Revealing the Mechanism and Activity of O2 Reduction Reaction of Co Nanocluster Encapsulated by Carbon Nanotube

Abstract

Exploration of inexpensive electrocatalysts with excellent catalytic activity and chemical stability for the O2 reduction reaction (ORR) is crucial for the widespread adoption of sustainable and renewable energy conversion technologies in practical applications. This study explored the potential of Co nanoparticle-encapsulated single-wall carbon nanotube (Co@SWCNT) as efficient electrocatalyst for ORR. We employed a quantum mechanical (QM) periodic hybrid B3LYP density functional theory (DFT) method with the dispersion corrections (-D3) (developed by Grimme and co-workers) to investigate the ORR mechanism. We examined the impact of Co nanoparticles on the electronic properties of the SWCNT and observed that Co@SWCNT has metallic characteristics in nature. The study focused on determining the adsorption energy (ΔE) of ORR species on the Co@SWCNT surface to comprehend its electrocatalytic efficiency and performance toward ORR. Furthermore, we proposed two potential ORR mechanisms: a direct 4e- transfer reaction pathway and a series of 2e- transfer reaction pathways. The value of ΔE of the 2O* ORR intermediate has been determined to be −0.35 eV, and for the OOH* ORR intermediate, the value of ΔE is about −3.59 eV. This suggests that the 4e- dissociative pathway could be the thermodynamically favorable path for the O2 reduction reaction compared to the 4e- associative and 2e- pathways of ORR. This research not only paves the way for the development of cost-effective and highly durable nonmetal catalytic materials but also holds great promise for advancing future renewable energy and fuel cell applications. © 2024 American Chemical Society