Synergistic co-doping induced high catalytic activities of La/Fe doped Co3O4 towards oxygen reduction/evolution reactions for Zn-air batteries

摘要

La/Fe co-doped Co3O4 nanoparticles supported on aminated carbon nanotubes (LaFe-Co3O4/NCNTs) have been demonstrated to be active bifunctional catalysts for oxygen reduction/revolution reactions (ORR/OER). With optimal La/Fe doping levels, LaFe-Co3O4/NCNTs exhibits an overall ORR/OER bifunctional catalytic activity higher than most catalysts reported recently. The high performance of LaFe-Co3O4/NCNTs mainly originates from the specific La/Fe co-doped structure of the LaFe-Co3O4 NPs, which increases both the ORR and OER catalytic activities of the LaFe-Co3O4 NPs to higher degrees. DFT calculations have shown that the La/Fe co-doping can decrease the overpotentials of both the ORR and the OER and increase the stability of the LaFe-Co3O4 NPs. Additionally, carbon coating can further increase the catalytic activities of LaFe-Co3O4/NCNTs by the decrease of the polarization losses caused by the electrical resistance. When used in zinc-air batteries (ZABs), the carbon coated LaFe-Co3O4/NCNTs (C@LaFe-Co3O4/NCNTs) can exhibit a maximum power density of 122.2 mW cm(-2), which is >20% higher than that of mixed catalysts of Pt/C + RuO2. This, along with the much higher cycling stability of C@LaFe-Co3O4/NCNTs, suggests great potential for its use as a bifunctional catalyst for practical applications.

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