Preparation And Electrocatalytic Activity Of Transition Metal-Nitrogen-Doped Porous Carbon Materials In Oxygen Reduction Reaction

Recenetly,transition metal-nitrogen-doped carbon（M-N-C）materials have attracted wide attention as one of the most promising candidate materials to replace noble metal-based catalysts in the field of oxygen reduction reaction（ORR）electrocatalysis owing to their adjustable composition and morphology,excellent electrocatalytic activity and stability.Although significant progress has been made in the development of M-N-C materials,it is still a challenge to increase the ORR performance of M-N-C by compositional and structural engineering.Therefore,in this dissertation,two kinds of electrocatalysts were rationally designed and prepared considering the compositional and morphological tailoring of M-N-C,and the electrocatalytic performance for oxygen reduction reaction of the resulting novel M-N-C was studied.The major research results are as follows:（1）Preparation and ORR performance of leaf-like porous carbon nanosheets（denoted Co,Zn/N,S-LPCS）derived from core-shelled ZIF-L_Co/Zn@TCA.By optimizing Co/Zn ratio and TCA amount,the core-shelled ZIF-L_Co/Zn@TCA composite was first synthesized through the coordination interaction between Co²⁺and–SH.Sequentially,the pyrolysis of ZIF-L_Co/Zn@TCA yielded Co,Zn/N,S-LPCS with hierarchical porosity and large specific surface area.The resulting Co,Zn/N,S-LPCS electrocatalyst exhibited higher ORR performance than the counterparts of Co,Zn/NC（no TCA）and Co/N,S-LPCS（no Zn）.Most importantly,the half-wave potential(E_1/2)of Co,Zn/N,S-LPCS was 30 m V larger than Pt/C in alkaline electrolyte,and close to Pt/C in acidic electrolyte.Notably,the long-time stability and anti-methanol property of the Co,Zn/N,S-LPCS largely outperformed Pt/C.The Co,Zn/N,S-LPCS-based primary Zn-air battery displayed a open-circuit voltage of 1.52 V,a specific capacity of 808.9 m Ah g_Zn^-1,and a power density of 106m W cm^-2that close to Pt/C-based device.The remarkable performance of the Co,Zn/N,S-LPCS electrocatalyst stems from the synergetic effect of multi-doping,hierarchical porosity,large specific surface area and 2D leaf-like architecture.（2）Preparation and ORR performance of porous carbon nanosheets derived from polydopamine（PDA）.At first,porous Fe-PDA nanospheres were crafted through emulsion assembly of F127 and trimethylbenzene（TMB）combined with the polymerization of dopamine.Cobalt salts and melamine were then added,forming a Co-melamine complex,which was interacted with Fe-PDA and yielded the hybrid materials Fe-PDA@Co@melamine.Subsequently,Fe,Co and N codoped porous carbon（denoted Fe₃N-FeCo@NC）were obtained by the pyrolysis of Fe-PDA@Co@melamine.The resulting Fe₃N-FeCo@NC displayed outstanding ORR performance.The onset potential(E_on)and the half-wave potential(E_1/2)of Fe₃N-FeCo@NC（1.05 V,0.88 V）were higher than that of Pt/C(E_on=0.97 V,E_1/2=0.85 V),and the limiting current density（J_L）was comparable to Pt/C.Notably,the long-time stability and anti-methanol property of the Fe₃N-FeCo@NC greatly outperformed Pt/C.The Fe₃N-FeCo@NC-based primary Zn-air battery displayed a open-circuit voltage of 1.50 V,a power density of 140.77 m W cm^-2and a specific capacity of 806.6 m Ah g_Zn^-1,which is better than those of Pt/C-based device.The excellent ORR performance of the Fe₃N-FeCo@NC electrocatalyst is the direct consequence of hierarchical porosity,large specific surface area,hybrid spere/sheet structure and synergetic effect of Fe₃N and FeCo.