Covalent Triazine Frameworks Anchored With Transition Metal Oxides Nanoparticles For Oxygen Reduction Reaction

Oxygen reduction reaction（ORR）is an important process in energy conversion devices,such as proton exchange membrane fuel cell and metal–air cell.Developing efficient,durable,and low-cost non-precious catalysts is crucial to commercialize the energy conversion devices.In this study,a novel hybrid ORR catalyst of transition metal oxides（TMOs）and covalent triazine framework（CTF）was prepared by in-situ growth of TMOs nanoparticles on CTF using the hydrothermal method,which exhibit synergistic catalytic effect.The main results of the thesis are shown below:（1）CTFs were synthesized by heating from 400 to 700°C using ionothermal method to explore the temperature influence for ORR activity.Electrochemical test revealed that the ORR activity improved with synthesis temperature increasing.CTF700 materials showed the highest ORR activity,whose half-wave potential is 0.79V and diffusion–limited current density is 3.98 mA cm^-2.Subsequently,Co₃O₄/CTFs hybrids were prepared using CTF400,CTF600 and CTF700.And Co₃O₄/CTF700hybrid also showed the best ORR activity.（2）A series of Co₃O₄/CTF700 hybrids were synthesized by hydrothermal method to explore the influence of Co₃O₄ contents for ORR activity and synergistic effect.XRD,TEM,XPS,BET and TGA results confirmed that Co₃O₄ nanoparticles were anchored on CTF700 materials successfully.Systematical electrochemical test revealed Co₃O₄/CTF700-1:1 hybrid exhibited the synergistic effect.The half-wave potential and diffusion–limited current density are 0.84 V and 5.43 mA cm^-2,respectively.And it shows the lowest Tafel slope,which is 44.0 mV dec^-1.All the results suggested it has the best ORR catalytic activity.The methanol resistance test result indicates Co₃O₄/CTF700-1:1 hybrid has excellent tolerance to methanol.And the stability test showed the relative current of Co₃O₄/CTF700-1:1 dropped to 91.8%after working for36000 s,which indicating it has better durability in alkaline solution than commercial Pt/C.（3）Mn₃O₄/CTFs hybrids were prepared to explore the ORR activity of hybrids combined by CTF700 and other transition metal oxides.Electrochemical test results indicate Mn₃O₄/CTF700-1:2 hybrid has the relative high half-wave potential and lowest Tafel slope.Notably,its diffusion–limited current density improved obviously,which value is 5.94 mA cm^-2.Meanwhile,it also has better tolerance to methanol and durability in alkaline solution than commercial Pt/C.