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RESEARCH ARTICLE|174 Article(s)
Shouchao ZHANG, Hongyu CHEN, Hongfei LIU, Yu YANG, Xin LI, and Defeng LIU
High energy particle bombardment of silicon carbide can lead to the accumulation of defects and lattice disorder, which can negatively affect physical property and reduce lifetime of SiC devices. Thus, it is essential to systematically study the damage of SiC in different radiation environment. Herein, 6H-SiC was irradiated by neutrons at the fluence of 5.74×1018, 1.74×1019, 2.58×1020 and 1.27×1021 n/cm2, and then annealed. Changes in lattice parameters from post-irradiation isochronal annealing for 30 min in the range of 500-1650 ℃ were measured using X-ray single crystal diffraction. The results showed that the lattice swelling and recovery behavior were isotropic. Based on the swelling data, it was concluded that the neutron irradiation-induced defects in 6H-SiC were primarity point defects. Both intrinsic and irradiation defects can introduce defect energy levels, which were mainly caused by vacancies and led to the absorption band edge redshift and band gap narrowing of SiC. The defect energy levels of these vacancies and vacancy-associated defects were determined by absorption spectra, luminescence spectra and Raman spectra. Experiments and first principles calculation showed that the silicon vacancies introduced defect levels above the valence band, while the carbon vacancies introduced levels below the conduction band. The infrared absorption at 1382 nm and 1685 nm and the emission at 550 nm of unirradiated 6H-SiC were mainly due to the intrinsic carbon vacancies. The luminescence of post-irradiated SiC at 415, 440 and 470 nm was mainly due to the silicon vacancy produced by irradiation and its related defect configuration. All above data revealed the luminescence mechanism of SiC based on the charge state and the defect energy level distribution. High energy particle bombardment of silicon carbide can lead to the accumulation of defects and lattice disorder, which can negatively affect physical property and reduce lifetime of SiC devices. Thus, it is essential to systematically study the damage of SiC in different radiation environment. Herein, 6H-SiC was irradiated by neutrons at the fluence of 5.74×1018, 1.74×1019, 2.58×1020 and 1.27×1021 n/cm2, and then annealed. Changes in lattice parameters from post-irradiation isochronal annealing for 30 min in the range of 500-1650 ℃ were measured using X-ray single crystal diffraction. The results showed that the lattice swelling and recovery behavior were isotropic. Based on the swelling data, it was concluded that the neutron irradiation-induced defects in 6H-SiC were primarity point defects. Both intrinsic and irradiation defects can introduce defect energy levels, which were mainly caused by vacancies and led to the absorption band edge redshift and band gap narrowing of SiC. The defect energy levels of these vacancies and vacancy-associated defects were determined by absorption spectra, luminescence spectra and Raman spectra. Experiments and first principles calculation showed that the silicon vacancies introduced defect levels above the valence band, while the carbon vacancies introduced levels below the conduction band. The infrared absorption at 1382 nm and 1685 nm and the emission at 550 nm of unirradiated 6H-SiC were mainly due to the intrinsic carbon vacancies. The luminescence of post-irradiated SiC at 415, 440 and 470 nm was mainly due to the silicon vacancy produced by irradiation and its related defect configuration. All above data revealed the luminescence mechanism of SiC based on the charge state and the defect energy level distribution.
Journal of Inorganic Materials
- Publication Date: Feb. 07, 2023
- Vol. 38, Issue 6, 678 (2023)
Shiyi WANG, Aihu FENG, Xiaoyan LI, and Yun YU
Ti3C2Tx MXene is a potential adsorbent of heavy metal ions due to its two-dimensional layered structure and abundant surface functional groups. However, it has disadvantages of limited layer spacing and poor stability in aqueous solution. Here, the modification strategy of Ti3C2Tx was explored to improve its chemical stability and ion adsorption capacity among which Fe3O4-Ti3C2Tx(FeMX) adsorbent with different doping amounts of Fe3O4 were prepared by one-step hydrothermal method. The results showed that the maximum theoretical Pb(II) adsorption capacity of FeMX adsorbent could reach 210.54 mg/g. Its adsorption mechanism was further revealed that Fe3O4 nanoparticles were evenly dispersed and intercalated between Ti3C2Tx nanosheets, which effectively increased specific surface area and layer spacing of Ti3C2Tx nanosheets, leading to improving Pb(II) removal ability. Therefore, this study provides a promising route for developing MXene matrix composites with excellent heavy metal ion adsorption properties. Ti3C2Tx MXene is a potential adsorbent of heavy metal ions due to its two-dimensional layered structure and abundant surface functional groups. However, it has disadvantages of limited layer spacing and poor stability in aqueous solution. Here, the modification strategy of Ti3C2Tx was explored to improve its chemical stability and ion adsorption capacity among which Fe3O4-Ti3C2Tx(FeMX) adsorbent with different doping amounts of Fe3O4 were prepared by one-step hydrothermal method. The results showed that the maximum theoretical Pb(II) adsorption capacity of FeMX adsorbent could reach 210.54 mg/g. Its adsorption mechanism was further revealed that Fe3O4 nanoparticles were evenly dispersed and intercalated between Ti3C2Tx nanosheets, which effectively increased specific surface area and layer spacing of Ti3C2Tx nanosheets, leading to improving Pb(II) removal ability. Therefore, this study provides a promising route for developing MXene matrix composites with excellent heavy metal ion adsorption properties.
Journal of Inorganic Materials
- Publication Date: Jan. 11, 2023
- Vol. 38, Issue 5, 521 (2023)
Xiangsong ZHANG, Yetong LIU, Yongying WANG, Zirui WU, Zhenzhong LIU, Yi LI, and Juan YANG
Ammonia with low cost, easily liquefied and high volumetric energy density is an attractive carbon-free fuel. Utilizing ammonia as anodic fuel, direct ammonia fuel cells are showing great interests to researchers. However, such amazing fuel cell device is limited by the sluggish anodic ammonia oxidation reaction. In this work, PtIr alloy aerogels with a three-dimensional porous network structure were prepared by nanoparticles (NPs) self-assembled under a simple and surfactant-free conditions. This structure provided a rich open interconnected proton transport channel and additional catalytically active sites which contributed to the dehydrogenation process of NH3 molecules in ammonia electrocatalytic oxidation. An optimal AOR activity was achieved at the 80/20 molar ratio of Pt/Ir. Effects of NH3 concentration and operating temperature on catalyst's ammonia oxidation performance were studied, which revealed that the AOR performance of Pt80Ir20 alloy aerogel was improved with the increase of ammonia concentration or operating temperature. For example, the mass specific activity, at 0.50 V of the Pt80Ir20 alloy aerogel, was estimated to be 44.03 A·g-1, which was about 4 times as that of the ammonia concentration at 0.05 mol/L. In the case of operating temperature effect, the mass activity was estimated to be 148.73 A·g-1, which was almost 12 times as that of the temperature rising (from 25 ℃) to 80 ℃. Encouragingly, the onset potential of the optimal Pt80Ir20 alloy aerogel catalyst displayed about 40 mV reduction during such a temperature change. Further calculations using the Arrhenius equation showed that its activation energy was reduced by about 9.43 kJ·mol-1 as compared with commercial Pt/C. Moreover, its AOR stability was improved as evidenced by a loss of ~50.6% mass activity after 2000 potential cycles when compared with commercial Pt/C (~74.9%). Ammonia with low cost, easily liquefied and high volumetric energy density is an attractive carbon-free fuel. Utilizing ammonia as anodic fuel, direct ammonia fuel cells are showing great interests to researchers. However, such amazing fuel cell device is limited by the sluggish anodic ammonia oxidation reaction. In this work, PtIr alloy aerogels with a three-dimensional porous network structure were prepared by nanoparticles (NPs) self-assembled under a simple and surfactant-free conditions. This structure provided a rich open interconnected proton transport channel and additional catalytically active sites which contributed to the dehydrogenation process of NH3 molecules in ammonia electrocatalytic oxidation. An optimal AOR activity was achieved at the 80/20 molar ratio of Pt/Ir. Effects of NH3 concentration and operating temperature on catalyst's ammonia oxidation performance were studied, which revealed that the AOR performance of Pt80Ir20 alloy aerogel was improved with the increase of ammonia concentration or operating temperature. For example, the mass specific activity, at 0.50 V of the Pt80Ir20 alloy aerogel, was estimated to be 44.03 A·g-1, which was about 4 times as that of the ammonia concentration at 0.05 mol/L. In the case of operating temperature effect, the mass activity was estimated to be 148.73 A·g-1, which was almost 12 times as that of the temperature rising (from 25 ℃) to 80 ℃. Encouragingly, the onset potential of the optimal Pt80Ir20 alloy aerogel catalyst displayed about 40 mV reduction during such a temperature change. Further calculations using the Arrhenius equation showed that its activation energy was reduced by about 9.43 kJ·mol-1 as compared with commercial Pt/C. Moreover, its AOR stability was improved as evidenced by a loss of ~50.6% mass activity after 2000 potential cycles when compared with commercial Pt/C (~74.9%).
Journal of Inorganic Materials
- Publication Date: Jan. 11, 2023
- Vol. 38, Issue 5, 511 (2023)
Han SUN, Wenjun LI, Zixuan JIA, Yan ZHANG, Liying YIN, Wanqi JIE, and Yadong XU
Terahertz (THz) technology has immersing potential applications in industrial non-destructive testing, scientific research and military engineering. However, as the most commonly used THz emission and detection electro-optical material, the ZnTe single crystal growth still faces great challenges. In order to achieve ZnTe single crystals with large size, good homogeneity and high performance, an accelerated crucible rotation technique (ACRT) was introduced in growing ZnTe crystals by temperature gradient solution growth method (TGSG). Intrinsic ZnTe single crystals with high crystalline quality were successfully prepared. Through the simulation of flow field and solute distribution at different rotation speeds, the influence of ACRT technology on the stability of solid-liquid interface and Te inclusions distribution in crystal growth were investigated. During the crystal growth, the ACRT technology can effectively promote the melt flow, improve the solute mass transfer ability and stabilize the solid-liquid interface, which not only avoids the appearance of mixed phase zone at the crystal tail, but also reduces the number and size of Te inclusions in the crystal. With the further optimizing parameters, a large size ZnTe single crystal with a diameter of 60 mm was prepared. Meanwhile, the high response area of terahertz exceeding 90% faces due to the great uniformity of ZnTe crystal, which meant the edge effect being significantly limited and the ZnTe crystal meeting the commercial imaging requirements. Therefore, introduction of ACRT technology can provide a new strategy for preparation of ZnTe based electro-optical crystals. Terahertz (THz) technology has immersing potential applications in industrial non-destructive testing, scientific research and military engineering. However, as the most commonly used THz emission and detection electro-optical material, the ZnTe single crystal growth still faces great challenges. In order to achieve ZnTe single crystals with large size, good homogeneity and high performance, an accelerated crucible rotation technique (ACRT) was introduced in growing ZnTe crystals by temperature gradient solution growth method (TGSG). Intrinsic ZnTe single crystals with high crystalline quality were successfully prepared. Through the simulation of flow field and solute distribution at different rotation speeds, the influence of ACRT technology on the stability of solid-liquid interface and Te inclusions distribution in crystal growth were investigated. During the crystal growth, the ACRT technology can effectively promote the melt flow, improve the solute mass transfer ability and stabilize the solid-liquid interface, which not only avoids the appearance of mixed phase zone at the crystal tail, but also reduces the number and size of Te inclusions in the crystal. With the further optimizing parameters, a large size ZnTe single crystal with a diameter of 60 mm was prepared. Meanwhile, the high response area of terahertz exceeding 90% faces due to the great uniformity of ZnTe crystal, which meant the edge effect being significantly limited and the ZnTe crystal meeting the commercial imaging requirements. Therefore, introduction of ACRT technology can provide a new strategy for preparation of ZnTe based electro-optical crystals.
Journal of Inorganic Materials
- Publication Date: Jan. 11, 2023
- Vol. 38, Issue 3, 310 (2023)
Yicun LI, Xuedong LIU, Xiaobin HAO, Bing DAI, Jilei LYU, and Jiaqi ZHU
Single crystal diamond is a kind of crystal material with excellent performance, which has important application value in advanced scientific field. In the field of single crystal diamond growth by microwave plasma chemical vapor deposition (MPCVD), improvement of crystal growth rate is still a key challenge, although corrent high energy density plasma has been a ralatively effective method. In this work, a special plasma focusing structure was designed through magnetohydrodynamic (MHD) model simulation which then was used in the growth experiment based on the simulation. The plasma properties were studied by means of spectral analysis and plasma imaging, and late on single crystal diamond samples were synthesized. The simulation results show that the core electric field and electron density under focusing conditions were 2 times higher than those under normal conditions. The growth experiment results show that plasma with high energy density (793.7 W/cm3) is obtained under conventional microwave power (3500 W) and growth pressure (18 kPa), which is consistent with the model calculation results. We find that a certain amount of nitrogen instead of high energy density growth conditions can significantly change the growth morphology and affect the quality of the crystal. With those findings, we realize the growth rate of single crystal diamond up to 97.5 μm/h. Different from the way to obtain high energy density by increasing the growth pressure, single crystal diamond can be synthesized with high energy density under normal growth pressure and microwave power. Single crystal diamond is a kind of crystal material with excellent performance, which has important application value in advanced scientific field. In the field of single crystal diamond growth by microwave plasma chemical vapor deposition (MPCVD), improvement of crystal growth rate is still a key challenge, although corrent high energy density plasma has been a ralatively effective method. In this work, a special plasma focusing structure was designed through magnetohydrodynamic (MHD) model simulation which then was used in the growth experiment based on the simulation. The plasma properties were studied by means of spectral analysis and plasma imaging, and late on single crystal diamond samples were synthesized. The simulation results show that the core electric field and electron density under focusing conditions were 2 times higher than those under normal conditions. The growth experiment results show that plasma with high energy density (793.7 W/cm3) is obtained under conventional microwave power (3500 W) and growth pressure (18 kPa), which is consistent with the model calculation results. We find that a certain amount of nitrogen instead of high energy density growth conditions can significantly change the growth morphology and affect the quality of the crystal. With those findings, we realize the growth rate of single crystal diamond up to 97.5 μm/h. Different from the way to obtain high energy density by increasing the growth pressure, single crystal diamond can be synthesized with high energy density under normal growth pressure and microwave power.
Journal of Inorganic Materials
- Publication Date: Jan. 11, 2023
- Vol. 38, Issue 3, 303 (2023)
Xuejun QI, Jian ZHANG, Lei CHEN, Shaohan WANG, Xiang LI, Yong DU, and Junfeng CHEN
As a multifunctional opto-electro material, Bi12GeO20 crystal shows high-speed photorefractive response in visible range, excellent piezoelectric, acousto-optic, magneto-optic, optical rotation, and electro-optic properties, etc. Presently, Czochralski (Cz) method, which is commonly used to grow Bi12GeO20 crystals, has several bottle-necks, such as high growth cost, irregular crystal boule shapes, low growth yield, poor optical quality in large crystals, and small effective crystal cross-sectional area. In this study, large Bi12GeO20 crystals were firstly grown by using modified vertical Bridgman method in platinum crucibles and air atmosphere. Morphology, distribution, and constitutes of main macroscopic defects in as-grown Bi12GeO20 crystals were investigated, and the formation process and causes of the main macroscopic defects during the crystal growth were studied. Dendrite and tubular inclusions are two types of main macroscopic defects existed in as-grown Bi12GeO20 crystals. The formation of dendrite inclusions is closely related to the platinum corrosion, while the formation of tubular inclusions is associated with precipitation of platinum, a mismatch in the stacking of growth units due to instability of the seeding interface, and instability temperature field. Technical approaches to eliminate or reduce these two types of macroscopic defects during the growth using vertical Bridgman method were proposed. High optical quality, large Bi12GeO20 crystals with sizes up to 55 mm×55 mm×80 mm and significantly improved optical transmittance were grown reproducibly by reducing control temperature, decreasing period of melt preserved at high temperature, and selecting seed crystals with better quality. As a multifunctional opto-electro material, Bi12GeO20 crystal shows high-speed photorefractive response in visible range, excellent piezoelectric, acousto-optic, magneto-optic, optical rotation, and electro-optic properties, etc. Presently, Czochralski (Cz) method, which is commonly used to grow Bi12GeO20 crystals, has several bottle-necks, such as high growth cost, irregular crystal boule shapes, low growth yield, poor optical quality in large crystals, and small effective crystal cross-sectional area. In this study, large Bi12GeO20 crystals were firstly grown by using modified vertical Bridgman method in platinum crucibles and air atmosphere. Morphology, distribution, and constitutes of main macroscopic defects in as-grown Bi12GeO20 crystals were investigated, and the formation process and causes of the main macroscopic defects during the crystal growth were studied. Dendrite and tubular inclusions are two types of main macroscopic defects existed in as-grown Bi12GeO20 crystals. The formation of dendrite inclusions is closely related to the platinum corrosion, while the formation of tubular inclusions is associated with precipitation of platinum, a mismatch in the stacking of growth units due to instability of the seeding interface, and instability temperature field. Technical approaches to eliminate or reduce these two types of macroscopic defects during the growth using vertical Bridgman method were proposed. High optical quality, large Bi12GeO20 crystals with sizes up to 55 mm×55 mm×80 mm and significantly improved optical transmittance were grown reproducibly by reducing control temperature, decreasing period of melt preserved at high temperature, and selecting seed crystals with better quality.
Journal of Inorganic Materials
- Publication Date: Jan. 11, 2023
- Vol. 38, Issue 3, 280 (2023)
Chenhui LU, Wanyin GE, Panpan SONG, Panfeng ZHANG, Meimei XU, and Wei ZHANG
SiAlON-based phosphor has become a research hotspot due to its excellent chemical and physical stability. Especially in the LEDs field, it has received extensive attention in recent years. Rare earth doped SiAlON phosphor is expected to become a new generation of lighting source. However, due to the lack of cyan light emission, the color rendering performance of white-LED (wLED) is often insufficient. In this research, β-Si5AlON7:Eu phosphors were synthesized by the traditional high-temperature solid-state route. The structure, morphology, elements and valence states were examined. The wavelength range of excitation spectrum and emission spectrum of Si5AlON7:Eu, as well as the thermal quenching performance were studied. It is found that the excitation wavelength range covered the ultraviolet to blue region, and the emission spectrum is a typical broad feature of Eu2+ transition. At 300 ℃, the emitted light intensity of the sample can still reach about 40% that of the room temperature, while the thermal activation energy (Ea) reaches 3.7 eV. Compared with the commercial YAG:Ce3+ (YAG) phosphor, the thermal stability of Si5AlON7:Eu is improved. The wLED with high color rendering of Ra=87 is realized after compounding with the blue chip, and the corresponding color temperature reaches the warm white light range (CCT=4501 K). In this study, SiAlON-based cyan emission is realized, and the phosphor with excellent thermal stability is obtained. Compared with commercial YAG, it also has obvious advantages in the sustainability of luminescence. SiAlON-based phosphor has become a research hotspot due to its excellent chemical and physical stability. Especially in the LEDs field, it has received extensive attention in recent years. Rare earth doped SiAlON phosphor is expected to become a new generation of lighting source. However, due to the lack of cyan light emission, the color rendering performance of white-LED (wLED) is often insufficient. In this research, β-Si5AlON7:Eu phosphors were synthesized by the traditional high-temperature solid-state route. The structure, morphology, elements and valence states were examined. The wavelength range of excitation spectrum and emission spectrum of Si5AlON7:Eu, as well as the thermal quenching performance were studied. It is found that the excitation wavelength range covered the ultraviolet to blue region, and the emission spectrum is a typical broad feature of Eu2+ transition. At 300 ℃, the emitted light intensity of the sample can still reach about 40% that of the room temperature, while the thermal activation energy (Ea) reaches 3.7 eV. Compared with the commercial YAG:Ce3+ (YAG) phosphor, the thermal stability of Si5AlON7:Eu is improved. The wLED with high color rendering of Ra=87 is realized after compounding with the blue chip, and the corresponding color temperature reaches the warm white light range (CCT=4501 K). In this study, SiAlON-based cyan emission is realized, and the phosphor with excellent thermal stability is obtained. Compared with commercial YAG, it also has obvious advantages in the sustainability of luminescence.
Journal of Inorganic Materials
- Publication Date: Jan. 20, 2023
- Vol. 38, Issue 1, 97 (2023)
Ruyi WANG, Guoliang XU, Lei YANG, Chonghai DENG, Delin CHU, Miao ZHANG, and Zhaoqi SUN
Bismuth vanadate (BVO) can be used for photoelectrochemical (PEC) water splitting to hydrogen. However, suffering from its high charge-recombination and slow surface catalytic reaction, the PEC performance is far below the expectation, and the modification of the co-catalysts only on the electrode cannot overcome this disadvantage. Here, we report FeNiOx cocatalyst decorated on the BVO photoanode, which can restrict the onset potential and improve the PEC performance. Moreover, a more effective dual modified-BVO photoanode is formed, with the loading of g-C3N4 before decoration of FeNiOx cocatalyst. The type-II p-n heterojunction composed by g-C3N4 nanosheets and BVO, can inhibit recombination of photogenerated charge, and promote the separation of charge effectively at the electrode. Results show that the charge separation efficiency of the electrode reaches 88.2% after the insertion of g-C3N4, which is nearly 1.5 times that of BVO/FeNiOx (60.6%). Moreover, surface charge injection efficiency of the dual-modified BVO/g-C3N4/FeNiOx electrode reaches 90.2%, while the current density reaches 4.63 mA∙cm-2 at 1.23 V (vs. RHE). This work provides a facile approach to develope high performance photoanodes for PEC water splitting. Bismuth vanadate (BVO) can be used for photoelectrochemical (PEC) water splitting to hydrogen. However, suffering from its high charge-recombination and slow surface catalytic reaction, the PEC performance is far below the expectation, and the modification of the co-catalysts only on the electrode cannot overcome this disadvantage. Here, we report FeNiOx cocatalyst decorated on the BVO photoanode, which can restrict the onset potential and improve the PEC performance. Moreover, a more effective dual modified-BVO photoanode is formed, with the loading of g-C3N4 before decoration of FeNiOx cocatalyst. The type-II p-n heterojunction composed by g-C3N4 nanosheets and BVO, can inhibit recombination of photogenerated charge, and promote the separation of charge effectively at the electrode. Results show that the charge separation efficiency of the electrode reaches 88.2% after the insertion of g-C3N4, which is nearly 1.5 times that of BVO/FeNiOx (60.6%). Moreover, surface charge injection efficiency of the dual-modified BVO/g-C3N4/FeNiOx electrode reaches 90.2%, while the current density reaches 4.63 mA∙cm-2 at 1.23 V (vs. RHE). This work provides a facile approach to develope high performance photoanodes for PEC water splitting.
Journal of Inorganic Materials
- Publication Date: Jan. 20, 2023
- Vol. 38, Issue 1, 87 (2023)
Tao LI, Pengfei CAO, Litao HU, Yong XIA, Yi CHEN, Yuejun LIU, and Aokui SUN
Suffering from strong electrostatic interactions between divalent Zn2+ and host framework, molybdenum disulfide exhibits slow reaction kinetics as cathode for aqueous zinc-ion batteries. The narrow layer spacing of MoS2 is difficulty in accommodating large size insertion of hydrated Zn2+, resulting in a lower discharge specific capacity. Here, NH4+ expanded MoS2-N was prepared by a simple ammonia-assisted hydrothermal. The result showed that the ammonia promoted hydrolysis of thioacetamide to provide reduced S2- and generated a large amount of NH4+ as intercalating particles. These particles expanded the layer spacing of pristine MoS2 from 0.62 nm to 0.92 nm, greatly reducing the Zn2+ inserting energy barrier (with its charge transfer resistance of MoS2-N only 35 Ω), and increased the discharge specific capacity to 149.9 mAh·g-1 at the current density of 0.1 A·g-1, 2 times that of MoS2 electrode without NH4+ expansion. Consequently, it exhibited a stable discharge capacity of about 110 mAh·g-1 at the current density of 1.0 A·g-1 with nearly 100% Coulombic efficiency after 200 cycles. The approach of ammonia-assisted layer expansion proposed in this study enriches the modification strategy to enhance the electrochemical performance of MoS2 and provides a new idea for subsequent cathode development. Suffering from strong electrostatic interactions between divalent Zn2+ and host framework, molybdenum disulfide exhibits slow reaction kinetics as cathode for aqueous zinc-ion batteries. The narrow layer spacing of MoS2 is difficulty in accommodating large size insertion of hydrated Zn2+, resulting in a lower discharge specific capacity. Here, NH4+ expanded MoS2-N was prepared by a simple ammonia-assisted hydrothermal. The result showed that the ammonia promoted hydrolysis of thioacetamide to provide reduced S2- and generated a large amount of NH4+ as intercalating particles. These particles expanded the layer spacing of pristine MoS2 from 0.62 nm to 0.92 nm, greatly reducing the Zn2+ inserting energy barrier (with its charge transfer resistance of MoS2-N only 35 Ω), and increased the discharge specific capacity to 149.9 mAh·g-1 at the current density of 0.1 A·g-1, 2 times that of MoS2 electrode without NH4+ expansion. Consequently, it exhibited a stable discharge capacity of about 110 mAh·g-1 at the current density of 1.0 A·g-1 with nearly 100% Coulombic efficiency after 200 cycles. The approach of ammonia-assisted layer expansion proposed in this study enriches the modification strategy to enhance the electrochemical performance of MoS2 and provides a new idea for subsequent cathode development.
Journal of Inorganic Materials
- Publication Date: Jan. 20, 2023
- Vol. 38, Issue 1, 79 (2023)
Yishuai YAO, Ruihua GUO, Shengli AN, Jieyu ZHANG, Kuochih CHOU, Guofang ZHANG, Yarong HUANG, and Gaofei PAN
Direct ethanol fuel cell (DEFC) has been widely studied because of its advantages of easy fuel availability, green and high effiency. However, DEFC catalysts are still frustrated with low catalytic efficiency and poor catalyst stability, which restrict its rapid development. In this work, XC-72R carbon black-loaded Pt1Cox/C high-index crystalline nanocatalysts were prepared in one step by liquid-phase hydrothermal synthesis, using polyvinylpyrrolidone (PVP k-25) as dispersant and reducing agent, glycine as surface control agent and co-reducing agent, and modulating the molar ratio of Pt-Co metal precursors to achieve the in-situ growth of catalyst particles on carbon carriers. The exposed high index crystalline facets of the Pt1Co1/3/C nanocatalyst mainly consisted of (410), (510) and (610) crystalline facets. The growth pattern of the Pt1Co1/3/C nanocatalyst grains varied from 'sphere-like' to cubic, and eventually to concave with high index grain orientation. The Pt1Co1/3/C nanocatalyst with high index crystalline surface has the highest electrocatalytic activity with an electrochemically active surface area of 18.46 m2/g, a current density of 48.70 mA/cm2 for the ethanol oxidation peak, a steady state current density of 8.29 mA/cm2 and a potential of 0.610 V for the CO oxidation peak. This indicates that the defect atoms such as steps and kinks on the surface of the catalyst with high index crystal plane can increase the active sites, thus showing excellent electrocatalytic performance. This study may provide a theoretical basis for the development and industrial application of high index crystalline catalyst materials. Direct ethanol fuel cell (DEFC) has been widely studied because of its advantages of easy fuel availability, green and high effiency. However, DEFC catalysts are still frustrated with low catalytic efficiency and poor catalyst stability, which restrict its rapid development. In this work, XC-72R carbon black-loaded Pt1Cox/C high-index crystalline nanocatalysts were prepared in one step by liquid-phase hydrothermal synthesis, using polyvinylpyrrolidone (PVP k-25) as dispersant and reducing agent, glycine as surface control agent and co-reducing agent, and modulating the molar ratio of Pt-Co metal precursors to achieve the in-situ growth of catalyst particles on carbon carriers. The exposed high index crystalline facets of the Pt1Co1/3/C nanocatalyst mainly consisted of (410), (510) and (610) crystalline facets. The growth pattern of the Pt1Co1/3/C nanocatalyst grains varied from 'sphere-like' to cubic, and eventually to concave with high index grain orientation. The Pt1Co1/3/C nanocatalyst with high index crystalline surface has the highest electrocatalytic activity with an electrochemically active surface area of 18.46 m2/g, a current density of 48.70 mA/cm2 for the ethanol oxidation peak, a steady state current density of 8.29 mA/cm2 and a potential of 0.610 V for the CO oxidation peak. This indicates that the defect atoms such as steps and kinks on the surface of the catalyst with high index crystal plane can increase the active sites, thus showing excellent electrocatalytic performance. This study may provide a theoretical basis for the development and industrial application of high index crystalline catalyst materials.
Journal of Inorganic Materials
- Publication Date: Jan. 20, 2023
- Vol. 38, Issue 1, 71 (2023)
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