Preparation And Electrocatalytic Application Of Carbon-Supported Nickel-Based Bimetallic Nanoparticles

In recent years,energy plays an important role in the rapid development of global technology and economy,as well as in the process of rapid population growth.Therefore,the development of green and sustainable energy technologies to reduce human society’s heavy reliance on fossil fuels has been attracting more and more attentions.Among them,zinc-air battery（ZAB）is regarded as a new type of energy storage and conversion equipment/technology with great market potential due to its high theoretical energy density,good safety,environmental friendliness and other merits.However,there are still some obstacles to the commercialization of ZABs,and the core to remove these obstacles lies on the development of efficient and stable air-cathode catalyst and advanced electrochemical technology.Therefore,the development of efficient,durable,low-cost catalysts for oxygen reduction reaction（ORR）and oxygen evolution reaction（OER）occurring at the ZAB air-cathode is critical for their large-scale commercial application.In this thesis,a series of nickel-based electrocatalysts with cost-effectiveness,excellent activity and robust long-term stability were prepared by green,facile and efficient strategies.Various characterization means were used to analyze the relationship between the morphologies,structures,properties and the catalytic activities of the material,and the activity and stability of the catalyst in practical application were studied by the preliminary ZABs battery test.The main content is as follows:（1）By employing Ni²⁺,Fe³⁺and melamine as raw materials,copolymer Pluronic123 as an agent to direct melamine for forming N-CNTs,a series of Ni_xFe_100-x@N-CNTs catalysts（where x denotes the Ni ratio in Ni Fe alloys）in which Ni Fe alloy nanoparticles embedded in the inner cavities of nitrogen-doped nanotubes with mesoporous structure were prepared by a simple one-pot method.Among the series of samples,Ni₅₀Fe₅₀@N-CNTs exhibited the best bifunctional electrocatalytic performance（OER and ORR）.In the OER test,the overpotential at current density of 10 m A cm^-2 was only 318 m V,and the catalytic activity and stability were superior to that of the state-of-the-art Ir O₂ catalyst.Moreover,the stability for ORR was far better than that of commercial Pt/C,while the electrochemical activity was slightly inferior to that of Pt/C.（2）Ni Mn alloy nanoparticles supported on carbon nanosheets were synthesized by a simple hydrothermal method,named as the Ni_xMn_y/CSs series（where x and y denote the initial molar amount of Ni and Mn atoms in Ni Mn alloy,respectively）.Ni_xMn_y/CSs was employed to catalyze OER and ORR.Among the series of samples,Ni₃Mn/CSs exhibited the best bifunctional electrocatalytic performance.In the OER and ORR test,the catalytic activity and stability were better than commercial Ir O₂ and Pt/C catalysts,respectively.（3）The above as-prepared Ni_xFe_100-x@N-CNTs and Ni_xMn_y/CSs were then employed as air cathode catalysts for self-assembled zinc-air batteries.（i）The zinc-air battery using Ni₅₀Fe₅₀@N-CNTs as the air cathode showed the best performance with the power density,energy density and specific capacity of 203.6 m W cm^-2,972 Wh·kg^-1 and 778 m A·h^-1,respectively,outperforming the noble-metal-based Pt/C+Ir O₂ catalyst based battery.It also showed a durable long cycle life（1200 charge-discharge cycles）,and the charge-discharge voltage gap of Ni₅₀Fe₅₀@N-CNTs only about 0.76 V.In addition,such ZAB cell also demonstrated a superlong stable rechargeability over 200 h without structural deletoriation.（ii）The zinc-air battery using Ni₃Mn/CSs as the air cathode showed the best battery performance in the Ni_xMn_y/CSs series,the power density and rechargeability exceed the Pt/C+Ir O₂ catalyst based battery,presenting great promises for practical applications.