Internal electric field modulation by copper vacancy concentration of cuprous sulfide nanosheets for enhanced selective CO_(2) photoreduction

Although the internal electric field(IEF)of photocatalysts is acknowledged as a potent driving force for photocharge separation,modulating the IEF intensity to achieve enhanced photocatalytic performances remains a challenge.Herein,cuprous sulfide nanosheets with different Cu vacancy concentration were employed to study IEF modulation and corresponding direct charge transfer.Among the samples,Cu_(1.8)S nanosheets possessed intensified IEF intensity compared with those of Cu_(2)S and Cu_(1.95)S nanosheets,suggesting that an enhanced IEF intensity could be achieved by introducing more Cu vacancies.This intensified IEF of Cu_(1.8)S nanosheets induced numerous photogenerated electrons to migrate to its surface,and the dissociative electrons were then captured by Cu vacancies,resulting in efficient charge separation spatially.In addition,the Cu vacancies on Cu_(1.8)S nanosheets accumulated electrons as active sites to lower the energy barrier of rate-determining step of CO_(2)photoreduction,leading to the selective conversion of CO_(2)to CO.Herein,the manipulation of IEF intensity through Cu vacancy concentration regulation of cuprous sulfide photocatalysts for efficient charge separation has been discussed,providing a scientific strategy to rationally improve photocata lytic performances for solar energy conversion.

Enhancing an internal electric field by a solid solution strategy for steering bulk-charge flow and boosting photocatalytic activity of Bi_(24)O_(31)Cl_(x)Br_(10-x)

Constructing bismuth oxyhalide solid solutions with a single homogeneous phase have intrigued the research community;however,a deeper understanding of the intrinsic origin for improved bulk-charge separation is still unclear.Herein,a series of Bi_(24)O_(31)Cl_(x)Br_(10-x) solid solutions with the same structural characteristics were synthesized by crystal structure regulation.Combining density functional theory calculation,Kelvin probe force microscopy,and zeta potential testing results,an enhanced internal electric field(IEF)intensity between[Bi_(24)O_(31)]and[X]layers was achieved by changing halogen types and ratios.This greatly facilitated bulk-charge separation and transfer efficiency,which is significant for the degradation of phenolic organic pollutants.Owing to the enhanced IEF intensity,the charge carrier density of Bi_(24)O_(31)Cl_(4)Br_(6) was 33.1 and 4.7 times stronger than that of Bi_(24)O_(31)Cl_(10) and Bi_(24)O_(31)Br_(10),respectively.Therefore,Bi24O31Cl4Br6 had an optimal photoactivity for the degradation of bisphenol A,which was 6.21 and 2.71 times higher than those of Bi_(24)O_(31)Cl_(10) and Bi_(24)O_(31)Br_(10),respectively.Thus,this study revealed the intrinsic mechanism of the solid solution strategy for photocatalytic performance enhancement with respect to an IEF.

Revisiting N,S co-doped carbon materials with boosted electrochemical performance in sodium-ion capacitors:The manipulation of internal electric field

Heteroatom doping has emerged as a prevailing strategy to enhance the storage of sodium ions in carbon materials.However,the underlying mechanism governing the performance enhancement remains undisclosed.Herein,we fabricated N/S co-doped carbon beaded fibers(S-N-CBFs),which exhibited glorious rate performance and durableness in Na+storage,showcasing no obvious capacity decay even after 3500 cycles.Furthermore,when used as anodes in sodium-ion capacitors,the S-N-CBFs delivered exceptional results,boasting a high energy density of 225 Wh·kg^(-1),superior power output of 22500 W·kg^(-1),and outstanding cycling stability with a capacity attenuation of merely 0.014%per cycle after 4000 cycles at 2 A·g^(-1).Mechanistic investigations revealed that the incorporation of both pyridinic N and pyrrolic N into the carbon matrix of S-N-CBFs induced internal electric fields(IEFs),with the former IEF being stronger than the latter,in conjunction with the doped S atom.Density functional theory calculations further unveiled that the intensity of the IEF directly influenced the adsorption of Na+,thereby resulting in the exceptional performances of S-N-CBFs as sodium-ion storage materials.This work uncovers the pivotal role of IEF in regulating the electronic structure of carbon materials and enhancing their Na^(+)storage capabilities,providing valuable insights for the development of more advanced electrode materials.

Regulating crystallinity in linear conjugated polymer to boost the internal electric field for remarkable visible-light-driven disinfection

Conjugated linear polymers are promising metal-free photocatalysts for visible-light-driven photocatalytic water disinfection,but it was still bottlenecked by the insufficient photogenerated charge separation and transport(CST)process.Herein,we obtained the highly crystalline imine-linked conjugated linear poly-mer(ODA-BPAH)with a greatly enhanced CST process.The highly crystalline ODA-BPAH exhibited excel-lent broad-spectrum water disinfection efficiency up to 99.99999%in 1 h,which is among the reported highest of state-of-the-art photocatalysts.The crystallinity of ODA-BPAH was regulated by simply turn-ing the solvent and the experiment results revealed that the ODA-BPAH with high crystallinity exhibited higher internal electric field strength and photocatalytic performance than that with low crystallinity,which indicates that higher crystallinity in linear conjugated polymers contributes to superior CST ef-ficiency as well as the generation of reactive oxygen species.This work highlights the impact of poly-mer crystallinity on the internal electric field and proves that linear poly-imine could be a new type of promising metal-free photocatalyst for water treatment.

Strong interface interaction and internal electric field promote electron transfer of Bi_(2)O_(2)S/NiFe_(2)O_(4) heterojunction for photocatalytic antibiotic degradation

Heterojunction photocatalysts have shown considerable activities for organic pollutants degradation.However,the faint connection interface and inferior charge shift efficiency critically block the property of heterojunction photocatalysis.Herein,Bi_(2)O_(2)S/NiFe_(2)O_(4) nanosheets heterojunction with ultrastrong inter-face interaction and high internal electric field are designed by an in-situ growth method.Tentative and theoretical consequences prove that the interfacial interaction and internal electric field not only act as the electron flow bridge but also decrease the electrons shift energy obstacle,thus speeding up electrons transfer and achieving effective spatial electron-hole separation.Therefore,a large amount of·O_(2)^(-)and holes as active species were generated.Remarkably,Bi_(2)O_(2) S/NiFe_(2)O_(4) establishes a considerably boosted photocatalytic performance for tetracycline degradation(0.032 min^(-1)),which is about 14.2-fold and 7.8-fold of the pristine BOS and NFO,respectively.This work provides a promising motivation for modulating charge transfer by interface control and internal electric field to boost photocatalytic performance.

Superstable potassium metal batteries with a controllable internal electric field

Stable potassium metal batteries(PMBs)are promising candidates for electrical energy storage due to their ability to reversibly store electrical energy at a low cost.However,dendritic growth and large volume changes hinder their practical application.Here,referring to the morphology and structure of a virus,a bionic virus-like-carbon microsphere(BVC)was designed as the anode host for a PMB.A BVC with a three-dimensional structure can not only control the electric field,which can suppress dendrite formation,but can also provide a larger space to accommodate the volume change during the cycle progress.The designed potassium(K)metal anode exhibits excellent cycle life and stability(during 1800 h of repeated plating/stripping of K at a current density of 0.1 mA cm−2,K-BVC can realize a very stable K metal anode with low voltage hysteresis).Stable cyclability and improved rate capability can be realized in a full cell using Prussian blue over 400 cycles.This research provides a new idea for the development of stable K metal anodes and may pave the way for the practical application of next-generation metal batteries.

Superposition of dual electric fields in covalent organic frameworks for efficient photocatalytic hydrogen evolution

Covalent organic frameworks(COFs)are promising materials for converting solar energy into green hydrogen.However,limited charge separation and transport in COFs impede their application in the photocatalytic hydrogen evolution reaction(HER).In this study,the intrinsically tunable internal bond electric field(IBEF)at the imine bonds of COFs was manipulated to cooperate with the internal molecular electric field(IMEF)induced by the donor-acceptor(D-A)structure for an efficient HER.The aligned orientation of IBEF and IMEF resulted in a remarkable H_(2) evolution rate of 57.3 mmol·g^(-1)·h^(-1)on TNCA,which was approximately 520 times higher than that of TCNA(0.11 mmol·g^(-1)·h^(-1))with the opposing electric field orientation.The superposition of the dual electric fields enables the IBEF to function as an accelerating field for electron transfer,kinetically facilitat-ing the migration of photogenerated electrons from D to A.Furthermore,theoretical calculations indicate that the inhomogeneous charge distribution at the C and N atoms in TNCA not only pro-vides a strong driving force for carrier transfer but also effectively hinders the return of free elec-trons to the valence band,improving the utilization of photoelectrons.This strategy of fabricating dual electric fields in COFs offers a novel approach to designing photocatalysts for clean energy synthesis.

SPONTANEOUS POLARIZATION AND THE DISTRIBUTION OF INTERNAL STRESS AND ELECTRIC FIELDS AROUND A TRIPLE POINT

In this article, distributions of internal stress and internal electric fields around a triple point of ferroelectric polycrystals generated by the spontaneous deformation and spontaneous polarization were investigated. It was found that when all three grains consist of a single domain, the internal stresses and the internal electric fields do not vanish. Though it may be determined according to the principle of energy, the spontaneous configuration will not be unique without involving other conditions due to the symmetry of the crystal structure.

The first-principles study of ferroelectric behaviours of PbTiO3/SrTiO3 and BaTiOn/SrTiO3 superlattices

We have performed the first-principles calculation to investigate the origins of ferroelectricities and different po- larization behaviours of superlattices BaTiO3/SrTiO3 and PbTiO3/SrTiO3. The density of state （DOS） and electronic charge profiles show that there are strong hybridizations between atoms Ti and O and between atoms Pb and O which play very important roles in producing the ferroelectricities of superlattices BaTiO3/SrTiO3 and PbTiO3/SrTiO3. Ow- ing to the decline of internal electric field in SrTiO3 （ST） layer, the tetragonality and polarizations of superlattices decrease with increasing the fraction of SrTiO3 in the superlattices. We find that the polarization of PbTiO3/SrTiO3 is largerthan that of BaTiO3/SrTiO3 at the same ratio of components, because the polarization mismatch between PbTiO3 and SrTiO3 is larger than that between BaTiO3 and SrTiO3. The polarization and tetragonality are en- hanced with respect to those of bulk tetragonal BaTiO3 in the superlattices BaTiO3/SrTiO3, while the polarization and tetragonality are reduced with respect to those of bulk tetragonal PbTiO3 in superlattices PbTiO3/SrTiO3.

Significantly enhanced charge transfer efficiency and surface reaction on NiP_(2)/g-C_(3)N_(4) heterojunction for photocatalytic hydrogen evolution

In this work,a novel NiP_(2)/g-C_(3)N_(4)heterojunction via homogeneous precipitation method assisted by thermal phosphorization reaction was designed and constructed,and the optimized sample showed the excellent photocatalytic H_(2)evolution activity under visible-light irradiation,which was nearly 112 times higher than that of pristine g-C_(3)N_(4)sample.Experimental characterizations and DFT calculations demonstrated that the NiP_(2)nanoparticles covered on the g-C_(3)N_(4)surface can form a built-in electric field at the interface to accelerate the transfer of photoexcited electrons from g-C_(3)N_(4)to NiP_(2),crucial for hindering the recombination of electron-hole pairs.Moreover,the energy barrier of hydrogen evolution reaction can also vastly reduce when combined NiP_(2)and g-C_(3)N_(4)to construct NiP_(2)/g-C_(3)N_(4)heterojunction.This work represents a method through combing experimental and theoretical tools to thoroughly investigate the mechanism of photocatalytic process.

Donor‐acceptor carbon nitride with electron‐withdrawing chlorine group to promote exciton dissociation

Carbon nitride(C_(3)N_(4))is promising for photocatalytic hydrogen production,but photogenerated electrons and holes in C_(3)N_(4)usually tend to exist as excitons due to intrinsic Coulomb interactions making its photocatalytic activity unsatisfactory.Herein,a well‐designed intramolecular C_(3)N_(4)‐based donor‐acceptor(D‐A)photocatalytic system was constructed to promote exciton dissociation.Due to its good chemical compatibility with melamine and appropriate sublimation property,2‐amino‐4,6‐dichloropyrimidine unit was chosen as the monomer to react with melamine to construct intramolecular D‐A system(CNCl_(x)).The hydrogen evolution rate of CNCl_(0.15)is 15.3 times higher than that of bulk C_(3)N_(4)under visible light irradiation,with apparent quantum efficiency of 13.6%at 420 nm.The enhanced activity is attributed to introduced electron‐withdrawing−Cl group as terminal group in the resulted CNCl_(x) samples,which can build internal electric field to promote the exciton dissociation into free electron and hole.In addition,lower work function value of CNCl_(x) samples indicates that internal electric field can help free electrons and holes transfer to the surface of CNCl_(x) samples for photocatalytic reaction.

碳量子点/四(4-羧基苯基)卟啉/BiOBr S型异质结用于高效光催化降解抗生素

太阳能光催化处理制药废水是缓解环境问题和能源危机的一种很有前途的方法.然而,提高其处理效率面临众多挑战,如光吸收效率低、光生载流子快速复合和光氧化还原电位低等.本文通过在BiOBr(BOB)微球上沉积碳量子点(CDs)和四(4-羧基苯基)卟啉(TCPP),巧妙地构建了TCPP/CDs/BOB有机/无机三元S型异质结,用于在可见光下有效降解水体中的盐酸四环素(TC).研究发现,由于两者之间的费米能级差异,在形成异质结时触发了电子从TCPP传递到BOB,从而在界面处构建内部电场(IEF).这极大推动了光诱导载流子的有效分离.此外,CDs作为电子收集器进一步提高了S型异质结的载流子分离能力,因此保留了在CDs中聚集更强还原能力的光电子和在BOB价带中更强氧化能力的空穴来参与光催化反应.在这些催化剂中,TCPP/CDs/BOB-2异质结催化剂在40 min内对TC的降解能力高达83.6%.TCPP/CDs/BOB-2的反应速率常数(k)分别约为BOB、CDs/BOB和TCPP/BOB的2.3、1.8和2.0倍.这项工作为探索用于水净化的有机/无机三元S型光催化剂提供了新的视角.

Unveiling an S-scheme F–Co_(3)O_(4)@Bi_(2)WO_(6) heterojunction for robust water purification

Devising a desirable nano-heterostructured photoelectrode based on the charge transfer kinetics mechanism is a pivotal strategy for implementing efficient photoelectrocatalytic(PEC)technology,since the charge separation and utilization efficiency of a photoelectrode is critical to its PEC performance.Herein,we fabricate a F–Co_(3)O_(4)@Bi_(2)WO_(6) core–shell hetero-array photoanode by coupling Bi_(2)WO_(6) nanosheets with F–Co_(3)O_(4) nanowires using a simple solvothermal solution method.The three-dimensional hierarchical heterostructure has a homogeneous chemical interface,helping it to promote an S-scheme-based carrier transport kinetics and maintain excellent cycling stability.Charge density difference calculations verify the electron migration trend from F–Co_(3)O_(4) to Bi_(2)WO_(6) upon hybridization and the formation of an internal electric field in the heterojunction,consistent with the S-scheme mechanism,which is identified by in situ irradiation X-ray photoelectron spectroscopy and by ultraviolet photoelectron spectroscopy.The optimized F–Co_(3)O_(4)@Bi_(2)WO_(6)-2 photoelectrode achieves high carrier utilization efficiency and exhibits superior PEC degradation performance for various organic pollutants,including reactive brilliant blue KN-R,rhodamine B,sulfamethoxazole,and bisphenol A.This work not only reveals that F–Co_(3)O_(4)@Bi_(2)WO_(6)-2 is effective for PEC water remediation but also provides a strategy to enhance carrier transport kinetics by designing binary oxides.

Z型电荷分离介导的0D/2D AgVO_(3)/TiO_(2)异质结用于增强光催化CO_(2)还原

合理利用Z型电荷调节机制是提高光催化CO_(2)还原效率的有效策略.在本工作中,通过将AgVO_(3)量子点(QDs)原位锚定在TiO_(2)纳米片(NSs)上,从而构建了0D/2D AgVO_(3)/TiO_(2)直接Z型异质结光催化剂.TiO_(2)NSs抑制了AgVO_(3)量子点自身的团聚,从而优化了体系的形貌结构.AgVO_(3)QDs增强了复合材料的光吸收能力,从而提高了对太阳光的利用效率.同时,两种单体之间匹配的能带结构和合适的内部界面电场(即(-)AgVO_(3)/(+)TiO_(2))促进了直接Z型异质结的构建,从而显著促进了光生电子-空穴对的分离,并保持了体系中最高的氧化还原电位.优化后的AgVO_(3)/TiO_(2)复合材料在没有任何助催化剂的情况下,表现出具有竞争力的光催化CO_(2)还原效率(CO,47.61μmol h-1g-1),是原始TiO_(2)NSs的20.97倍.本工作提出了一种直接Z型异质结的合理设计方法,为高效光催化CO_(2)还原催化剂的开发提供了指导.

Surface defect and lattice engineering of Bi_(5)O_(7)Br ultrathin nanosheets for efficient photocatalysis

The effective separation and migration of photogenerated charge carriers in bulk and on the surface of photocatalysts will significantly promote photocatalytic efficiency.However,the synchronous regulation of photocharges on both counts is challenging.Herein,the simultaneous separation of bulk and surface photocharges is conducted to enhance photocatalytic activity by coupling the surface defects and lattice engineering of bismuth oxybromide.The depth-modulated Bi_(5)O_(7)Br ultrathin nanosheets with an abundance of bismuth in the crystal structure increased the internal electric field,which propelled the separation and migration of photocharges from bulk to the surface.Creation of oxygen vacancies(OVs)on the nanosheet surface forms local electric fields,which can stimulate the migration of charges to active sites on the catalyst surface.Therefore,the OV-assembled Bi_(5)O_(7)Br nanosheets demonstrated enhanced photocatalytic degradation efficiency under simulated solar-light illumination.This study proved the possibility of charge governing via electric field modulation based on an integrated strategy.

Fabrication of graphene modified CeO_(2)/g-C_(3)N_(4)heterostructures for photocatalytic degradation of organic pollutants

A specific type S-scheme photocatalyst CeO_(2)@N-GO/g-C_(3)N_(4)was successfully synthesized,resulting in a 2-mer-captobenzothiazole(MBT)degradation rate of 100%,which is more than twice that of g-C_(3)N_(4)and CeO_(2).The improved degradation performance can be attributed to the introduction of N-graphene oxide(N-GO),which facilitates the electron transfer.Additionally,the unique Ce^(4+)→Ce^(3+)conversion property enhances the charge carrier utilization,and thereby the photocatalytic activity.Furthermore,theoretical calculations suggest the formation of an interfacial internal electric field(IEF)formed between CeO_(2)(the(200)and(311)planes)and g-C_(3)N_(4)(the(002)plane)to enhance the delocalization of the charge carriers.Moreover,various photo-electrochemical analyses are employed for the in-depth mechanism on MBT degradation and IEF-induced S-scheme over CeO_(2)@N-GO/g-C_(3)N_(4),where the differential charge proves the electron transfer path from CeO_(2)to g-C_(3)N_(4)that significantly prolongs its lifetime.The radical capture and electron spin resonance(ESR)results proved the existence of the active species of·OH,·O_(2)^(-),and h^(+)in the S-scheme photocatalytic system.

Emerging Bismuth-Based Step-Scheme Heterojunction Photocatalysts for Energy and Environmental Applications

Photocatalysis has been expected to be a promising advanced oxidation process to endlessly convert exhaustless solar energy into storable,transportable,and usable chemical energy.As a kind of visible light-response semiconductors,Bi-based semiconductors can be developed into step-scheme(S-scheme)heterojunction photocatalysts,consisting of a reductive photocatalyst(RP)and an oxidative photocatalyst(OP)with band edge bending.This review sums up the state-of-the-art progress in Bi-based S-scheme heterojunctions,as well as the in-/ex-situ experiments and theoretical calculations to uncover the unique heterostructure and charge transfer mechanism of Bi-based S-scheme heterojunctions in depth.We can find that Bi-based S-scheme heterojunction photocatalysts have advantages in impeding the recombination of photo-induced electron-hole pairs,expediting the charge transfer,broadening solar energy utilization,and maximizing the potential energy of photo-redox reaction sites.Additionally,the recently published work on the potential applications of Bi-based S-scheme heterojunctions is also summarized,including photocatalytic H_(2) production,CO_(2) reduction with water,pollutant degradation,H_(2)O_(2) production,and N_(2) photofixation for ammonia and urea production by comparing and discussing their photocatalytic efficiency.On the basis of research progress,the immediate challenges and future perspectives of Bi-based S-scheme heterojunction photocatalysts are critically debated.

Enhanced photocatalytic degradation and H_(2) evolution performance of N-CDs/S-C_(3)N_(4)S-scheme heterojunction constructed byπ-πconjugate self-assembly

Constructing heterojunction between two semiconductors with matched energy band structure is an effective modification method to obtain excellent photocatalysts.The experimental scheme adopts a simple solvent method to self-assemble nitrogen doped carbon dots(N-CDs)on the surface of sulfur doped carbon nitride(S-C_(3)N_(4))semiconductor throughπ-πconjugate interaction.Based on this,a novel 0D/2D S-scheme heterojunction N-CDs/S-C_(3)N_(4)hybrid was successfully prepared.The degradation kinetic constants of N-CDs/S-C_(3)N_(4)for rhodamine B(RhB)and p-nitrophenol(PNP)reached 0.23522 and 0.01342 min^(−1),repectively,which were 2.72 and 2.65 times that of S-C_(3)N_(4).The highest photocatalytic hydrogen evolution rate was observed under the simulated sunlight irradiation,which was 2.30 times that of S-C_(3)N_(4).The improvement of photocatalytic performance was mainly based on the formation of the S-scheme heterojunction between S-C_(3)N_(4)and N-CDs.The effects of internal electric field,π-πconjugate interaction and band bending promoted the photogenerated h^(+)and e^(−) with low redox ability to recombine and retained the beneficial h+and e−with strong redox ability,which contributed to the production of more active species of h^(+) and•O_(2)−,therefore the photocatalytic degradation and hydrogen evolution performance were significantly enhanced.

Crystal-chemistry insight into the photocatalytic activity of BiOCI_(x)Br_(1_x)nanoplate solid solutions

In this study,a facile alcoholysis method was developed to synthesize BiOCI_(x)Br_(1_x)nanoplates at room temperature and atmospheric pressure.In this route,strong acid or alkaline environment was absolutely avoided to realize the high exposure of{001}crystal facets.The regular changes in XRD peaks and cell parameters as a function of the Br content strongly declared that the obtained BiOCIxBrl_x products belonged to a group of solid solutions.The 2D nanosheets with in-plane wrinkles were clearly observed in TEM images.Interestingly,as the Br content increased,band gaps of BiOCI_(x)Br_(1_x)solid solutions gradually decreased.The photocatalytic degradation of RhB under simulated sunlight irradiation indicated that BiOCI0.sBr0.5 had the best photocatalytic activity.From the viewpoint of crystal chemistry,the photocatalytic activity of BiOCI_(x)Br_(1_x)solid solutions was closely related with the exposure amount of{001}facets,interlayer spacing of(001)plane and energy-level position of valence band.

Promoting intramolecular charge transfer of graphitic carbon nitride by donor-acceptor modulation for visible-light photocatalytic H_(2) evolution

To satisfy the requirements of substantial green development,it is urgent to explore an innovative eco‐friendly semiconductor photocatalyst to efficiently achieve visible‐light‐driven photocatalytic H 2 evolution(PHE).The strategy of promoting the spatial separation efficiency of photoinduced carriers can essentially enhance the PHE performance of a photocatalyst.Herein,a graphitic carbon nitride(g‐C 3 N 4)‐based donor–acceptor(D‐A)copolymer(CNDM x)is constructed by simple one‐pot thermal polycondensation,using urea and 5,8‐DibroMoquinoxaline(as an electron donor)as precursors.The electron D-A modulation consequently creates an internal electric field to facilitate the intramolecular charge transfer within the copolymer.A series of experimental characterizations and density functional theory calculations are applied to elucidate the variation and correlation of the structure and PHE performance of the as-prepared catalysts.It is found that the best average PHE rate of 3012.5μmolg^(−1) h^(−1) can be achieved over the optimal D-A copolymer under visible‐light(400<λ<800nm)irradiation,which is~3.3 times that of pure urea-derived g-C_(3)N_(4).The corresponding apparent quantum efficiency is 1.3% at 420nm.This study provides a protocol for designing effective visible-light photocatalysts via D-A modulation of polymeric semiconductors.