Methanol steam reforming for hydrogen production driven by an atomically precise Cu catalyst

Plasmon-induced hot-electron transfer from metal nanostructures is being intensely pursed in current photocatalytic research,however it remains elusive whether molecular-like metal clusters with excitonic behavior can be used as light-harvesting materials in solar energy utilization such as photocatalytic methanol steam reforming.In this work,we report an atomically precise Cu_(13)cluster protected by dual ligands of thiolate and phosphine that can be viewed as the assembly of one top Cu atom and three Cu_(4)tetrahedra.The Cu_(13)H_(10)(SR)_(3)(PR’_(3))_(7)(SR=2,4-dichlorobenzenethiol,PR’_(3)=P(4-FC_(6)H_(4))_(3))cluster can give rise to highly efficient light-driven activity for methanol steam reforming toward H_(2)production.

Effects of different methods of introducing Mo on denitration performance and anti‐SO_(2)poisoning performance of CeO_(2)

Cerium‐based catalysts are very attractive for the catalytic abatement of nitrogen oxides(NOx)emitted from stationary sources.However,the main challenge is still achieving satisfactory catalytic activity in the low‐temperature range and tolerance to SO2 poisoning.In the present work,two series of Mo‐modified CeO_(2)catalysts were respectively obtained through a wet impregnation method(Mo‐CeO_(2))and a co‐precipitation method(MoCe‐cp),and the roles of the Mo species were systematically investigated.Activity tests showed that the Mo‐CeO_(2)catalyst displayed much higher NO conversion at low temperature and anti‐SO2 ability than MoCe‐cp.The optimal Mo‐CeO_(2)catalyst displayed over 80%NO elimination efficiency even at 150°C and remarkable SO2 resistance at 250°C(nearly no activity loss after 40 h test).The characterization results indicated that the introduced Mo species were highly dispersed on the Mo‐CeO_(2)catalyst surface,thereby providing more Brønsted acid sites and inhibiting the formation of stable adsorbed NOx species.These factors synergistically promote the selective catalytic reduction(SCR)reaction in accordance with the Eley‐Rideal(E‐R)reaction path on the Mo‐CeO_(2)catalyst.Additionally,the molybdenum surface could protect CeO_(2)from SO2 poisoning;thus,the reducibility of the Mo‐CeO_(2)catalyst declined slightly to an adequate level after sulfation.The results in this work indicate that surface modification with Mo species may be a simple method of developing highly efficient cerium‐based SCR catalysts with superior SO2 durability.

A 3-Node Co-Rotational Triangular Finite Element for Non-Smooth,Folded and Multi-Shell Laminated Composite Structures

Based on the first-order shear deformation theory,a 3-node co-rotational triangular finite element formulation is developed for large deformation modeling of non-smooth,folded and multi-shell laminated composite structures.The two smaller components of the mid-surface normal vector of shell at a node are defined as nodal rotational variables in the co-rotational local coordinate system.In the global coordinate system,two smaller components of one vector,together with the smallest or second smallest component of another vector,of an orthogonal triad at a node on a non-smooth intersection of plates and/or shells are defined as rotational variables,whereas the two smaller components of the mid-surface normal vector at a node on the smooth part of the plate or shell(away from non-smooth intersections)are defined as rotational variables.All these vectorial rotational variables can be updated in an additive manner during an incremental solution procedure,and thus improve the computational efficiency in the nonlinear solution of these composite shell structures.Due to the commutativity of all nodal variables in calculating of the second derivatives of the local nodal variables with respect to global nodal variables,and the second derivatives of the strain energy functional with respect to local nodal variables,symmetric tangent stiffness matrices in local and global coordinate systems are obtained.To overcome shear locking,the assumed transverse shear strains obtained from the line-integration approach are employed.The reliability and computational accuracy of the present 3-node triangular shell finite element are verified through modeling two patch tests,several smooth and non-smooth laminated composite shells undergoing large displacements and large rotations.

Quantitative discrimination of surface adsorbed NO_(x) species on CeO_(2) via spectrophotometry for SCR denitration investigation

CeO_(2)-based catalysts are widely investigated for selective catalytic reduction(SCR)of NO with NH3.Interaction of NO/O_(2) with CeO_(2) generally produces two surface species,i.e.,nitrates and nitrites.However,the explicit quantification of these two species is still unresolved.Herein,we reported that spectrophotometry characterization was effective in determining surface adsorbed NOx species on CeO_(2) by measuring the corresponding ions(NO_(2)-and NO_(3)^(-))dissolved in aqueous solution.Experimental results show that both nitrate(-NO_(3))and nitrite(-NO_(2))species can be quantitatively evaluated and the accuracy is verified by calibrating with NOx-TPD result.Exclusive transfer of adsorbed NOx from catalyst surface to aqueous solution is confirmed and the dissolution process can be accelerated by ultrasonic treatment.Moreover,useful information related to evolution of surface NOx species under various conditions(O_(2) treatment,different adsorption temperature and duration)and over different catalysts(Fe_(2)O_(3),MnO_(2) and MnOx—CeO_(2))are provided.The result of present study demonstrates the potential of spectrophotometry for quantitative discrimination of surface NOx species on CeO_(2) and other oxide-based materials,which is conducive to mechanism analysis of SCR reaction.

Promotion effect of bulk sulfates over CeO_(2)for selective catalytic reduction of NO by NH_(3)at high temperatures

Understanding the influence of sulfates over catalysts for selective catalytic reduction of NO with NH_(3)(NH_(3)-SCR)is crucial due to the universal presence of SO_(2)in exhaust gas.Depending on the degree of sulfation,there mainly exist surface and bulk sulfates and NH_(3)-SCR activity is generally considered to suffer more from bulk sulfates.Herein,the unique function of bulk sulfates over Ce O_(2)in promoting hightemperature SCR reaction is revealed.Notably,compared with CeO_(2)dominated with surface sulfates(S-CeO_(2)-4h)and commercial V_2O_5-WO_(3)/TiO_(2),CeO_(2)with bulk sulfates(S-Ce O_(2)-72h)exhibits admirable NO conversion at the temperature range of 400-550℃.Bulk sulfates provide more Br?nsted acid sites with stronger strength for NH_(3)adsorption.Moreover,the oxidation ability of Ce O_(2)is significantly inhibited due to electron-withdrawing effect from bulk sulfates,which alleviates NH_(3)oxidation at high temperatures.More NH_(3)adsorption with high stability and limited NH_(3)oxidation capacity ensure the excellent catalytic performance for S-CeO_(2)-72h in high-temperature denitration.This work provides new insight of bulk sulfates in promoting SCR activity and open a new avenue to design de NO_xcatalysts employed at high temperatures.

Influence of CeO2 loading on structure and catalytic activity for NH3-SCR over TiO2-supported CeO2

A series of supported CeO2/TiO2 catalysts were prepared to explore the influence of CeO2 loading on these catalysts for the selective catalytic reduction of NO3 by NH3(NH3-SCR).The catalysts were investigated in detail by means of XRD,Raman,H2-TPR,NH3-TPD,XPS,in situ DRIFTS,and NH3-SCR reaction.The activity of the catalyst is closely related to the content of CeO2.When the loading of CeO2 is near the dispersion capacity(1.16 mmol Ce4+/100 m^2 TiO2),the catalytic activity is better.This may be because that the dispersed CeO2 is the active species and the catalyst has appropriate redox property,along with the larger amounts of surface Ce content and surface adsorbed oxygen species.Finally,a possible reaction mechanism via the Langmuir-Hinshelwood(L-H)mechanism is tentatively proposed to further understand the NH3-SCR reaction.

Enhancing low-temperature NH_(3)-SCR performance of Fe-Mn/CeO_(2)catalyst by Al_(2)O_(3)modification

In the work,supported catalysts of FeO_(x) and MnO_(x) co-supported on aluminum-modified CeO_(2)was synthesized for low-temperature NH_(3)-selective catalytic reduction(NH_(3)-SCR)of NO.Impressively,the SCR activity of the obtained catalyst is markedly influenced by the adding amount of Al and the appropriate Ce/Al molar ratio is 1/2.The activity tests demonstrate that Fe-Mn/Ce1 Al2 catalyst shows over 90%NO conversion at 75-250℃and exhibits better SO_(2)resistance compared to Fe-Mn/CeO_(2).Fe-Mn/Ce1 Al2 shows the expected physicochemical characters of the ideal catalyst including the larger surface and increased active reaction active sites by controlling the amount of Al doping.Also,the better catalytic activity is well correlated with the present advantaged surface adsorption oxygen species,Mn^(4+)species,Ce^(3+)species and the enhanced reducibility of Fe-Mn/Ce1 Al2,which is superior to the Fe-Mn/CeO_(2)catalyst.More importantly,we further demonstrate that the amount and strength of surface acid sites are improved by Al-doping and more active intermediates(monodentate nitrate)is generated during NH_(3)-SCR reaction.This work provides certain insight into the rational creation of simple and practical denitration catalyst environmental purification.

Solid-phase impregnation promotes Ce doping in TiO_(2) for boosted denitration of CeO_(2)/TiO_(2) catalysts

CeO_(2)/TiO_(2)(denoted as Ce Ti) catalysts obtained by solid-phase impregnation behaved better in lowtemperature selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR) than that by conventional wet impregnation.To explore the main factors for activity distinction,the texture property,CeO_(2)dispersion and structure changes of TiO_(2)were comprehensively analyzed.It was found that surface changes of TiO_(2)had a significant impact on the improved activity.From results of inductively coupled plasma atomic emission spectrometer (ICP-AES),diffuse reflectance UV-vis spectroscopy (UV-vis-DRS) and Raman,it was inferred that Ce ions were partially incorporated into TiO_(2)lattice,accompanied with the formation of defects and vacancies during solid-phase impregnation.Accordingly,Ce Ti catalysts from solid-phase impregnation exhibited superiority in adsorption and activation of reactants.Further result from monitoring the preparation process indicated that the evolved NO played an important role in promoting Ce doping through depriving oxygen atoms on TiO_(2)surface.The interaction between Ce and Ti was enhanced.The catalyst performed better in NH_(3)-SCR,especially at low temperature,which testified the solid-phase impregnation could be an effective method to modulate interface structure for designing efficient catalyst.