| Proton exchange membrane fuel cell(PEMFC) represents one of the representative fuel cells. Due to its high efficiency, high power density fast startup and zero emission, it is supposed to be a promising energy source for mobile application.However, the prominent problems like high cost, low activity and durability, limit the commercialization of PEMFC. The electrocatalyst is considered to be the origin of the high cost and the low durability because of a large amount of platinum-based catalysts are used to catalyze the oxidation of hydrogen or other liquid fuel at the anode and to catalyze oxygen reduction reaction(ORR) at the cathode. To date, Pt-based catalyst is still the dominating material especially for ORR catalyst although its limited durability and high price greatly increase the cost of a PEMFC. Therefore, it is crucial to develop a highly active and cheap catalyst for the commercialization of PEMFC.This paper aims to prepare high stability and high durability non-precious metal catalyst for ORR instead of Pt catalyst. So as to achieve the destination of greatly reducing the cost of PEMFC, we proposed two kinds of methods to develop higher active and stable ORR catalyst based on non-precious metal composited with polymer.The obtained catalysts use non-precious metal to replace precious metals and to reap the same or better ORR performance at the same time. Based on the above recognition, in this thesis our research was carried out as follows:Chapter one firstly reviews the research progress of PEMFCs and the non-precious metal ORR catalysts. After that we introduce the construction of non-precious metal catalyst precursor components: carbon support, transition metal,azo polymer precursor. Then the reseach content is introduced in details.Chapter two illustrates the instruments and the chemical reagents used in the experiments, and briefly introduces the necessary preparation experiment as well,such as the pretreatment of raw materials which have been bought.In chapter three, we use fluidic acrylonitrile telomere(ANT) as precursor to prepare N and S dual-doped Co/ANT/C catalyst via a facile heat treatment of themixture of Co salt, ANT and carbon black. As such, the increasing contact area between ANT and cobalt salt leads to a highly catalytic activity toward oxygen reduction reaction. Most importantly, by using ANT as precursor, the catalyst showed a remarkable improvement in the onset potential and current density. Besides, the as-made Co/ANT/C catalyst at high loadings demonstrated a comparable catalytic activity with commercial expensive Pt/C. In addition, the catalyst participated promotes a direct four-electron reduction of O2 to OH- and long term operation stability in an alkaline medium. Owing to its superb ORR performance, low cost and facile synthesis approach, such prepared Co/ANT/C catalyst exhibits great potential applications in PEMFCs.In chapter four, by using BSA instead of ANT, we propose an effective synthetic route to prepare catalysts by introducing BSA as precursor. A novel kind of N/S-doped ORR catalyst(Fe/BSA/C) has been successfully synthesized by a simple hetero-doping procedure using low-cost and nontoxic BSA as the nitrogen and sulfur source. The entire synthesis is simple and environmentally friendly. The resulted Fe/BSA/C catalyst shows enhanced ORR activity comparable with commercial Pt/C catalyst and superior durability than Pt/C, which is attributed to the combined contributions by the hierarchical structure, high relative content of pyridinic N and favorable graphitic degree. The outstanding catalytic activity, stability, and environmental-friendly of Fe/BSA/C for ORR allow its direct use as the cathode ORR catalyst in PEMFCs. We report for the first time that the design and one-step synthesis of N and S dual-doped carbon material only by using Bovine Serum Albumin(BSA)as a doped agent. This work will pave the way to a large variety of carbonaceous materials promoted by using BSA as precursor. |
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