Asymmetric Active Sites for Boosting Oxygen Evolution Reaction.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Transition metal-nitrogen-carbon materials with atomically dispersed active sites are promising catalysts for the oxygen evolution reaction (OER).
• Symmetric active sites often suffer from poor OER intrinsic activity due to suboptimal oxygen species adsorption.
• Developing catalysts with tailored active sites is crucial for efficient electrocatalysis.

Purpose of the Study:

• To design and synthesize a novel catalyst with asymmetric active sites for improved OER performance.
• To investigate the effect of asymmetric active sites on oxygen species adsorption and OER intrinsic activity.
• To evaluate the catalyst's performance in an alkaline water electrolyzer (AWE).

Main Methods:

• In silico screening to identify optimal transition metals.
• Synthesis of asymmetric metal-nitrogen-carbon active sites (a-MN4@NC) based on g-C3N4.
• Electrochemical characterization including overpotential measurements and alkaline water electrolysis tests.

Main Results:

• Asymmetric active sites (a-CoN4@NC) demonstrated a 48.4% enhancement in intrinsic activity compared to symmetric sites.
• The catalyst exhibited an onset potential of 179 mV for OER.
• The a-CoN4@NC catalyst achieved current densities of 150 mA cm-2 at 1.7 V and 500 mA cm-2 at 2.1 V in an AWE device.

Conclusions:

• Asymmetric active sites effectively modulate oxygen species adsorption, leading to superior OER intrinsic activity.
• The developed a-CoN4@NC catalyst shows excellent potential for efficient water splitting applications.
• This work provides a new strategy for designing high-performance electrocatalysts by manipulating active site symmetry.