Design,Preparation Of Cobalt-Based Oxide Coupled With N-rGO Bifunctional Materials And Their Photothermal-Enhanced Electrocatalytic Performance

Oxygen reduction reaction（ORR）and oxygen evolution reaction（OER）are crucial for rechargeable metal-air batteries.In order to improve their efficiency,people have been dedicated to develop highly active OER and ORR bifunctional oxygen electrode catalysts.However,traditional noble-metal electrocatalysts only exhibit excellent performance for ORR or OER.In addition,they possess high cost,poor stability and other problems,which limited the practical use of catalysts containing noble-metal.So,it is highly desirable to develop low-cost and durable bifunctional electrocatalysts with high ORR and OER activity.To this end,nanostructured cobalt-based materials such as cobalt oxide（Co₃O₄）have been widely studied,showing huge potential as efficient catalysts.In order to further promote electrocatalytic properties of the cobalt-base materials,their nanostructure design and mixture with high conductive non-metal heteroatom doped carbon materials can greatly enhance the catalytic activity by altering its electrochemical structure.What’s more,under near-infrared light irradiation,the photothermal composite catalysts can achieve in-situ self-heating by the intrinsic highly efficient non-radiative relaxation,which can improve their originally slow kinetics of OER and ORR.Here,we designed and prepared a series of cobalt-based oxide/nitrogen-doped redox graphene（N-r GO）materials with photothermal effect.Under the irradiation of near-infrared light,cobalt-based oxide/N-r GO electrode shows excellent electrocatalytic performance.The specific research results are as follows:1.Using cobalt acetate as cobalt source,ammonia as nitrogen source and graphene as carbon source,a series of Co₃O₄/N-r GO composite nanomaterials were synthesized by hydrothermal method.The experimental results showed that Co₃O₄/N-r GO material has excellent ORR and OER properties in alkaline medium under the irradiation of near-infrared light.The overpotential of light-assisted OER decreased from 299m V to 255 m V at the current density of 10 m A cm^-2,and the Tafel slope decreased from 141 m V dec^-1 to 87 m V dec^-1.The properties of light-assisted ORR were shown as follows:the onset potential of the material was 0.915V（vs RHE）with a better half-wave potential（0.835 V vs RHE）.It also has improved methanol tolerance and stability.Based on the ORR/OER bifunctional electrocatalyst,a high performance zinc-air battery was constructed.Under the light conditions,the power density reached 299m W/cm² with a specific capacity of 763 m A h g^-1,and after 180 hours of the charge-discharge,there was no obvious damping,indicating good stability.2.In order to further improve the ORR/OER properties of bifunctional cobalt oxide/N-r GO composite,high-performance Co O/Co₃O₄/N-doped redox graphene（N-r GO）bifunctional catalysts were synthesized using a series of linear PAA-b-PS as the ligand,which was prepared by ATRP,and cobalt acetate as the cobalt source,through thermal decomposition,followed by combination with N-r GO.Under light irradiation,the experimental results showed that the OER overpotential was 220 m V at the current density of 10 m A cm^-2.For the ORR,the material has an onset potential of 0.922 V（vs RHE）and a half-wave potential of 0.752 V（vs RHE）,as well as excellent stability and methanol tolerance under light conditions.