Bi_(2)Te_(3)-based materials have drawn much attention from the thermoelectric community due to their excellent thermoelectric performance near room temperature.However,the stability of existing n-type Bi_(2)(Te,Se)_(...Bi_(2)Te_(3)-based materials have drawn much attention from the thermoelectric community due to their excellent thermoelectric performance near room temperature.However,the stability of existing n-type Bi_(2)(Te,Se)_(3)materials is still low due to the evaporation energy of Se(37.70 kJ mol^(-1))being much lower than that of Te(52.55 kJ mol^(-1)).The evaporated Se from the material causes problems in interconnects of the module while degrading the efficiency.Here,we have developed a new approach for the high-performance and stable n-type Se-free Bi_(2)Te_(3)-based materials bymaximizing the electronic transport while suppressing the phonon transport,at the same time.Spontaneously generated FeTe_(2)nanoinclusions within the matrix during the melt-spinning and subsequent spark plasma sintering is the key to simultaneous engineering of the power factor and lattice thermal conductivity.The nanoinclusions change the fermi level of the matrix while intensifying the phonon scattering via nanoparticles.With a fine-tuning of the fermi level with Cu doping in the n-type Bi_(2)Te_(3)-0.02FeTe_(2),a high power factor of∼41×10^(-4)Wm^(-1)K^(-2)with an average zT of 1.01 at the temperature range 300-470 K are achieved,which are comparable to those obtained in n-type Bi_(2)(Te,Se)_(3)materials.The proposed approach enables the fabrication of high-performance n-type Bi_(2)Te_(3)-based materials without having to include volatile Se element,which guarantees the stability of the material.Consequently,widespread application of thermoelectric devices utilizing the n-type Bi_(2)Te_(3)-based materials will become possible.展开更多
The oxygen evolution reaction(OER)of electrochemical water splitting represents a source of hydrogen(H_(2))energy.Precious-metal-based RuO_(x)and IrO_(x)are expensive and degrade in the presence of electrolyte;thus,th...The oxygen evolution reaction(OER)of electrochemical water splitting represents a source of hydrogen(H_(2))energy.Precious-metal-based RuO_(x)and IrO_(x)are expensive and degrade in the presence of electrolyte;thus,the development of low-cost and eco-friendly OER electrocatalysts is needed.This review summarizes the recent status of the nonprecious manganese metal-oxide-based electrocatalysts with reference to nanostructure,defect engineering,hybrid composite formation,and core-shell formation to achieve efficient OER performance.In particular,we focus on the strategies used to lower the onset potential and the Tafel slope of the water oxidation process.Future prospects for the development of manganese-oxide-based electrocatalysts are discussed.展开更多
基金supported by Nano·Material Technology Development Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(2022M3H4A1A04076667)
文摘Bi_(2)Te_(3)-based materials have drawn much attention from the thermoelectric community due to their excellent thermoelectric performance near room temperature.However,the stability of existing n-type Bi_(2)(Te,Se)_(3)materials is still low due to the evaporation energy of Se(37.70 kJ mol^(-1))being much lower than that of Te(52.55 kJ mol^(-1)).The evaporated Se from the material causes problems in interconnects of the module while degrading the efficiency.Here,we have developed a new approach for the high-performance and stable n-type Se-free Bi_(2)Te_(3)-based materials bymaximizing the electronic transport while suppressing the phonon transport,at the same time.Spontaneously generated FeTe_(2)nanoinclusions within the matrix during the melt-spinning and subsequent spark plasma sintering is the key to simultaneous engineering of the power factor and lattice thermal conductivity.The nanoinclusions change the fermi level of the matrix while intensifying the phonon scattering via nanoparticles.With a fine-tuning of the fermi level with Cu doping in the n-type Bi_(2)Te_(3)-0.02FeTe_(2),a high power factor of∼41×10^(-4)Wm^(-1)K^(-2)with an average zT of 1.01 at the temperature range 300-470 K are achieved,which are comparable to those obtained in n-type Bi_(2)(Te,Se)_(3)materials.The proposed approach enables the fabrication of high-performance n-type Bi_(2)Te_(3)-based materials without having to include volatile Se element,which guarantees the stability of the material.Consequently,widespread application of thermoelectric devices utilizing the n-type Bi_(2)Te_(3)-based materials will become possible.
基金This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(NRF-2018R1A6A1A03024962,NRF-2019R111A3A01041454).
文摘The oxygen evolution reaction(OER)of electrochemical water splitting represents a source of hydrogen(H_(2))energy.Precious-metal-based RuO_(x)and IrO_(x)are expensive and degrade in the presence of electrolyte;thus,the development of low-cost and eco-friendly OER electrocatalysts is needed.This review summarizes the recent status of the nonprecious manganese metal-oxide-based electrocatalysts with reference to nanostructure,defect engineering,hybrid composite formation,and core-shell formation to achieve efficient OER performance.In particular,we focus on the strategies used to lower the onset potential and the Tafel slope of the water oxidation process.Future prospects for the development of manganese-oxide-based electrocatalysts are discussed.
