Silica-modified Pt/TiO_(2) catalysts with tunable suppression of strong metal-support interaction for cinnamaldehyde hydrogenation

Tuning Strong Metal-support Interactions(SMSI)is a key strategy to obtain highly active catalysts,but conventional methods usually enable TiO_(x) encapsulation of noble metal components to minimize the exposure of noble metals.This study demonstrates a catalyst preparation method to modulate a weak encapsulation of Pt metal nanoparticles(NPs)with the supported TiO_(2),achieving the moderate suppression of SMSI effects.The introduction of silica inhibits this encapsulation,as reflected in the characterization results such as XPS and HRTEM,while the Ti^(4+) to Ti^(3+) conversion due to SMSI can still be found on the support surface.Furthermore,the hydrogenation of cinnamaldehyde(CAL)as a probe reaction revealed that once this encapsulation behavior was suppressed,the adsorption capacity of the catalyst for small molecules like H_(2) and CO was enhanced,which thereby improved the catalytic activity and facilitated the hydrogenation of CAL.Meanwhile,the introduction of SiO_(2) also changed the surface structure of the catalyst,which inhibited the occurrence of the acetal reaction and improved the conversion efficiency of C=O and C=C hydrogenation.Systematic manipulation of SMSI formation and its consequence on the performance in catalytic hydrogenation reactions are discussed.

Achieving asymmetric redox chemistry for oxygen evolution reaction through strong metal-support interactions

Water electrolysis poses a significant challenge for balancing catalytic activity and stability of oxygen evolution reaction(OER)electrocatalysts.In this study,we address this challenge by constructing asymmetric redox chemistry through elaborate surface OO–Ru–OH and bulk Ru–O–Ni/Fe coordination moieties within single-atom Ru-decorated defective NiFe LDH nanosheets(Ru@d-NiFe LDH)in conjunction with strong metal-support interactions(SMSI).Rigorous spectroscopic characterization and theoretical calculations indicate that single-atom Ru can delocalize the O 2p electrons on the surface and optimize d-electron configurations of metal atoms in bulk through SMSI.The^(18)O isotope labeling experiment based on operando differential electrochemical mass spectrometry(DEMS),chemical probe experiments,and theoretical calculations confirm the encouraged surface lattice oxygen,stabilized bulk lattice oxygen,and enhanced adsorption of oxygen-containing intermediates for bulk metals in Ru@d-NiFe LDH,leading to asymmetric redox chemistry for OER.The Ru@d-NiFe LDH electrocatalyst exhibits exceptional performance with an overpotential of 230 mV to achieve 10 mA cm^(−2)and maintains high robustness under industrial current density.This approach for achieving asymmetric redox chemistry through SMSI presents a new avenue for developing high-performance electrocatalysts and instills confidence in its industrial applicability.

Strong metal-support interactions between highly dispersed Cu^(+) species and ceria via mix-MOF pyrolysis toward promoted water-gas shift reaction

The modulation of metal-support interfacial interaction is significant but challenging in the design of high-efficiency and high-stability supported catalysts.Here,we report a synthetic strategy to upgrade Cu-CeO_(2)interfacial interaction by the pyrolysis of mixed metal-organic framework(MOF)structure.The obtained highly dispersed Cu/CeO_(2)-MOF catalyst via this strategy was used to catalyze water-gas shift reaction(WGSR),which exhibited high activity of 40.5μmolCOgcat^(-1).s^(-1)at 300℃and high stability of about 120 h.Based on comprehensive studies of electronic structure,pyrolysis strategy has significant effect on enhancing metal-support interaction and then stabilizing interfacial Cu^(+)species under reaction conditions.Abundant Cu^(+)species and generated oxygen vacancies over Cu/CeO_(2)-MOF catalyst played a key role in CO molecule activation and H2O molecule dissociation,respectively.Both collaborated closely and then promoted WGSR catalytic performance in comparison with traditio nal supported catalysts.This study shall offer a robust approach to harvest highly dispersed catalysts with finely-tuned metal-support interactions for stabilizing the most interfacial active metal species in diverse heterogeneous catalytic reactions.

Confined cobalt single-atom catalysts with strong electronic metal-support interactions based on a biomimetic self-assembly strategy

Designing high-performance and low-cost electrocatalysts for oxygen evolu-tion reaction(OER)is critical for the conversion and storage of sustainable energy technologies.Inspired by the biomineralization process,we utilized the phosphorylation sites of collagen molecules to combine with cobalt-based mononuclear precursors at the molecular level and built a three-dimensional(3D)porous hierarchical material through a bottom-up biomimetic self-assembly strategy to obtain single-atom catalysts confined on carbonized biomimetic self-assembled carriers(Co SACs/cBSC)after subsequent high-temperature annealing.In this strategy,the biomolecule improved the anchoring efficiency of the metal precursor through precise functional groups;meanwhile,the binding-then-assembling strategy also effectively suppressed the nonspecific adsorption of metal ions,ultimately preventing atomic agglomeration and achieving strong electronic metal-support interactions(EMSIs).Experimental characterizations confirm that binding forms between cobalt metal and carbonized self-assembled substrate(Co–O_(4)–P).Theoretical calculations disclose that the local environment changes significantly tailored the Co d-band center,and optimized the binding energy of oxygenated intermediates and the energy barrier of oxygen release.As a result,the obtained Co SACs/cBSC catalyst can achieve remarkable OER activity and 24 h durability in 1 M KOH(η10 at 288 mV;Tafel slope of 44 mV dec-1),better than other transition metal-based catalysts and commercial IrO_(2).Overall,we presented a self-assembly strategy to prepare transition metal SACs with strong EMSIs,providing a new avenue for the preparation of efficient catalysts with fine atomic structures.

Preparation of highly dispersed iron species over ZSM-5 with enhanced metal-support interaction through freeze-drying impregnation

Supported metal catalysts play a vital role in the chemical industry, and the metal-support interaction is an important property of the catalyst. However, in the traditional impregnation method, it is difficult to obtain sufficient metal-support interactions owing to the mobility of the metal precursor during evaporation drying. Here, freeze drying is applied during impregnation instead of evaporation drying for enhancing the metal-support interactions. 57 Fe ZSM-5 was chosen as a representative catalyst. A quantitative analysis was conducted based on Mossbauer spectroscopy. Compared with traditional evaporation-drying catalyst, freeze-drying catalyst has stronger metal-support interactions. In addition, more iron species are confined in the channel and smaller metal sizes and less diversity are obtained. The compositional change is also proved because of the superior performance of the freeze-drying catalyst during N2O decomposition. This method can be extended to other supported metal catalysts prepared through an impregnation method, which can be used to tune the metal-support interactions and metal sizes.

Enhancing the CO_(2) methanation activity of Ni/CeO_(2) via activation treatment-determined metal-support interaction

The metal-support interaction is of critical importance to enhance the catalytic activity and selectivity.However,it is still challenging to construct an appropriate interaction starting from the catalyst fabrication and/or activation.We herein established low-temperature treatment of Ni^(2+)ions impregnated on ceria in reductive atmosphere and reduction-oxidation cycles as effective approachs to regulate the metal-support interaction and raise the catalytic performance in the CO_(2)methanation.The proposed construction approach yielded Ni/Ce O_(2)that displayed highly dispersed Ni nanoparticles in contact with Ce O_(2)(111)and(100)facet,higher density of surface oxygen vacancies and larger amounts of weak basic sites relative to the reference samples,which increased the capacity for H2 and CO_(2)adsorption/activation.The interaction resulted in appreciably(2-3 fold)higher activity in the CO_(2)methanation with maintaining almost full selectivity to CH4 and high stability.Coverage of Ni surface by Ce O_(2)-x thin layer as a typical structure of strong metal-support interaction resulting from high-temperature reduction,can be alleviated via reduction-oxidation cycles.We also demonstrate the activation treatment-determined metalsupport interaction effect can generally extend to(Ti O_(2)and Zr O_(2))supported Ni catalysts.

Boron Nanosheet-Supported Rh Catalysts for Hydrogen Evolution:A New Territory for the Strong Metal-Support Interaction Effect

High-efficiency electrochemical hydrogen evolution reaction(HER)offers a promising strategy to address energy and environmental crisis.Platinum is the most effective electrocatalyst for the HER.However,challenging scarcity,valuableness,and poor electrochemical stability still hinder its wide application.Here,we designed an outstanding HER electrocatalyst,highly dispersed rhodium(Rh)nanoparticles with an average diameter of only 3 nm supported on boron(B)nanosheets.The HER catalytic activity is even comparable to that of commercial platinum catalysts,with an overpotential of only 66 mV in 0.5 M H_(2)SO_(4) and 101 mV in 1 M KOH to reach the current density of 10 mA cm−2.Meanwhile,the catalyst exhibited impressive electrochemical durability during long-term electrochemical processes in acidic and alkaline media,even the simu-lated seawater environment.Theoretical calculations unraveled that the structure-activity relationship between B(104)crystal plane and Rh(111)crystal plane is beneficial to the release of hydrogen,and surface O plays a vital role in the catalysis process.Our work may gain insights into the development of supported metal catalysts with robust catalytic performance through precise engineering of the strong metal-supported interaction effect.

Photo-enhanced thermal catalytic CO_(2) methanation activity and stability over oxygen-deficient Ru/TiO_(2) with exposed TiO_(2){001}facets:Adjusting photogenerated electron behaviors by metal-support interactions

In this study,two Ru/TiO_(2)samples with different TiO_(2)facets were prepared to investigate their photo-thermal catalytic CO_(2)+H_(2)reaction behavior.Without UV irradiation,the Ru/TiO_(2)with 67%{001}facet(3 RT)displayed improved thermal catalytic activity for CO_(2)methanation than that of Ru/TiO_(2)with 30%{001}facet(0 RT).After H_(2)pretreatment,both samples exhibited enhanced thermal catalytic activities,but the H_(2)-treated 3 RT(3 RT-H)exhibited superior activity to that of the H_(2)-treated 0 RT(0 RT-H).Under UV irradiation,3 RT-H exhibited apparent photo-promoted thermal catalytic activity and stability,but the enhanced catalytic activity was lower than that of 0 RT-H.Based on the characterization results,it is proposed that both the surface oxygen vacancies(Vos)(activating CO_(2))and the metallic Ru nanoparticles(activating H_(2))were mainly responsible for CO_(2)methanation.For 0 RT,H_(2)pretreatment and subsequent UV irradiation did not promote the formation of Vos,resulting in low catalytic activity.For 3 RT,on the one hand,H_(2)pretreatment promoted the formation of Vos,which were regenerated under UV irradiation;on the other hand,the photogenerated electrons from TiO_(2)transferred to Ru to maintain the metallic Ru nanoparticles.Both behaviors promoted the activation of CO_(2)and H_(2)and enhanced CO_(2)methanation.Moreover,the photogenerated holes favored the dissociated H at Ru migrating to TiO_(2),also promoting CO_(2)methanation.These behaviors occurring on 3 RT-H may be attributed to the suitable metal-support interaction between the Ru nanoparticles and TiO_(2){001},resulting in the easy activation of lattice oxygen in TiO_(2)to Vos.With reference to the analysis of intermediates,a photo-thermal reaction mechanism is proposed for the Ru/TiO_(2){001}facet sample.

Metal-Support Interactions on Ag/Co_(3)O_(4)Nanowire Monolithic Catalysts Promoting Catalytic Soot Combustion

Tuning metal-support interactions(MSIs)is an important strategy in heterogeneous catalysis to realize the desirable metal dispersion and redox ability of metal catalysts.Herein,we use pre-reduced Co_(3)O_(4)nanowires(Co-NWs)in situ grown on monolithic Ni foam substrates to support Ag catalysts(Ag/Co-NW-R)for soot combustion.The macroporous structure of Ni foam with crossed Co_(3)O_(4)nanowires remarkably increases the soot-catalyst contact effi ciency.Our characterization results demonstrate that Ag species exist as Ag 0 because of the equation Ag^(+)+Co^(2+)=Ag^(0)+Co^(3+),and the pre-reduction treatment enhances interactions between Ag and Co_(3)O_(4).The number of active oxygen species on the Ag-loaded catalysts is approximately twice that on the supports,demonstrating the signifi cant role of Ag sites in generating active oxygen species.Additionally,the strengthened MSI on Ag/Co-NW-R further improves this number by increasing metal dispersion and the intrinsic activity determined by the turnover frequency of these oxygen species for soot oxidation compared with the catalyst without pre-reduction of Co-NW(Ag/Co-NW).In addition to high activity,Ag/Co-NW-R exhibits high catalytic stability and water resistance.The strategy used in this work might be applicable in related catalytic systems.

Manipulating metal-support interactions of metal catalysts for Fischer-Tropsch synthesis

For supported metal catalyst systems,the impact on catalysis originates from the interaction between metal nanoparticles and their support.Metal-support interactions(MSI)can change electronic properties,geometric morphologies,or chemical compositions of metal nanoparticles to make active sites have specific properties and catalytic activities.Fischer-Tropsch synthesis(FTS)is one of the most effective ways to convert cheap non-petroleum-based carbon sources into high value-added chemicals or ultraclean liquid fuels.In this review,we summarize and classify the impact of MSI on the catalytic activity,selectivity and stability of FTS catalysts.The strategies to tune MSI are introduced in detail,and the recent development of high-efficiency FTS catalysts through the manipulation of SMI strategies has been highlighted.It is emphasized that the active metal sites,which are endowed with special functions by MSI,can change the strength of adsorption bond of adsorbates,consequently controlling the product distribution.

Dry Reforming of Ethane over FeNi/Al-Ce-O Catalysts:Composition-Induced Strong Metal-Support Interactions

Dry reforming of ethane(DRE)has received significant attention because of its potential to produce chemical raw materials and reduce carbon emissions.Herein,a composition-induced strong metal-support interaction(SMSI)effect over FeNi/Al-Ce-O catalysts is revealed via X-ray photoelectron spectroscopy(XPS),H_(2)-temperature programmed reduction(TPR),and energy dispersive X-ray spectroscopy(EDS)elemental mapping.The introduction of Al into Al-Ce-O supports significantly influences the dispersion of surface active components and improves the catalytic performance for DRE over supported FeNi catalysts due to enhancement of the SMSI effect.The catalytic properties,for example,C_(2)H_(6) and CO_(2) conversion,CO selectivity and yield,and turnover frequencies(TOFs),of supported FeNi catalysts first increase and then decrease with increasing Al content,following the same trend as the theoretical effective surface area(TESA)of the corresponding catalysts.The FeNi/Ce-Al_(0.5) catalyst,with 50%Al content,exhibits the best DRE performance under steady-state conditions at 873 K.As observed by with in situ Fourier transform infrared spectroscopy(FTIR)analysis,the introduction of Al not only increases the content of surface Ce3+and oxygen vacancies but also promotes the dispersion of surface active components,which further alters the catalytic properties for DRE over supported FeNi catalysts.

A Review on Metal-support Interaction in Automotive Catalysts

TWC-equipped exhausts are widely used in gasoline-fueled vehicles to meet stringent emission regulations. The main components in TWCs are precious metals such as palladium (Pd), platinum (Pt), and rhodium (Rh) as the active component, and inorganic oxides such as γ-alumina (Al 2 O 3 ), ceria (CeO 2 ), zirconia (ZrO 2 ) and ceria-zirconia (CeO 2-ZrO 2 ) are used as the support. Interaction of precious metals and support plays an important role in the thermal stability and catalytic performance of TWCs. The support can improve the dispersion of precious metals and suppress the sintering of precious metals at high temperature. In the same, precious metals can also enhance the redox performance and oxygen storage capacity of support. This paper reviews the reaction phenomenon and mechanism of precious metals (Pt, Pd, Rh) and supports such as Al 2 O 3 , CeO 2-based composite oxides.

A New Type of Strong Metal-Support Interaction Caused by Antimony Species

Interactions between metals and supports are of fundamental interest in heterogeneous catalysis, Noble metal particles supported on transition metal oxides (TMO) may undergo a so-called strong metal-support interaction via encapsulation. This perspective addresses catalytic properties of the metal catalysts in the SMSI state which can be explained on the basis of complementary studies. The electronic geometric and bifunctional effects originating from strong metal-support interactions (SMSI) that are responsible for the catalyst’s activity, selectivity, and stability are key factors that determine performance. A series of Pd-Sb supported on different metal oxide (i.e. SiO2, γ-Al2O3, TiO2, and ZrO2) were prepared by the impregnation method. The catalysts were characterized by N2 adsorption (BET-SA and pore size distribution), TEM (transmission electron microscope), TPR (temperature-programmed reduction), CO-chemisorption, the structural characterization of Pd (dispersity, surface area), interaction between Pd and Sb2O3 and also the influence of the nature of the support were investigated. SiO2 supported Pd catalyst exhibited the highest surface area (192.6 m2/g) and pore volume (0.542 cm3/g) compared to the other supported oxides catalysts. The electron micrographs of these catalysts showed a narrow size particle distribution of Pd, but with varying sizes which in the range from 1 to 10 nm, depending on the type of support used. The results show almost completely suppressed of CO chemisorption when the catalysts were subjected to high temperature reduction (HTR), this suppression was overcome by oxidation of a reduced Pd/MeOx catalysts followed by re-reduction in hydrogen at 453 K low temperature reduction (LTR), almost completely restored the normal chemisorptive properties of the catalysts, this suppression was attributed by SbOx species by a typical SMSI effect as known for other reducible supports such as TiO2, ZrO2, CeO2, and Nb2O5.

Study on the mechanism and reaction characteristics of metal-supported phosphogypsum as oxygen carrier in a chemical looping gasification application

This study aimed to explore the chemical looping gasification(CLG)reaction characteristics of the metal-supported composite phosphogypsum(PG)oxygen carriers(OCs)and the thermodynamic mechanism.The FactSage 7.1 thermodynamic simulation was used to explore the oxygen release and H_(2)S removal mechanisms.The experimental results showed that the syngas yield of CLG with PG-CuFe_(2)O_(4)was more than that with PG-Fe_(2)O_(3)20/CuO40 or PG-Fe_(2)O_(3)30/CuO30 OC at 1023 K when the water vapor content was 0.3.Furthermore,the maximum syngas yield of the CO selectivity was 70.3% and of the CO_(2)selectivity was 23.8%.The H_(2)/CO value was 0.78,and the highest carbon conversion efficiency was 91.9% in PG-CuFe_(2)O_(4)at the gasification temperature of 1073 K.The metal-supported PG composite oxygen carrier was proved not only as an oxygen carrier to participate in the preparation of syngas but also as a catalyst to catalyze coal gasification reactions.Furthermore,both the experimental results and FactSage 7.1 thermodynamic analysis revealed that the trapping mechanism of H_(2)S by composite OCs was as follows:CuO first lost lattice oxygen as an oxygen carrier to generate Cu_(2)O,which,in turn,reacted with H_(2)S to generate Cu_(2)S.This study provided efficient guidance and reference for OC design in CLG.

Enhancing alkyne semi-hydrogenation through engineering metal-support interactions of Pd on oxides

Supported Pd catalysts show superior activities for olefin productions from alkynes through semi-hydrogenation reactions,but over-hydrogenation into alkanes highly decreases olefin selectivity.Using phenylacetylene semi-hydrogenation as a model reaction,here we explore the optimization approaches toward better Pd catalysts for alkyne semi-hydrogenation through investigating support effect and metal-support interactions.The results show that the states of Pd with supports can be tuned by varying oxide reducibility,loading ratios,and post-treatments.In our system,0.06 wt.%Pd on rutile-TiO_(2) nanorods shows the highest activity owing to the synergistic effects of single-atoms and clusters.Support reducibility can change the filling degrees of Pd 4d orbitals through varying interfacial bonding strengths,which further affect catalytic activity and selectivity.

Exploration of Strong Metal-Support Interaction in Heterogeneous Catalysts by in situ Transmission Electron Microscopy

The phenomenon of strong metal-support interaction(SMSI)observed in supported metal catalysts,usually accompanied by the formation of the encapsulation layer on metal nanoparticles,has attracted extensive research attention due to its significance in heterogeneous catalysis.Notably,great progress has been made in recent years in investigating SMSI by in situ transmission electron microscopy(TEM),along with an enhanced comprehension of the underlying mechanisms governing SMSI formation.This emerging topic summarizes recent progress utilizing in situ TEM to study the interaction between metal and support and the relationship between the structure and performance of the supported catalyst under reaction conditions.A brief perspective about the use of in situ TEM for further study of SMSI is also presented,showing prospects in this field that will stimulate further upsurging research in promoting the catalytic efficiency of supported catalysts.

Investigating the impact of dynamic structural changes of Au/rutile catalysts on the catalytic activity of CO oxidation

The surface properties of oxidic supports and their interaction with the supported metals play critical roles in governing the catalytic activities of oxide‐supported metal catalysts.When metals are supported on reducible oxides,dynamic surface reconstruction phenomena,including strong metal–support interaction(SMSI)and oxygen vacancy formation,complicate the determination of the structural–functional relationship at the active sites.Here,we performed a systematic investigation of the dynamic behavior of Au nanocatalysts supported on flame‐synthesized TiO_(2),which takes predominantly a rutile phase,using CO oxidation above room temperature as a probe reaction.Our analysis conclusively elucidated a negative correlation between the catalytic activity of Au/TiO_(2) and the oxygen vacancy at the Au/TiO_(2) interface.Although the reversible formation and retracting of SMSI overlayers have been ubiquitously observed on Au/TiO_(2) samples,the catalytic consequence of SMSI remains inconclusive.Density functional theory suggests that the electron transfer from TiO_(2) to Au is correlated to the presence of the interfacial oxygen vacancies,retarding the catalytic activation of CO oxidation.

CeO_(2)-supported Fe,Co and Ni toward CO_(2) hydrogenation:Tuning catalytic performance via metal-support interaction

The chemical transformation of CO_(2) produces carbon compounds that can be used as precursors for the production of chemicals and fuels.Here,we investigated the activity and selectivity of the transition metals(Fe,Co,and Ni)supported on CeO_(2) catalyst for CO_(2) hydrogenation at atmospheric pressure.We found that Ni/CeO_(2) shows the highest CO_(2)conversion compared with Fe/CeO_(2) and Co/CeO_(2).Besides,Co/CeO_(2)and Ni/CeO_(2) exhibit nearly 100%CH_(4)selectivity while Fe/CeO_(2) inclines to produce CO.The characterization results show that the metal-support interaction order is Fe/CeO_(2)>Co/CeO_(2)>Ni/CeO_(2),the weak metal-support inte raction over Ni/CeO_(2)benefits the activation of H_(2) and then promotes the activity of CO_(2) hydrogenation.Additionally,in situ DRIFTS results demonstrate that monodentate formate species rather than bidentate formate are the active intermediates.The main route of CO_(2) hydrogenation to CH_(4) is that CO_(2) is firstly transformed to m-HCOO*and then direct hydrogenation of the m-HCOO*to CH_(4).This study provides insights into the understanding of the mechanisms of CO_(2) hydrogenation on CeO_(2)based catalysts.

Light-enhanced metal-support interaction for synergetic photo/thermal catalytic formaldehyde oxidation

The strong metal-support interaction(SMSI)plays a pivotal role in regulating electronic properties and activating surface oxygen species.In this work,we report light-irradiation-modulated SMSI for enhanced formaldehyde(HCHO)oxidation.Specifically,the SMSI between Pt nanoparticles(NPs)and Bi_(2)MoO_(6)cre-ated surface-active oxygen at Pt-Bi_(2)MoO_(6)interfaces to activate HCHO to dioxymethylene(DOM).Notably,light irradiation boosted the SMSI and catalytic activity.Moreover,photogenerated holes in Bi_(2)MoO 6 im-proved HCHO adsorption and activation,while photogenerated electrons migrated from Bi_(2)MoO_(6)to Pt NPs to promote O_(2)adsorption and activation,accelerating the oxidation of DOM to CO_(2)and H_(2)O.The light-modulated SMSI and the synergy between photocatalysis and thermocatalysis lead to enhanced cat-alytic oxidation activity,providing a practical strategy for indoor volatile organic compound(VOC)de-composition under ambient conditions.

Progress on metal-support interactions in Pd-based catalysts for automobile emission control

The interactions between metals and oxide supports,so-called metal-support interactions(MSI),are of great importance in heterogeneous catalysis.Pd-based automotive exhaust control catalysts,especially Pd-based three-way catalysts (TWCs),have received considerable research attention owing to its prominent oxidation activity of HCs/CO,as well as excellent thermal stability.For Pd-based TWCs,the dispersion,chemical state and thermal stability of Pd species,which are crucial to the catalytic performance,are closely associated with interactions between metal nanoparticles and their supporting matrix.Progress on the research about MSI and utilization of MSI in advanced Pd-based three-way catalysts are reviewed here.Along with the development of advanced synthesis approaches and engine control technology,the study on MSI would play a notable role in further development of catalysts for automobile exhaust control.