Cobalt–Platinum Nanoparticle Encapsulated within Carbon Nanotube for Superior O₂ Reduction Reaction

The ever-increasing energy demand has led us to use more environmentally friendly green energy conversion devices, such as fuel cells and metal-air batteries. The slow reaction kinetics of the O2 reduction reaction (ORR) occurring at the cathode side determines the efficiency of the fuel cells. The much-recognized high-cost platinum-based catalysts must be replaced by non-precious-metal-based electrocatalysts for improved ORR activity. In this study, we have explored the cobalt–platinum (CoPt) nanoparticle encapsulated by a carbon nanotube (CNT), e.g., CoPt@CNT material, as an efficient electrocatalyst for ORR by employing the first-principles-based density functional theory (DFT) method. We studied the structural and electronic properties of the CoPt@CNT system. We found that the equilibrium structure of the CoPt@CNT system has zero electronic band gap (Eg = 0). The presence of a large electron density of states (DOS) around the Fermi level (EF) in the total DOS confirms its conducting nature. The ORR mechanisms have been investigated on the surface of CoPt@CNT by calculating the change in adsorption energy (ΔE) and Gibbs free energy (ΔG) of each reaction intermediate. Our energy calculations demonstrate that the active sites on the CoPt@CNT material are thermodynamically and energetically favorable for ORR. The four-electron (4e–) transfer mechanism of ORR including both dissociative and associative paths has been explored on the surface of the CoPt@CNT system. It should be mentioned here that the active basal plane of the subject material exhibits excellent catalytic activity toward the ORR with high four-electron-reduction pathway selectivity. Hence, it will be a promising solution to use CoPt@CNT material as an efficient electrocatalyst for the ORR in fuel cells to substitute the Pt electrodes.