Dry reforming of methane(DRM)converts CH4 and CO_(2) to syngas.Photothermal DRM,which integrates temperature and light,is a sustainable method for storing solar energy in molecules.However,challenges such as limited l...Dry reforming of methane(DRM)converts CH4 and CO_(2) to syngas.Photothermal DRM,which integrates temperature and light,is a sustainable method for storing solar energy in molecules.However,challenges such as limited light absorption,low photocarrier separation efficiency,Ni sintering,and carbon deposition hinder DRM stability.Herein,we regulated Ni contents in(Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalysts to enhance the optical characteristics while addressing Ni sintering and carbon deposition issues.The(3Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalyst had insufficient Ni content,while the(9Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalyst showed excessive carbon deposition,leading to lower stability compared to the(6Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalyst,which achieved CH4 and CO_(2) rates to 231.0 μmol gcat^(-1)s^(-1) and 294.3 μmol gcat^(-1)s^(-1) ,respectively,at 973 K,with only 0.2 wt.%carbon deposition and no Ni sintering.This work adjusted Ni contents in(Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalysts to enhance DRM performance,which has implications for improving other reactions.展开更多
The Ni single-atom catalyst dispersed on nitrogen doped graphene support has attracted much interest due to the high selectivity in electro-catalyzing CO_(2)reduction to CO,yet the chemical inertness of the metal cent...The Ni single-atom catalyst dispersed on nitrogen doped graphene support has attracted much interest due to the high selectivity in electro-catalyzing CO_(2)reduction to CO,yet the chemical inertness of the metal center renders it to exhibit electrochemical activity only under high overpotentials.Herein,we report P-and S-doped Ni single-atom catalysts,i.e.symmetric Ni_(1)/PN_(4)and asymmetric Ni1/SN_(3)C can exhibit high catalytic activity of CO_(2)reduction with stable potential windows.It is revealed that the key intermediate*COOH in CO_(2)electroreduction is stabilized by heteroatom doping,which stems from the upward shift of the axial d_(z2)orbital of the active metal Ni atom.Furthermore,we investigate the potential-dependent free energetics and dynamic properties at the electrochemical interface on the Ni1/SN3C catalyst using ab initio molecular dynamics simulations with a full explicit solvent model.Based on the potential-dependent microkinetic model,we predict that S-atom doped Ni SAC shifts the onset potential of CO_(2)electroreduction from–0.88 to–0.80 V vs.RHE,exhibiting better activity.Overall,this work provides an in-depth understanding of structure-activity relationships and atomic-level electrochemical interfaces of catalytic systems,and offers insights into the rational design of heteroatom-doped catalysts for targeted catalysis.展开更多
Transition metal-carbonate interfaces often act as active sites in heterogeneous catalytic reactions.The interface between transition metal and metal carbonate exhibits a dynamic equilibrium during the CO_(2)hydrogena...Transition metal-carbonate interfaces often act as active sites in heterogeneous catalytic reactions.The interface between transition metal and metal carbonate exhibits a dynamic equilibrium during the CO_(2)hydrogenation reaction,involving surface carbonate hydrogenation and CO_(2)chemisorption.Nonetheless,there have been few reports on engineering the activity of the interface between transition metal and alkaline earth metal carbonate for catalytic CO_(2)conversion.This work demonstrated that the incorporation of CaH_(2)in Ni/CaCO_(3)enhances the CO_(2)methanation activity of the catalysts.The CO_(2)conversion for Ni/CaH_(2)-CaCO_(3)reached 68.5%at 400°C,which was much higher than that of the Ni/CaCO_(3)(31.6%) and Ni/CaH_(2)-CaO (42.4%) catalysts.Furthermore,the Ni/CaH_(2)-CaCO_(3)catalysts remained stable during the stability test for 24 h at 400°C and 8 bar.Our research revealed that CaH_(2)played a crucial role in promoting the activity of the Ni-carbonate interface for CO_(2)methanation.CaH_(2)could modify the electronic structure of Ni and tune the structural properties of CaCO_(3)to generate medium basic sites (OH groups),which are favorable for the activation of H2and CO_(2).In-situ Fourier transform infrared spectroscopy (FTIR) analysis combined with density functional theory calculations demonstrated that CO_(2)activation occurs at the hydroxyl group (OH) on the CaH_(2)-modified Ni-carbonate surface,leading to the formation of CO_(3)H*species.Furthermore,our study has confirmed that CO_(2)methanation over the Ni/CaH_(2)-CaCO_(3)catalysts proceeds via the formate pathway.展开更多
This work synthesized a series of Ni/CeO_(2)/Al_(2)O_(3) catalysts with varying CeO_(2) doping amounts to enhance low-temperature CO_(2) methanation.The introduction of CeO_(2) weakens the interaction between Ni and A...This work synthesized a series of Ni/CeO_(2)/Al_(2)O_(3) catalysts with varying CeO_(2) doping amounts to enhance low-temperature CO_(2) methanation.The introduction of CeO_(2) weakens the interaction between Ni and Al_(2)O_(3),leading to the formation of Ni-CeO_(2) active sites.This results in a high dispersion of Ni and CeO_(2),improved catalyst reducibility,increased number of active sites,and enhanced the CO_(2) methanation.This work further investigated the impact of WHSV and catalyst stacking configuration to enhance the reaction.When the catalyst is stacked into three segments with a temperature gradient of 330℃,300℃,and 250℃under WHSV=9000 ml·h^(-1)·g^(-1),the CO_(2) conversion significantly increases to 95%,which is remarkably close to the thermodynamic equilibrium(96%).展开更多
The catalytic hydrogenation of p-nitrophenol to p-aminophenol was investigated over Ni/TiO2 catalysts prepared by a liquid-phase chemical reduction method. The catalysts were characterized by inductively coupled plasm...The catalytic hydrogenation of p-nitrophenol to p-aminophenol was investigated over Ni/TiO2 catalysts prepared by a liquid-phase chemical reduction method. The catalysts were characterized by inductively coupled plasma (ICP), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and temperature-programmed reduction (TPR). Results show that the titania structure has favorable influence on physio-chemical and catalytic properties of Ni/TiO2 catalysts. Compared to commercial Raney nickel, the catalytic activity of Ni/TiO2 catalyst is much superior, irrespective of the titania structure. The catalytic activity of anatase titania supported nickel catalyst Ni/TiO2(A) is higher than that of rutile titania supported nickel catalyst Ni/TiO2(R), possibly because the reduction of nickel oxide to metallic nickel for Ni/TiO2(A) is easier than that for Ni/TiO2(R) at similar reaction conditions.展开更多
A titania pillared interlayered clay（Ti-PILC） supported vanadia catalyst（V2O5/TiO2-PILC） was prepared by wet impregnation for the selective catalytic reduction（SCR） of NO with ammonia. Compared to the traditiona...A titania pillared interlayered clay（Ti-PILC） supported vanadia catalyst（V2O5/TiO2-PILC） was prepared by wet impregnation for the selective catalytic reduction（SCR） of NO with ammonia. Compared to the traditional V2O5/TiO2 and V2O5-MoO3/TiO2 catalysts, the V2O5/TiO2-PILC catalyst exhibited a higher activity and better SO2 and H2O resistance in the NH3-SCR reaction. Characterization using TPD, in situ DRIFT and XPS showed that surface sulfate and/or sulfite species and ionic SO4^（2-）species were formed on the catalyst in the presence of SO2. The ionic SO4^（2-） species on the catalyst surface was one reason for deactivation of the catalyst in SCR. The formation of the ionic SO4^（2-） species was correlated with the amount of surface adsorbed oxygen species. Less adsorbed oxygen species gave less ionic SO4^（2-） species on the catalyst.展开更多
Electrochemical CO_(2) reduction to produce value-added chemicals and fuels is one of the research hotspots in the field of energy conversion.The development of efficient catalysts with high conductivity and readily a...Electrochemical CO_(2) reduction to produce value-added chemicals and fuels is one of the research hotspots in the field of energy conversion.The development of efficient catalysts with high conductivity and readily accessible active sites for CO_(2) electroreduction remains challenging yet indispensable.In this work,a reliable poly(ethyleneimine)(PEI)-assisted strategy is developed to prepare a hollow carbon nanocomposite comprising a single-site Ni-modified carbon shell and confined Ni nanoparticles(NPs)(denoted as Ni@NHCS),where PEI not only functions as a mediator to induce the highly dispersed growth of Ni NPs within hollow carbon spheres,but also as a nitrogen precursor to construct highly active atomically-dispersed Ni-Nx sites.Benefiting from the unique structural properties of Ni@NHCS,the aggregation and exposure of Ni NPs can be effectively prevented,while the accessibility of abundant catalytically active Ni-Nx sites can be ensured.As a result,Ni@NHCS exhibits a high CO partial current density of 26.9 mA cm^(-2) and a Faradaic efficiency of 93.0% at-1.0 V vs.RHE,outperforming those of its PEI-free analog.Apart from the excellent activity and selectivity,the shell confinement effect of the hollow carbon sphere endows this catalyst with long-term stability.The findings here are anticipated to help understand the structure-activity relationship in Ni-based carbon catalyst systems for electrocatalytic CO_(2) reduction.Furthermore,the PEI-assisted synthetic concept is potentially applicable to the preparation of high-performance metal-based nanoconfined materials tailored for diverse energy conversion applications and beyond.展开更多
The influence of calcination temperature on the structure and catalytic behavior of Ni/TiO2-SiO2 catalyst, for CO2 reforming of methane to synthesis gas under atmospheric pressure, was investigated. The results showed...The influence of calcination temperature on the structure and catalytic behavior of Ni/TiO2-SiO2 catalyst, for CO2 reforming of methane to synthesis gas under atmospheric pressure, was investigated. The results showed that the Ni/TiO2-SiO2 catalyst calcined at 700 ℃ had high and stable activity while the catalysts calcined at 550 and 850 ℃ had low and unstable activity. Depending on the calcination temperature, one, two, or three of the following Ni-containing species, NiO, Ni2.44Ti0.72Si0.07O4, and NiTiO3 were identified by combining the temperature programmed reduction （TPR） and X-ray diffraction （XRD） results. Their reducibility decreased in the sequence： NiO〉Ni2.44Ti0.72Si0.07O4〉NiTiO3. It suggests that high and stable activities observed over the Ni/TiO2-SiO2 catalyst calcined at 700 ~C were induced by the formation of Ni2.44Ti0.72Si0.07O4 and smaller NiO species crystallite size.展开更多
基金support from the National Natural Science Foundation of China(22078134)State Key Laboratory of Clean and Efficient Coal Utilization of Taiyuan University of Technology(SKL2022006)Natural Science Foundation of Chongqing(CSTB2023NSCQ-MSX0162)are greatly appreciated for the work.
文摘Dry reforming of methane(DRM)converts CH4 and CO_(2) to syngas.Photothermal DRM,which integrates temperature and light,is a sustainable method for storing solar energy in molecules.However,challenges such as limited light absorption,low photocarrier separation efficiency,Ni sintering,and carbon deposition hinder DRM stability.Herein,we regulated Ni contents in(Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalysts to enhance the optical characteristics while addressing Ni sintering and carbon deposition issues.The(3Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalyst had insufficient Ni content,while the(9Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalyst showed excessive carbon deposition,leading to lower stability compared to the(6Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalyst,which achieved CH4 and CO_(2) rates to 231.0 μmol gcat^(-1)s^(-1) and 294.3 μmol gcat^(-1)s^(-1) ,respectively,at 973 K,with only 0.2 wt.%carbon deposition and no Ni sintering.This work adjusted Ni contents in(Ni/Ce_(0.8)Zr_(0.2)O_(2))@SiO_(2) catalysts to enhance DRM performance,which has implications for improving other reactions.
文摘The Ni single-atom catalyst dispersed on nitrogen doped graphene support has attracted much interest due to the high selectivity in electro-catalyzing CO_(2)reduction to CO,yet the chemical inertness of the metal center renders it to exhibit electrochemical activity only under high overpotentials.Herein,we report P-and S-doped Ni single-atom catalysts,i.e.symmetric Ni_(1)/PN_(4)and asymmetric Ni1/SN_(3)C can exhibit high catalytic activity of CO_(2)reduction with stable potential windows.It is revealed that the key intermediate*COOH in CO_(2)electroreduction is stabilized by heteroatom doping,which stems from the upward shift of the axial d_(z2)orbital of the active metal Ni atom.Furthermore,we investigate the potential-dependent free energetics and dynamic properties at the electrochemical interface on the Ni1/SN3C catalyst using ab initio molecular dynamics simulations with a full explicit solvent model.Based on the potential-dependent microkinetic model,we predict that S-atom doped Ni SAC shifts the onset potential of CO_(2)electroreduction from–0.88 to–0.80 V vs.RHE,exhibiting better activity.Overall,this work provides an in-depth understanding of structure-activity relationships and atomic-level electrochemical interfaces of catalytic systems,and offers insights into the rational design of heteroatom-doped catalysts for targeted catalysis.
基金National Natural Science Foundation of China (Nos. 22371244 and 21573192)Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX22_3463)。
文摘Transition metal-carbonate interfaces often act as active sites in heterogeneous catalytic reactions.The interface between transition metal and metal carbonate exhibits a dynamic equilibrium during the CO_(2)hydrogenation reaction,involving surface carbonate hydrogenation and CO_(2)chemisorption.Nonetheless,there have been few reports on engineering the activity of the interface between transition metal and alkaline earth metal carbonate for catalytic CO_(2)conversion.This work demonstrated that the incorporation of CaH_(2)in Ni/CaCO_(3)enhances the CO_(2)methanation activity of the catalysts.The CO_(2)conversion for Ni/CaH_(2)-CaCO_(3)reached 68.5%at 400°C,which was much higher than that of the Ni/CaCO_(3)(31.6%) and Ni/CaH_(2)-CaO (42.4%) catalysts.Furthermore,the Ni/CaH_(2)-CaCO_(3)catalysts remained stable during the stability test for 24 h at 400°C and 8 bar.Our research revealed that CaH_(2)played a crucial role in promoting the activity of the Ni-carbonate interface for CO_(2)methanation.CaH_(2)could modify the electronic structure of Ni and tune the structural properties of CaCO_(3)to generate medium basic sites (OH groups),which are favorable for the activation of H2and CO_(2).In-situ Fourier transform infrared spectroscopy (FTIR) analysis combined with density functional theory calculations demonstrated that CO_(2)activation occurs at the hydroxyl group (OH) on the CaH_(2)-modified Ni-carbonate surface,leading to the formation of CO_(3)H*species.Furthermore,our study has confirmed that CO_(2)methanation over the Ni/CaH_(2)-CaCO_(3)catalysts proceeds via the formate pathway.
基金financial support of the National Natural Science Foundation of China(22178265)Tianjin Science and Technology Project(21JCYBJC00400)Open Project for Ningbo Key Laboratory of Green Petrochemical Carbon Emission Reduction Technology and Equipment(ZITJU2023-ZYDK001).
文摘This work synthesized a series of Ni/CeO_(2)/Al_(2)O_(3) catalysts with varying CeO_(2) doping amounts to enhance low-temperature CO_(2) methanation.The introduction of CeO_(2) weakens the interaction between Ni and Al_(2)O_(3),leading to the formation of Ni-CeO_(2) active sites.This results in a high dispersion of Ni and CeO_(2),improved catalyst reducibility,increased number of active sites,and enhanced the CO_(2) methanation.This work further investigated the impact of WHSV and catalyst stacking configuration to enhance the reaction.When the catalyst is stacked into three segments with a temperature gradient of 330℃,300℃,and 250℃under WHSV=9000 ml·h^(-1)·g^(-1),the CO_(2) conversion significantly increases to 95%,which is remarkably close to the thermodynamic equilibrium(96%).
基金Supported by the National Basic Research Program (No.2003CB615702) and the National Natural Science Foundation of Chin(No.20436030).
文摘The catalytic hydrogenation of p-nitrophenol to p-aminophenol was investigated over Ni/TiO2 catalysts prepared by a liquid-phase chemical reduction method. The catalysts were characterized by inductively coupled plasma (ICP), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and temperature-programmed reduction (TPR). Results show that the titania structure has favorable influence on physio-chemical and catalytic properties of Ni/TiO2 catalysts. Compared to commercial Raney nickel, the catalytic activity of Ni/TiO2 catalyst is much superior, irrespective of the titania structure. The catalytic activity of anatase titania supported nickel catalyst Ni/TiO2(A) is higher than that of rutile titania supported nickel catalyst Ni/TiO2(R), possibly because the reduction of nickel oxide to metallic nickel for Ni/TiO2(A) is easier than that for Ni/TiO2(R) at similar reaction conditions.
基金supported by the National Natural Science Foundation of China(21277009,21577005)~~
文摘A titania pillared interlayered clay（Ti-PILC） supported vanadia catalyst（V2O5/TiO2-PILC） was prepared by wet impregnation for the selective catalytic reduction（SCR） of NO with ammonia. Compared to the traditional V2O5/TiO2 and V2O5-MoO3/TiO2 catalysts, the V2O5/TiO2-PILC catalyst exhibited a higher activity and better SO2 and H2O resistance in the NH3-SCR reaction. Characterization using TPD, in situ DRIFT and XPS showed that surface sulfate and/or sulfite species and ionic SO4^（2-）species were formed on the catalyst in the presence of SO2. The ionic SO4^（2-） species on the catalyst surface was one reason for deactivation of the catalyst in SCR. The formation of the ionic SO4^（2-） species was correlated with the amount of surface adsorbed oxygen species. Less adsorbed oxygen species gave less ionic SO4^（2-） species on the catalyst.
文摘Electrochemical CO_(2) reduction to produce value-added chemicals and fuels is one of the research hotspots in the field of energy conversion.The development of efficient catalysts with high conductivity and readily accessible active sites for CO_(2) electroreduction remains challenging yet indispensable.In this work,a reliable poly(ethyleneimine)(PEI)-assisted strategy is developed to prepare a hollow carbon nanocomposite comprising a single-site Ni-modified carbon shell and confined Ni nanoparticles(NPs)(denoted as Ni@NHCS),where PEI not only functions as a mediator to induce the highly dispersed growth of Ni NPs within hollow carbon spheres,but also as a nitrogen precursor to construct highly active atomically-dispersed Ni-Nx sites.Benefiting from the unique structural properties of Ni@NHCS,the aggregation and exposure of Ni NPs can be effectively prevented,while the accessibility of abundant catalytically active Ni-Nx sites can be ensured.As a result,Ni@NHCS exhibits a high CO partial current density of 26.9 mA cm^(-2) and a Faradaic efficiency of 93.0% at-1.0 V vs.RHE,outperforming those of its PEI-free analog.Apart from the excellent activity and selectivity,the shell confinement effect of the hollow carbon sphere endows this catalyst with long-term stability.The findings here are anticipated to help understand the structure-activity relationship in Ni-based carbon catalyst systems for electrocatalytic CO_(2) reduction.Furthermore,the PEI-assisted synthetic concept is potentially applicable to the preparation of high-performance metal-based nanoconfined materials tailored for diverse energy conversion applications and beyond.
文摘The influence of calcination temperature on the structure and catalytic behavior of Ni/TiO2-SiO2 catalyst, for CO2 reforming of methane to synthesis gas under atmospheric pressure, was investigated. The results showed that the Ni/TiO2-SiO2 catalyst calcined at 700 ℃ had high and stable activity while the catalysts calcined at 550 and 850 ℃ had low and unstable activity. Depending on the calcination temperature, one, two, or three of the following Ni-containing species, NiO, Ni2.44Ti0.72Si0.07O4, and NiTiO3 were identified by combining the temperature programmed reduction （TPR） and X-ray diffraction （XRD） results. Their reducibility decreased in the sequence： NiO〉Ni2.44Ti0.72Si0.07O4〉NiTiO3. It suggests that high and stable activities observed over the Ni/TiO2-SiO2 catalyst calcined at 700 ~C were induced by the formation of Ni2.44Ti0.72Si0.07O4 and smaller NiO species crystallite size.
