Development of active iron based water oxidation for designing an ideal artificial photosynthesis devices operating under benign neutral pH is highly demanded. We investigated the electrocatalytic activity of Ruddlesd...Development of active iron based water oxidation for designing an ideal artificial photosynthesis devices operating under benign neutral pH is highly demanded. We investigated the electrocatalytic activity of Ruddlesden-Pop-per-type strontium ferrite (Sr3Fe2O7) toward the oxygen evolution reaction (OER). Owing to the temperature-dependent efficiency of the charge disproportionation of Fe4+, the OER activity of Sr3Fe2O7 varied with the temperature, and the onset potential for the OER at a neutral pH underwent a negative shift of approximately 200 mV by increasing the temperature for the stabilization of Fe4+. When metal substitution was made to Sr3Fe2O7 for stabilizing Fe4+ at room temperature, the temperature dependence of the OER activity disappeared and the OER was driven at a small overpotential without increasing the temperature, indicating that the stabilization of Fe4+ is substantially important for achieving high OER activity.展开更多
Rhodium oxides, including a misfitlayered structure with alternate stacking of a rock salttype layer and a hexagonal RhO2 layer, are expected to have good thermoelectric properties. Among them, the thermoelectric prop...Rhodium oxides, including a misfitlayered structure with alternate stacking of a rock salttype layer and a hexagonal RhO2 layer, are expected to have good thermoelectric properties. Among them, the thermoelectric properties (electrical conductivity (σ), Seebeck coefficient (S), Figure of merit (ZT) and calculated thermal conductivity (κ) by S, σ, ZT, and absolute temperature (T)) of bismuth-based rhodium oxides ((Bi1-x,Pbx) 2Sr2Rh2Oy, x = 0 and 0.02, hereafter BSR and BPSR, respectively) were investigated. In comparison with Bi2Sr2Co2Oy (BSC) at 700°C, S and κ enhanced (increased S, 110 (BSR) and 105 μV K-1 (BPSR) from 85 μV K-1 (BSC) and decreased κ, 0.32 (BSR) and 0.50 W m-1 K-1 (BPSR) from 1.75 W m-1 K-1 (BSC)), whereas σ decreased (15 (BSR) and 31 S cm-1 (BPSR) from 70 S cm-1 (BSC)). BPSR reached the highest ZT value of 0.067 at 700°C, compared to those of 0.056 (BSR) and 0.027 (BSC).展开更多
Visible light-sensitive photocatalyst was developed by combining n-type silicon (n-Si) and tungsten trioxide (WO3, n-Si/WO3), yielding an ohmic contact in between. In this system, the ohmic contact acted as an electro...Visible light-sensitive photocatalyst was developed by combining n-type silicon (n-Si) and tungsten trioxide (WO3, n-Si/WO3), yielding an ohmic contact in between. In this system, the ohmic contact acted as an electron-and-hole mediator for the transfer of electrons and holes in the conduction band (CB) of WO3 and in the valence band (VB) of n-Si, respectively. Utilizing thus- constructed n-Si/WO3, the decomposition of 2-propanolto CO2 via acetone was achieved under visible light irradiation, by the contribution of holes in the VB of WO3 to decompose 2-propanol and the consumption of electrons in the CB of n-Si to reduce O2. The combination of p-type Si (p-Si) and WO3 (p-Si/ WO3), not the ohmic contact but the rectifying contact, was much less effective, compared to n-Si/WO3.展开更多
Visible light-induced two-step overall water-splitting was achieved by combining two types of photocatalysts, which were prepared by introducing foreign elements into rutile titanium dioxide (TiO2) and strontium titan...Visible light-induced two-step overall water-splitting was achieved by combining two types of photocatalysts, which were prepared by introducing foreign elements into rutile titanium dioxide (TiO2) and strontium titanate (SrTiO3) with a controlled electronic band structure. Rutile TiO2 and SrTiO3 were doped with chromium and tantalum (Cr,Ta-TiO2) and with rhodium (Rh-SrTiO3), respectively, to introduce visible-light sensitivity. Under irradiation with only visible light from a 420-nm LED lamp, the simultaneous liberation of hydrogen and oxygen with a molar ratio of ~2:1 was achieved with these two types of photocatalysts in the presence of iodate ion/iodide ion as a redox mediator.展开更多
Silver (Ag) and silver antimonate (AgSbO3) composites with different amounts of Sb3+ were synthesized by normal sintering with the aim of realizing a thermoelectric material. The electrical conductivity (σ) increased...Silver (Ag) and silver antimonate (AgSbO3) composites with different amounts of Sb3+ were synthesized by normal sintering with the aim of realizing a thermoelectric material. The electrical conductivity (σ) increased in the sample containing larger amount of Sb3+, whereas Seebeck coefficient (S) decreased. Producing Sb3+ caused the generation of oxygen vacancies in the material, and thus the corresponding donor levels are created in the bandgap, providing more conduction electrons. The conductive Ag particles would contribute to the conduction path as bypasses for carrier transport. The thermal conductivity (κ) was slightly lower in the presence of Ag defects in AgSbO3.展开更多
文摘Development of active iron based water oxidation for designing an ideal artificial photosynthesis devices operating under benign neutral pH is highly demanded. We investigated the electrocatalytic activity of Ruddlesden-Pop-per-type strontium ferrite (Sr3Fe2O7) toward the oxygen evolution reaction (OER). Owing to the temperature-dependent efficiency of the charge disproportionation of Fe4+, the OER activity of Sr3Fe2O7 varied with the temperature, and the onset potential for the OER at a neutral pH underwent a negative shift of approximately 200 mV by increasing the temperature for the stabilization of Fe4+. When metal substitution was made to Sr3Fe2O7 for stabilizing Fe4+ at room temperature, the temperature dependence of the OER activity disappeared and the OER was driven at a small overpotential without increasing the temperature, indicating that the stabilization of Fe4+ is substantially important for achieving high OER activity.
文摘Rhodium oxides, including a misfitlayered structure with alternate stacking of a rock salttype layer and a hexagonal RhO2 layer, are expected to have good thermoelectric properties. Among them, the thermoelectric properties (electrical conductivity (σ), Seebeck coefficient (S), Figure of merit (ZT) and calculated thermal conductivity (κ) by S, σ, ZT, and absolute temperature (T)) of bismuth-based rhodium oxides ((Bi1-x,Pbx) 2Sr2Rh2Oy, x = 0 and 0.02, hereafter BSR and BPSR, respectively) were investigated. In comparison with Bi2Sr2Co2Oy (BSC) at 700°C, S and κ enhanced (increased S, 110 (BSR) and 105 μV K-1 (BPSR) from 85 μV K-1 (BSC) and decreased κ, 0.32 (BSR) and 0.50 W m-1 K-1 (BPSR) from 1.75 W m-1 K-1 (BSC)), whereas σ decreased (15 (BSR) and 31 S cm-1 (BPSR) from 70 S cm-1 (BSC)). BPSR reached the highest ZT value of 0.067 at 700°C, compared to those of 0.056 (BSR) and 0.027 (BSC).
文摘Visible light-sensitive photocatalyst was developed by combining n-type silicon (n-Si) and tungsten trioxide (WO3, n-Si/WO3), yielding an ohmic contact in between. In this system, the ohmic contact acted as an electron-and-hole mediator for the transfer of electrons and holes in the conduction band (CB) of WO3 and in the valence band (VB) of n-Si, respectively. Utilizing thus- constructed n-Si/WO3, the decomposition of 2-propanolto CO2 via acetone was achieved under visible light irradiation, by the contribution of holes in the VB of WO3 to decompose 2-propanol and the consumption of electrons in the CB of n-Si to reduce O2. The combination of p-type Si (p-Si) and WO3 (p-Si/ WO3), not the ohmic contact but the rectifying contact, was much less effective, compared to n-Si/WO3.
文摘Visible light-induced two-step overall water-splitting was achieved by combining two types of photocatalysts, which were prepared by introducing foreign elements into rutile titanium dioxide (TiO2) and strontium titanate (SrTiO3) with a controlled electronic band structure. Rutile TiO2 and SrTiO3 were doped with chromium and tantalum (Cr,Ta-TiO2) and with rhodium (Rh-SrTiO3), respectively, to introduce visible-light sensitivity. Under irradiation with only visible light from a 420-nm LED lamp, the simultaneous liberation of hydrogen and oxygen with a molar ratio of ~2:1 was achieved with these two types of photocatalysts in the presence of iodate ion/iodide ion as a redox mediator.
文摘Silver (Ag) and silver antimonate (AgSbO3) composites with different amounts of Sb3+ were synthesized by normal sintering with the aim of realizing a thermoelectric material. The electrical conductivity (σ) increased in the sample containing larger amount of Sb3+, whereas Seebeck coefficient (S) decreased. Producing Sb3+ caused the generation of oxygen vacancies in the material, and thus the corresponding donor levels are created in the bandgap, providing more conduction electrons. The conductive Ag particles would contribute to the conduction path as bypasses for carrier transport. The thermal conductivity (κ) was slightly lower in the presence of Ag defects in AgSbO3.
