| With the advent of the energy crisis and the increasingly serious environmental pollution problems,the development of clean energy systems represented by energy storage batteries has become crucial for the development of human society.The rechargeable zinc-air battery is expected to become a new generation of power battery due to its high theoretical specific energy,environmental friendly and abundant material resources.During the discharge and charge of zinc-air batteries,oxygen reduction reactions(ORR)and oxygen evolution reactions(OER)occur on the air electrodes,respectively.The development of low-cost and high-efficiency electrode reaction catalysts has become a bottleneck for the development of zinc-air batteries.In this paper,four composite electrocatalysts were prepared,and their oxygen electrocatalytic performance and the application in zinc-air battery were studied.The main contents are as follows:1)The electrocatalyst possesing three activities of ORR,OER and HER was constructed by the Co-B-O nanosheets sticking grown on N,P double-doped carbon nanosheets.Boron as a media element closely connects two heterogeneous materials,showing a synergistic catalytic effect.The presence of Co-B-O nanosheets effectively reduces the content of pyridine-N-oxide groups in the carbon substrate.The prepared Co-B-O/NPC-50%catalyst showed excellent ORR/OER/HER trifunctional catalytic activity.When this catalyst was applied to a rechargeable zinc-air battery,the power density obtained was 110.7 mW/cm~2,and the charge-discharge cycle was stable for more than 60 hours.2)A three-dimensional carbon foam(Co-NCF)was prepared,in which metal cobalt,graphene nitride and fibrous carbon are interwoved together.The carbon foam has the characteristics of shape-designable,ferromagnetic,high oil-absorption and light weight.It was found that the metallic cobalt particles were wrapped in graphitized carbon shell,forming the microstructure of cobalt-carbon nanocage.The Co-N bonds between the cobalt metal and the carbon shell further activate the ORR catalytic performance of the carbon foam.The catalyst showed excellent ORR performance,with a greater limiting current density(5.74 mA/cm~2),higher onset potential(0.91 V),higher half-wave potential(0.83 V)and long-term catalytic stability.When this catalyst was applied to a zinc-air battery,the power density obtained was 134 mW/cm~2.3)A novel Co-carbon nanocage/N,S double-doped carbon composite catalyst was prepared by a novel boron introduction method.It was found that the introduction of a small amount of boron can significantly increase the nitrogen content in the catalyst.Moreover,the binding ability between the metal and heteroatom has also been improved.In the ORR process,the prepared Co-NBSC catalyst showed an onset potential of 0.93 V,a half-wave potential of 0.84 V,and a limiting current density of 5.58 m A/cm~2.When this catalyst was applied to a zinc-air battery,the power density obtained was 121.2 mW/cm~2.4)CoFeP nanocrystal/N,P double-doped carbon composite catalyst was prepared by high-temperature carbonization.CoFeP alloy particles provide high active sites for OER,and N,P double-doped carbon provides high active sites for ORR.The catalyst has excellent OER/ORR bifunctional activity;in the ORR process,it shows an onset potential of 0.90 V,a half-wave potential of 0.80 V and a limiting current density of 6.16 mA/cm~2.In the OER process,only a 336 mV overpotential is required to achieve a current density of 10 mA/cm~2.When this catalyst was applied to a rechargeable zinc-air battery,the power density obtained was 143.5 mW/cm2,and the charge-discharge cycle was stable for more than 200 hours. |
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