Vanadium-doped cobalt selenide nanoparticles embedded in mesoporous hollow carbon spheres as highly efficient bifunctional electrocatalyst for rechargeable Zn-air batteries

초록

The growing demand for sustainable energy has brought rechargeable Zn-air batteries (ZABs) into focus due to their high energy density and low cost. However, their performance is severely hindered by sluggish oxygen electrocatalysis at the air cathode. Herein, we report the rational design and synthesis of a vanadium-doped cobalt diselenide embedded in a mesoporous hollow carbon sphere framework (V-CoSe2@MHCS) via a sol-gel templating, vacuum impregnation, and thermal selenization process. The hierarchical hollow carbon architecture ensures efficient mass transport and abundant active site exposure, while vanadium incorporation modulates the electronic structure of CoSe2, generating defect-rich surfaces and enhancing intrinsic redox activity. Benefiting from these synergistic structural and electronic features, V-CoSe2@MHCS exhibits outstanding bifunctional electrocatalytic activities. Based on the electrocatalytic performance test using Hg/HgO (1.0 M KOH) reference electrode, the prepared electrocatalyst shows low overpotential of 342 mV at 10 mA cm-2 for oxygen evolution reaction (OER) and a high half-wave potential of 0.825 V for oxygen reduction reaction (ORR). When applied as the air cathode in aqueous ZAB, V-CoSe2@MHCS delivers a high specific capacity of 732.5 mAh gZn-1, a peak power density of 154.8 mW cm-2, and exceptional long-term cycling stability. Furthermore, when integrated into a quasi-solid-state flexible ZAB, the catalyst demonstrates exceptional electrochemical performance and a stable output under repeated bending conditions. The device achieves a high current density of 173.4 mA cm-2 at 0.3 V and a peak power density of 65.2 mW cm-2, and demonstrating stable cycling performance over 70 cycles.

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