Preparation Of M-N_x-C Non-Noble Metal ORR Catalyst And Application In Zn-Air Battery

The energy crisis and increasing environmental pollution have forced people to seek environmentally friendly clean energy conversion technologies,and metal-air batteries and fuel cells have received increasing attention from researchers as high energy density and environmentally friendly clean energy conversion technologies.However,their development is currently limited by the high cost,low abundance and low stability of noble metal catalysts,so it is particularly important to develop cheap and efficient oxygen reduction reaction（ORR）and oxygen evolution reaction（OER）catalysts to replace traditional noble metal catalysts.In this thesis,non-precious metal catalysts were prepared by doping or modulating Covalent Organic Frameworks（COFs）and Metal Organic Frameworks（MOFs）with non-precious metals and improving catalytic activity,stability and methanol tolerance in the catalytic process,which consisted of four main parts as follows:1.COF-derived Fe-N_x nanocluster catalysts for Zn-air batteryPorous Fe-N_x nanoclusters/carbon catalysts were prepared by pyrolysis of Fe³⁺-containing CTF-PO71,and Fe-N_x nanoclusters were shown to be effective ORR active sites.By optimizing the synthesis conditions,the optimal catalyst(Fe_1.2NC-0.02-800)exhibited excellent performance in Zn-air batteries in terms of discharge voltage,power density and specific capacity.Fe_1.2NC-0.02-800 achieves a maximum power density of 210 mW cm^-2 at a current density of 330 m A cm^-2,exceeding the maximum power density of commercial Pt/C(170 mW cm^-2)at a current density of 240 m A cm^-2.The Fe_1.2NC-0.02-800 electrode has a specific capacity of 713.1 m A h g_Zn^-1,which is higher than that of commercial Pt/C(679.9 m A h g_Zn^-1).2.COF-derived Cu single-atom catalysts for Zn-air batterySingle-atom catalysts loaded on porous carbon were prepared by pyrolysis of Cu²⁺-chelated CTF-PO71.The Cu NC-800-U-1 catalyst has good catalytic activity,close to that of commercial Pt/C,but possesses higher stability and methanol tolerance than commercial Pt/C.The Cu NC-800-U-1 catalyst exhibited excellent performance when assembled into a zinc-air batteries with a peak power density of 187 mW cm^-2 at 270 m A cm^-2,which exceeding the maximum power density of commercial Pt/C(158 mW cm^-2)at a current density of 230 m A cm^-2.The specific capacity of Cu NC-800-U-1 is 740 m A h g_Zn^-1,which is higher than that of commercial Pt/C at 725 m A h g_Zn^-1,and the discharge voltage decay is relatively weak.3.Preparation of nitrogen-doped carbon catalysts from Mn²⁺-regulated ZIF-8 and applicationfor Zn-air batteryThe non-metallic NC catalysts were prepared by regulating the growth process of ZIF-8 by Mn²⁺,and then the metal was detached from the carbon carrier by lowering the boiling point of the metal by forming an alloy of Mn and Zn under high temperature conditions.The catalytic performance is close to that of commercial Pt/C,but its cycling stability and methanol tolerance are significantly better than that of commercial Pt/C.When assembled into Zn-air batteries,the performance is close to that of commercial Pt/C in terms of power density,discharge voltage under variable current discharge,and specific capacity.The open-circuit voltage of（Mn）NC-0.4-1100 is 1.33 V,which is close to the commercial Pt/C at 1.38V.The peak power density of 153 mW cm^-2 is achieved at current density of 281 m A cm^-2,which is close to the peak power density(167 mW cm^-2)reached by commercial Pt/C at 262m A cm^-2.The specific capacity of（Mn）NC-0.4-1100 is 740 m A h g_Zn^-1,which is close to the760 m A h g_Zn^-1 of commercial Pt/C.4.Preparation of bifunctional catalysts from Fe and Cu co-doped ZIF-8 and application for rechargeable Zn-air batteryThe Fe₁Cu₁-NC-900 catalyst prepared by Fe and Cu elemental co-doping of ZIF-8exhibited better performance than commercial Pt/C in terms of catalytic activity,stability and methanol tolerance.And it exhibits with a certain OER performance,which provides the possibility to assemble rechargeable Zn-air batteries.When assembled into Zn-air batteries,its power density,discharge voltage at different current densities,and specific capacity exhibit better performance than commercial Pt/C.In rechargeable testing,its cycling stability is better than that of the Pt/C+Ir O₂ combination.Fe₁Cu₁-NC-900 achieves a peak power density of 185 mW cm^-2 at a current density of 280 m A cm^-2,which is comparable to that of commercial Pt/C(166 mW cm^-2)at 255 m A cm^-2.The voltage retention of Fe₁Cu₁-NC-900 is significantly better than that of commercial Pt/C.The specific capacity of Fe₁Cu₁-NC-900 is 790 m A h g_Zn^-1 with better discharge voltage and less voltage decay,which is higher to commercial Pt/C at 760 m A h g_Zn^-1.In rechargeable testing,the batteries performance exhibited superiority over commercial Pt/C and Ir O₂ at 15-60 h.