Turning main-group element magnesium into a highly active electrocatalyst for oxygen reduction reaction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Main-group metals typically exhibit low catalytic activity due to broad sp-band interactions with adsorbates.
• Enzymatic cofactors, like magnesium (Mg), demonstrate high catalytic activity in biochemical reactions.

Purpose of the Study:

• To investigate the catalytic potential of main-group metals (Mg, Al, Ca) for oxygen reduction reaction (ORR).
• To understand the coordination environment's effect on Mg's catalytic activity.
• To develop an efficient electrocatalyst for ORR using atomically dispersed Mg.

Main Methods:

• Density functional theory (DFT) calculations to model adsorption strengths and electronic properties.
• Experimental synthesis of atomically dispersed Mg cofactors within a graphene framework.
• Electrochemical testing in alkaline media to determine half-wave potential for ORR.

Main Results:

• DFT calculations revealed that Mg, Al, and Ca are limited by strong binding with hydroxyl intermediates.
• A specific coordination environment with two nitrogen atoms optimizes Mg's adsorption strength for ORR intermediates.
• Atomically dispersed Mg cofactors in graphene achieved a high half-wave potential of 910 mV for ORR.

Conclusions:

• The coordination environment significantly influences the catalytic activity of main-group metals.
• Atomically dispersed Mg cofactors in graphene can transform a typically inactive s/p-band metal into a highly active electrocatalyst for oxygen reduction.
• This work opens new avenues for designing efficient and cost-effective electrocatalysts using earth-abundant elements.