Cubic boron nitride particles coated by titanium nitride (TiN/cBN) as well as diamond particles coated by titanium carbide (TiC/diamond) were prepared by Ti molten salt deposition followed by heat-treatment process. c...Cubic boron nitride particles coated by titanium nitride (TiN/cBN) as well as diamond particles coated by titanium carbide (TiC/diamond) were prepared by Ti molten salt deposition followed by heat-treatment process. cBN or diamond particles were mixed separately with Ti powders and molten salts (KCl, NaCl and K<sub>2</sub>TiF<sub>6</sub>). The mixture was heated at 900 °C under argon atmosphere. The produced particles were heat-treated under hydrogen at 1000 °C. The morphologies and chemical compositions of the produced particles were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and focused ion beam (FIB). The results show that the cBN and the diamond particles are coated by nano-sized Ti layers. By heat-treatment of the Ti/cBN and TiC/diamond coated particles under hydrogen atmosphere, the deposited Ti layers were interacted by the in-situ transformation reaction with the surfaces of cBN and diamond particles and converted to titanium compounds (TiN and TiC), respectively.展开更多
The properties of high entropy alloys(HEAs)depend on their phase structures and compositions.However,it is difficult to control the composition of the HEAs that contain highly volatile metals by the conventional arc m...The properties of high entropy alloys(HEAs)depend on their phase structures and compositions.However,it is difficult to control the composition of the HEAs that contain highly volatile metals by the conventional arc melting method.In this paper,homogeneous powdery face centered cubic(FCC)phase Fe_(0.5)CoNiCuZn_(x) HEAs were prepared by the electrolysis of metal oxides in molten Na_(2)CO_(3)-K_(2)CO_(3) using a stable Ni11Fe10Cu inert oxygen-evolution anode.The use of oxide precursors and relatively low synthetic temperature are beneficial to efficiently preparing HEAs that contain highly volatile elements such as Zn.Moreover,the microstructures and compositions of the electrolytic HEAs can be easily tailored by adjusting the components of oxide precursors,then further regulating its properties.Thus,the electrocatalytic activity of Fe_(0.5)Co NiCuZn_(x) HEAs towards oxygen evolution reactions(OER)was investigated in 1 M KOH.The results show that Zn promotes the OER activity of Fe_(0.5)CoNiCuZn_(x) HEAs,i.e.,the HEA(Zn_(0.8))shows the best OER activity exhibiting a low overpotential of 340 m V at 10 m A/cm^(2) and excellent stability of 24 h.Hence,molten salt electrolysis not only provides a green approach to prepare Fe_(0.5)CoNiCuZn_(x) HEAs but also offers an effective way to regulate the structure of the alloys and thereby optimizes the electrocatalytic activities for water electrolysis.展开更多
The reduction mechanism of Ir in the NaCl-KCl-IrCl3 molten salt was investigated by cyclic voltammetry and chronopotentiometry, and Ir film was deposited effectively on platinum in potentiostatic mode. The morphology ...The reduction mechanism of Ir in the NaCl-KCl-IrCl3 molten salt was investigated by cyclic voltammetry and chronopotentiometry, and Ir film was deposited effectively on platinum in potentiostatic mode. The morphology and constitution of Ir film were examined by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS） and X-ray diffraction （XRD）. It is found that the reduction mechanism of Ir（III） is a three-electron step and electro reaction is a reversible diffusion controlled process; the diffusion coefficients of Ir（III） at 1083, 1113, 1143 and 1183 K are 1.56×10-4, 2.23×10-4, 2.77×10-4 and 4.40×10-4 cm2/s, respectively, while the activation energy of the electrode reaction is 102.95 kJ/mol. The compacted Ir film reveals that the applied potential greatly affects the deposition of Ir, the thickness of Ir film deposited at the potential of reduction peak is the highest, the temperature of the molten salt also exerts an influence on deposition, the film formed at a lower temperature is thinner, but more micropores would occur on film when the temperature went too high.展开更多
Metastable molybdenum carbide(α-MoC),as a catalyst and an excellent support for metal catalysts,has been widely used in thermo/electro-catalytic reactions.However,the selective synthesis ofα-MoC remains a great chal...Metastable molybdenum carbide(α-MoC),as a catalyst and an excellent support for metal catalysts,has been widely used in thermo/electro-catalytic reactions.However,the selective synthesis ofα-MoC remains a great challenge.Herein,a simple one-pot synthetic strategy for the selective preparation of metastableα-MoC is proposed by electrochemical co-reduction of CO_(2)and MoO_(3)in a low-temperature eutectic molten carbonate.The synthesizedα-MoC shows a reed flower-like morphology.By controlling the electrolysis time and monitoring the phase and morphology of the obtained products,the growth process ofα-MoC is revealed,where the carbon matrix is deposited first followed by the growth ofα-MoC from the carbon matrix.Moreover,by analyzing the composition of the electrolytic products,the formation mechanism forα-MoC is proposed.In addition,through this one-pot synthetic strategy,S-dopedα-MoC is successfully synthesized.Density functional theory(DFT)calculations reveal that S doping enhanced the HER performance ofα-MoC by facilitating water absorption and dissociation and weakening the bond energy of Mo-H to accelerate H desorption.The present work not only highlights the valuable utilization of CO_(2) but also offers a new perspective on the design and controllable synthesis of metal carbides and their derivatives.展开更多
Effective electrocatalysis is crucial for enhancing the efficiency of water splitting to obtain clean fuels.Herein,we report a system of interesting and high-performance Sr-doped perovskite electrocatalysts with porou...Effective electrocatalysis is crucial for enhancing the efficiency of water splitting to obtain clean fuels.Herein,we report a system of interesting and high-performance Sr-doped perovskite electrocatalysts with porous structures,obtained via a facile molten salt method and applied in the oxygen evolution reaction(OER).With increasing the Sr content,the valence states of Co and Fe ions do not clearly increase,according to the Co-L2,3 and Fe-L2,3 as well as the Co-K and the Fe-K X-ray absorption spectroscopy,whereas doped holes are clearly observed in the 0-K edge.High-resolution transmission electron microscopy indicates the appearance of an amorphous layer after the electrochemical reaction.We conclude that the formation of the amorphous layer at the surface,induced by Sr doping,is crucial for achieving high OER activity,and we offer insights into the self-reconstruction of the OER catalyst.展开更多
文摘Cubic boron nitride particles coated by titanium nitride (TiN/cBN) as well as diamond particles coated by titanium carbide (TiC/diamond) were prepared by Ti molten salt deposition followed by heat-treatment process. cBN or diamond particles were mixed separately with Ti powders and molten salts (KCl, NaCl and K<sub>2</sub>TiF<sub>6</sub>). The mixture was heated at 900 °C under argon atmosphere. The produced particles were heat-treated under hydrogen at 1000 °C. The morphologies and chemical compositions of the produced particles were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and focused ion beam (FIB). The results show that the cBN and the diamond particles are coated by nano-sized Ti layers. By heat-treatment of the Ti/cBN and TiC/diamond coated particles under hydrogen atmosphere, the deposited Ti layers were interacted by the in-situ transformation reaction with the surfaces of cBN and diamond particles and converted to titanium compounds (TiN and TiC), respectively.
基金supported by the National Natural Science Foundation of China(Nos.51874211,52031008)the Fundamental Research Funds for the Central Universities(No.2042020kf0219)。
文摘The properties of high entropy alloys(HEAs)depend on their phase structures and compositions.However,it is difficult to control the composition of the HEAs that contain highly volatile metals by the conventional arc melting method.In this paper,homogeneous powdery face centered cubic(FCC)phase Fe_(0.5)CoNiCuZn_(x) HEAs were prepared by the electrolysis of metal oxides in molten Na_(2)CO_(3)-K_(2)CO_(3) using a stable Ni11Fe10Cu inert oxygen-evolution anode.The use of oxide precursors and relatively low synthetic temperature are beneficial to efficiently preparing HEAs that contain highly volatile elements such as Zn.Moreover,the microstructures and compositions of the electrolytic HEAs can be easily tailored by adjusting the components of oxide precursors,then further regulating its properties.Thus,the electrocatalytic activity of Fe_(0.5)Co NiCuZn_(x) HEAs towards oxygen evolution reactions(OER)was investigated in 1 M KOH.The results show that Zn promotes the OER activity of Fe_(0.5)CoNiCuZn_(x) HEAs,i.e.,the HEA(Zn_(0.8))shows the best OER activity exhibiting a low overpotential of 340 m V at 10 m A/cm^(2) and excellent stability of 24 h.Hence,molten salt electrolysis not only provides a green approach to prepare Fe_(0.5)CoNiCuZn_(x) HEAs but also offers an effective way to regulate the structure of the alloys and thereby optimizes the electrocatalytic activities for water electrolysis.
文摘The reduction mechanism of Ir in the NaCl-KCl-IrCl3 molten salt was investigated by cyclic voltammetry and chronopotentiometry, and Ir film was deposited effectively on platinum in potentiostatic mode. The morphology and constitution of Ir film were examined by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS） and X-ray diffraction （XRD）. It is found that the reduction mechanism of Ir（III） is a three-electron step and electro reaction is a reversible diffusion controlled process; the diffusion coefficients of Ir（III） at 1083, 1113, 1143 and 1183 K are 1.56×10-4, 2.23×10-4, 2.77×10-4 and 4.40×10-4 cm2/s, respectively, while the activation energy of the electrode reaction is 102.95 kJ/mol. The compacted Ir film reveals that the applied potential greatly affects the deposition of Ir, the thickness of Ir film deposited at the potential of reduction peak is the highest, the temperature of the molten salt also exerts an influence on deposition, the film formed at a lower temperature is thinner, but more micropores would occur on film when the temperature went too high.
基金the financial support from National Natural Science Foundation of China(Nos.22071070,21971077).
文摘Metastable molybdenum carbide(α-MoC),as a catalyst and an excellent support for metal catalysts,has been widely used in thermo/electro-catalytic reactions.However,the selective synthesis ofα-MoC remains a great challenge.Herein,a simple one-pot synthetic strategy for the selective preparation of metastableα-MoC is proposed by electrochemical co-reduction of CO_(2)and MoO_(3)in a low-temperature eutectic molten carbonate.The synthesizedα-MoC shows a reed flower-like morphology.By controlling the electrolysis time and monitoring the phase and morphology of the obtained products,the growth process ofα-MoC is revealed,where the carbon matrix is deposited first followed by the growth ofα-MoC from the carbon matrix.Moreover,by analyzing the composition of the electrolytic products,the formation mechanism forα-MoC is proposed.In addition,through this one-pot synthetic strategy,S-dopedα-MoC is successfully synthesized.Density functional theory(DFT)calculations reveal that S doping enhanced the HER performance ofα-MoC by facilitating water absorption and dissociation and weakening the bond energy of Mo-H to accelerate H desorption.The present work not only highlights the valuable utilization of CO_(2) but also offers a new perspective on the design and controllable synthesis of metal carbides and their derivatives.
基金supported by the “Transformational Technologies for clean Energy and Demonstration”,Strategic Priority Research Program of the Chinese Academy of Sciences(XDA2100000)the Youth Innovation Promotion Association,Chinese Academy of Sciences(2014237)+1 种基金the National Natural Science Foundation of China(21876183)the Scientific Instrument Developing Project of the Chinese Academy of Sciences(YJKYYQ20180066)~~
文摘Effective electrocatalysis is crucial for enhancing the efficiency of water splitting to obtain clean fuels.Herein,we report a system of interesting and high-performance Sr-doped perovskite electrocatalysts with porous structures,obtained via a facile molten salt method and applied in the oxygen evolution reaction(OER).With increasing the Sr content,the valence states of Co and Fe ions do not clearly increase,according to the Co-L2,3 and Fe-L2,3 as well as the Co-K and the Fe-K X-ray absorption spectroscopy,whereas doped holes are clearly observed in the 0-K edge.High-resolution transmission electron microscopy indicates the appearance of an amorphous layer after the electrochemical reaction.We conclude that the formation of the amorphous layer at the surface,induced by Sr doping,is crucial for achieving high OER activity,and we offer insights into the self-reconstruction of the OER catalyst.
