The complexity of calcareous deposits processes in a marine environment results in simultaneous effects of the following parameters： temperature, polarization potential, interfacial pH, chemical composition, etc.. Th...The complexity of calcareous deposits processes in a marine environment results in simultaneous effects of the following parameters： temperature, polarization potential, interfacial pH, chemical composition, etc.. The comprehension of these processes implies studies in artificial seawater and a follow-up of the parameters by voltarnperometry and chronoamperometry. Calcareous deposits electrochemically are very often used to follow up the evolution of scale deposition in desalination circuits. Again, the scale formation is brought about by electrochemical reduction of dissolved oxygen. The hydroxyl ions formed on the metallic surface engender a rise of interfacial pH which causes calcareous deposition （CaCOs and Mg（OH）2）. This reaction goes with reaction of hydrogen evolution which could disrupt the formed deposit, A study is carried out in a solution of seawater ASTM without calcium and without magnesium （so that the deposit will not be formed） on a titanium rotating disk electrode monitored between 300 and 1000 rpm. Study shows that Levich criterion is checked for the four values of selected potential on the diffusion plateau and a very cathodic polarization potential and a high temperature favors hydrogen current rate.展开更多
Oxygen reduction reaction(ORR)constitutes the core process of many energy storage and conversion devices including metal–air batteries and fuel cells.However,the kinetics of ORR is very sluggish and thus highperforma...Oxygen reduction reaction(ORR)constitutes the core process of many energy storage and conversion devices including metal–air batteries and fuel cells.However,the kinetics of ORR is very sluggish and thus highperformance ORR electrocatalysts are highly regarded.Despite recent progress on minimizing the ORR halfwave potential as the current evaluation indicator,in-depth quantitative kinetic analysis on overall ORR electrocatalytic performance remains insufficiently emphasized.In this paper,a quantitative kinetic analysis method is proposed to afford decoupled kinetic information from linear sweep voltammetry profiles on the basis of the Koutecky–Levich equation.Independent parameters regarding exchange current density,electron transfer number,and electrochemical active surface area can be respectively determined following the proposed method.This quantitative kinetic analysis method is expected to promote understanding of the electrocatalytic effect and point out further optimization direction for ORR electrocatalysis.展开更多
Magnesium ions, which exist in formation water and injection water under downhole conditions in the oil and gas production industry, are a key determinant in the CaCO_3 scale formation. Many studies have focused their...Magnesium ions, which exist in formation water and injection water under downhole conditions in the oil and gas production industry, are a key determinant in the CaCO_3 scale formation. Many studies have focused their attention on the effect of magnesium on the kinetics, the morphology and the content of Mg in the CaCO_3 scale. Little attention has been paid to the effect of Mg 2+ on the initial stages of CaCO_3 formation on a metal surface. In this study, an electrochemical technique was used to study the influence of Mg 2+ on the initial stages of CaCO_3 scale formed on a metal surface. With this electrochemical technique, the reduction of the dissolved oxygen in an analysis solution is considered on the surface of a rotating disk electrode(RDE) under potentiostatic control.The rate of oxygen reduction on the surface of the RDE enables the extent of surface coverage of scale to be assessed. With this electrochemical technique, a new insight into the effect of Mg 2+ on CaCO_3 scale formed on a metal surface is given.展开更多
39 mol% SiC of ceramic pellets ZrB<sub>2</sub>-αSiC and TiB<sub>2</sub>-αSiC were synthesized by the reactive hot pressure RHP process at 1850°C under 40 Mpa in vacuum. The XR diffrac...39 mol% SiC of ceramic pellets ZrB<sub>2</sub>-αSiC and TiB<sub>2</sub>-αSiC were synthesized by the reactive hot pressure RHP process at 1850°C under 40 Mpa in vacuum. The XR diffraction displays the absence of other reagents apart from ZrB<sub>2</sub>, SiC and TiB<sub>2</sub> confirming the purity of the pellets. The cathodic exploitation of both of them through electrochemical study shows that TiB<sub>2</sub>-αSiC is the most active for Hydrogen Evolution Reaction (HER) and Hydrogen Oxidation Reaction (HOR) in 0.5 M of H<sub>2</sub>SO<sub>4</sub> solution at room temperature. Moreover, the kinetic exploitation shows that for both pellets the system is controlled by mass transport when they are used as HER. However, in the case of HOR, the system is controlled by the electron transfer.展开更多
文摘The complexity of calcareous deposits processes in a marine environment results in simultaneous effects of the following parameters： temperature, polarization potential, interfacial pH, chemical composition, etc.. The comprehension of these processes implies studies in artificial seawater and a follow-up of the parameters by voltarnperometry and chronoamperometry. Calcareous deposits electrochemically are very often used to follow up the evolution of scale deposition in desalination circuits. Again, the scale formation is brought about by electrochemical reduction of dissolved oxygen. The hydroxyl ions formed on the metallic surface engender a rise of interfacial pH which causes calcareous deposition （CaCOs and Mg（OH）2）. This reaction goes with reaction of hydrogen evolution which could disrupt the formed deposit, A study is carried out in a solution of seawater ASTM without calcium and without magnesium （so that the deposit will not be formed） on a titanium rotating disk electrode monitored between 300 and 1000 rpm. Study shows that Levich criterion is checked for the four values of selected potential on the diffusion plateau and a very cathodic polarization potential and a high temperature favors hydrogen current rate.
基金supported by Beijing Natural Science Foundation(JQ20004)National Key Research and Development Program(2016YFA0202500)Scientific and Technological Key Project of Shanxi Province(20191102003).
文摘Oxygen reduction reaction(ORR)constitutes the core process of many energy storage and conversion devices including metal–air batteries and fuel cells.However,the kinetics of ORR is very sluggish and thus highperformance ORR electrocatalysts are highly regarded.Despite recent progress on minimizing the ORR halfwave potential as the current evaluation indicator,in-depth quantitative kinetic analysis on overall ORR electrocatalytic performance remains insufficiently emphasized.In this paper,a quantitative kinetic analysis method is proposed to afford decoupled kinetic information from linear sweep voltammetry profiles on the basis of the Koutecky–Levich equation.Independent parameters regarding exchange current density,electron transfer number,and electrochemical active surface area can be respectively determined following the proposed method.This quantitative kinetic analysis method is expected to promote understanding of the electrocatalytic effect and point out further optimization direction for ORR electrocatalysis.
文摘Magnesium ions, which exist in formation water and injection water under downhole conditions in the oil and gas production industry, are a key determinant in the CaCO_3 scale formation. Many studies have focused their attention on the effect of magnesium on the kinetics, the morphology and the content of Mg in the CaCO_3 scale. Little attention has been paid to the effect of Mg 2+ on the initial stages of CaCO_3 formation on a metal surface. In this study, an electrochemical technique was used to study the influence of Mg 2+ on the initial stages of CaCO_3 scale formed on a metal surface. With this electrochemical technique, the reduction of the dissolved oxygen in an analysis solution is considered on the surface of a rotating disk electrode(RDE) under potentiostatic control.The rate of oxygen reduction on the surface of the RDE enables the extent of surface coverage of scale to be assessed. With this electrochemical technique, a new insight into the effect of Mg 2+ on CaCO_3 scale formed on a metal surface is given.
文摘39 mol% SiC of ceramic pellets ZrB<sub>2</sub>-αSiC and TiB<sub>2</sub>-αSiC were synthesized by the reactive hot pressure RHP process at 1850°C under 40 Mpa in vacuum. The XR diffraction displays the absence of other reagents apart from ZrB<sub>2</sub>, SiC and TiB<sub>2</sub> confirming the purity of the pellets. The cathodic exploitation of both of them through electrochemical study shows that TiB<sub>2</sub>-αSiC is the most active for Hydrogen Evolution Reaction (HER) and Hydrogen Oxidation Reaction (HOR) in 0.5 M of H<sub>2</sub>SO<sub>4</sub> solution at room temperature. Moreover, the kinetic exploitation shows that for both pellets the system is controlled by mass transport when they are used as HER. However, in the case of HOR, the system is controlled by the electron transfer.
