Oxygen Catalysts And Zinc Electrode Interface For Rechargeable Zinc-Air Battery

In response to the goal of"double carbon",it is imperative to develop clean energy to gradually replace traditional fossil energy.Zinc-air batteries（ZABs）are regarded as one of the next-generation green and safe electrochemical energy storage systems,which has attracted great attention.The performance index of the battery is closely related to the oxygen catalytic efficiency of the positive electrode and the electrochemical interface.Developing cheap and high-performance electrocatalysts to replace commercial precious metals is a current research hotspot.Generally,the electrocatalytic performance is closely associated with the exposed active sites at the surface/interface.Atomic-engineering strategy can regulate the electronic structure of the surface/interface of nanomaterials,which is the key to improve the catalyitic activity.In addition,in order to meet the application requirements of quasi-solid-state（QSS）ZABs in extreme conditions,it is also important to develop gel electrolytes with good interface compatibility and temperature-tolerance.Based on the above problems,the basic scientific issues related to confinement catalysis with carbon encapsulation,anchoring atomic dispersion metal sites,constructing coordination structure,cationic doping and oxygen vacancy（V_o）double regulation,high-valence atomically dispersed metal doped hydroxide,and regulation of H-bond structure and electrochemical interface of gel electrolyte are investigated.The main research works and results are shown as follows:（1）Carbon encapsulation of FeCo alloy nanoparticle supported on graphite-N-dominated doped graphene catalyst（FeCo NP-NG）was prepared by a simple one-step solid-phase pyrolysis method.Compared to carbon encapsulation of single metal nanoparticle,FeCo NP-NG shows better oxygen reduction/oxygen evolution reaction（ORR/OER）bifunctional properties in alkaline medium.The bifunctional potential difference of FeCo NP-NG is only 0.68 V,which is better than the noble metal catalyst.Meanwhile,FeCo NP-NG has excellent electrocatalytic durability and structural stability.（2）The atomically dispersed Co sites anchored on the nitrogen-doped curved graphenes（Co SA-NDGs）catalyst were prepared by hydrothermal treatment and subsequent pyrolysis.The graphene curvature enhances the catalytic capability of Co-N₄ sites.Co SA-NDGs showed excellent ORR/OER performance with a low potential gap of0.71 V.By adjusting the H-bond structure in the gel electrolyte,the interface stability and temperature adaptability simultaneously.The assembled QSS ZABs achieve a record-level cycling rate performance(50 h@100 m A cm^-2)at room temperature.In addition,the QSS ZABs still maintains strong cycling stability at-60 and 60℃.（3）The atomically dispersed Mn sites anchored on nitrogen-doped porous carbon（Mn₁-NPC）were prepared by host-guest strategy and high-temperature treatment.Mn₁-NPC has Mn-N₄-C₁₂ coordination structure,abundant defective-edge,high specific surface area and high conductivity.It shows excellent alkaline ORR/OER performance with a bifunctional potential difference of as low as 0.685 V.Adjusting the polar groups of gel electrolytes can significantly improve interface stability and low-temperature tolerance.The assembled QSS ZABs demonstrates an extremely high critical current density of 8 m A cm^-2 at-40 ℃,a single battery can continue to discharge for 645 h with a pronounced capacity of1.29 Ah.（4）Ultrathin Fe-Co-O nanosheets（Fe-Co-O NSs）catalysts were prepared by cyano-bridged and wet chemical reduction strategy.The electronic structure of Co₃O₄ nanosheets was optimized via the combined introduction of Fe cation and oxygen vacancy（V_o）.The ultrathin nanosheets promote the sufficient exposure of surface-active sites and rapid charge transfer.The oxygen-deficient Fe-Co-O NSs display overpotential of 260 m V@10 m A cm^-2and Tafel slope of 53 m V dec^-1,outperforming those of noble metal catalysts.Meanwhile,the dual regulation of Ni substitution and V_o can also lead to an improved catalytic activity.（5）The atomically dispersed Mo dopedα-Co（OH）₂nanosheet（Mo-α-Co（OH）₂）was prepared by solvothermal method.The porosity and enlarged spacing in the nanosheets promote ion diffusion kinetic;the strong electron coupling between Mo andα-Co（OH）₂ makes that Co sites have high electron density and reduce OER overpotential.Mo-α-Co（OH）₂requiered a low overpotential of 232 m V to reach a current density of 10m A cm^-2.In situ Raman results show that high oxidation potential drive amorphization of Mo-α-Co（OH）₂.Reducing the charging voltage can improve the cyclinging stability of the battery.Meanwhile,the abundant polar groups in PAM-CNFs organohydrogel electrolyte have strong interaction with Zn²⁺and H₂O molecules,exhibiting excellent interfacial stability and ultra-low temperature tolerance.The high critical current densities of 6.0 and 1.5 m A cm^-2were achieved at-40 and-60℃for QSS ZABs,respectively;and the long lifespan of 900 and 200 cycles were achieved at 1 and 2 m A cm^-2at-60℃.