An investigation of electrocatalytic activity of the FeCe nanoparticle encapsulated carbon nanotube towards oxygen reduction reaction

Abstract

The sluggish O₂ reduction reaction (ORR) that occurs in fuel cells requires an efficient electrocatalyst to increase the efficiency of the fuel cells. It is necessary to replace the widely acknowledged Pt-based electrocatalyst with a low-cost, non-precious metal-based electrocatalyst to efficiently catalyze the ORR. Herein, we propose a material comprising Fe–Ce nanoparticles encapsulated within a carbon nanotube, e.g., FeCe@CNT, as a promising electrocatalyst for the ORR. The structural and electronic properties, i.e., electronic band structure and total density of states (DOS), of the FeCe@CNT material were studied by employing a first-principles-based DFT-D3 method. Our current study found that the FeCe@CNT material has conducting properties due to its zero electronic band gap (E_g). The electronic bands cross the Fermi energy level (E_F) with a large electron density of states around the Fermi level in total DOS, confirming the conducting nature of the subject material. This study explored all the reaction steps involved in the ORR mechanism on the surface of the FeCe@CNT system. The O₂ adsorption on the surface of the FeCe@CNT system occurred with an adsorption energy (ΔE) of −1.67 eV. This study found that the ORR mechanism on the surface of the FeCe@CNT material proceeds through the four-electron (4e⁻) transfer mechanism. The associative pathway of the ORR, along with various reaction intermediates, was explored using the adsorption energy. Our energy calculation demonstrates that the active sites on the FeCe@CNT material are thermodynamically favorable for catalyzing the ORR. Our study found that the FeCe@CNT material is a potential candidate that can be used in the fuel cell as a cathodic electrode material. The valuable insights from the strong FeCe nanoparticle interaction with the CNT will help advance the interfacial design of novel electrocatalysts towards the ORR.