Controlled Synthesis Of Novel Carbon-based Non-precious Metal Catalysts With High-Efficiency ORR Performance

As a novel clean energy device, fuel cells have advantages of high energy conversion efficiency, high power density, low operation temperature, fast start and Environmentally Friendly. However, due to the sluggish kinetics of the cathodic oxygen reduction reaction(ORR), precious metals such as Pt, Pd are needed to meet practical requirements. The high cost and poor durability are two major drawbacks hindering the widespread application of Pt-based catalysts. To overcome these problems, considerable attention has been paid to the development of non-precious metal ORR catalysts. Carbon-based non-precious metal ORR catalysts can effectively reduce the costs of fuel cells. So far, the existing non-precious metal electrocatalysts have poor catalytic activity and stability, which do not meet the requirement of practical applications in fuel cells. This thesis focus on the fabrication of carbon-based non precious metal ORR catalysts with new microstructures and composites. The main results are listed as follows:1. A new class of metal free catalysts based on graphene quantum dots(GQDs) supported by graphene nanoribbons(GNRs) has been developed through a one-step simultaneous reduction reaction, leading to ultrahigh performance for oxygen reduction via a 4e ORR process with an excellent electrocatalytic activity(higher limiting current density and lower overpotential than those of platinum), high selectivity and stability in alkaline media –comparable to the best metal-free and other ORR catalysts reported so far.2. Two types of Fe-/N- co-doped carbon-based catalysts(noted as Fe-N-C-pd and Fe-N-C-py, respectively) are controlled synthesized a novel in-situ reduction of halohydrocarbon by iron powder with the presence of pyridine and pyrrole, respectively. The study of ORR in alkaline media showed that the Fe-N-C-pd catalyst with higher pyridinic-N content exhibits stronger electrocatalytic activity than that of Fe-N-C-py catalysts with high content of pyrrolic-N. Impressively, the obtained Fe-N-C-pd and Fe-N-C-py catalysts have a much better tolerance to methanol crossover effect than that of commercial Pt-C catalysts.