First-principles study of the relationship between the formation of single atom catalysts and lattice thermal conductivity

Single atom catalysts(SACs)have been in the forefront of catalysts research because of their high efficiency and low cost and provide new ideas for development of renewable energy conversion and storage technologies.However,the relationship between the intrinsic properties of materials such as lattice thermal conductivity and catalysis remains to be explored.In this work,the lattice thermal conductivity of BN and graphene was calculated by Sheng BTE.In addition,the adsorption properties of 3d-TM(TM=V,Cr,Mn,Fe,Co,Ni)on BN and graphene were investigated using first-principles methods,and it was found that Ni atom can form relatively stable SACs compared to other TMs.The molecular dynamics(MD)simulation and migration barrier of Ni loaded on BN and graphene were calculated.Our study found that graphene has higher thermal conductivity and is easier to form SACs than BN,but the SACs formed on BN surface have higher thermodynamic stability.

Nitric oxide assists nitrogen reduction reaction on 2D MBene: A theoretical study

Electrocatalytic synthesis of ammonia as an environment-friendly and sustainable development method has received widespread attention in recent years.Two-dimensional(2D)materials are a promising catalyst for ammonia synthesis due to their large surface area.In this work,we have constructed a series of 2D metal borides(MBenes)with transition metal(TM)defects(TMd-MBenes)and comprehensively calculated the reactivity of electrocatalytic synthesis of ammonia-based on density functional theory.The results have demonstrated that the TMd-MBenes can effectively activate nitrogen oxide(NO)and nitrogen(N2)molecules thermodynamically.Particularly interesting,the co-chemisorption of O atoms,dissociated from NO,can facilitate the spilled of the inert N2 molecules into single N atoms,which can further hydrogenate into ammonia easily with an ultralow limiting potential of 0.59 V on TMd-MnB.Our research has not only provided clues for catalyst design for experimental study but also paved the way for the industrial application of electrocatalytic ammonia synthesis.

全有机S型异质结PDI-Ala/S-C_(3)N_(4)光催化剂增强光催化性能

有机光催化剂以其适宜的氧化还原能带、低成本、高化学稳定性、分子结构和电子结构的可调控性而备受关注。PDI-Ala(N,N’-二(丙酸)-苝-3,4,9,10-四羧酸二亚胺)是一种新型的有机光催化剂,具有较强的可见光响应、低价带位置、强氧化能力等特点。然而,低的光生电荷转移速率和高的载流子复合率限制了它的应用。由于g-C_(3)N_(4)存在芳香杂环结构且PDI-Ala的刚性平面结构存在着离域大π键,g-C_(3)N_(4)和PDI-Ala可以通过π–π相互作用和N―C键紧密结合。通过硫掺杂g-C_(3)N_(4)合成了S-C_(3)N_(4),其能带结构相比于g-C_(3)N_(4)更能与PDI-Ala相匹配。电子离域效应、内建电场和新形成的界面化学键共同促进了PDI-Ala与S-C_(3)N_(4)之间光生载流子的分离与迁移。因此,采用原位自组装的方法制备了一种由有机半导体PDI-Ala和S-C_(3)N_(4)组成的S型(阶梯型)异质结光催化剂。在制备过程中,PDI-Ala通过横向氢键和纵向π–π堆积自组装成超分子。采用X射线衍射(XRD)、透射电子显微镜(TEM)、能谱仪(EDS)、X射线光电子能谱(XPS)、紫外可见漫反射光谱(UVVis-DRS)、电化学阻抗谱(EIS)、Mott-Schottky曲线(MS)等多种表征方法,对PDI-Ala/S-C_(3)N_(4)光催化剂的晶体结构、形貌、价态、光学性能、稳定性和能带结构进行了系统的分析和研究;利用密度泛函理论(DFT)计算了材料的功函数和界面耦合特性。研究了合成的光催化剂在H2O2生产中的光催化活性以及在可见光照射下对四环素(TC)和对硝基苯酚(PNP)的降解作用。该S型异质结具有能带匹配和紧密的界面结合,加速了分子间的电子转移,拓宽了异质结的可见光响应范围。此外,在PDI-Ala/S-C_(3)N_(4)光催化降解反应过程中,产生并积累了多种活性物种(h^(+)、·O^(-)_(2)和H_(2)O_(2))。因此,PDI-Ala/SC_(3)N_(4)异质结在降解TC、PNP和H_(2)O_(2)生产方面表现出更强的光催化性能。在可见光照射下,30%PDI-Ala/S-C_(3)N_(4)样品在90 min内去除了90%的TC,H_(2)O_(2)的产率为28.3μmol·h^(-1)·g^(-1),分别是PDI-Ala的2.9倍和S-C_(3)N_(4)的1.6倍。结果表明,由苝二酰亚胺(PDIs)基超分子和S-C_(3)N_(4)组成的全有机光催化剂可有效地用于降解有机污染物和生产H_(2)O_(2)。本研究不仅为全有机S型异质结的设计提供了一种新的策略,而且为理解具有有效界面键合的异质结构催化剂的构效关系提供了新的见解和参考。

A review on hydrogen production from ammonia borane:Experimental and theoretical studies

Ammonia borane(NHsBH3,AB)is an ideal raw material of hydrogen production with higher hydrogen storage capacity.In this paper,the catalytic processes of AB dehydrogenation were described from different ways,including thermal dehydrogenation,hydrolysis,methanolysis,photocatalysis and photopiezoelectric synergy catalysis with experimental research and theoretical calculations.Catalyst models include bulk materials,two-dimensional materials,nanocluster particles and single/diatomic structures.Among them,the proportion of H2 released is different,and the reaction conditions are also different,which are suitable for different application scenarios.Through this review,we could have a preliminary comprehensive understanding of AB dehydrogenation reaction.

Laser-ablated violet phosphorus/graphene heterojunction as ultrasensitive ppb-level room-temperature NO sensor

Two dimensional(2D)materials are promising gas sensing materials,but the most of them need to be heated to show promising sensing performance.Sensing structures with high sensing performance at room-temperature are urgent.Here,another 2D material,violet phosphorus(VP)nanoflake is investigated as gas sensing material.The VP nanoflakes have been effectively ablated to have layers of 1–5 layers by laser ablation in glycol.The VP nanoflakes are combined with graphene to form VP/G heterostructuresbased NO sensor.An ultra-high gauge factor of 3×10^(7)for ppb-level sensing and high resistance response of 59.21%with ultra-short recovery time of 6s for ppm-level sensing have been obtained.The sensing mechanism is also analysed by density functional theory(DFT)calculations.The adsorption energy of VP/G is calculated to be-0.788 e V,resulting in electrons migration from P to N to form a P-N bond in the gap between VP and graphene sheet.This work provides a facile approach to ablate VP for mass production.The as-produced structures have also provided potential gas sensors with ultrasensitive performance as ppb-level room-temperature sensors.

Turning the V site in V@2D-BC_(3)N_(2)complex to high curvature state for efficient CO_(2)electroreduction to hydrocarbons

Hydrocarbons are promising products for CO_(2)electroreduction(CRR)while is impeded by the low selectivity.Turning the curvature of the active site is an effective strategy to change the adsorption properties and further regulate the product distribution and reactivity.Herein,we have designed a novel V single atom catalyst(SAC)based on rolled two-dimensional(2D)BC_(3)N_(2)substrate with different curvatures.The results have demonstrated that increased curvature can enhance the adsorption strength of CRR intermediates,which follows different mechanisms for systems with low and high curvature.This character eventually leads to the deviation away from the scaling line between Ead[CO]∼Ead[COOH]based on transition metals for V@2D-BC_(3)N_(2)systems.3-3 system is screened as the optimal candidate for hydrocarbons production due to the enhanced binding ability of adsorbates,which can increase the reactivity for hydrocarbons production and hinder the production of H2 and HCOOH simultaneously.

Selective conformer detection of short-lived base pair tautomers: A computational study of the unusual guanine-cytosine pairs using ultrafast resonance Raman spectroscopy

Base pair mismatch has been regarded as the main source of DNA point mutations, where minor shortlived tautomers were usually involved. However, the detection and characterization of these unnatural species pose challenges to existing techniques. Here, by using systematic structural and ultrafast resonance Raman(RR) spectral analysis for the four possible conformers of guanine-cytosine base pairs, the prominent marker Raman bands were identified. We found that the hydrogen bonding vibrational region from 2300 cm^(-1) to 3700 cm^(-1) is ideal for the identification of these short live species. The marker bands provide direct evidence for the existence of the tautomer species, thus offering an effective strategy to detect the short-lived minor species. Ultrafast resonance Raman spectroscopy would be a powerful tool to provide direct evidence of critical dynamical details of complex systems involving protonation or tautomerization.

Highly active Fe_(36)Co_(44) bimetallic nanoclusters catalysts for hydrolysis of ammonia borane: The first-principles study

In this paper,Fe_(36)Co_(44)nanocluster structure is used to catalyze the hydrolysis reaction of ammonia borane to produce H_(2).Firstly,we complete the construction of Fe_(36)Co_(44)cluster structure and calculate the electronic properties of the cluster.By comparing the adsorption process of Ammonia Borane (AB) in active sites of the cluster,which have different Effective Coordination Number (ECN),the qualitative relationship between ECN and the catalytic activation of AB is clarified,and the optimal catalytic active site is obtained.Then,from the perspective of different reaction paths,we study the hydrolysis reaction of AB in multiple paths,and obtain 5 different reaction paths and energy profiles.The calculation results show that in the case of N–H bond priority break (path 5),the reaction has the minimum rate-determining step (RDS) barrier (about 1.02 e V) and the entire reaction is exothermic (about 0.40 e V).So,path 5 is an optimal catalytic reaction path.This study will have an important guiding significance for the study of the AB hydrolysis reaction mechanism.

A novel method for atomization energy prediction based on natural-parameter network

Atomization energy(AE)is an important indicator for measuring material stability and reactivity,which refers to the energy change when a polyatomic molecule decomposes into its constituent atoms.Predicting AE based on the structural information of molecules has been a focus of researchers,but existing methods have limitations such as being time-consuming or requiring complex preprocessing and large amounts of training data.Deep learning(DL),a new branch of machine learning(ML),has shown promise in learning internal rules and hierarchical representations of sample data,making it a potential solution for AE prediction.To address this problem,we propose a natural-parameter network(NPN)approach for AE prediction.This method establishes a clearer statistical interpretation of the relationship between the network’s output and the given data.We use the Coulomb matrix(CM)method to represent each compound as a structural information matrix.Furthermore,we also designed an end-to-end predictive model.Experimental results demonstrate that our method achieves excellent performance on the QM7 and BC2P datasets,and the mean absolute error(MAE)obtained on the QM7 test set ranges from 0.2 kcal/mol to 3 kcal/mol.The optimal result of our method is approximately an order of magnitude higher than the accuracy of 3 kcal/mol in published works.Additionally,our approach significantly accelerates the prediction time.Overall,this study presents a promising approach to accelerate the process of predicting structures using DL,and provides a valuable contribution to the field of chemical energy prediction.

Capture and separation of CO_(2)on BC_(3)nanosheets:A DFT study

In order to reduce the greenhouse effect caused by the rapid increase of CO_(2)concentration in the atmosphere,it is necessary to develop more efficient,controllable,and highly sensitive adsorbing materials.In this study,the adsorption behavior of CO_(2)on BC_(3)nanosheets under an external electric field was explored based on density functional theory(DFT).It was found that CO_(2)experienced a transition from physisorption to chemisorption in the electric field range of 0.0060-0.0065 a.u..In addition,the adsorption/desorption of CO_(2)is reversible and can be precisely controlled by switching on/off at the electric field of 0.0065 a.u..The selective adsorption of CO_(2)/H_(2)/CH_(4)by BC_(3)can also be used to realize gas separation and purification under different electric fields.This study highlighted the potential application of BC_(3)nanosheets as a high-performance,controllable material for CO_(2)capture,regeneration,and separation in an electric field.

A periodic DFT study on adsorption of small molecules(CH4,CO,H2O,H2S,NH3)on the WO3(001) surface-supported Au

Gas molecules(such as CH4,CO,H2O,H2S,NH_3)adsorption on the pure and Au-doped WO3(001)surface have been studied by Density functional theory calculations with generalized gradient approximation.Based on the the calculation of adsorption energy,we found the most stable adsorption site for gas molecules by comparing the adsorption energies of different gas molecules on the WO3(001)surface.We have also compared the adsorption energy of five different gas molecules on the WO3(001)surface,our calculation results show that when the five kinds of gases are adsorbed on the pure WO3(001)surface,the order of the surface adsorption energy is CO>H2S>CH4>H2O>NH3.And the results show that NH3 is the most easily adsorbed gas among the other four gases adsorbed on the surface of pure WO3(001)surface.We also calculated the five different gases on the Au-doped WO3(001)surface.The order of adsorption energy was found to be different from the previous calculation:CO>CH4>H2S>H2O>NH3.These results provide a new route for the potential applications of Au-doped WO3 in gas molecules adsorption.

Principles for designing CO_(2) adsorption catalyst: Serving thermal conductivity as the determinant for reactivity

CO_(2)is a representative prototype model in energy and environmental fields.Many factors for CO_(2)capture and activation have been investigated extensively but the research on the influence of thermal conductivity is still absence.We herein have calculated many properties,including dipole moment,electric structure,and adsorption energies,on Pt doped graphene and 2D BC_(3)N_(2)substrates and served the thermal conductivity as the bridge.Our results have demonstrated that the lower (higher) thermal conductivity for 2D BC_(3)N_(2)(graphene) corresponds to larger (lower) dipole moment,which is beneficial for CO_(2)activation (capture) process.Our research have not only revealed the dominant role of heat conductivity for CO_(2)capture and activation,but also paved the way for further catalyst design of various areas.

Hydrogen generation of ammonia borane hydrolysis catalyzed by Fe_(22)@Co_(58) core-shell structure

In this paper,the process of ammonia borane(AB)hydrolysis generate H_(2) on the transition metal Fe@Co core-shell structure has been obtained.According to the different roles played by H_(2)O molecules and the number of H_(2)O molecules involved,there are three schemes of reaction paths.RouteⅠdoes not involve the dissociation of H_(2)O molecules and all H atoms come from AB.Moreover,the H_(2)O molecule has no effect on the breaking of the B—H bond or the N—H bond.The reaction absorbs more heat during the formation of the second and third H_(2) molecules.RouteⅡincludes the dissociation of H_(2)O molecules and the cleavage of B—H or N—H bonds,respectively,and the reaction shows a slight exotherm.RouteⅢstarted from the break of the B—N bond and obtained 3H_(2) molecules through the participation of different numbers of H_(2)O molecules.After multiple comparative analyses,the optimal hydrolysis reaction path has been obtained,and the reaction process can proceed spontaneously at room temperature.

Constructing a novel Ag nanowire@CeVO_(4) heterostructure photocatalyst for promoting charge separation and sunlight driven photodegradation of organic pollutants

Exploiting efficient and recyclable photocatalysts is a vital matter for environmental purification. Herein, cerium vanadate (CeVO_(4)) sub-microspheres and silver nanowire (AgNW)@CeVO_(4) with core-shell architecture as photocatalysts are rationally constructed by hydrothermal approach. The AgNW@CeVO_(4) photocatalyst obtained by depositing CeVO_(4) on the surface of Ag NWs possess one dimensional continuous structure, which expand the optical absorption range and reduce the band gap of CeVO_(4) photocatalyst. Moreover, the resultant AgNW@CeVO_(4) photocatalyst demonstrates superior photocatalytic performance in the degradation of rhodamine B, methylene blue, and 4-nitrophenol pollutants upon solar light irradiation, compared with pure CeVO_(4). The excellent photocatalytic activity can be ascribed to the introduction of Ag NWs, which afford rapid charge transport channels and reservoir for the electrons in the AgNW@CeVO_(4) heterostructure to promote separation of electron-hole pairs. The first-principles investigations reveal increase of adsorption energy of oxygen molecules on the CeVO_(4) surface with the presence of Ag. Meanwhile, Ag NWs can further improve the photocatalytic efficiency of the AgNW@CeVO_(4) based on the plasmonic effect. More importantly, the good structural stability and recyclability of AgNW@CeVO_(4) are observed due to the strong synergistic effect, which ensures long-term usability of photocatalyst and great promise in water purification. This work can offer valuable reference into designs and construction of Ce-based heterojunction photocatalysts for environmental remediation.

An efficient single atom catalysts Os/P_(3)C sheet for ammonia borane dehydrogenation

Ammonia borane(NH_(3)BH_(3),AB)has been considered to be a promising chemical hydrogen storage material.Based on density functional theory,a series of transition metal atoms supported P_(3)C(P_(3)C_O)sheet is systematically investigated to screen out the most promising catalyst for dehydrogenation of AB.The results indicate that the Os/P_(3)C and Os/P_(3)C_O could be an efficient single atom catalyst(SACs)and the stepwise reaction pathway with free energy barrier of 2.07 and 1.54 e V respectively.Remarkably,the rate constant further quantitatively confirmed the real situation of the first step of dehydrogenation of AB on the Os/P_(3)C and Os/P_(3)C_O substrates.We found that k_(f1)at 400 K is equivalent to k_(f2)at 800 K,which greatly improves the temperature of the first step of AB dehydrogenation on P_(3)C_O.We hope this work can provide a promising method for the design of catalysts for AB dehydrogenation reactions on the surface of two-dimensional materials(2D).

A DFT study of two-dimensional P_2Si monolayer modified by single transition metal(Sc-Cu)atoms for efficient electrocatalytic CO_(2)reduction

In the present work,a stable two-dimensional(2D)P_(2)Si monolayer was predicted.The monolayer is semimetallic/metallic under the PBE/HSE06 functional and is mechanically isotropic.The stability of the P_(2)Si monolayer has been proved via cohesive energy,mechanical criteria,molecular dynamics simulation,and phonon dispersion respectively,and the monolayer possesses high carrier mobility which is three times that of Mo S_(2).On the other hand,the catalytic performance of the P_(2)Si monolayer modified with a single transition metals(M=Sc-Cu)atom for the electrochemical reduction of CO_(2)was investigated,and the monolayer can catalyze CO_(2)with three constraints:stable molecular dynamics,high migration potential of metal atoms,and suitable band gap for electrocatalyst after metal doping exhibiting excellent catalytic stabilization activity and CRR selectivity.In addition,the reduction product of V@P_(2)Si is HCOOH with an overpotential as low as 0.75 V,and the most suitable reaction path is^(*)CO_(2)→^(*)CHOO→O^(*)CHOH→^(*)+HCOOH with the final reduction product HCOOH obtained.As a whole,the above results endow the P_(2)Si monolayer to be a good 2D material holding great promises for applications in nanoelectronics and CO_(2)reduction catalysts.

A promising controllable CO_(2)capture and separation materials for CO_(2)/CH_(4)/H_(2)under electric field

As the greenhouse effect concerns increases,the development of new materials for the efficient capture and separation of CO_(2)gas from gas mixtures has become a matter of urgency.In this study,we performed density functional theory(DFT)calculations to investigate the adsorption and separation behavior of CO_(2)/CH_(4)/H_(2)on the surface of two-dimensional(2D)Al_(2)C materials under positive/negative applied electric fields.In the absence of an electric field CO_(2)is weakly physisorbed on the Al_(2)C surface,but with the application of an applied electric field,the adsorption state of CO_(2)gradually changes from physical to chemisorption(adsorption energy changes from-0.29 e V to-3.61 e V),while the negative electric field has little effect on the adsorption of CO_(2).We conclude that the C=O bond in adsorbed CO_(2)can be activated under an external electric field(maximum activation of 15%under an external electric field of 0-0.005 a.u.).Only in the presence of an applied electric field of 0.0033 a.u.and temperatures above525 K/675 K can the adsorption/separation reaction of CO_(2)single adsorption and CO_(2)/CH_(4)/H_(2)mixture be spontaneous.The adsorption/desorption of CO_(2)on Al_(2)C nanosheet in an electric field of 0.003-0.0033 a.u.is all exothermic,which can be easily controlled by switching on/off the electric field without any energy barriers.The capacity of Al_(2)C to capture CO_(2)per unit electric field decreases with increasing CO_(2)concentration,but still has efficient gas separation properties for CO_(2)/CH_(4)/H_(2).Our theoretical results could provide guidance for designing high-capacity and high-selectivity CO_(2)capture materials.

Computational design of BC_(3)N_(2) based single atom catalyst for dramatic activation of inert CO_(2) and CH4 gasses into CH_(3)COOH with ultralow CH_(4) dissociation barrier

The production of CH_(3)COOH from CO_(2)and CH_(4) has stimulated much interest due to the high energy density of C2 species.Various kinds of catalysts have been developed while the high dissociation barrier of CH_(4) and low selectivity still hinders the efficiency of the reaction.We have herein proposed a novel catalyst with single metals loaded on 2D BC_(3)N_(2) substrate(M@2D-BC_(3)N_(2))based on density functional theory.Among numerous candidates,Pt@2D-BC_(3)N_(2) possesses the most favorable reactivity with an ultralow barrier of CH_(4) splitting(0.26 e V),which is due to the efficient capture ability of CH_(4) on Pt site.Besides,the selectivity for CH_(3)COOH is also very high,which mainly stems from the unique electronic properties of molecules and substrate:The degenerated states,including s,px,pyand pz,in CO_(2)reflects the existence of delocalizedπbonds between C and O.This can interact with states of Pt(s),Pt(pz),Pt(dxz),Pt(dyz),and Pt(z2)in Pt@2D-BC_(3)N_(2).The kinetics model also proves that our system can promote CH_(3)COOH production via simply increasing the temperature or the coverage of CH_(4) and CO_(2).Our results provide a reasonable illustration in clarifying mechanism and propose promising candidates with high reactivity for further study.

Porous carbon framework nested nickel foam as freestanding host for high energy lithium sulfur batteries

Constructing 3 D multifunctional conductive framework as stable sulfur cathode contributes to develop advanced lithium-sulfur(Li-S)batteries.Herein,a freestanding electrode with nickel foam framework and nitrogen doped porous carbon(PC)network is presented to encapsulate active sulfur for Li-S batteries.In such a mutually embedded architecture with high stability,the interconnected carbon network and nickel foam matrix can expedite ionic/electro nic tra nsport and sustain volume variations of sulfur.Furthermore,rationally designed porous structures provide sufficient internal space and large surface area for high active sulfur loading and polar polysulfides anchoring.Benefiting from the synergistic superiority,the Ni/PC-S cathode exhibits a high initial capacity of around 1200 mAh/g at 0.2 C,excelle nt rate perfo rmance,and high cycling stability with a low decay rate of 0.059%per cycle after 500 cycles.This work provides a useful strategy to exploit freestanding porous framework for diverse applications.

Rich B active centers in Penta-B_(2)C as high-performance photocatalyst for nitrogen reduction

The photocatalytic nitrogen reduction reaction(NRR) has mild reaction conditions and only requires sunlight energy as a driving force to replace the traditional ammonia synthesis method. We herein investigate the catalytic activity and selectivity on Penta-B_(2)C for NRR by using density functional theory calculations. Penta-B_(2)C is a semiconductor with an indirect bandgap(2.328 e V) and is kinetically stable based on molecular dynamic simulations. The optical absorption spectrum of Penta-B;C is achieved in the ultraviolet and visible range. Effective light absorption is more conducive to generate photo-excited electrons and improving photocatalytic performances. Rich B atoms as activation sites in Penta-B_(2)C facilitate capturing N_(2). The activated N_(2)molecule prefers the side-on adsorption configuration on Penta-B_(2)C, which facilitates the subsequent reduction reaction. Among considered NRR mechanisms on Penta-B_(2)C, the best pathway prefers the enzymatic mechanism, only required a low onset potential of 0.23 V. The hydrogen evolution reaction is inhibited when the hydrogen adsorption concentration is increased or N_(2)molecules first occupy the adsorption sites. Our results indicate Penta-B_(2)C is a highly reactive and selective photocatalyst for NRR. Our work provides theoretical insights into the experiments and has guiding significance to synthesize efficient NRR photocatalysts.