Oxygen Reduction Reaction Mechanism on the Square Paddle-Wheel Cage Site of TM-BTC (TM=Mn, Fe, Cu) Metal Organic Framework

Abstract

We study the oxygen reduction reaction (ORR) mechanism on the square paddle-wheel cage active site of TM-BTC (TM= Mn, Fe, Cu) metal organic framework by using a combination of DFT and microkinetic calculations. By using a small cluster for modeling the TM-BTC active site structure, we have successfully reproduced the experimental trend of ORR activity on the TM-BTC systems: Mn-BTC > Fe-BTC > Cu-BTC. We also show that the unusual ORR activity trend from experiments for Mn and Fe systems is originated from the strength of OH adsorption on these systems. Mn-BTC system has better ORR activity than the Fe-BTC system because it has weaker OH adsorption. A very strong OH adsorption makes the final OH reduction step become more sluggish, and hence hindering the ORR process.

Keywords

• Oxygen reduction reaction
• MOF
• TM-BTC
• density functional theory
• microkinetic