The Controlled Construction Of Highly Efficient Fe-based Transition Metal Electrocatalysts And Their Oxygen Reduction Reaction

The oxygen reduction reaction?ORR?plays a crucial role in the metal-air batteries and fuel cells.ORR in cathode is kinetically sluggish and it severely rely on the platinum group metal electrocatalysts.Nevertheless,the large-scale commercialization of metal-air batteries and fuel cells is hampered by the limited natural abundance,exorbitant price and relatively low durability.Therefore,development of cost-effective and highly efficient platinum group metal-free ORR electrocatalysts is of significant importance and urgently needed for their wholesale application.Herein,by employing the Fe-based nonprecious metal catalysts as the research object,by optimizing the synthesis condition to control the morphologies of the electrocatalysts,to acquire the classic electrocatalytic activity.It also has significant importance to investigate the relationship between the composition and electrocatalytic properties of the as-developed electrocatalysts.We further reveal their applications of the synthesized electrocatalyst in zinc-air batteries.The key research results are show as follows:?1?We report a highly efficient ORR electrocatalyst with rich Fe-N_x active sites and Fe nanocrystals decorated three dimension?3D?porous carbonaceous matrix by a rational designed general carbonaceous spheres templated and vapour deposition assistanted strategy.The reason for the enhanced ORR performance of the synthesized electrocatalyst was revealed.The as result electrocatalyst with high specific surface area and active N content exhibits outstanding ORR activity with large onset potential,half-wave potential,superior stability and excellent methanol tolerance capacity in alkaline media,which is much better than the state-of-the-art catalysts Pt/C.?2?A facile and cost-efficient sol-gel route is developed for making Fe/Fe₃C@Fe-N_x-C bifunctional oxygen electrocatalyst.The efficient oxygen electrocatalyst consists of dispersed Fe/Fe₃C nanoparticles and Fe-N_x active sites.The Fe/Fe3C@Fe-Nx-C electrocatalyst exhibits superb ORR/OERperformance along with significantly enhanced durability,excellent methanol tolerance.The mechanism of ORR/OER performance enhancement was revealed,and the application of ORR/OER bifunctional electrocatalyst in Zn-air battery was explored.The coexistence of porous structure,high content of Fe-N_x active sites and Fe/Fe₃C boost the electrocatalytic activity.The constructed Zn-air battery based on Fe/Fe₃C@Fe-N_x-C air cathode possesses exceptionally good peak power density and outstanding cycling stability with a small potential gap.?3?We develop a superior nonprecious bifunctional oxygen electrocatalyst Fe/Fe3C-N-C,fabricated through cultivating pyridinic N riched carbon nanotubes?CNTs?doped with high density Fe-N_x active sites and Fe/Fe₃C nanoparticles.This special tubular structure effectively avoids the corrosion of Fe/Fe3C nanoparticles in acid and alkaline media and the agglomeration of these nanoparticles.The bifunctional oxygen electrocatalyst with tubular structure developed by high temperature carbonization process has high density active sites and good conductivity.The mechanism of ORR/OER performance enhancement was revealed,and the application of ORR/OER bifunctional electrocatalyst in Zn-air battery was explored.It is revealed that Fe/Fe3C nanoparticles and Fe-Nx active sites play synergistic effect on boosting the ORR/OER electrocatalytic activity.Zn-air battery assembled with tubular Fe/Fe3C-N-C high efficiency oxygen electrocatalyst as air cathode exhibits excellent power density and charge-discharge cycle stability.