Acidic environments enhance CO_(2) utilization during CO_(2) electrolysis via a buffering effect that converts carbonates formed at the electrode surface back into CO_(2).Nevertheless,further investigation into acidic...Acidic environments enhance CO_(2) utilization during CO_(2) electrolysis via a buffering effect that converts carbonates formed at the electrode surface back into CO_(2).Nevertheless,further investigation into acidic CO_(2) electrolysis is required to improve its selectivity towards certain CO_(2) reduction reaction(CO_(2)RR)products,such as multicarbon(C2+)species,while enhancing its overall stability.In this study,liquid product recirculation in the catholyte and local OH−accumulation were identified as primary factors contributing to the degradation of gas diffusion electrodes mounted in closed‐loop catholyte configurations.We demonstrate that a single‐pass catholyte configuration prevents liquid product recirculation and maintains a continuous flow of acidic‐pH catholyte throughout the reaction while using the same volume as a closed‐loop setup.This approach improves electrode durability and maintains a Faradaic efficiency of 67%for multicarbon products over 4 h of CO_(2) electrolysis at−600 mA cm^(-2).展开更多
The typical climatic and environmental conditions in Central Asia are major natural factors causing local rock masses to face considerable risks of damage due to constant freeze-thaw cycles. In addition, these are exa...The typical climatic and environmental conditions in Central Asia are major natural factors causing local rock masses to face considerable risks of damage due to constant freeze-thaw cycles. In addition, these are exacerbated by the dense acidic environments in certain industrialized areas, such as Northern Sinkiang, China. To provide local engineering design with workable solutions, it is crucial to analyze the mechanical performance of rock masses and its mechanisms under the coupling action of corrosive acid and freeze-thaw cycles. In this study, granite samples from the northern Tien Shan Mountains near Urumchi, Xinjiang Province, as well as two kinds of sandstone samples for comparison, were subjected to different soaking conditions, including nitric acid soaking at various pH values. One or both of the freeze-thaw cycle tests and uniaxial compression test were then executed. Speculations regarding the mechanism of the performance of granite rock masses under the action of corrosive acid and freeze-thaw cycles were developed based on the results of these tests. X-ray diffraction and scanning electron microscopy were implemented to demonstrate the feasibility of the speculated mechanism. In this paper, the identification of the white crumb-like substance as SiO_(2) gel were confirmed.展开更多
In order to investigate stress corrosion cracking （SCC） of X70 pipeline steel and its weld joint area in acidic soil environ- ment in China, two simulating methods were used： one was to obtain bad microstructures i...In order to investigate stress corrosion cracking （SCC） of X70 pipeline steel and its weld joint area in acidic soil environ- ment in China, two simulating methods were used： one was to obtain bad microstructures in heat affected zone by annealing at 1300 ℃ for 10 min and then, quenching in water; the other was to get different simulating solutions of acidic soil in Yingtan in south- east China. The SCC susceptibilities of X70 pipeline steel before and after quenching in the simulating solutions were analyzed using slow stain rate test （SSRT） and potentiodynamic polarization technique to investigate the SCC electrochemical mechanism of different microstructures further. The results show that SCC appears in the original microstructure and the quenched microstructure as the polarization potential decreases. Hydrogen revolution accelerates SCC of the two tested materials within the range of-850 mV to -1200 mV vs. SCE. Microstructural hardening and grain coarsening also increase SCC. The SCC mechanisms are different, anodic dissolution is the key of causing SCC as the polarization potential is higher than the null current potential, and hydrogen embrittlement will play a more important role to SCC as the polarization potential lower than the null current potential.展开更多
Proton exchange membrane fuel cell(PEMFC)has important implications for the success of clean transportation in the future.One of the key factors affecting the cost and performance of PEMFC is the cathode electrocataly...Proton exchange membrane fuel cell(PEMFC)has important implications for the success of clean transportation in the future.One of the key factors affecting the cost and performance of PEMFC is the cathode electrocatalyst for the oxygen reduction reaction(ORR)to overcome sluggish kinetics and instability in an acidic environment.As an essential component of the electrocatalyst,the support material largely determines the activity,mass transfer,charge transfer,and durability of the electrocatalyst.Thereby,the support material plays a critical role in the overall performance of the electrocatalyst.Carbonbased materials are widely used as electrocatalyst supports because of their high porosity,conductivity,chemical stability,and tunable morphology.Recently,some new carbon-based materials with excellent structure have been introduced,such as carbon nanotubes,carbon nanowires,graphene,metal-organic framework(MOF)-derived carbon,and biomass-derived carbon materials.Combined with a variety of strategies,such as controllable construction of porous structures and surface defects,proper doping heteroatoms,the ingenious design of model electrocatalysts,and predictive theoretical calculation,a new reliable path was provided for further improving the performance of electrocatalysts and exploring the catalytic mechanism.Based on the topic of carbon-based materials for ORR in acidic medium,this review summarizes the up-to-date progress and breakthroughs,highlights the factors affecting the catalytic activity and stability of ORR electrocatalysts in acids,and discusses their future application and development.展开更多
The corrosion behavior of the as-received steel and the spheroidized steel in acidic chloride environment was investigated. The results indicate the corrosion mode and corrosion rate of two steels are diverse due to t...The corrosion behavior of the as-received steel and the spheroidized steel in acidic chloride environment was investigated. The results indicate the corrosion mode and corrosion rate of two steels are diverse due to their difference in microstructure. For as-received steel with ferrite-pearlite microstructure, severe localized corrosion happens on the pearlite regions, and plenty of cathodic cementite remains in the pits, further strengthening the micro-galvanic effect and accelerating the corrosion rate. While for spheroidized steel with tempered martensite microstructure, the nanosized cementite particles evenly distributed on the ferrite substrate are easy to fall off, which can significantly reduce the cementite accumulation on the steel surface, relieving the acceleration effect of micro-galvanic corrosion.展开更多
The short-term corrosion behavior of API X100 steel in an acidic simulated soil was investigated by electrochemical measurements and soaking experiments,followed by corrosion morphology observations and X-ray photoele...The short-term corrosion behavior of API X100 steel in an acidic simulated soil was investigated by electrochemical measurements and soaking experiments,followed by corrosion morphology observations and X-ray photoelectron spectroscopy analyses.The results show that X100 steel exhibits an obvious pitting susceptibility in an acidic soil environment.Pits nucleate after approximately 10 h of immersion.Along with the nucleation and growth of the pits,the charge-transfer resistance and open-circuit potential first increase sharply,then decrease slowly,and eventually reach a steady state.The maxima of the charge-transfer resistance and open-circuit potential are attained at approximately 10 h.The evolution of the electrochemical process is confirmed by the analysis of the product film.The product film exhibits a porous and loose structure and could not protect the substrate well.The product film is primarily composed of ferrous carbonate and ferrous hydroxide（Fe（OH）2）.The concentration of Fe（OH）2 in the product film increases from the inside to the outside layer.展开更多
A series of austenitic cast iron samples with different compositions were cast and a part of nickel in the samples was replaced by manganese for economic reason. Erosion–corrosion tests were conducted under 2wt% sulf...A series of austenitic cast iron samples with different compositions were cast and a part of nickel in the samples was replaced by manganese for economic reason. Erosion–corrosion tests were conducted under 2wt% sulfuric acid and 15wt% quartz sand. The results show that the matrix of cast irons remains austenite after a portion of nickel is replaced with manganese.（Fe,Cr）3C is a common phase in the cast irons, and nickel is the main alloying element in high-nickel cast iron; whereas,（Fe,Mn）3C is observed with the increased manganese content in low-nickel cast iron. Under erosion–corrosion tests, the weight-loss rates of the cast irons increase with increasing time. Wear plays a more important role than corrosion in determining the weight loss. It is indicated that the processes of weight loss for the cast irons with high and low nickel contents are different. The erosion resistance of the cast iron containing 7.29wt% nickel and 6.94wt% manganese is equivalent to that of the cast iron containing 13.29wt% nickel.展开更多
The effects of temperature on corrosion and the electrochemical behavior of Ni82.3Cr7Fe3Si4.5B3.2 glassy alloy in HC1,H2SO4,and H3PO4 acids were studied using AC and DC techniques.Impedance data reveal that the suscep...The effects of temperature on corrosion and the electrochemical behavior of Ni82.3Cr7Fe3Si4.5B3.2 glassy alloy in HC1,H2SO4,and H3PO4 acids were studied using AC and DC techniques.Impedance data reveal that the susceptibility to localized corrosion increases with increasing temperature.Potentiodynamic polarization curves reveal that the bulk glassy alloy is spontaneously passivated at all the investigated temperature in H2SO4 and H3PO4 solutions.A localized corrosion effect in HCl solution is clearly observed.The apparent activation energies in the regions of Tafel,active,and passive,as well as the enthalpies and entropies of the dissolution process were determined and discussed.The high apparent activation energy（Ea） value for H3PO4 solution in Tafel region is explained by the low aggressivity of PO4^3- ions.展开更多
To investigate the galvanic corrosion behavior of a copper(Cu)-304 stainless steel curved surface coupling system in a chloride-containing acidic environment,wire beam electrode(WBE)technology was innovatively integra...To investigate the galvanic corrosion behavior of a copper(Cu)-304 stainless steel curved surface coupling system in a chloride-containing acidic environment,wire beam electrode(WBE)technology was innovatively integrated with dynamic electrochemical monitoring.The approach enabled a systematic analysis of how the geometric characteristics of a curved surface and variations in cathode area jointly influence local corrosion dynamics.A series of flat and curved(curvature radius:3 mm)Cu WBE models,along with cathode areas of varying diameters(φ0.3–0.9 mm),were constructed.By coupling these with in situ current distribution mapping,electrochemical impedance spectroscopy,and polarization curve analysis,it was revealed that the curved surface geometry significantly enhanced chloride ions/proton mass transport and facilitated the dynamic breakdown of passive films,thereby elevating the local corrosion intensity index to 2.9 times that observed under flat-surface conditions.Further investigations demonstrated that a moderate cathode size(φ0.7 mm diameter)effectively optimized the interfacial microenvironment,markedly suppressed the anodic dissolution rate(total current density reduced by 28%).And it increased the breakdown potential of the stainless steel passivation film,enhanced the self-repairing ability of the passivation film.This study,for the first time,elucidates the dynamic mechanisms underlying the synergistic regulation of galvanic current distribution by surface curvature and cathode area,offering critical theoretical insights for the corrosion-resistant design and life prediction of dissimilar metal joints with complex geometries in aggressive environments.展开更多
Non-precious metal cobalt-based oxide inevitably dissolves for acid oxygen evolution reaction(OER).Designing an efficient deposition channel for leaching cobalt species is a promising approach.The dissolution-depositi...Non-precious metal cobalt-based oxide inevitably dissolves for acid oxygen evolution reaction(OER).Designing an efficient deposition channel for leaching cobalt species is a promising approach.The dissolution-deposition equilibrium of Co is achieved by doping Mn in the lattice of LaCo_(1-x)Mn_(x)O_(3),prolonging the lifespan in acidic conditions by 14 times.The lattice doping of Mn produces a strain that enhances the adsorption capacity of OH^(-).The self-catalysis of Mn causes the leaching Co to be deposited in the form of CoO_(2),which ensures that the long-term stability of LaCo_(1-x)Mn_(x)O_(3)is 70 h instead of 5 h for LaCoO_(3).Mn doping enhances the deprotonation of^(*)OOH→O_(2)in acidic environments.Notably,the over-potential of optimized LaCo_(1-x)Mn_(x)O_(3)is 345 mV at 10 mA cm^(-2)for acidic OER.This work presents a promising method for developing noble metal-free catalysts that enhance the acidic OER activity and stability.展开更多
The corrosion behavior of C110 bushing at high temperature and high pressure with a high H2S / CO2 was studied, and a basis for the materials selection of sour gas well bushing was provided in H2S, CO2 and saline coex...The corrosion behavior of C110 bushing at high temperature and high pressure with a high H2S / CO2 was studied, and a basis for the materials selection of sour gas well bushing was provided in H2S, CO2 and saline coexisting environment. Under acidic condiction, hydrogen atoms greatly entered into the material and caused the material properties changed. Weight loss method was used to study the corrosion rate of hydrogen charging samples and original untreated samples in simulated oil field environment. PAR2273 electrochemical workstation was used to examine the electrochemical performance of samples untreated, hydrogen charging after reacting in autoclave. The corrosion product film was observed through SEM. The experimental results show that sample with hydrogen charging has a much more obvious partial corrosion and pitting corrosion than the untreated blank sample even the downhole corrosion speed of bushing is increased after being used for a period of time. Polarization curve shows the corrosion tendency is the same between sample with or without hydrogen charging and corrosion tendency is reduced by corrosion product film. A layer of dense product film formed on the surface of samples provides a certain protective effect to the matrix, but cracked holes which will accelerate partial corrosion of the sample were also observed.展开更多
In North China,iodine-rich groundwater has been extensively studied,but few in South China.This study aimed to investigate the characteristics of iodine-rich groundwater in South China and identify potential contamina...In North China,iodine-rich groundwater has been extensively studied,but few in South China.This study aimed to investigate the characteristics of iodine-rich groundwater in South China and identify potential contamination sources.The results revealed that the average concentration of iodine in groundwater was 890μg/L,with a maximumconcentration of 6350μg/L,exceeding the permitted levels recommended by the World Health Organization(5–300μg/L).Notably,the enrichment of iodide occurred in acidic conditions(pH=6.6)and a relatively low Eh environment(Eh=198.4 mV).Pearson correlation and cluster analyses suggested that the enrichment of iodide could be attributed to the intensified redox process involving Mn(II),iodine(I_(2)),or iodate(IO_(3)^(−))in the soil.The strong affinity between Mn(II)and I_(2)/IO_(3)^(−)facilitated their interaction,resulting in the formation and mobilization of I^(−)from the soil to the groundwater.Leaching experiments further confirmed that reducing substances(such as sodium sulfides,ascorbic acids,and fulvic acids)in the soil with low dissolved oxygen(DO)levels(<1.0 mg/L)enhanced the dissolution of iodine species.Conversely,higher DO content(>3.8 mg/L)promoted the oxidation of I^(−)into I_(2)or IO_(3)^(−),leading to its stabilization.This research provides new insights into the characteristics and mechanisms of I^(−)enrichment in groundwater in South China,and emphasizes the significance of the redox reactions involving Mn(II)and I_(2)/IO_(3)^(−),as well as the influence of soil properties in regulating the occurrence and transportation of iodine species within groundwater systems.展开更多
The structure of concrete generally serves in multi-media environments; various environments act differently on concrete. The compound action of some severe environments will threaten the duration of concrete and decr...The structure of concrete generally serves in multi-media environments; various environments act differently on concrete. The compound action of some severe environments will threaten the duration of concrete and decrease the service life of a concrete structure if improperly handled. In this paper the microstructure of concrete is observed by using Scanned Electric Microscope (SEM) through contrasting experiments in media of acid, alkali and salt with that of freezing-thawing in the same medium environment. This study is to supply a certain basis for changing traditional thinking of mechanical design and to combine construction reliability design with durability of concrete design.展开更多
In the paper entitled"Efficient adsorption of Mn(Ⅱ)by layered double hydroxides intercalated with di ethylenetriaminepentaacetic acid and the mechanistic study"in Journal of Environmental Sciences,volume 85...In the paper entitled"Efficient adsorption of Mn(Ⅱ)by layered double hydroxides intercalated with di ethylenetriaminepentaacetic acid and the mechanistic study"in Journal of Environmental Sciences,volume 85,page 56-65,there were problems with mathematical notation and dimensional errors in the calculation for Giibbs free energy.In Section 2.5:Adsorption isotherms and thermodynamics studies,authors calculated the Gibbs free energy change(△G°)展开更多
The problems of traditional concrete such as brittleness,poor toughness and short service life of concrete engineering under acid rain or marine environment need to be solved urgently.Hydrated calcium silicate(C-S-H)i...The problems of traditional concrete such as brittleness,poor toughness and short service life of concrete engineering under acid rain or marine environment need to be solved urgently.Hydrated calcium silicate(C-S-H)is a key component to improve the mechanical properties and durability of concrete.However,the traditional method of concrete material design based on empirical models or comparative tests has become a bottleneck restricting the sustainable development of concrete.The synthesis method,molecular structure and properties of C-S-H were systematically described in this paper;The interface structure and interaction of graphene oxide/calcium silicate hydrate(C-S-H/GO)were discussed.On this basis,the saturated and unsaturated transport characteristics of ions and water molecules in C-S-H/GO nanochannels under the environment of ocean and acid rain were introduced.The contents of this review provide the basis for improving the multi-scale transmission theory and microstructure design of concrete.It has important guiding significance for analyzing and improving the service life of concrete in complex environment.展开更多
Photodynamic therapy(PDT)is a widely-used technology for cancer therapy,but conventional photosensitizers still face some drawbacks,such as hydrophobicity,inadequate pharmacokinetics,low cell/tissue specificity,and un...Photodynamic therapy(PDT)is a widely-used technology for cancer therapy,but conventional photosensitizers still face some drawbacks,such as hydrophobicity,inadequate pharmacokinetics,low cell/tissue specificity,and uncontrollable photodynamic performance during the therapeutic process.Herein,we present a controllable photodynamic performance based on two-dimensional metal-organic frameworks(2D Zn-TCPP MOF)that displayed a week PDT effect under a neutral environment upon exposure to a 660 nm laser due to the degeneracy of Q bands of TCPP.However,the 2D Zn-TCPP MOF showed a significantly enhanced PDT effect in an acidic environment under irradiation with a 660 nm laser due to the released TCPP from decomposed MOF structure.From the in vitro outcomes,the 2D Zn-TCPP MOF showed controllable photodynamic performance from neutral to acidic environments.Due to the acidic tumor microenvironment,the 2D Zn-TCPP MOF presented the strongest antitumor effect in vivo under irradiation with a 660 nm laser.This work offers a promising strategy to develop a next-generation photosensitizer.展开更多
Photocatalytic oxidation of hydrocarbons to value-added oxygen-containing compounds is a green and sustainable method.However,the efficient activation of C(sp^(3))-H bonds under mild conditions remains a significant c...Photocatalytic oxidation of hydrocarbons to value-added oxygen-containing compounds is a green and sustainable method.However,the efficient activation of C(sp^(3))-H bonds under mild conditions remains a significant challenge.In this study,we prepared BiOBr/Bi_(2)MoO_(6)Z-scheme heterostructure for photocatalytic selective oxidation of toluene to benzaldehyde utilizing acetic acid as solvent.A small amount of water as an additive established an acidic environment to facilitate the formation of highly reactive hydroxyl radicals(·OH)through the O_(2)→·O_(2)^(−)→H_(2)O_(2)→·OH process.The·OH together with photogenerated holes acted as reactive species dissociate C(sp^(3))-H bonds,which is regarded as the rate-determining step for this reaction,boosting photocatalytic activity.Compared to the reaction system without water,the conversion of toluene increased from 23.6%to 39.0%,reaching a toluene conversion rate of 6110μmol·g^(-1)·h^(-1).Additionally,there is a slight improvement in the selectivity of benzaldehyde.展开更多
Proton exchange membrane water electrolysis(PEMWE)is recognized as an advanced technology for green hydrogen production and renewable energy conversion.However,the prohibitive cost and limited availability of precious...Proton exchange membrane water electrolysis(PEMWE)is recognized as an advanced technology for green hydrogen production and renewable energy conversion.However,the prohibitive cost and limited availability of precious-metal catalysts for the oxygen evolution reaction(OER)hamper its industrial application,and it is imperative to reduce the precious-metal loading by incorporating other elements or exploring alternative materials.Given the low cost and abundant reserves,manganese(Mn)-related catalysts have garnered increasing attention.This review systematically summarizes the progress of Mn-containing catalysts for acidic OER.Initially,we present an overview of fundamental characteristics and OER performance,especially the excellent stability,of Mn oxides.Then,we introduce the modulating effect of Mn in terms of the support,electronic structure,reaction mechanism,and surface reconstruction,followed by an analysis of the advancement of Mn-containing catalysts in PEMWE.Finally,the unresolved issues and future research directions for Mn-containing catalysts in acidic OER are critically discussed.展开更多
Textile reinforced mortar is widely used as an overlay for the repair,rehabilitation,and retrofitting of concrete structures.Recently,textile reinforced concrete has been identified as a suitable lining material for i...Textile reinforced mortar is widely used as an overlay for the repair,rehabilitation,and retrofitting of concrete structures.Recently,textile reinforced concrete has been identified as a suitable lining material for improving the durability of existing concrete structures.In this study,we developed a textile-reinforced mortar mix using river sand and evaluated the different characteristics of the textile-reinforced mortar under various exposure conditions.Studies were carried out in two phases.In the first phase,the pullout strength,temperature resistance,water absorption,and compressive and bending strength values of three different textile-reinforced mortar mixes with a single type of textile reinforcement were investigated.In the second phase,the chemical resistance of the mix that showed the best performance in the abovementioned tests was examined for use as an overlay for a concrete substrate.Investigations were performed on three different thicknesses of the textile reinforced mortar overlaid on concrete specimens that were subjected to acidic and alkaline environments.The flexural responses and degradations of the textile reinforced mortar overlaid specimens were examined by performing bending tests.The experimental findings indicated the feasibility of using textile reinforced mortar as an overlay for durable concrete construction practices.展开更多
基金supported by the EPFL,EMPA and the National Research Foundation of Singapore(Urban Solutions and Sustainability,Industry Alignment Fund[Pre‐Positioning]Programme)(A‐0004543‐00‐00)。
文摘Acidic environments enhance CO_(2) utilization during CO_(2) electrolysis via a buffering effect that converts carbonates formed at the electrode surface back into CO_(2).Nevertheless,further investigation into acidic CO_(2) electrolysis is required to improve its selectivity towards certain CO_(2) reduction reaction(CO_(2)RR)products,such as multicarbon(C2+)species,while enhancing its overall stability.In this study,liquid product recirculation in the catholyte and local OH−accumulation were identified as primary factors contributing to the degradation of gas diffusion electrodes mounted in closed‐loop catholyte configurations.We demonstrate that a single‐pass catholyte configuration prevents liquid product recirculation and maintains a continuous flow of acidic‐pH catholyte throughout the reaction while using the same volume as a closed‐loop setup.This approach improves electrode durability and maintains a Faradaic efficiency of 67%for multicarbon products over 4 h of CO_(2) electrolysis at−600 mA cm^(-2).
基金Financial support from the Project of Shanghai Soft Science Research Plans(No.18692106100)the China Scholarship Council is gratefully acknowledged.
文摘The typical climatic and environmental conditions in Central Asia are major natural factors causing local rock masses to face considerable risks of damage due to constant freeze-thaw cycles. In addition, these are exacerbated by the dense acidic environments in certain industrialized areas, such as Northern Sinkiang, China. To provide local engineering design with workable solutions, it is crucial to analyze the mechanical performance of rock masses and its mechanisms under the coupling action of corrosive acid and freeze-thaw cycles. In this study, granite samples from the northern Tien Shan Mountains near Urumchi, Xinjiang Province, as well as two kinds of sandstone samples for comparison, were subjected to different soaking conditions, including nitric acid soaking at various pH values. One or both of the freeze-thaw cycle tests and uniaxial compression test were then executed. Speculations regarding the mechanism of the performance of granite rock masses under the action of corrosive acid and freeze-thaw cycles were developed based on the results of these tests. X-ray diffraction and scanning electron microscopy were implemented to demonstrate the feasibility of the speculated mechanism. In this paper, the identification of the white crumb-like substance as SiO_(2) gel were confirmed.
基金supported by the National Science and Technology Infrastructure Platforms Construction Projects of China (No.2005DKA 10400)the Major Fund in the Tenth Five-Year Development Plan of China (No.50499333-08)
文摘In order to investigate stress corrosion cracking （SCC） of X70 pipeline steel and its weld joint area in acidic soil environ- ment in China, two simulating methods were used： one was to obtain bad microstructures in heat affected zone by annealing at 1300 ℃ for 10 min and then, quenching in water; the other was to get different simulating solutions of acidic soil in Yingtan in south- east China. The SCC susceptibilities of X70 pipeline steel before and after quenching in the simulating solutions were analyzed using slow stain rate test （SSRT） and potentiodynamic polarization technique to investigate the SCC electrochemical mechanism of different microstructures further. The results show that SCC appears in the original microstructure and the quenched microstructure as the polarization potential decreases. Hydrogen revolution accelerates SCC of the two tested materials within the range of-850 mV to -1200 mV vs. SCE. Microstructural hardening and grain coarsening also increase SCC. The SCC mechanisms are different, anodic dissolution is the key of causing SCC as the polarization potential is higher than the null current potential, and hydrogen embrittlement will play a more important role to SCC as the polarization potential lower than the null current potential.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.U1710256 and U1810115)the Shanxi Science and Technology Major Project(Grant Nos.20181102019 and 20201101016)。
文摘Proton exchange membrane fuel cell(PEMFC)has important implications for the success of clean transportation in the future.One of the key factors affecting the cost and performance of PEMFC is the cathode electrocatalyst for the oxygen reduction reaction(ORR)to overcome sluggish kinetics and instability in an acidic environment.As an essential component of the electrocatalyst,the support material largely determines the activity,mass transfer,charge transfer,and durability of the electrocatalyst.Thereby,the support material plays a critical role in the overall performance of the electrocatalyst.Carbonbased materials are widely used as electrocatalyst supports because of their high porosity,conductivity,chemical stability,and tunable morphology.Recently,some new carbon-based materials with excellent structure have been introduced,such as carbon nanotubes,carbon nanowires,graphene,metal-organic framework(MOF)-derived carbon,and biomass-derived carbon materials.Combined with a variety of strategies,such as controllable construction of porous structures and surface defects,proper doping heteroatoms,the ingenious design of model electrocatalysts,and predictive theoretical calculation,a new reliable path was provided for further improving the performance of electrocatalysts and exploring the catalytic mechanism.Based on the topic of carbon-based materials for ORR in acidic medium,this review summarizes the up-to-date progress and breakthroughs,highlights the factors affecting the catalytic activity and stability of ORR electrocatalysts in acids,and discusses their future application and development.
基金financial support of the Natural Science Foundation of Liaoning Province,China(2019JH3/30100037)the National Natural Science Foundation of China(No.U1867216)the State Key Laboratory of Metal Material for Marine Equipment and Application(No.SKLMEA-K201907)。
文摘The corrosion behavior of the as-received steel and the spheroidized steel in acidic chloride environment was investigated. The results indicate the corrosion mode and corrosion rate of two steels are diverse due to their difference in microstructure. For as-received steel with ferrite-pearlite microstructure, severe localized corrosion happens on the pearlite regions, and plenty of cathodic cementite remains in the pits, further strengthening the micro-galvanic effect and accelerating the corrosion rate. While for spheroidized steel with tempered martensite microstructure, the nanosized cementite particles evenly distributed on the ferrite substrate are easy to fall off, which can significantly reduce the cementite accumulation on the steel surface, relieving the acceleration effect of micro-galvanic corrosion.
基金financially supported by the National High-Tech Research and Development Program of China (No.2012AA040105)the National Nature Science Foundation of China (Nos. 51131001 and 51741034)the Beijing Higher Education Young Elite Teacher Project
文摘The short-term corrosion behavior of API X100 steel in an acidic simulated soil was investigated by electrochemical measurements and soaking experiments,followed by corrosion morphology observations and X-ray photoelectron spectroscopy analyses.The results show that X100 steel exhibits an obvious pitting susceptibility in an acidic soil environment.Pits nucleate after approximately 10 h of immersion.Along with the nucleation and growth of the pits,the charge-transfer resistance and open-circuit potential first increase sharply,then decrease slowly,and eventually reach a steady state.The maxima of the charge-transfer resistance and open-circuit potential are attained at approximately 10 h.The evolution of the electrochemical process is confirmed by the analysis of the product film.The product film exhibits a porous and loose structure and could not protect the substrate well.The product film is primarily composed of ferrous carbonate and ferrous hydroxide（Fe（OH）2）.The concentration of Fe（OH）2 in the product film increases from the inside to the outside layer.
基金financially supported by the National Nature Science Foundation of China (No. 51101109)
文摘A series of austenitic cast iron samples with different compositions were cast and a part of nickel in the samples was replaced by manganese for economic reason. Erosion–corrosion tests were conducted under 2wt% sulfuric acid and 15wt% quartz sand. The results show that the matrix of cast irons remains austenite after a portion of nickel is replaced with manganese.（Fe,Cr）3C is a common phase in the cast irons, and nickel is the main alloying element in high-nickel cast iron; whereas,（Fe,Mn）3C is observed with the increased manganese content in low-nickel cast iron. Under erosion–corrosion tests, the weight-loss rates of the cast irons increase with increasing time. Wear plays a more important role than corrosion in determining the weight loss. It is indicated that the processes of weight loss for the cast irons with high and low nickel contents are different. The erosion resistance of the cast iron containing 7.29wt% nickel and 6.94wt% manganese is equivalent to that of the cast iron containing 13.29wt% nickel.
基金supported by the Kink Abdulaziz City of Science and Technology (KACST) (No.GSP–14–105)
文摘The effects of temperature on corrosion and the electrochemical behavior of Ni82.3Cr7Fe3Si4.5B3.2 glassy alloy in HC1,H2SO4,and H3PO4 acids were studied using AC and DC techniques.Impedance data reveal that the susceptibility to localized corrosion increases with increasing temperature.Potentiodynamic polarization curves reveal that the bulk glassy alloy is spontaneously passivated at all the investigated temperature in H2SO4 and H3PO4 solutions.A localized corrosion effect in HCl solution is clearly observed.The apparent activation energies in the regions of Tafel,active,and passive,as well as the enthalpies and entropies of the dissolution process were determined and discussed.The high apparent activation energy（Ea） value for H3PO4 solution in Tafel region is explained by the low aggressivity of PO4^3- ions.
基金the Special Funds for the Construction of an Innovative Province of Hunan(2019GK2231).
文摘To investigate the galvanic corrosion behavior of a copper(Cu)-304 stainless steel curved surface coupling system in a chloride-containing acidic environment,wire beam electrode(WBE)technology was innovatively integrated with dynamic electrochemical monitoring.The approach enabled a systematic analysis of how the geometric characteristics of a curved surface and variations in cathode area jointly influence local corrosion dynamics.A series of flat and curved(curvature radius:3 mm)Cu WBE models,along with cathode areas of varying diameters(φ0.3–0.9 mm),were constructed.By coupling these with in situ current distribution mapping,electrochemical impedance spectroscopy,and polarization curve analysis,it was revealed that the curved surface geometry significantly enhanced chloride ions/proton mass transport and facilitated the dynamic breakdown of passive films,thereby elevating the local corrosion intensity index to 2.9 times that observed under flat-surface conditions.Further investigations demonstrated that a moderate cathode size(φ0.7 mm diameter)effectively optimized the interfacial microenvironment,markedly suppressed the anodic dissolution rate(total current density reduced by 28%).And it increased the breakdown potential of the stainless steel passivation film,enhanced the self-repairing ability of the passivation film.This study,for the first time,elucidates the dynamic mechanisms underlying the synergistic regulation of galvanic current distribution by surface curvature and cathode area,offering critical theoretical insights for the corrosion-resistant design and life prediction of dissimilar metal joints with complex geometries in aggressive environments.
基金financially supported by the Shandong Provincial Natural Science Foundation(ZR2023LFG005)the National Natural Science Foundation of China(Nos.22479161,52274308 and U22B20144)the Fundamental Research Funds for the Central Universities(No.24CX03012A)。
文摘Non-precious metal cobalt-based oxide inevitably dissolves for acid oxygen evolution reaction(OER).Designing an efficient deposition channel for leaching cobalt species is a promising approach.The dissolution-deposition equilibrium of Co is achieved by doping Mn in the lattice of LaCo_(1-x)Mn_(x)O_(3),prolonging the lifespan in acidic conditions by 14 times.The lattice doping of Mn produces a strain that enhances the adsorption capacity of OH^(-).The self-catalysis of Mn causes the leaching Co to be deposited in the form of CoO_(2),which ensures that the long-term stability of LaCo_(1-x)Mn_(x)O_(3)is 70 h instead of 5 h for LaCoO_(3).Mn doping enhances the deprotonation of^(*)OOH→O_(2)in acidic environments.Notably,the over-potential of optimized LaCo_(1-x)Mn_(x)O_(3)is 345 mV at 10 mA cm^(-2)for acidic OER.This work presents a promising method for developing noble metal-free catalysts that enhance the acidic OER activity and stability.
基金Funded by the National Natural Science Foundation of China(No. 50904050)the Basic Projects of Sichuan Province(2011JY0106)the Postdoctoral Science Foundation(20110490810)
文摘The corrosion behavior of C110 bushing at high temperature and high pressure with a high H2S / CO2 was studied, and a basis for the materials selection of sour gas well bushing was provided in H2S, CO2 and saline coexisting environment. Under acidic condiction, hydrogen atoms greatly entered into the material and caused the material properties changed. Weight loss method was used to study the corrosion rate of hydrogen charging samples and original untreated samples in simulated oil field environment. PAR2273 electrochemical workstation was used to examine the electrochemical performance of samples untreated, hydrogen charging after reacting in autoclave. The corrosion product film was observed through SEM. The experimental results show that sample with hydrogen charging has a much more obvious partial corrosion and pitting corrosion than the untreated blank sample even the downhole corrosion speed of bushing is increased after being used for a period of time. Polarization curve shows the corrosion tendency is the same between sample with or without hydrogen charging and corrosion tendency is reduced by corrosion product film. A layer of dense product film formed on the surface of samples provides a certain protective effect to the matrix, but cracked holes which will accelerate partial corrosion of the sample were also observed.
基金supported by the National Key Research and Development Program of China(No.2019YFC1803900)and the 111 Project(No.B18060)as well as Shenzhen Municipal Science and Technology Plan Project(No.JCYJ20160519095007940).
文摘In North China,iodine-rich groundwater has been extensively studied,but few in South China.This study aimed to investigate the characteristics of iodine-rich groundwater in South China and identify potential contamination sources.The results revealed that the average concentration of iodine in groundwater was 890μg/L,with a maximumconcentration of 6350μg/L,exceeding the permitted levels recommended by the World Health Organization(5–300μg/L).Notably,the enrichment of iodide occurred in acidic conditions(pH=6.6)and a relatively low Eh environment(Eh=198.4 mV).Pearson correlation and cluster analyses suggested that the enrichment of iodide could be attributed to the intensified redox process involving Mn(II),iodine(I_(2)),or iodate(IO_(3)^(−))in the soil.The strong affinity between Mn(II)and I_(2)/IO_(3)^(−)facilitated their interaction,resulting in the formation and mobilization of I^(−)from the soil to the groundwater.Leaching experiments further confirmed that reducing substances(such as sodium sulfides,ascorbic acids,and fulvic acids)in the soil with low dissolved oxygen(DO)levels(<1.0 mg/L)enhanced the dissolution of iodine species.Conversely,higher DO content(>3.8 mg/L)promoted the oxidation of I^(−)into I_(2)or IO_(3)^(−),leading to its stabilization.This research provides new insights into the characteristics and mechanisms of I^(−)enrichment in groundwater in South China,and emphasizes the significance of the redox reactions involving Mn(II)and I_(2)/IO_(3)^(−),as well as the influence of soil properties in regulating the occurrence and transportation of iodine species within groundwater systems.
文摘The structure of concrete generally serves in multi-media environments; various environments act differently on concrete. The compound action of some severe environments will threaten the duration of concrete and decrease the service life of a concrete structure if improperly handled. In this paper the microstructure of concrete is observed by using Scanned Electric Microscope (SEM) through contrasting experiments in media of acid, alkali and salt with that of freezing-thawing in the same medium environment. This study is to supply a certain basis for changing traditional thinking of mechanical design and to combine construction reliability design with durability of concrete design.
基金funded by the National Natural Science Foundation of China(Nos.31971551,31470573 and 31070478)the Tianjin Key Projects of Scientific and Technological Support(Nos.17YFZCNC00220 and 18YFZCNC01270)
文摘In the paper entitled"Efficient adsorption of Mn(Ⅱ)by layered double hydroxides intercalated with di ethylenetriaminepentaacetic acid and the mechanistic study"in Journal of Environmental Sciences,volume 85,page 56-65,there were problems with mathematical notation and dimensional errors in the calculation for Giibbs free energy.In Section 2.5:Adsorption isotherms and thermodynamics studies,authors calculated the Gibbs free energy change(△G°)
基金This work was supported by a Doctoral program of Zhejiang University of science and technology(F701104L08)。
文摘The problems of traditional concrete such as brittleness,poor toughness and short service life of concrete engineering under acid rain or marine environment need to be solved urgently.Hydrated calcium silicate(C-S-H)is a key component to improve the mechanical properties and durability of concrete.However,the traditional method of concrete material design based on empirical models or comparative tests has become a bottleneck restricting the sustainable development of concrete.The synthesis method,molecular structure and properties of C-S-H were systematically described in this paper;The interface structure and interaction of graphene oxide/calcium silicate hydrate(C-S-H/GO)were discussed.On this basis,the saturated and unsaturated transport characteristics of ions and water molecules in C-S-H/GO nanochannels under the environment of ocean and acid rain were introduced.The contents of this review provide the basis for improving the multi-scale transmission theory and microstructure design of concrete.It has important guiding significance for analyzing and improving the service life of concrete in complex environment.
基金This work is supported by the National Natural Science Foundation of China(NSFC)(Nos.51903162 and U1903120)Science foundation of Guangdong Second Provincial General Hospital(No.YN2018-001).
文摘Photodynamic therapy(PDT)is a widely-used technology for cancer therapy,but conventional photosensitizers still face some drawbacks,such as hydrophobicity,inadequate pharmacokinetics,low cell/tissue specificity,and uncontrollable photodynamic performance during the therapeutic process.Herein,we present a controllable photodynamic performance based on two-dimensional metal-organic frameworks(2D Zn-TCPP MOF)that displayed a week PDT effect under a neutral environment upon exposure to a 660 nm laser due to the degeneracy of Q bands of TCPP.However,the 2D Zn-TCPP MOF showed a significantly enhanced PDT effect in an acidic environment under irradiation with a 660 nm laser due to the released TCPP from decomposed MOF structure.From the in vitro outcomes,the 2D Zn-TCPP MOF showed controllable photodynamic performance from neutral to acidic environments.Due to the acidic tumor microenvironment,the 2D Zn-TCPP MOF presented the strongest antitumor effect in vivo under irradiation with a 660 nm laser.This work offers a promising strategy to develop a next-generation photosensitizer.
基金financially supported by the National Natural Science Foundation of China(Nos.22322804,21938002,and 22278119).
文摘Photocatalytic oxidation of hydrocarbons to value-added oxygen-containing compounds is a green and sustainable method.However,the efficient activation of C(sp^(3))-H bonds under mild conditions remains a significant challenge.In this study,we prepared BiOBr/Bi_(2)MoO_(6)Z-scheme heterostructure for photocatalytic selective oxidation of toluene to benzaldehyde utilizing acetic acid as solvent.A small amount of water as an additive established an acidic environment to facilitate the formation of highly reactive hydroxyl radicals(·OH)through the O_(2)→·O_(2)^(−)→H_(2)O_(2)→·OH process.The·OH together with photogenerated holes acted as reactive species dissociate C(sp^(3))-H bonds,which is regarded as the rate-determining step for this reaction,boosting photocatalytic activity.Compared to the reaction system without water,the conversion of toluene increased from 23.6%to 39.0%,reaching a toluene conversion rate of 6110μmol·g^(-1)·h^(-1).Additionally,there is a slight improvement in the selectivity of benzaldehyde.
基金supported by the National Natural Science Foundation of China(52025013,22121005)the Fundamental Research Funds for the Central Universities.
文摘Proton exchange membrane water electrolysis(PEMWE)is recognized as an advanced technology for green hydrogen production and renewable energy conversion.However,the prohibitive cost and limited availability of precious-metal catalysts for the oxygen evolution reaction(OER)hamper its industrial application,and it is imperative to reduce the precious-metal loading by incorporating other elements or exploring alternative materials.Given the low cost and abundant reserves,manganese(Mn)-related catalysts have garnered increasing attention.This review systematically summarizes the progress of Mn-containing catalysts for acidic OER.Initially,we present an overview of fundamental characteristics and OER performance,especially the excellent stability,of Mn oxides.Then,we introduce the modulating effect of Mn in terms of the support,electronic structure,reaction mechanism,and surface reconstruction,followed by an analysis of the advancement of Mn-containing catalysts in PEMWE.Finally,the unresolved issues and future research directions for Mn-containing catalysts in acidic OER are critically discussed.
文摘Textile reinforced mortar is widely used as an overlay for the repair,rehabilitation,and retrofitting of concrete structures.Recently,textile reinforced concrete has been identified as a suitable lining material for improving the durability of existing concrete structures.In this study,we developed a textile-reinforced mortar mix using river sand and evaluated the different characteristics of the textile-reinforced mortar under various exposure conditions.Studies were carried out in two phases.In the first phase,the pullout strength,temperature resistance,water absorption,and compressive and bending strength values of three different textile-reinforced mortar mixes with a single type of textile reinforcement were investigated.In the second phase,the chemical resistance of the mix that showed the best performance in the abovementioned tests was examined for use as an overlay for a concrete substrate.Investigations were performed on three different thicknesses of the textile reinforced mortar overlaid on concrete specimens that were subjected to acidic and alkaline environments.The flexural responses and degradations of the textile reinforced mortar overlaid specimens were examined by performing bending tests.The experimental findings indicated the feasibility of using textile reinforced mortar as an overlay for durable concrete construction practices.
