Vanadium doped CoSe2 on mesoporous hollow carbon spheres with selenium vacancies for Zn-air Batteries

초록

Rechargeable Zinc-air batteries (ZABs) are promising energy conversion and storage devices that offer excellent efficiency. ZABs are especially notable for their high energy density and environmental friendliness, making them a potential sustainable energy storage solution. However, their performance is hindered by slow kinetics and high overpotentials due to the four-electron reaction pathway of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) at the air cathode during charge and discharge processes. Traditionally, noble metal-based materials, such as ruthenium oxides (RuO2) and platinum supported on carbon (Pt/C), have been used as highly efficient electrocatalysts for both OER and ORR. However, these commercial catalysts are limited by their high cost, poor long-term durability, and scarcity. Consequently, transition metal chalcogenides (TMCs), such as transition metal selenides, have emerged as viable alternatives due to their superior electrical conductivity, excellent electrochemical stability, low cost, and outstanding redox performance. Additionally, defect engineering has been extensively employed to tune the electronic structure of these materials, resulting in enhanced electrocatalytic performance. Specifically, the introduction of selenium vacancies in transition metal selenides can modulate the adsorption/desorption free energies of reaction intermediates (*O, *OH, and *OOH) during both OER and ORR in alkaline solutions. In this study, vanadium-doped CoSe2 embedded in mesoporous hollow carbon spheres (MHCS) with Se-doped mesoporous carbon was synthesized through a carbonization and etching process, followed by a subsequent annealing treatment. First, composites of resorcinol-formaldehyde spheres and silica were synthesized using the facile Stober method. These composites were then treated by carbonization at 800°C for 2 h. The resulting particles were stirred with 1.6 M HF for 2 hours to obtain MHCS, which were then used as