Highly selective conversion of methane(CH_(4))to methanol(CH_(3)OH)is an emerging attractive but challenging process for future development of hydrogen economy,which requires efficient catalysts.Herein,we systematical...Highly selective conversion of methane(CH_(4))to methanol(CH_(3)OH)is an emerging attractive but challenging process for future development of hydrogen economy,which requires efficient catalysts.Herein,we systematically explore the catalytic properties of Pt(111)overlayer on transition metal oxides(TMOs)for CH_(4) conversion by first principles calculations.The Pt(111)monolayer supported by Ce-terminated CeO_(2)(111)substrate exhibits high activity and selectivity for CH_(4) conversion to CH_(3)OH,with the kinetic barrier of rate-limiting step of 1.05 eV.Intriguingly,the surface activity of Pt overlayer is governed by its d-band center relative to the energy of bonding states of adsorbed molecules,which in turn depends on the number of charge transfer between Pt(111)monolayer and underlying TMOs substrates.These results provide useful insights in the design of metal overlayers as catalysts with high-ultra performance and atomic utilization.展开更多
Hematite(α-Fe_(2)O_(3)) based photoanodes have been extensively studied due to various intriguing features that make them viable candidates for a photoelectrochemical(PEC) water splitting photoanode.Herein,we propose...Hematite(α-Fe_(2)O_(3)) based photoanodes have been extensively studied due to various intriguing features that make them viable candidates for a photoelectrochemical(PEC) water splitting photoanode.Herein,we propose a Zr-doped Fe_(2)O_(3) photoanode decorated with facilely spin-coated Au nanoparticles(NPs) and microwave-assisted attached Si co-doping in conjunction with a SiO_(x) overlayer that displayed a remarkable photocurrent density of 2.01 mA/cm^(2) at 1.23 V vs.RHE.The kinetic dynamics at the photoelectrode/-electrolyte interface was examined by employing systematic electrochemical investigations.The Au NPs played a dual role in increasing PEC water splitting.First,the Schottky interface that was formed between Au NPs and Zr-Fe_(2)O_(3) lectrode ensured the prevention of electron flow from the photoanode to the metal,increasing the number of available charges as well as suppressing surface charge recombination.Second,Au extracted photoholes from the bulk of the Zr-Fe_(2)O_(3) and transported them to the outer SiO_(x) overlayer,while the SiO_(x) overlayer efficiently collected the photoholes and promoted the hole injection into the electrolyte.Further,Si co-doping enhanced bulk conductivity by reducing bulk charge transfer resistance and improving charge carrier density.This study outlines a technique to design a metallic charge transfer path with an overlayer for solar energy conversion.展开更多
The adsorption of CO on Fe(110)with different coverages of tita- nia has been studied by AES,XPS,UPS.It is proposed that the adsorption sites of CO in this system are not only blocked by the deposited TiO_X,but also b...The adsorption of CO on Fe(110)with different coverages of tita- nia has been studied by AES,XPS,UPS.It is proposed that the adsorption sites of CO in this system are not only blocked by the deposited TiO_X,but also by the products of the dissociation of CO which is promoted by the deposited TiO_X.展开更多
The preparation, characterization and properties of titania overlayer on Fe(110) substrate is hereby reported. The TiO_X overlayer was found to form in a layer-by-layer mode with a suboxide of titanium in the form of ...The preparation, characterization and properties of titania overlayer on Fe(110) substrate is hereby reported. The TiO_X overlayer was found to form in a layer-by-layer mode with a suboxide of titanium in the form of TiO migrating into the Fe substrate and Fe migrating into the deposited layer of TiO_X simultaneously during the deposition.展开更多
Photoelectrochemical(PEC)H_(2)O_(2)production through water oxidation reaction(WOR)is a promising strategy,however,designing highly efficient and selective photoanode materials remains challenging due to competitive r...Photoelectrochemical(PEC)H_(2)O_(2)production through water oxidation reaction(WOR)is a promising strategy,however,designing highly efficient and selective photoanode materials remains challenging due to competitive reaction pathways.Here,for highly enhanced PEC H_(2)O_(2)production,we present a conformal amorphous titanyl phosphate(a-TP)overlayer on nanoparticulate TiO_(2)surfaces,achieved via lysozyme-molded in-situ surface reforming.The a-TP overlayer modulates surface adsorption energies for reaction intermediates,favoring WOR for H_(2)O_(2)production over the competing O_(2)evolution reaction.Our density functional theory calculations reveal that a-TP/TiO_(2)exhibits a substantial energy uphill for the O·*formation pathway,which disfavors O_(2)evolution but promotes H_(2)O_(2)production.Additionally,the a-TP overlayer strengthens the built-in electric field,resulting in favorable kinetics.Consequently,a-TP/TiO_(2)exhibits 3.7-fold higher Faraday efficiency(FE)of 63%at 1.76 V vs.reversible hydrogen electrode(RHE)under 1 sun illumination,compared to bare TiO_(2)(17%),representing the highest FE among TiO_(2)-based WOR H_(2)O_(2)production systems.Employing the a-TP overlayer constitutes a promising strategy for controlling reaction pathways and achieving efficient solar-to-chemical energy conversion.展开更多
The oxygen reduction reaction （ORR） and oxygen evolution reaction （OER） are crucial processes for energy conversion/storage systems, such as fuel cells, metal-air batteries, and water splitting. However, both reac...The oxygen reduction reaction （ORR） and oxygen evolution reaction （OER） are crucial processes for energy conversion/storage systems, such as fuel cells, metal-air batteries, and water splitting. However, both reactions are severely restricted by their sluggish kinetics, thus requiring highly active, cost-effective, and durable electrocatalysts. Herein, we develop novel bifunctional nanocatalysts through surface nanoengineering of dealloying-driven nanoporous gold （NPG）. Pd overlayers were precisely deposited onto the NPG ligament surface by epitaxial layer-by-layer growth. More importantly, the obtained NPG-Pd overlayer nanocatalysts exhibit remarkably enhanced electrocatalytic activities toward both the ORR and OER in alkaline media, benchmarked against a state- of-the-art Pt/C catalyst. The improved electrocatalytic performance is rationalized by the unique three-dimensional nanoarchitecture of NPG, enhanced Pd utilization efficiency from precise control of the Pd overlayers, and change in electronic structure, as revealed by density functional theory calculations.展开更多
WO_(3),an abundant transition metal semiconductor,is one of the most discussed materials to be used as a photoanode in photoelectrochemical water-splitting devices.The photoelectrochemical properties,such as photoacti...WO_(3),an abundant transition metal semiconductor,is one of the most discussed materials to be used as a photoanode in photoelectrochemical water-splitting devices.The photoelectrochemical properties,such as photoactivity and selectivity of WO_(3) in different electrolytes,are already well understood.However,the understanding of stability,one of the most important properties for utilization in a commercial device,is still in the early stages.In this work,a photoelectrochemical scanning flow cell coupled to an inductively coupled plasma mass spectrometer is applied to determine the influence of co-catalyst overlayers on photoanode stability.Spray-coatedWO_(3) photoanodes are used as a model system.Iridium is applied to the electrodes by atomic layer deposition in controlled layer thickness,as determined by ellipsometry and x-ray photoelectron spectroscopy.Photoactivity of the iridium-modified WO_(3) photoanodes decreases with increasing iridium layer thickness.Partial blocking of the WO_(3) surface by iridium is proposed as the main cause of the decreased photoelectrochemical performance.On the other hand,the stability of WO_(3) is notably increased even in the presence of the thinnest investigated iridium overlayer.Based on our findings,we provide a set of strategies to synthesize nanocomposite photoelectrodes simultaneously possessing high photoelectrochemical activity and photostability.展开更多
The synthesis of high-quality ultrathin overlayers is critically dependent on the surface structure of substrates,especially involving the overlayer–substrate interaction.By using in situ surface measurements,we demo...The synthesis of high-quality ultrathin overlayers is critically dependent on the surface structure of substrates,especially involving the overlayer–substrate interaction.By using in situ surface measurements,we demonstrate that the overlayer–substrate interaction can be tuned by doping near-surface Ar nanobubbles.The interfacial coupling strength significantly decreases with near-surface Ar nanobubbles,accompanying by an“anisotropic to isotropic”growth transformation.On the substrate containing near-surface Ar,the growth front crosses entire surface atomic steps in both uphill and downhill directions with no difference,and thus,the morphology of the two-dimensional(2D)overlayer exhibits a round-shape.Especially,the round-shaped 2D overlayers coalesce seamlessly with a growth acceleration in the approaching direction,which is barely observed in the synthesis of 2D materials.This can be attributed to the immigration lifetime and diffusion rate of growth species,which depends on the overlayer–substrate interaction and the surface catalysis.Furthermore,the“round to hexagon”morphological transition is achieved by etching-regrowth,revealing the inherent growth kinetics under quasi-freestanding conditions.These findings provide a novel promising way to modulate the growth,coalescence,and etching dynamics of 2D materials on solid surfaces by adjusting the strength of overlayer–substrate interaction,which contributes to optimization of large-scale production of 2D material crystals.展开更多
Dry reforming of methane(DRM)over Ni-based catalysts is an economically reasonable technology for large-scale CO_(2)utilization.However,prolonged Ni sintering and carbon deposition reduce the durability and efficiency...Dry reforming of methane(DRM)over Ni-based catalysts is an economically reasonable technology for large-scale CO_(2)utilization.However,prolonged Ni sintering and carbon deposition reduce the durability and efficiency of DRM,hindering its engineering application.Herein,we propose a facile approach by combining continuous microscale coprecipitation with solid-state reactions to construct a BaAl_(2)O_(4)-overlayer-confined Ni catalyst.The 5-wt%-Ni@BaAl_(2)O_(4)catalyst exhibited advanced CO_(2)and CH_(4)conversions of 96% and 86% at 800℃ and a GHSV of 144 L g_(cat)^(-1).h^(-1).Moreover,the k_(d)-CO_(2)and k_(d)-CH_(4)of Ni@BaAl_(2)O_(4)were 0.0063 and 0.0029 h^(-1);which are approximately half and one-thirds of those of Ni/BaAl_(2)O_(4)and slightly better than those of Ni@MgAl_(2)O_(4),underscoring the versatility of the proposed synthesis protocol for constructing core-shell structures.XAS,HAADF-STEM-EDS,and CO transmission-IR characterizations confirmed the SMSI of~2-nm amorphous BaAl_(2)O_(4)-overlaid~10 nm Ni with an overall mesoporous structure.After a long-term test,the sintering and coking inhibition effects of Ni@BaAl_(2)O_(4)(10→11 nm,0.55 mgCg_(cat)^(-1).h^(-1))outperformed Ni/BaAl_(2)O_(4)(13→22 nm,1.90 mgCg_(cat)^(-1).h^(-1))and Ni@MgAl_(2)O_(4).In situ time-resolved CH4→CO_(2)transient response,DRIFTS experiments,and DFT calculations suggested that Ni@BaAl_(2)O_(4)and Ni/BaAl_(2)O_(4)followed the Mars-van Krevelen and Langmuir-Hinshelwood redox mechanisms,respectively.The functional interfacial lattice oxygen promoted the removal of C_(ads)^(*)on Ni and core-shell structure induced fast CO_(2)adsorption and CO desorption.The present study provides a facile approach for constructing a stable and active Ni-based core-shell catalyst.Furthermore,it offers novel insights into the functionalities of non-reducible spinel overlayers in the DRM process.展开更多
This research presents a numerical simulation methodology for optimizing circular composite overlays’dimensions and pressure characteristics with orthotropic mechanical properties,specifically,for metal conduits with...This research presents a numerical simulation methodology for optimizing circular composite overlays’dimensions and pressure characteristics with orthotropic mechanical properties,specifically,for metal conduits with temperature-dependent elastoplastic behavior.The primary objective of the proposed method is to prevent crack propagation during pressure surges from operational to critical levels.This study examines the“Beineu-Bozoy-Shymkent”steel gas conduit,examining its performance across a temperature range of−40 to+50℃.This work builds on prior research on extended avalanche destruction in steel gas conduits and crack propagation prevention techniques.Theanalysis was conducted using a dynamic finite-element approach with the ANSYS-19.2/ExplicitDynamics software.Simulations of unprotected conduits revealed that increasing gas-dynamic pressure can convert a partial-depth crack into a through-crack,extending longitudinally to approximately seven times its initial length.Notably,at T=+50℃,the developed crack length was 1.2%longer than that at T=−40℃,highlighting the temperature sensitivity of crack progression.The modeling results indicate that crack propagation can be effectively controlled using a circular composite overlay with a thickness between 37.5%and 50%of the crack depth and a length approximately five times that of the initial crack,centered symmetrically over the crack.In addition,preliminary stress analysis indicated that limiting the overlay-induced pressure to 5%of the operational pressure effectively arrested crack growth without generating significant stress concentrations near the overlay boundaries,thereby preventing conduit integrity.展开更多
This research extends ongoing efforts to develop methods for reinforcing damaged main gas pipelines to prevent catastrophic failure.This study establishes the use of scaled-down experimental models for assessing the d...This research extends ongoing efforts to develop methods for reinforcing damaged main gas pipelines to prevent catastrophic failure.This study establishes the use of scaled-down experimental models for assessing the dynamic strength of damaged pipeline sections reinforced with wire wrapping or composite sleeves.A generalized dynamic model is introduced for numerical simulation to evaluate the effectiveness of reinforcement techniques.The model incorporates the elastoplastic behavior of pipe and wire materials,the influence of temperature on mechanical properties,the contact interaction between the pipe and the reinforcement components(including pretensioning),and local material failure under transient internal pressure.Based on these parameters,a finite element model was developed using ANSYS 19.2 to enable parametric studies.The accuracy of the proposed model was verified by comparing the simulation results with the experimental findings.Pipeline section samples containing non-penetrating longitudinal crackswere subjected to comparative analyses and transient pressure until critical failure.The unreinforced and steel wire-wrapped sections were investigated.The results confirm the feasibility of applying the computational model to study the dynamic strength of reinforced damaged pipe sections.Furthermore,pipelines with longitudinal cracks reinforced using circular composite overlays with orthotropic mechanical properties were examined,and recommendations are provided for selecting the geometric parameters of such overlays.展开更多
基金supported by the National Natural Science Foundation of China(Nos.11974068,91961204,and 12004065)the Fundamental Research Funds for the Central Universities of China(No.DUT20LAB110)+1 种基金the Liaoning Provincial Natural Science Foundation of China(No.2019JH3/30100002)Key Research and Development Project of Liaoning Province(No.2020JH2/10500003).
文摘Highly selective conversion of methane(CH_(4))to methanol(CH_(3)OH)is an emerging attractive but challenging process for future development of hydrogen economy,which requires efficient catalysts.Herein,we systematically explore the catalytic properties of Pt(111)overlayer on transition metal oxides(TMOs)for CH_(4) conversion by first principles calculations.The Pt(111)monolayer supported by Ce-terminated CeO_(2)(111)substrate exhibits high activity and selectivity for CH_(4) conversion to CH_(3)OH,with the kinetic barrier of rate-limiting step of 1.05 eV.Intriguingly,the surface activity of Pt overlayer is governed by its d-band center relative to the energy of bonding states of adsorbed molecules,which in turn depends on the number of charge transfer between Pt(111)monolayer and underlying TMOs substrates.These results provide useful insights in the design of metal overlayers as catalysts with high-ultra performance and atomic utilization.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(NRF-2021R1A2C1095669,NRF-2021R1F1A1049366 and NRF2023R1A2C1003088)supported by the GRDC(Global Research Development Center)Cooperative Hub Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(MSIT)(RS-202300258911)。
文摘Hematite(α-Fe_(2)O_(3)) based photoanodes have been extensively studied due to various intriguing features that make them viable candidates for a photoelectrochemical(PEC) water splitting photoanode.Herein,we propose a Zr-doped Fe_(2)O_(3) photoanode decorated with facilely spin-coated Au nanoparticles(NPs) and microwave-assisted attached Si co-doping in conjunction with a SiO_(x) overlayer that displayed a remarkable photocurrent density of 2.01 mA/cm^(2) at 1.23 V vs.RHE.The kinetic dynamics at the photoelectrode/-electrolyte interface was examined by employing systematic electrochemical investigations.The Au NPs played a dual role in increasing PEC water splitting.First,the Schottky interface that was formed between Au NPs and Zr-Fe_(2)O_(3) lectrode ensured the prevention of electron flow from the photoanode to the metal,increasing the number of available charges as well as suppressing surface charge recombination.Second,Au extracted photoholes from the bulk of the Zr-Fe_(2)O_(3) and transported them to the outer SiO_(x) overlayer,while the SiO_(x) overlayer efficiently collected the photoholes and promoted the hole injection into the electrolyte.Further,Si co-doping enhanced bulk conductivity by reducing bulk charge transfer resistance and improving charge carrier density.This study outlines a technique to design a metallic charge transfer path with an overlayer for solar energy conversion.
文摘The adsorption of CO on Fe(110)with different coverages of tita- nia has been studied by AES,XPS,UPS.It is proposed that the adsorption sites of CO in this system are not only blocked by the deposited TiO_X,but also by the products of the dissociation of CO which is promoted by the deposited TiO_X.
文摘The preparation, characterization and properties of titania overlayer on Fe(110) substrate is hereby reported. The TiO_X overlayer was found to form in a layer-by-layer mode with a suboxide of titanium in the form of TiO migrating into the Fe substrate and Fe migrating into the deposited layer of TiO_X simultaneously during the deposition.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government,Ministry of Science and ICT(MSIT)(NRF-2020M3D1A2102837)the Korea Institute of Energy Technology Evaluation and Planning(KETEP)grant funded by the Korea government(MOTIE)(20214000000500,training program of CCUS for the green growth)。
文摘Photoelectrochemical(PEC)H_(2)O_(2)production through water oxidation reaction(WOR)is a promising strategy,however,designing highly efficient and selective photoanode materials remains challenging due to competitive reaction pathways.Here,for highly enhanced PEC H_(2)O_(2)production,we present a conformal amorphous titanyl phosphate(a-TP)overlayer on nanoparticulate TiO_(2)surfaces,achieved via lysozyme-molded in-situ surface reforming.The a-TP overlayer modulates surface adsorption energies for reaction intermediates,favoring WOR for H_(2)O_(2)production over the competing O_(2)evolution reaction.Our density functional theory calculations reveal that a-TP/TiO_(2)exhibits a substantial energy uphill for the O·*formation pathway,which disfavors O_(2)evolution but promotes H_(2)O_(2)production.Additionally,the a-TP overlayer strengthens the built-in electric field,resulting in favorable kinetics.Consequently,a-TP/TiO_(2)exhibits 3.7-fold higher Faraday efficiency(FE)of 63%at 1.76 V vs.reversible hydrogen electrode(RHE)under 1 sun illumination,compared to bare TiO_(2)(17%),representing the highest FE among TiO_(2)-based WOR H_(2)O_(2)production systems.Employing the a-TP overlayer constitutes a promising strategy for controlling reaction pathways and achieving efficient solar-to-chemical energy conversion.
基金The authors gratefully acknowledge financial support by the National Basic Research Program of China （No. 2012CB932800）, National Natural Science Foundation of China （Nos. 51371106 and 51222202）, and Young Tip-top Talent Support Project （the Organization Department of the Central Committee of the CPC）. The Institute of Materials of Ruhr University Bochum （Germany） is acknowledged for the support of SEM and TEM characterization. This work also made use of the resources of the Center of Electron Microscopy of Zhejiang University.
文摘The oxygen reduction reaction （ORR） and oxygen evolution reaction （OER） are crucial processes for energy conversion/storage systems, such as fuel cells, metal-air batteries, and water splitting. However, both reactions are severely restricted by their sluggish kinetics, thus requiring highly active, cost-effective, and durable electrocatalysts. Herein, we develop novel bifunctional nanocatalysts through surface nanoengineering of dealloying-driven nanoporous gold （NPG）. Pd overlayers were precisely deposited onto the NPG ligament surface by epitaxial layer-by-layer growth. More importantly, the obtained NPG-Pd overlayer nanocatalysts exhibit remarkably enhanced electrocatalytic activities toward both the ORR and OER in alkaline media, benchmarked against a state- of-the-art Pt/C catalyst. The improved electrocatalytic performance is rationalized by the unique three-dimensional nanoarchitecture of NPG, enhanced Pd utilization efficiency from precise control of the Pd overlayers, and change in electronic structure, as revealed by density functional theory calculations.
基金German Ministry of Education and Reseach(BMBF),Grant/Award Number:03SF0564ADeutsche Forschungsgemeinschaft(DFG),Grant/Award Number:429730598。
文摘WO_(3),an abundant transition metal semiconductor,is one of the most discussed materials to be used as a photoanode in photoelectrochemical water-splitting devices.The photoelectrochemical properties,such as photoactivity and selectivity of WO_(3) in different electrolytes,are already well understood.However,the understanding of stability,one of the most important properties for utilization in a commercial device,is still in the early stages.In this work,a photoelectrochemical scanning flow cell coupled to an inductively coupled plasma mass spectrometer is applied to determine the influence of co-catalyst overlayers on photoanode stability.Spray-coatedWO_(3) photoanodes are used as a model system.Iridium is applied to the electrodes by atomic layer deposition in controlled layer thickness,as determined by ellipsometry and x-ray photoelectron spectroscopy.Photoactivity of the iridium-modified WO_(3) photoanodes decreases with increasing iridium layer thickness.Partial blocking of the WO_(3) surface by iridium is proposed as the main cause of the decreased photoelectrochemical performance.On the other hand,the stability of WO_(3) is notably increased even in the presence of the thinnest investigated iridium overlayer.Based on our findings,we provide a set of strategies to synthesize nanocomposite photoelectrodes simultaneously possessing high photoelectrochemical activity and photostability.
基金the National Natural Science Foundation of China(Nos.21872169,91845109,21688102,and 21825203)the National Key R&D Program of China(No.2016YFA0200200)+2 种基金Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB17020000)China Postdoctoral Science Foundation(No.2019M651997)Natural Science Foundation of Jiangsu Province(No.BK20200257).
文摘The synthesis of high-quality ultrathin overlayers is critically dependent on the surface structure of substrates,especially involving the overlayer–substrate interaction.By using in situ surface measurements,we demonstrate that the overlayer–substrate interaction can be tuned by doping near-surface Ar nanobubbles.The interfacial coupling strength significantly decreases with near-surface Ar nanobubbles,accompanying by an“anisotropic to isotropic”growth transformation.On the substrate containing near-surface Ar,the growth front crosses entire surface atomic steps in both uphill and downhill directions with no difference,and thus,the morphology of the two-dimensional(2D)overlayer exhibits a round-shape.Especially,the round-shaped 2D overlayers coalesce seamlessly with a growth acceleration in the approaching direction,which is barely observed in the synthesis of 2D materials.This can be attributed to the immigration lifetime and diffusion rate of growth species,which depends on the overlayer–substrate interaction and the surface catalysis.Furthermore,the“round to hexagon”morphological transition is achieved by etching-regrowth,revealing the inherent growth kinetics under quasi-freestanding conditions.These findings provide a novel promising way to modulate the growth,coalescence,and etching dynamics of 2D materials on solid surfaces by adjusting the strength of overlayer–substrate interaction,which contributes to optimization of large-scale production of 2D material crystals.
基金financially supported by the National Natural Science Foundation of China(22378227)the National Research Foundation,Singapore,and A*STAR under its Low-Carbon Energy Research(LCER)Funding Initiative(FI)Project(U2102d2011,WBS:A-8000278-00-00)the Medium Energy X-ray Absorption Spectroscopy beamline at the Australian Synchrotron,part of ANSTO。
文摘Dry reforming of methane(DRM)over Ni-based catalysts is an economically reasonable technology for large-scale CO_(2)utilization.However,prolonged Ni sintering and carbon deposition reduce the durability and efficiency of DRM,hindering its engineering application.Herein,we propose a facile approach by combining continuous microscale coprecipitation with solid-state reactions to construct a BaAl_(2)O_(4)-overlayer-confined Ni catalyst.The 5-wt%-Ni@BaAl_(2)O_(4)catalyst exhibited advanced CO_(2)and CH_(4)conversions of 96% and 86% at 800℃ and a GHSV of 144 L g_(cat)^(-1).h^(-1).Moreover,the k_(d)-CO_(2)and k_(d)-CH_(4)of Ni@BaAl_(2)O_(4)were 0.0063 and 0.0029 h^(-1);which are approximately half and one-thirds of those of Ni/BaAl_(2)O_(4)and slightly better than those of Ni@MgAl_(2)O_(4),underscoring the versatility of the proposed synthesis protocol for constructing core-shell structures.XAS,HAADF-STEM-EDS,and CO transmission-IR characterizations confirmed the SMSI of~2-nm amorphous BaAl_(2)O_(4)-overlaid~10 nm Ni with an overall mesoporous structure.After a long-term test,the sintering and coking inhibition effects of Ni@BaAl_(2)O_(4)(10→11 nm,0.55 mgCg_(cat)^(-1).h^(-1))outperformed Ni/BaAl_(2)O_(4)(13→22 nm,1.90 mgCg_(cat)^(-1).h^(-1))and Ni@MgAl_(2)O_(4).In situ time-resolved CH4→CO_(2)transient response,DRIFTS experiments,and DFT calculations suggested that Ni@BaAl_(2)O_(4)and Ni/BaAl_(2)O_(4)followed the Mars-van Krevelen and Langmuir-Hinshelwood redox mechanisms,respectively.The functional interfacial lattice oxygen promoted the removal of C_(ads)^(*)on Ni and core-shell structure induced fast CO_(2)adsorption and CO desorption.The present study provides a facile approach for constructing a stable and active Ni-based core-shell catalyst.Furthermore,it offers novel insights into the functionalities of non-reducible spinel overlayers in the DRM process.
基金supported by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan(Grant No.AP19680589).
文摘This research presents a numerical simulation methodology for optimizing circular composite overlays’dimensions and pressure characteristics with orthotropic mechanical properties,specifically,for metal conduits with temperature-dependent elastoplastic behavior.The primary objective of the proposed method is to prevent crack propagation during pressure surges from operational to critical levels.This study examines the“Beineu-Bozoy-Shymkent”steel gas conduit,examining its performance across a temperature range of−40 to+50℃.This work builds on prior research on extended avalanche destruction in steel gas conduits and crack propagation prevention techniques.Theanalysis was conducted using a dynamic finite-element approach with the ANSYS-19.2/ExplicitDynamics software.Simulations of unprotected conduits revealed that increasing gas-dynamic pressure can convert a partial-depth crack into a through-crack,extending longitudinally to approximately seven times its initial length.Notably,at T=+50℃,the developed crack length was 1.2%longer than that at T=−40℃,highlighting the temperature sensitivity of crack progression.The modeling results indicate that crack propagation can be effectively controlled using a circular composite overlay with a thickness between 37.5%and 50%of the crack depth and a length approximately five times that of the initial crack,centered symmetrically over the crack.In addition,preliminary stress analysis indicated that limiting the overlay-induced pressure to 5%of the operational pressure effectively arrested crack growth without generating significant stress concentrations near the overlay boundaries,thereby preventing conduit integrity.
基金funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan(Grant No.AP19680589).
文摘This research extends ongoing efforts to develop methods for reinforcing damaged main gas pipelines to prevent catastrophic failure.This study establishes the use of scaled-down experimental models for assessing the dynamic strength of damaged pipeline sections reinforced with wire wrapping or composite sleeves.A generalized dynamic model is introduced for numerical simulation to evaluate the effectiveness of reinforcement techniques.The model incorporates the elastoplastic behavior of pipe and wire materials,the influence of temperature on mechanical properties,the contact interaction between the pipe and the reinforcement components(including pretensioning),and local material failure under transient internal pressure.Based on these parameters,a finite element model was developed using ANSYS 19.2 to enable parametric studies.The accuracy of the proposed model was verified by comparing the simulation results with the experimental findings.Pipeline section samples containing non-penetrating longitudinal crackswere subjected to comparative analyses and transient pressure until critical failure.The unreinforced and steel wire-wrapped sections were investigated.The results confirm the feasibility of applying the computational model to study the dynamic strength of reinforced damaged pipe sections.Furthermore,pipelines with longitudinal cracks reinforced using circular composite overlays with orthotropic mechanical properties were examined,and recommendations are provided for selecting the geometric parameters of such overlays.
