Preparation And Mechanism Study Of Novel Non-noble-Metal Catalysts For Fuel Cells And Water Splitting

Comprehensive utilization of hydrogen energy via fuel cells and water electrolysis systems is an ideal system to realize sustainable development of human being.In this thesis,we focused on the exploration and preparation for novel non-noble-metal catalysts for fuel cell and water electrolysis system,and further explored their catalytic mechanism.The main results are as follows:1.We firstly fabricated a new class of low cost non-noble-metal catalysts(CPMPDA-NaCl)for oxygen reduction reaction without using any transition metals via a quite simple way.This novel catalyst performed outstanding ORR catalytic activity with a lowest overpotential in theory(0.369 V).In 0.1 M KOH aqueous solution,the limited diffusion current density reached 4.05 mA/cm'2,the half-wave potential was 0.905 V,hydrogen peroxide yield less than 7%and the calculation of single molecule obtained electron transfer number was 4.CPMPDA-NaCl even out performed Pt/C catalyst.2.We discovered a new class of N-doped carbon catalysts with the never-before-seen ion-coupled delocalized active sites(ICDASs),which are highly ORR active and even better than commercial Pt/C.3.The electron withdrawing ability of the N dopant could be enhanced by Na+-Cl-to impart positive charges to not only carbon atoms directly connected to the N-dopant but also those carbon atoms further away from the N-dopant to form the ion-coupled delocalized active site(ICDAS)consisting of-C+n-Cl--Na+-N--C+m-,leading to significantly improved ORR activity.4.Na+-Cl-dramatically enhances the ORR activity of nonactive quaternary-N doped carbon.As a result,the theoretical overpotential reduced from 1.08 V to 0.369 V5.Our design strategy and facile experimental approach for the large-area delocalized ORR active sites are useful for the design and development of various novel low-cost and high-efficient catalysts.6.We successfully constructed a structure that partially oxidized Co nanoparticles anchored in N-doped carbon regular dodecahedron frameworks(Co@Co3O4-NC)via a MOF-routed method.The Co3O4 shell works as efficient charge separate functional layer while the metallic Co inner core transport the separated charges immediately to N-carbon framework.Owing to its unique structure,charge separate/transport process speeded up thus the electrocatalytic activies dramatically enhanced.As a result,Co@Co3O4-NC was demonstrated to be a bifunctional HER/OER eletrocatalyst with excellent activity and stability performance.This together with its element abundant and facile fabricate method,makes Co@Co3O4-NC as a promising electrocatalyst for overall water splitting system in alkaline media.