| Zn-air batteries（ZABs）are regarded as promising alternatives to address both energy conversion and environmental pollution issues,due to their plentiful Zn reserves,high theoretical energy,and excellent reliability.As a discharging half-reaction in ZABs,the high overpotentials and the sluggish kinetics of oxygen reduction reaction（ORR）severely restrict the large-scale application of ZABs.Precious metal Pt is widely used as an ORR electrocatalyst due to its excellent performance,but the expensive price and low availability on the planet are the actual obstacles to the development of fuel cells.To tackle this issue,the design of p H-universal ORR electrocatalysts with low cost,performance,and stability close to platinum is highly anticipated.The main contents are as follows:（1）Due to its aqueous phase manufacturing process,two-dimensional shape,and abundance of coordination unsaturated sites on its outer surface,two-dimensional leafy ZIF-L has garnered increased attention in recent years.In Chapter 2,by precisely regulating the metal ratio（Zn,Co）of ZIF-Ls and employing them as precursors,this article presents for the first time a method for Co S2 nanoparticles encapsulated in N-doped carbon hybrids（Co S2@NC-X）.Serves as a dual-functional electrocatalyst.Co S2@NC-60 exhibits outstanding activity and high stability for ORR and OER because of the synergistic effect of hierarchical porous structure,Co S2 nanoparticles,and the core-shell structure generated after heteroatom doping.The half-wave potential of ORR is 0.84 V（relative to RHE）,compared with RHE of OER,when driving 10 m A cm-2current,the over-potential is 350 m V.Also,utilizing Co S2@NC-60 as an air cathode catalyst,and its power density of 170.6 m W cm-2 demonstrates good performance and long-term stability（550 hours）.（2）The research will focus our research on monoatomic ORR catalysts in Chapter3.In-situ methods of a double-layered leaf-like structure（ZIF-L@PDA）with dopamine hydrochloride-assisted precursor ZIF-L,in which Fephen grows on the prepared ZIF-L@PDA extranuclear（ZIF-L@PDA-Fephen）to prepared a defect-rich single Fe spot catalyst loaded on CN carrier（Fe-N4@NC-PCSs）.After research,it was found that the manufactured Fe-N4@NC-PCSs ORR performance of the catalyst is outstanding across the p H-universal.In comparison to RHE,the half-wave potential(E1/2)of 0.1 mol/L KOH solution is 0.947 V,0.5 mol/L H2SO4 is 0.77 V,and 0.1 mol/L PBS is 0.8 V.According to the test results in this chapter,it can be inferred that ORR activity in the p H-universal range is due to the abundant defects generated by the evaporation of metallic zinc during the entire pyrolysis process,which reveals that the increasing defects will decrease the delocalizedπelectron stability,increase the Lewis alkalinity of the CN substrate,optimize the orbital（dz2）and the binding ability of the Fe active substance and the reactive substance.（3）N,S co-doped Fe single atom embedded porous carbon nanosheets/carbon nanotubes were prepared by pyrolysis of ZIF-L impregnated with iron salts（Fe-NX@NSCST-ZL）in chapter 4.The created electrocatalyst is rich in monoatomic active sites,porous structure,and has a large specific surface area of 937 m2 g-1.Fe-NX@NSCST-ZL performs satisfactorily in terms of ORR when the catalyst loading is0.383 mg cm-2.Compared to RHE,the half-wave potential of the solution(E1/2)is 0.95V in 0.1 mol/L KOH,0.77 V in 0.5 mol/L H2SO4,and 0.74 V in 0.1 mol/L PBS.The constructed liquid Zn-air battery and all-solid-state flexible exhibits impressive performance,particularly large power density and outstanding stability tests,surpassing the Pt/C&Ru O2-based battery.It is striking that the Fe-NX@NSCST-ZL-based Zn-air battery demonstrated stable operation for 765 h with a discharge/charge gap of 0.85～0.92 V.These findings demonstrate that atom-doping and morphological control can significantly enhance the ORR performance of monoatomic catalysts. |
PDF Full Text Request