate-assisted mechanism design approach for advanced nitrogen species electrocatalysis.

Main Methods:

• Synthesis of an exsolved Pt3Ni alloy on a perovskite scaffold.
• In situ Fourier transform infrared spectroscopy (FTIR) to study reaction intermediates.
• Density functional theory (DFT) calculations to elucidate the reaction mechanism.
• Electrochemical performance testing in a solar-driven ammonia electrolyzer.

Main Results:

• The Pt3Ni alloy catalyst selectively stabilizes *OOH and strengthens *NH2 binding, enhancing the eAOR.
• The catalyst exhibits a mass activity of 862 A gPt−1, surpassing current benchmarks.
• In a solar-driven electrolyzer, it achieved 13.7 mA at 1.0 V and stable hydrogen production (394 L kWh−1).

Conclusions:

• Controlling oxygenated co-adsorbates is an effective strategy to steer the adsorbate-evolution pathway in eAOR.
• The exsolved Pt3Ni alloy catalyst demonstrates superior performance and stability for sustainable ammonia electrooxidation.
• This work provides a new mechanism-based design approach for developing efficient electrocatalysts for nitrogen-based reactions.