Developing high-performance electrode materials is critical for sustainable energy devices including fuel cells, water electrolyzers, and metal-air batteries, which are based on water/oxygen electrocatalysis. The focus of the thesis is on two kinds of energy materials, namely, perovskite oxides and carbon. Defect engineering methods are utilized to adjust their structural, electronic, and electrocatalytic properties, to make highly-active electrode materials. The relationship among structure, property, and activity is also clarified. For perovskite oxides, the effect of dopants in either A-site or B-site is systematically investigated on a model parent material, i.e., BaFeO_3-δ, for solid oxide fuel cell (SOFC) operation. A novel isovalent/lower-valence co-doping strategy is furt...[ Read more ]

Developing high-performance electrode materials is critical for sustainable energy devices including fuel cells, water electrolyzers, and metal-air batteries, which are based on water/oxygen electrocatalysis. The focus of the thesis is on two kinds of energy materials, namely, perovskite oxides and carbon. Defect engineering methods are utilized to adjust their structural, electronic, and electrocatalytic properties, to make highly-active electrode materials. The relationship among structure, property, and activity is also clarified. For perovskite oxides, the effect of dopants in either A-site or B-site is systematically investigated on a model parent material, i.e., BaFeO_3-δ, for solid oxide fuel cell (SOFC) operation. A novel isovalent/lower-valence co-doping strategy is further proposed to prepare a highly active SOFC cathode material, i.e., Ba_0.95Ca_0.05Fe_0.95In_0.05O_3-δ. In addition to high-temperature SOFC applications, a layered double perovskite (NdBaMn₂O_5.5) is used as a room-temperature water splitting catalyst that produces hydrogen. In that regard, the role of oxygen vacancies is carefully investigated on the water electrolysis activity of perovskite oxides. Even though the intrinsic activity of perovskite oxides for room-temperature electrolysis is high, they suffer from the shortcomings of low surface areas and electrical conductivities. Carbon materials can solve these problems. Regarding carbons, metallic and non-metallic heteroatoms are introduced into the carbon material framework to modify their electronic structure and enhance the number of active sites. Finally, A perovskite oxide and carbon are combined to make full use of their potential and obtain a promising bifunctional electrode material, i.e., Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ/N-doped carbon hybrid, for reversible oxygen electrocatalysis. This thesis will contribute to the rational design of highly-active electrode materials and accelerate the commercialization of those sustainable energy devices.