Electronic Couplings for Singlet Oxygen Photosensitization and Its Molecular Orbital Overlap Description

The reaction of triplet fusion,also named triplet-triplet annihilation,has attracted a lot of research interests because of its wide applications in photocatalytic,solar cells,and bioimaging.As for the singlet oxygen photosensitization,the reactive singlet oxygen species are generated through the energy transfers from photosensitizer(PS)to ground triplet oxygen molecule.In this work,we computed the electronic coupling for singlet oxygen photosensitization using the nonadiabatic coupling from the quantum chemical calculation.Then we utilized the molecular orbital(MO)overlaps to approximate it,where the MOs were computed from isolated single molecules.As demonstrated with quantitative results,this approach well describes the distribution of the coupling strength as the function of the intermolecular distance between the sensitizer and O_(2),providing us a simple but effective way to predict the coupling of triplet fusion reactions.

Accurate Calculation of Equilibrium Reduced Density Matrix for the System-Bath Model:a Multilayer Multiconfiguration Time-Dependent Hartree Approach and its Comparison to a Multi-Electronic-State Path Integral Molecular Dynamics Approach

An efficient and accurate method for computing the equilibriurn reduced density matrix is presented for treating open quantum systems characterized by the systern-bath model. The method employs the rnultilayer nmlticonfiguration tirne-dependent Hartree theory for imag- inary time propagation and an importance sampling procedure for calculating the quantum mechanical trace. The method is applied to the spin-boson Harniltonian, which leads to ac- curate results in agreement with those produced by the rnulti-electronic-state path integral molecular dynamics method.

Electro‑copolymerized film of ruthenium catalyst and redox mediator for electrocatalytic water oxidation

Electro-copolymerized film containing ruthenium complexes as electron-transfer(or redox)mediators and water-oxidation catalysts by an oxidative copolymerization method is presented.The addition of the redox mediator significantly improved the electrocatalytic water-oxidation activity and reduced the overpotential to 220 mV.The prepared electrode showed a water-oxidation catalytic rate constant kobs of 31.7 s^(-1)and an initial turnover frequency of 1.01 s^(-1)in 1000 s by potential electrolysis at 1.7 V applied bias vs NHE(normal hydrogen electrode).The kinetic isotope effect study suggests that the catalytic water oxidation reaction on the electrode surface occurs via a bimolecular coupling mechanism.

Bifunctional functionalized two-dimensional transition metal borides for fast reaction redox kinetics in lithium-sulfur batteries

Lithium-sulfur(Li-S)batteries are regarded as one of the most promising next-generation energy storage systems due to their high theoretical specific energy density and low cost.However,serious shuttle effect and sluggish lithium polysulfides(LiPSs)redox kinetics severely impede the practical application of Li-S batteries.Employing polar sulfur hosts is an effective strategy to alleviate the above problems.Herein,the potential of two-dimensional(2D)Ti_(2)B-based sulfur hosts for Li-S batteries was comprehensively explored using first-principles calculations.The results show that functional groups of Ti_(2)B can significantly modulate its structural properties,thus affecting its interaction with sulfurcontaining species.Among S,Se,F,Cl,and Br elements,Ti_(2)B terminated with S and Se atoms possess stronger adsorption capability towards soluble Li_(2)S_(8),Li_(2)S_(6),and Li_(2)S_(4),obviously stronger than organic electrolytes,which indicates that they can completely suppress the shuttle effect.Besides,Ti_(2)BS_(2)and Ti_(2)BSe_(2)can powerfully expedite the electrochemical conversion of LiPSs.Moreover,the decomposition energy barrier of Li_(2)S and diffusion energy barrier of single Li ion on them are also fairly low,manifesting their excellent catalytic performance towards the oxidation of Li_(2)S.Finally,Ti_(2)BS_(2)and Ti_(2)BSe_(2)always keep metallic conductivity during the whole charge/discharge process.Taking all this into account,Ti_(2)BS_(2)and Ti_(2)BSe_(2)are proposed as promising bifunctional sulfur hosts for Li-S batteries.Our results suggest that increasing the proportion of S and Se groups during the synthesis of Ti_(2)B monolayers is greatly helpful for obtaining high-performance Li-S batteries.Besides,our work not only reveals the huge potential of 2D transition metal borides in Li-S batteries,but also provides insightful guidance for the design and screening of new efficient sulfur cathodes.

Alkyl chain modulation of asymmetric hexacyclic fused acceptor synergistically with wide bandgap third component for high efficiency ternary organic solar cells

Herein,two asymmetric hexacyclic fused small molecule acceptors(SMAs),namely BP4F-HU and BP4F-UU,were synthesized.The elongated outside chains in the BP4F-UU molecule played a crucial role in optimizing the morphology of blend film,thereby improving charge mobility and reducing energy loss within the corresponding film.Notably,the PM6:BP4F-UU device exhibited a higher open-circuit voltage(V_(oc))of 0.878 V compared to the PM6:BP4F-HU device with a V_(oc)of 0.863 V.Further,a new wide bandgap SMA named BTP-TA was designed and synthesized as the third component to the PM6:BP4F-UU host binary devices,which showed an ideal complementary absorption spectrum in PM6:BP4F-UU system.In addition,BTP-TA can achieve efficient intermolecular energy transfer to BP4F-UU by fluorescence resonance energy transfer(FRET)pathway,due to the good overlap between the photoluminescence(PL)spectrum of BTP-TA and the absorption region of BP4F-UU.Consequently,ternary devices with 15wt%BTP-TA exhibits broader photon utilization,optimal blend morphology,and reduced charge recombination compared to the corresponding binary devices.Consequently,PM6:BP4F-UU:BTP-TA ternary device achieved an optimal power conversion efficiency(PCE)of 17.83%with simultaneously increased V_(oc)of 0.905 V,short-circuit current density(J_(sc))of 26.14 mA/cm^(2),and fill factor(FF)of 75.38%.

Nitrogen-doping boosts ^(*)CO utilization and H_(2)O activation on copper for improving CO_(2) reduction to C_(2+) products

To improve the electrocatalytic transformation of carbon dioxide (CO_(2)) to multi-carbon (C_(2+)) products is of great importance.Here we developed a nitrogen-doped Cu catalyst,by which the maximum C_(2+) Faradaic efficiency can reach 72.7%in flow-cell system,with the partial current density reaching 0.62 A cm^(-2).The in situ Raman spectra demonstrate that the *CO adsorption can be strengthened on such a N-doped Cu catalyst,thus promoting the *CO utilization in the subsequent C–C coupling step.Simultaneously,the water activation can be well enhanced by N doping on Cu catalyst.Owing to the synergistic effects,the selectivity and activity for C_(2+) products over the N-deoped Cu catalyst are much improved.

Polymer Fiber Rigid Network with High Glass Transition Temperature Reinforces Stability of Organic Photovoltaics

Organic photovoltaics(OPVs)need to overcome limitations such as insufficient thermal stability to be commercialized.The reported approaches to improve stability either rely on the development of new materials or on tailoring the donor/acceptor morphology,however,exhibiting limited applicability.Therefore,it is timely to develop an easy method to enhance thermal stability without having to develop new donor/acceptor materials or donor–acceptor compatibilizers,or by introducing another third component.Herein,a unique approach is presented,based on constructing a polymer fiber rigid network with a high glass transition temperature(T_(g))to impede the movement of acceptor and donor molecules,to immobilize the active layer morphology,and thereby to improve thermal stability.A high-T_(g) one-dimensional aramid nanofiber(ANF)is utilized for network construction.Inverted OPVs with ANF network yield superior thermal stability compared to the ANF-free counterpart.The ANF network-incorporated active layer demonstrates significantly more stable morphology than the ANF-free counterpart,thereby leaving fundamental processes such as charge separation,transport,and collection,determining the device efficiency,largely unaltered.This strategy is also successfully applied to other photovoltaic systems.The strategy of incorporating a polymer fiber rigid network with high T_(g) offers a distinct perspective addressing the challenge of thermal instability with simplicity and universality.

Critical approaches in the catalytic transformation of sugar isomerization and epimerization after Fischer-History,challenges,and prospects

The transformation of aldose to ketose or common sugars into rare saccharides,including rare ketoses and aldoses,is of great value and interest to the food industry and for saccharidic biomass utilization,medicine,and the synthesis of drugs.Nowadays,high-fructose corn syrup(HFCS)is industrially produced in more than 10 million tons annually using immobilized glucose isomerase.Some low-calorie saccharides such as tagatose and psicose,which are becoming popular sweeteners,have also been produced on a pilot scale in order to replace sucrose and HFCS.However,current catalysts and catalytic processes are still difficult to utilize in biomass conversion and also have strong substrate dependence in producing high-value,rare sugars.Considering the specific reaction properties of saccharides and catalysts,since the pioneering discovery by Fischer,various catalysts and catalytic systems have been discovered or developed in attempts to extend the reaction pathways,improve the reaction efficiency,and to potentially produce commercial products.In this review,we trace the history of sugar isomerization/epimerization reactions and summarize the important breakthroughs for each reaction as well as the difficulties that remain unresolved to date.

Hydrogen generation from NaBH_(4) for portable proton exchange membrane fuel cell

Sodium borohydride(NaBH_(4)) is considered as the most potential hydrogen storage material for portable proton exchange membrane fuel cells(PEMFC)because of its high theoretical hydrogen capacity.However,the slow and poor kinetic stability of hydrogen generation from NaBH_(4) hydrolysis limits its application.There are two main factors influencing the kinetics stability of hydrogen generation from NaBH_(4).One factor is that the alkaline byproducts(NaBO_(2)) of the hydrolysis reaction can increase the pH of the solution,thus inhibiting the reaction process.It mainly happens in the NaBH_(4) solution hydrolysis system.Another factor is that the monotonous increase in reaction temperature leads to uncontrollable and unpredictable hydrolysis rates in the solid NaBH_(4) hydrolysis system.This is due to the excess heat generated from this exothermic reaction in the initial reaction of NaBH_(4) hydrolysis.In this perspective,we summarize the latest research progress in hydrogen generation from NaBH_(4) and emphasize the design principles of catalysts for hydrogen generation from NaBH_(4) solution and solid state NaBH_(4).The importance of carbon as catalyst support material for NaBH_(4) hydrolysis is also highlighted.

Influence of preparation methods on the physicochemical properties and catalytic performance of MnO_x-CeO_2 catalysts for NH_3-SCR at low temperature

This work examines the influence of preparation methods on the physicochemical properties and catalytic performance of MnOx‐CeO2 catalysts for selective catalytic reduction of NO by NH3 (NH3‐SCR) at low temperature. Five different methods, namely, mechanical mixing, impregnation,hydrothermal treatment, co‐precipitation, and a sol‐gel technique, were used to synthesizeMnOx‐CeO2 catalysts. The catalysts were characterized in detail, and an NH3‐SCR model reaction waschosen to evaluate the catalytic performance. The results showed that the preparation methodsaffected the catalytic performance in the order: hydrothermal treatment > sol‐gel > co‐precipitation> impregnation > mechanical mixing. This order correlated with the surface Ce3+ and Mn4+ content,oxygen vacancies and surface adsorbed oxygen species concentration, and the amount of acidic sitesand acidic strength. This trend is related to redox interactions between MnOx and CeO2. The catalystformed by a hydrothermal treatment exhibited excellent physicochemical properties, optimal catalyticperformance, and good H2O resistance in NH3‐SCR reaction. This was attributed to incorporationof Mnn+ into the CeO2 lattice to form a uniform ceria‐based solid solution (containing Mn‐O‐Cestructures). Strengthening of the electronic interactions between MnOx and CeO2, driven by thehigh‐temperature and high‐pressure conditions during the hydrothermal treatment also improved the catalyst characteristics. Thus, the hydrothermal treatment method is an efficient and environment‐friendly route to synthesizing low‐temperature denitrification (deNOx) catalysts.

ZnCo2O4/ZnO induced lithium deposition in multi-scaled carbon/nickel frameworks for dendrite-free lithium metal anode

Lithium metal attracts growing attention as an ideal anode candidate for next generation lithium battery systems owing to its high capacity,low density,and low working potential.However,the volume expansion of the bulk and dendrite growth on the surface of lithium anode limits its practical application.Herein,we fabricate a composite lithium host featuring both multiple scaled structure and lithiophilic property to address obstacles at both aspects of bulk and surface simultaneously.In which,the multiple scaled structure provides void space to accommodate lithium volume change while zinc and cobalt oxides sites derived from Zeolitic Imidazolate Frameworks can react with lithium and form a stable solid electrolyte interphase,leading to a stable cycling of lithium symmetrical cell for more than 500 cycles with voltage hysteresis of only 88 mV at 2 mAcm^-2 and 5 mAh cm^-2.Moreover,full cells paired with LiFePO4 cathode can realize 500 cycles with 99.2%capacity retention,showing great potential for practical applications.The excellent electrochemical performance of the composite lithium anode proves the effectiveness of our anode design with multiple scaled structure and lithiophilic feature,which can be also expanded to other metal anodes for batteries.

Bimetallic Ru-Ni/TiO2 catalysts for hydrogenation of N-ethylcarbazole:Role of TiO2 crystal structure

Hydrogenation of N-ethylcarbazole(NEC),the hydrogen lean form of a liquid organic hydrogen carrier,on TiO2 supported Ru-Ni bimetallic catalysts is investigated.Crystal structure of TiO2 plays a critical role on the hydrogenation activity and selectivity towards fully hydrogenated product.Ru/anatase catalyst exhibits higher selectivity but lower reactivity compared to Ru/rutile catalyst.Ni addition significantly promotes the performance of Ru/anatase catalyst while causes severe performance deterioration of Ru/rutile catalyst.Commercial P25,a mixture of anatase and rutile phases in approximate ratio A/R1/4,is found to be the best TiO2 support for NEC hydrogenation.Ru/P25 catalyst outperforms both Ru/rutile and Ru/anatase and its activity can be further slightly improved by Ni addition.The unexpected synergism between the two different TiO2 phases for Ru based NEC hydrogenation catalysts is related to metal-support interaction and Ru-Ni interaction.

Core-shell meso/microporous carbon host for sulfur loading toward applications in lithium-sulfur batteries

Lithium-sulfur（Li-S） batteries belong to one of the promising technologies for high-energy-density rechargeable batteries.However,sulfur cathodes suffer from inherent problems of its poor electronic conductivity and the shuttling of highly dissoluble lithium polysulfides generated during the cycles.Loading sulfur into porous carbons has been proved to be an effective approach to alleviate these issues.Mesoporous and microporous carbons have been widely used for sulfur accommodation,but mesoporous carbons have poor sulfur confinement,whereas microporous carbons are impeded by low sulfur loading rates.Here,a core-shell carbon,combining both the merits of mesoporous carbon with large pore volume and microporous carbon with effective sulfur confinement,was prepared by coating the mesoporous CMK-3 with a microporous carbon（MPC） shell and served as the carbon host（CMK-3 @MPC） to accommodate sulfur.After sulfur infusion,the as-obtained S/（CMK-3@MPC） cathode delivered a high initial capacity of up to 1422 mAh·g-1 and sustained 654 mAh·g-1 reversible specific capacity after 36 cycles at 0.1 C.The good performance is ascribed to the unique core-shell structure of the CMK-3@MPC matrix,in which sulfur can be effectively confined within the meso/microporous carbon host,thus achieving simultaneously high electrochemical utilization.

Sustainable synthesis of supported metal nanocatalysts for electrochemical hydrogen evolution

Among the various types of heterogeneous catalysts,supported metal nanocatalysts(SMNCs)have attracted widespread interest in chemistry and materials science,due to their advantageous features,such as high efficiency,stability,and reusability for catalytic reactions.However,to obtain well-defined SMNCs and inhibit nanoparticle aggregation,traditional approaches generally involve numerous organic reagents,complex steps,and specialized equipment,thus hindering the practical and large-scale synthesis of SMNCs.In this review,we summarize green and sustainable synthetic methodologies for the assembly of SMNCs,including low temperature pyrolysis and solid-state,surfactant-and reductant-free,and ionic liquid assisted syntheses.The conventional application of SMNCs for electrochemical hydrogen evolution and the corresponding achievements are subsequently discussed.Finally,future perspectives toward the sustainable production of SMNCs are presented.

Oxidative co-dehydrogenation of ethane and propane over h-BN as an effective means for C-H bond activation and mechanistic investigations

Hexagonal boron nitride(h-BN)is a highly selective catalyst for oxidative dehydrogenation of light alkanes to produce the corresponding alkenes.Despite intense recent research effort,many aspects of the reaction mechanism,such as the observed supra-linear reaction order of alkanes,remain unresolved.In this work,we show that the introduction of a low concentration of propane in the feed of ethane oxidative dehydrogenation is able to enhance the C_(2)H_(6) conversion by 47%,indicating a shared reaction intermediate in the activation of ethane and propane.The higher activity of propane makes it the dominant radical generator in the oxidative co-dehydrogenation of ethane and propane(ODEP).This unique feature of the ODEP renders propane an effective probe molecule to deconvolute the two roles of alkanes in the dehydrogenation chemistry,i.e.,radical generator and substrate.Kinetic studies indicate that both the radical generation and the dehydrogenation pathways exhibit a first order kinetics toward the alkane partial pressure,leading to the observed second order kinetics of the overall oxidative dehydrogenation rate.With the steady-state approximation,a radical chain reaction mechanism capable of rationalizing observed reaction behaviors is proposed based on these insights.This work demonstrates the potential of ODEP as a strategy of both activating light alkanes in oxidative dehydrogenation on BN and mechanistic investigations.

Significant influence of doping effect on photovoltaic performance of efficient fullerene-free polymer solar cells

The modification mechanism of the water/alcohol cathode interlayer is one of the most complicated problems in the field of organic photovoltaics,which has not been clearly elucidated yet;this greatly restricts the further enhancement of the PCE for polymer solar cells.Herein,we clarified the different effects of PFN and its derivatives,namely,poly[(9,9-bis(3’-((N,N-dimethyl)-N-ethylammonium)-propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)](PFN-Br) in modifying fullerene-free PSCs.It is found for the first time that doping on IT-4F by the amino group of PFN leads to the unfavorable charge accumulation,and hence,forms a dense layer of electronegative molecule due to the poor electron transport capacity of the non-fullerene acceptor IT-4F.The electronegative molecular layer can block the electron transfer from the active layer to the interlayer and cause serious charge recombination at the active layer/cathode interface.This mechanism could be verified by the ESR measurement and electron-only devices.By replacing PFN with PFN-Br,the excessive doping effect between the cathode interlayer and IT-4F is eliminated,by which the charge transport and collection can be greatly improved.As a result,a high PCE of 13.5%was achieved in the fullerene-free PSCs.

Cobalt phthalocyanine-graphene complex for electro-catalytic oxidation of dopamine

Cobalt phthalocyanine-graphene （CoPc-Gr） complex are fabricated through 7r-Tr interaction of each components, with CoPc adsorbed/inserted on/in the graphene sheets. The obtained complex could be used in the electro-chemical detection of various medicines. CoPc-Gr modified glassy electrode shows excellent response to the electro-oxidation of dopamine （DA） and ascorbic acid （AA）, much better than those of CoPc, graphene oxide （GrO） or graphene （Gr） modified electrode. Significantly, the detection of dopamine is a diffusion-controlled process, highly selective, and has a low detection limit and broad linear range.

Acidichromism in the LB film of bolaform Schiff base

A bolaform （BNC10） and single-headed （HNOA） amphiphilic Schiff bases containing naphthyl group were designed and their Langmuir-Blodgett films were investigated. It was found that both the LB films show acidichromism, i.e. a reversible color change upon alternatively exposing the films to HC1 and NH3 gases, respectively. It was further found that the bolaform Schiff bases film could trap NH3 gas during the acidichromic process.

Regulating surface In–O in In@InO_(x) core‐shell nanoparticles for boosting electrocatalytic CO_(2) reduction to formate

To solve the excessive emission of CO_(2) caused by the excessive use of fossil fuels and the corre‐sponding environmental problems,such as the greenhouse effect and climate warming,electrocat‐alytic CO_(2) reduction to liquid fuel with high selectivity is of huge significance for energy conversion and storge.Indium has been considered as a promising and attractive metal for the reduction of CO_(2) to formate.However,the current issues,such as low selectivity and current activity,largely limit the industrial application for electrocatalytic CO_(2) reduction,the design optimization of the catalyst structure and composition is extremely important.Herein,we develop a facile strategy to regulate surface In–O of In@InO_(x) core‐shell nanoparticles and explore the structure‐performance relation‐ship for efficient CO_(2)‐to‐formate conversion though air calcination and subsequent in situ electro‐chemical reconstruction,discovering that the surface In–O is beneficial to stabilize the CO_(2) interme‐diate and generate formate.The optimized AC‐In@InO_(x)‐CNT catalyst exhibits a C1 selectivity up to 98%and a formate selectivity of 94%as well as a high partial formate current density of 32.6 mA cm^(-2).Furthermore,the catalyst presents an excellent stability for over 25 h with a limited activity decay,outperforming the previously reported In‐based catalysts.These insights may open up op‐portunities for exploiting new efficient catalysts by manipulating their surface.

Modification of Reflectron Time-of-Flight Mass Spectrometer for Photodissociation of Mass-Selected Cluster lons

We introduce a modification of reflectron time-of-flight mass spectrometer for laser photodissociation of mass-selected ions. In our apparatus, the ions of interests were selected by a mass gate near the first space focus point and decelerated right after the mass gate, were then crossed by a laser beam for dissociation. The daughter ions and surviving parent ions were re-accelerated and analyzed by the reflectron time-of-flight mass spectrometer. Compared to the designs reported by other research groups, our selection-deceleration-dissociation-reacceleration approach has better daughter-parent-ions-separation, easier laser timing, and better overlapping between the ion beam and laser beam. We also conducted detailed cal- culations on the parent ion and daughter ion flight times, and provided a simplified formula for the calibration of daughter ion mass.