Synthesis of a highly efficient bifunctional Co2P@N-doped carbon nanotubes electrocatalyst by GO-Induced assembly strategy for rechargeable Zn-air batteries

• Published in: Journal of alloys and compounds 2021-12, Vol.889, p.161628, Article 161628
• Main Authors: Peng, Xianhui, Liu, Yang, Hu, Siqi, Zheng, Pengfei, Fu, Yidan, Dong, Peng, Xiao, Jie, Han, Lina, Zhang, Yingjie
• Format: Article
• Language: English
• Subjects: Assembly; Carbon nanotubes; Co2P nanoparticles; Commercialization; Electrocatalysts; Graphene; Graphitization; Metal air batteries; N-doped carbon nanotubes; Nanoparticles; Oxygen reduction reaction; Oxygen reduction reactions; Phosphides; Rechargeable batteries; Synergistic effect; Synthesis; Transition metals; Zinc-oxygen batteries; Zn-air battery
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2021.161628

•A GO-induced assembly strategy was used for the scalable manufacture of Co2P@NCNTs.•The tube-like Co2P@NCNTs can be obtained by adjusting the amount of adding graphene.•The Co2P@NCNTs-15 with higher graphitization degree, rich pyridine N and graphitic N, exhibits best ORR and OER performance.•Co2P@NCNTs-15-based Zn-air battery has a highest peak power density, specific capacity and excellent stability. Due to the bonding force between the surface Co atom and the adsorbed intermediate are so strong that intermediate cannot desorb from Co atom, the oxygen reduction reaction of Co2P based electrocatalyst cannot satisfy the commercialized application of the Zn-air battery. In this work, a GO-induced assembly strategy was designed to construct cobalt phosphide (Co2P) nanoparticles encapsulated in N-doped carbon nanotubes (Co2P@NCNTs). The experimental results show that adding graphene oxide (GO) content has a significant impact on the formation of well-defined Co2P@NCNTs nanotubes structures and the exaltation of the graphitization degree. Benefitting from the synergistic effect between N-doped nanotubes and Co2P, the Co2P@NCNTs-15 electrocatalysts exhibited better catalytic performance, a more positive onset potential (0.90 V vs RHE) and half-wave potential (0.82 V vs RHE), maximum limiting diffusion current density (5.5 mA cm−2) and Tafel slope only 73 mV dec−1. The potential gap (ΔE) between Ej=10 of OER and ORR half-wave potential (E1/2) of Co2P@NCNTs-15 is only 0.93 V, which lower than Pt/C electrocatalyst (1.15 V). More importantly, the Co2P@NCNTs-15-based rechargeable Zn-air battery performed the highest peak power density (159.7 mW cm−2), specific capacity (792.6 mAh g−1 at 10 mA cm−2) and remarkable cycle stability. This method also offers a high yield and cost-effective synthesis strategy for preparing the other transition metal phosphide electrocatalysts.