Surface-supported isolated atoms in single-atom catalysts(SACs)grant maximum utilization of metals in heterogeneous catalysis.Herein,we report a feasible pyrolysis strategy to synthesize Pd single atoms by thermally m...Surface-supported isolated atoms in single-atom catalysts(SACs)grant maximum utilization of metals in heterogeneous catalysis.Herein,we report a feasible pyrolysis strategy to synthesize Pd single atoms by thermally melting Pd nanoparticles on an oxygen-vacancy-rich tungsten-oxide matrix at reduction atmosphere.Near ambient pressure X-ray photoelectron spectroscopy was used to monitor the formation of zero-valence Pd single atoms and the increased metallic feature of WO_(3-x)substrate.Accordingly,the as-obtained zero-valence Pd single-atom catalyst exhibits a markedly boosted HER activity with a low overpotential(η_(10)=70 mV)at the current density of 10 mA/cm2and a small Tafel slope(b=68 mV/dec),nearly 150 mV and a 3,0-fold enhancement than those of Pd nanoparticles(η_(10)=220 mV,b=133 mV/dec)under the same conditions.In addition,quasi in situ XPS results suggest the hydrogen spillover effect is more likely to occur on Pd single atoms during the electrochemical process.Our work may pave an interesting route for the rational design of highly-efficient single-atom catalysts,and the elucidation of corresponding enhanced reaction mechanisms by the utilization of advanced characterization techniques.展开更多
The oxidation of porous Ni-yttria-stabilized zirconia(YSZ)and Ni-gadolinia-doped ceria(GDC)ceramicmetal(cermet)electrodes in H_(2)O and CO_(2)atmospheres was studied by near-ambient pressure X-ray photoelectron spectr...The oxidation of porous Ni-yttria-stabilized zirconia(YSZ)and Ni-gadolinia-doped ceria(GDC)ceramicmetal(cermet)electrodes in H_(2)O and CO_(2)atmospheres was studied by near-ambient pressure X-ray photoelectron spectroscopy(NAP-XPS).We show that the oxidation of nickel by the two gases is not similar,as is commonly believed,but it depends on the ceramic type.Nickel is vulnerable to oxidation in H_(2)O but it resists to CO_(2)in Ni-GDC,as compared to the Ni-YSZ electrode.Inspired by this observation we conceptualize and fabricate Ni-YSZ electrodes modified by ceria nanoparticles,which show significantly higher resistance to CO_(2)oxidation as compared with conventional Ni-YSZ electrodes.The preparation of tailormade cermet electrodes with identical bulk/mechanical characteristics but very different surface properties offers a promising fabrication strategy for high-performance and durability solid oxide electrolysis cells for CO_(2)conversion.展开更多
Sustainable methanol production via CO_(2) hydrogenation leads to increased interest in the understanding of active phase of Cu/ZnO/Al_(2)O_(3)(CZA) catalyst. Model catalysts of ZnO/Cu(111) with structures varied from...Sustainable methanol production via CO_(2) hydrogenation leads to increased interest in the understanding of active phase of Cu/ZnO/Al_(2)O_(3)(CZA) catalyst. Model catalysts of ZnO/Cu(111) with structures varied from two-dimensional planar to three-dimensional nanoparticles were prepared by atomic layer deposition(ALD) method. By combing scanning tunneling microscopy(STM) and X-ray photoelectron spectroscopy(XPS) at near-ambient pressure of CO_(2) hydrogenation, we reveal that the submonolayer ZnO/Cu(111) transformed into Cu-Zn alloy under 10 mbar CO_(2)/H_(2) at 493 K, and underwent a partial reoxidation during evacuation. The dynamic phase transformation of ZnO/Cu(111) may partly explain the existence of differences and apparently contradictory theories to account for the origin of active phase in CZA catalysts.展开更多
Ultrathin ZnO nano structures prese nt in teresti ng two-dimensi on al(2D)graphene-like structure in contrast to wurtzite structure in bulk ZnO.Growth on Au(111)has been regarded as a well-established route to the 2D ...Ultrathin ZnO nano structures prese nt in teresti ng two-dimensi on al(2D)graphene-like structure in contrast to wurtzite structure in bulk ZnO.Growth on Au(111)has been regarded as a well-established route to the 2D ZnO layers while controlled growth of uniform ZnO nano structures remains as a challe nge.Here,reactive deposition of Zn in O3 and NO2 was employed,which is investigated by sea nning tunneling microscopy and X-ray photoelectr on spectroscopy(XPS).We dem on strate that uniform ZnO mono layer nanoislands and films can be obtained on Au(111)using O3 and uniform ZnO bilayer nanoislands and films form on Au(111)using NO2,respectively.Formation of atomic oxyge n overlayers on Au(111)via exposure to O3 is critical to the formatio n of uniform ZnO mono layer nano structures atop.Near ambient pressure XPS studies revealed that n early full hydroxy lati on occurs on mono layer ZnO structures upon exposure to near ambient pressure water vapor or atomic hydrogen species,while partial surface hydroxylation happens on bilayer ZnO under the same gaseous exposure conditions.展开更多
The interface between a two-dimensional(2D)atomic crystal and a metal surface can be regarded as a nanoreactor, in which molecule adsorption and catalytic reactions may occur. In this work, we demonstrate that oxygen ...The interface between a two-dimensional(2D)atomic crystal and a metal surface can be regarded as a nanoreactor, in which molecule adsorption and catalytic reactions may occur. In this work, we demonstrate that oxygen intercalation and desorption occur at the interface between hexagonal boron nitride(h-BN) overlayer and Pt(111) surface by using near-ambient pressure X-ray photoelectron spectroscopy(NAP-XPS), photoemission electron microscopy, and low-energy electron microscopy.Furthermore, CO oxidation under the h-BN cover was also observed by NAP-XPS. The present results indicate that the nanospace under the 2D cover can be used for surface reactions, in which novel surface chemistry may be induced by the nanoconfinement effect.展开更多
The dynamic redox process of surface oxide layers on metal surfaces is of great significance for understanding the active phase in catalytic reactions.We studied the formation of surface oxide layers on Cu(111)and Cu(...The dynamic redox process of surface oxide layers on metal surfaces is of great significance for understanding the active phase in catalytic reactions.We studied the formation of surface oxide layers on Cu(111)and Cu(110)in O2,as well as the subsequent reduction by CO using in situ scanning tunneling microscopy(STM)and X-ray photoelectron spectroscopy(XPS).By monitoring and comparing the oxidation process of Cu(111)and Cu(110)surfaces,we found a crystal-plane-dependent reaction mechanism,which also applies to the reduction of surface oxide layers on Cu surfaces.We found XPS Cu spectra cannot be used to identify the various surface oxide layer on Cu surfaces,suggesting their presence in catalytic reactions might have been overlooked.The combination of STM and XPS studies are thus advantageous in identifying surface oxide structures and pinpointing the active phases in the redox process,which paves the way for engineering the catalyst and reaction environment for optimized catalytic performances.展开更多
基金the support from the National Key R&D Program of China(No.2022YFA1503801)the National Natural Science Foundation of China(No.22172190,No.22202232 and No.22109171)。
文摘Surface-supported isolated atoms in single-atom catalysts(SACs)grant maximum utilization of metals in heterogeneous catalysis.Herein,we report a feasible pyrolysis strategy to synthesize Pd single atoms by thermally melting Pd nanoparticles on an oxygen-vacancy-rich tungsten-oxide matrix at reduction atmosphere.Near ambient pressure X-ray photoelectron spectroscopy was used to monitor the formation of zero-valence Pd single atoms and the increased metallic feature of WO_(3-x)substrate.Accordingly,the as-obtained zero-valence Pd single-atom catalyst exhibits a markedly boosted HER activity with a low overpotential(η_(10)=70 mV)at the current density of 10 mA/cm2and a small Tafel slope(b=68 mV/dec),nearly 150 mV and a 3,0-fold enhancement than those of Pd nanoparticles(η_(10)=220 mV,b=133 mV/dec)under the same conditions.In addition,quasi in situ XPS results suggest the hydrogen spillover effect is more likely to occur on Pd single atoms during the electrochemical process.Our work may pave an interesting route for the rational design of highly-efficient single-atom catalysts,and the elucidation of corresponding enhanced reaction mechanisms by the utilization of advanced characterization techniques.
基金financial support from Strasbourg University via the Id EX-2018(Postdoctorants)projectfinancial support by the project CALIPSOplus under the proposal number 20200271 from the EU Framework Program HORIZON 2020。
文摘The oxidation of porous Ni-yttria-stabilized zirconia(YSZ)and Ni-gadolinia-doped ceria(GDC)ceramicmetal(cermet)electrodes in H_(2)O and CO_(2)atmospheres was studied by near-ambient pressure X-ray photoelectron spectroscopy(NAP-XPS).We show that the oxidation of nickel by the two gases is not similar,as is commonly believed,but it depends on the ceramic type.Nickel is vulnerable to oxidation in H_(2)O but it resists to CO_(2)in Ni-GDC,as compared to the Ni-YSZ electrode.Inspired by this observation we conceptualize and fabricate Ni-YSZ electrodes modified by ceria nanoparticles,which show significantly higher resistance to CO_(2)oxidation as compared with conventional Ni-YSZ electrodes.The preparation of tailormade cermet electrodes with identical bulk/mechanical characteristics but very different surface properties offers a promising fabrication strategy for high-performance and durability solid oxide electrolysis cells for CO_(2)conversion.
基金financially supported by the National Natural Science Foundation of China (No. 91845109, No. 21872169)。
文摘Sustainable methanol production via CO_(2) hydrogenation leads to increased interest in the understanding of active phase of Cu/ZnO/Al_(2)O_(3)(CZA) catalyst. Model catalysts of ZnO/Cu(111) with structures varied from two-dimensional planar to three-dimensional nanoparticles were prepared by atomic layer deposition(ALD) method. By combing scanning tunneling microscopy(STM) and X-ray photoelectron spectroscopy(XPS) at near-ambient pressure of CO_(2) hydrogenation, we reveal that the submonolayer ZnO/Cu(111) transformed into Cu-Zn alloy under 10 mbar CO_(2)/H_(2) at 493 K, and underwent a partial reoxidation during evacuation. The dynamic phase transformation of ZnO/Cu(111) may partly explain the existence of differences and apparently contradictory theories to account for the origin of active phase in CZA catalysts.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.21825203,91545204,21688102,and 21621063)the National Key Research and Development Program of China(Nos.2016YFA0200200 and 2017YFB0602205)+1 种基金Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB17020000)The authors thank the support for Nano-X from Suzhou Institute of Nano-Tech and Nano-Bionics(SINANO).The fruitful discussion with Yuemin Wang in Karlsruhe Institute of Technology(KIT)is highly appreciated.
文摘Ultrathin ZnO nano structures prese nt in teresti ng two-dimensi on al(2D)graphene-like structure in contrast to wurtzite structure in bulk ZnO.Growth on Au(111)has been regarded as a well-established route to the 2D ZnO layers while controlled growth of uniform ZnO nano structures remains as a challe nge.Here,reactive deposition of Zn in O3 and NO2 was employed,which is investigated by sea nning tunneling microscopy and X-ray photoelectr on spectroscopy(XPS).We dem on strate that uniform ZnO mono layer nanoislands and films can be obtained on Au(111)using O3 and uniform ZnO bilayer nanoislands and films form on Au(111)using NO2,respectively.Formation of atomic oxyge n overlayers on Au(111)via exposure to O3 is critical to the formatio n of uniform ZnO mono layer nano structures atop.Near ambient pressure XPS studies revealed that n early full hydroxy lati on occurs on mono layer ZnO structures upon exposure to near ambient pressure water vapor or atomic hydrogen species,while partial surface hydroxylation happens on bilayer ZnO under the same gaseous exposure conditions.
基金supported by the National Natural Science Foundation of China(21222305,21373208,and21033009)the National Basic Research Program of China(2011CB932704,2013CB933100,and 2013CB834603)+1 种基金the Key Research Program of the Chinese Academy of Science(KGZD-EWT05)The Advanced Light Source and beamlines 11.0.2 and 9.3.1 are supported by the Director,Office of Energy Research,Office of Basic Energy Sciences,and Chemical Sciences Division of the US Department of Energy under contracts No.DE-AC02-05CH11231
文摘The interface between a two-dimensional(2D)atomic crystal and a metal surface can be regarded as a nanoreactor, in which molecule adsorption and catalytic reactions may occur. In this work, we demonstrate that oxygen intercalation and desorption occur at the interface between hexagonal boron nitride(h-BN) overlayer and Pt(111) surface by using near-ambient pressure X-ray photoelectron spectroscopy(NAP-XPS), photoemission electron microscopy, and low-energy electron microscopy.Furthermore, CO oxidation under the h-BN cover was also observed by NAP-XPS. The present results indicate that the nanospace under the 2D cover can be used for surface reactions, in which novel surface chemistry may be induced by the nanoconfinement effect.
基金This work was financially supported by Ministry of Science and Technology of China(Nos.2017YFB0602205 and 2016YFA0202803)National Natural Science Foundation of China(Nos.21972144,91545204,and 11227902)The authors thank the support from Analytical Instrumentation Center(No.SPST-AIC10112914),SPST,ShanghaiTech University.
文摘The dynamic redox process of surface oxide layers on metal surfaces is of great significance for understanding the active phase in catalytic reactions.We studied the formation of surface oxide layers on Cu(111)and Cu(110)in O2,as well as the subsequent reduction by CO using in situ scanning tunneling microscopy(STM)and X-ray photoelectron spectroscopy(XPS).By monitoring and comparing the oxidation process of Cu(111)and Cu(110)surfaces,we found a crystal-plane-dependent reaction mechanism,which also applies to the reduction of surface oxide layers on Cu surfaces.We found XPS Cu spectra cannot be used to identify the various surface oxide layer on Cu surfaces,suggesting their presence in catalytic reactions might have been overlooked.The combination of STM and XPS studies are thus advantageous in identifying surface oxide structures and pinpointing the active phases in the redox process,which paves the way for engineering the catalyst and reaction environment for optimized catalytic performances.
