Preparation And Properties Of Zinc-Iron-Sulfur Doped Carbon-Based Oxygen Reducyion Catalysts

To alleviate the current environmental crisis and energy problems,the large-scale application of highly efficient,stable and renewable energy sources such as fuel cells and zinc-air batteries are urgently needed.However,the slow reaction and poor stability of noble metal catalysts（Pt-based）,which is used as the air cathode of zinc-air batteries during the discharge process,limit its development of zinc-air batteries in a large scale.Therefore,it is urgent to develop the non-precious metal catalysts with low cost,high activity and long-term stability.In this work,zeolitic imidazole frameworks（ZIFs）have been used as precursors to prepare two ZIFs-derived carbon-based oxygen reduction reaction（ORR）catalysts,the main research contents are as follows:（1）A simple synthetic method is proposed to prepare the carbon-based ORR catalyst Fe-Zn S-N-C with a composite structure of Fe-N_x and Zn S nanoparticles.Electrochemical tests show that the Fe-Zn S-N-C catalyst exhibits excellent oxygen reduction activity(E_1/2=0.862 V)in 0.1M KOH compared to commercial Pt/C(E_1/2=0.846 V).Meanwhile,Fe-Zn S-N-C also shows superior stability and methanol resistance,as well as broader prospect for practical application.A series of characterizations reveal that the Fe-Zn S-N-C catalyst integrates the features of Fe-N_x and Zn S.Specifically,its abundant N content and defects,large specific surface area and optimal pore size distribution benefit for the ORR process.This chapter provides a simple and effective synthesis method and paves a way for the design of highly efficient ORR catalysts.（2）A lattice doping strategy has been developed to introduce Fe³⁺into Zn S particles(Zn_0.566Fe_0.434S),which is loaded onto carbon support to form the ORR catalyst Zn_0.566Fe_0.434S-N-C.Electrochemical tests showed that the catalytic activity of Zn_0.566Fe_0.434S-N-C in 0.1 M KOH was greatly improved(E_1/2=0.891 V)compared with commercial Pt/C(E_1/2=0.846V).Besides,the E_1/2 of Zn_0.566Fe_0.434S-N-C attains 0.788 V in 0.1 M HCl O₄solutions.Meanwhile,Zn_0.566Fe_0.434S-N-C also performs well in stability and methanol resistance.These results show that Fe³⁺is incorporated into the Zn S lattice to form Zn_0.566Fe_0.434S solid solutions by lattice doping,which significantly improves the catalytic activity of the catalyst.A series of characterization techniques confirm the successful preparation of Zn_0.566Fe_0.434S particles.Additionally,other metal ions(Co²⁺,Mn²⁺,Cu²⁺,etc.)verify the general applicability of this lattice doping method.The Zn_0.566Fe_0.434S-N-C catalyst possesses a peak power density of 240.98 m W cm^-2 and a stable operation for more than 180 hours at a current of 5 m A cm^-2 for the zinc-air battery,exhibiting great potential for practical application.The lattice doping strategy presented in this chapter provides new insights into the design of non-noble metal-based ORR catalysts.