Synthesis Of Fe,Co-Based Subnano Cluster Catalysts And Their Oxygen Reduction Reaction Performance

Fuel cells are recognized as one of the most promising energy conversion devices to potentially the energy and environmental crisis.At present,the oxygen reduction reaction（ORR）of fuel cells is highly dependent on the precious metal Pt-based catalyst.But the high price and poor long-term stability of Pt make it difficult to meet the growing demands.Therefore,it is critical to develop simple and effective synthetic methods to prepare catalysts with high catalytic efficiency and stability.In this thesis,simple and efficient synthetic methods were developed to prepare non-precious metal iron and cobalt oxygen reduction electrocatalysts and their ORR catalytic activities were investigated.The main contents were listed as follows.（1）Iron-based nitrogen-doped carbon catalyst（Fe-NC）was prepared with glucose as carbon source,dicyandiamide as a nitrogen source,and ferric nitrate as an iron source by calcination at high temperatures.XRD,BET,TEM,and XPS characterizations,revealed that it had high metal exposure and was beneficial to mass transfer during the reaction.Fe-NC showed excellent alkaline ORR performance.The initial and half-wave potentials were measured to be 1.01 V and 0.86 V,respectively.The Tafel slope was calculated to be127.0 m V dec^-1.The kinetic current density at 0.80 V,0.85 V and 0.90 V was determined to be 4.63 m A cm^-2,2.41 m A cm^-2,and 1.18 m A cm^-2,respectively.Fe-NC catalyst showed improved electrocatalytic ORR activity than commercial Pt/C.In addition,Fe-NC catalyst has excellent stability after 10000 potential cycles,with half wave potential loss of merely16.2 m V.（2）Cobalt clusters were deposited onto nitrogen-doped carbon support by simple impregnation and high temperature pyrolysis treatments.XRD,BET,TEM,and XPS characterizations confirmed that the Co CNG has a higher metal exposure degree,which is beneficial to mass transfer in the reaction process.Co CNG catalyst showed good ORR activity and stability in alkaline electrolytes,with the onset potential and half-wave potential of Co CNG were 1.05 V and 0.92 V,respectively,and the activity decreased by only 7 m V after 10000 cycles.The results demonstrate that this catalyst can efficiently activate O₂ in an alkaline solution and generate OH^-through 4e^-transfer pathway.