Advances in ORR Catalysis Promoted by Graphene-Supported Low-Cost Metal Clusters: A DFT Study

Area of Science:

• Electrochemistry and Catalysis
• Materials Science
• Computational Chemistry

Background:

• The oxygen reduction reaction (ORR) is crucial for renewable energy but limited by slow kinetics.
• Transition metal clusters on graphene show potential for ORR catalysis.
• Understanding reaction intermediates is key to improving catalyst design.

Purpose of the Study:

• To explore the ORR energy profile on metal clusters (Fe5, Co5, Pt5) supported on graphene.
• To investigate the influence of "unconventional" intermediates on ORR thermodynamics and kinetics.
• To evaluate catalytic performance using density functional theory (DFT) calculations.

Main Methods:

• Density functional theory (DFT) calculations were employed.
• Thermodynamic stability and adsorption energies of standard and unconventional ORR intermediates were analyzed.
• Calculations considered metal clusters (Fe5, Co5, Pt5) on undoped and nitrogen-doped graphene under electrochemical conditions.

Main Results:

• Unconventional intermediates (*O*OH, *OH*OH) significantly alter ORR thermodynamics, revealing a more favorable pathway.
• Fe5 clusters on nitrogen-doped graphene (Fe5@NGr) exhibited the highest catalytic activity with a near-zero theoretical overpotential (ηORR) in the unconventional mechanism.
• All studied catalysts showed good stability and high activity for both reduction mechanisms.

Conclusions:

• The electronic and structural properties of metal clusters and graphene supports critically influence ORR intermediate stability and catalytic performance.
• The unconventional ORR pathway offers a more energetically favorable route for catalysis.
• Fe5@NGr demonstrates superior performance, highlighting the importance of N-doping graphene for designing efficient, low-cost ORR catalysts.