Co₂P Nanoparticles Encapsulated in N-Doped Carbon Nanotubes as a Bifunctional Oxygen Catalyst for a High-Performance Rechargeable Zn–Air Battery

Abstract

A significant but challenging task is the development of a rechargeable Zn–air battery bifunctional catalyst. Here, a supramolecular self-assembly of poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123) was designed to construct Co2P nanoparticles encapsulated in N-doped carbon nanotubes (Co2P@NCNT-x). The results show that P123 is an important factor in the formation of N-doped carbon nanotubes coated with Co2P nanoparticles. The Co2P@NCNT-4 catalyst exhibits the maximum limiting diffusion current density (5.2 mA·cm–2 under 808.9 hPa) and a more positive onset potential (0.90 V vs RHE) and half-wave potential (0.84 V vs RHE) due to the greater specific surface area and higher graphitization degree. Its potential gap is only 0.87 V versus RHE which is between the half-wave potential of the oxygen reduction reaction and the E j = 10 of the oxygen evolution reaction. The Co2P@NCNT-4-based rechargeable Zn–air battery shows the highest peak power density (217 mW·cm–2), the highest specific capacity (831.25 mA h·gZn –1 at 10 mA·cm–2), and remarkable cycle stability. This preparation method can provide ideas for designing other transition metal phosphide catalysts in the future.

Application of changing the valence state of metals through the reaction time for efficient oxygen evolution reaction

“…46 The presence of O was attributed to atmospheric oxygen. This result indicates that the FeNiS/CNTs were composed of four elements: Fe, Ni, C, and S. 47 In the Fe 2p spectrum (Fig. 2B), the peaks were fitted into six sub-peaks, corresponding to Fe 2+ (711.4 and 724.2 eV), Fe 3+ (713.9 and 727.4 eV), and their corresponding satellite peaks (717.7 and 735.6 eV), respectively.…”

“…The scanning spectrum of C 1s could be fitted into three peaks: C–C (284.8 eV), O–C–O (287.5 eV), and C–N (285.4 eV), respectively. 47 In the Fe 2p spectrum (Fig. 2B), the peaks were fitted into six sub-peaks, corresponding to Fe 2+ (711.4 and 724.2 eV), Fe 3+ (713.9 and 727.4 eV), and their corresponding satellite peaks (717.7 and 735.6 eV), respectively.…”

Multisite photocatalytic depolymerization of lignin model compound utilizing full-spectrum light over magnetic microspheres

“…The peaks at 783.9 and 800.9 eV corresponded to Co 2p 3/2 and Co 2p 1/2 , respectively, which are characteristic of the Co 2+ valence state in FeCoRu@SiO 2 –TiO 2 . 38 , 39 , 40 The peaks at 779.1 and 794.9 eV were for Co 3+ , which was produced by surface oxidation. Peaks for Ru 3 d in FeCoRu@SiO 2 –TiO 2 appeared at 285.0 eV (Ru 3d 3/2 ) and 280.8 eV (Ru 3d 5/2 ).…”