Modulating charge separation and transfer for high-performance photoelectrodes via built-in electric field

Constructing a built-in electric field has emerged as a key strategy for enhancing charge separation and transfer,thereby improving photoelectrochemical performance.Recently,considerable efforts have been devoted to this endeavor.This review systematically summarizes the impact of built-in electric fields on enhancing charge separation and transfer mechanisms,focusing on the modulation of built-in electric fields in terms of depth and orderliness.First,mechanisms and tuning strategies for built-in electric fields are explored.Then,the state-of-the-art works regarding built-in electric fields for modulating charge separation and transfer are summarized and categorized according to surface and interface depth.Finally,current strategies for constructing bulk built-in electric fields in photoelectrodes are explored,and insights into future developments for enhancing charge separation and transfer in high-performance photoelectrochemical applications are provided.

Long-range electron synergy over Pt_(1)-Co_(1)/CN bimetallic single-atom catalyst in enhancing charge separation for photocatalytic hydrogen production

The development of novel single-atom catalysts with optimal electron configuration and economical noble-metal cocatalyst for efficient photocatalytic hydrogen production is of great importance,but still challenging.Herein,we fabricate Pt and Co single-atom sites successively on polymeric carbon nitride(CN).In this Pt_(1)-Co_(1)/CN bimetallic single-atom catalyst,the noble-metal active sites are maximized,and the single-atomic Co_(1)N_4sites are tuned to Co_(1)N_3sites by photogenerated electrons arising from the introduced single-atomic Pt_(1)N_4sites.Mechanism studies and density functional theory(DFT)calculations reveal that the 3d orbitals of Co_(1)N_3single sites are filled with unpaired d-electrons,which lead to the improved visible-light response,carrier separation and charge migration for CN photocatalysts.Thereafter,the protons adsorption and activation are promoted.Taking this advantage of long-range electron synergy in bimetallic single atomic sites,the photocatalytic hydrogen evolution activity over Pt_(1)-Co_(1)/CN achieves 915.8 mmol g^(-1)Pt h^(-1),which is 19.8 times higher than Co_(1)/CN and 3.5 times higher to Pt_(1)/CN.While this electron-synergistic effect is not so efficient for Pt nanoclusters.These results demonstrate the synergistic effect at electron-level and provide electron-level guidance for the design of efficient photocatalysts.

Incoherent Oscillations Accompanying Charge Separation in Photosynthetic Reaction Centers

Early events of charge separation in reaction centers (RCs) of bacterial photosynthesis are modeled by kinetic equations with time-dependent rate constants. An illustrative case of regular motion along a “slow” coordinates leading to oscillations in the kinetics is examined. Different schemes of charge separation are investigated. A good fitting of experimental kinetics of native Rba. sphaeroides RCs is achieved in the five states model P*1BAHA↔P*2BAHA↔I↔P+HA↔P+BA with two excited states BAHA and BAHA and three charge separated states I, P+HA and P+BA (P is a primary electron donor, bacteriochlorophyll dimer, BA and HA are an electron acceptor, monomeric bacteriochlorophyll and bacteriopheophytin in active A-branch, respectively). In the model only the first excited state is directly populated by optical excitation. The emission of the two excited states is assumed to be at 905 and 940 nm, respectively. The intermediate state I is assumed to absorb at 1020 nm as well as the P+HA state. The model explains the deep oscillations in the kinetics of the stimulated emission and of the absorption. In the simpler schemes without the I state or with only one excited state the accordance with the experiment is achieved at unreal parameter values. A possible nature of the I and BAHA states and a possible incoherent nature of the oscillations are discussed.

First Principles Probing of Photo-Generated Intermolecular Charge Transfer State in Conjugated Oligomers

We perform density functional theory calculations to investigate the polaron pair （charge transfer state） photo-generation in donor-acceptor oligomer methyl-capped （4,7- benzo[2,1,3]thiadiazole-2,6-（4,4-bis（2-ethylhexyl）-4H-cyclopent a[1,2-b;3,4-b＇]dithiophene-4, 7-benzo[2,1,3]thiadiazole） （CPDTBT）. Results show that effective photo-generation of charge transfer state can happen in CPDTBT dimer when the group 4,7-benzo[2,1,3]thiadiazole （BT） in one monomer deviates against the conjugated plane （onset torsion angle is about 20°）. The lower excitation energy （530 nm） can only generate the intramolecular excitonic state, while the higher excitation energy （370 nm） can generate the intermolecular charge transfer state, in good agreement with the experiment. Moreover, the mechanism of charge separation in CPDTBT oligorners is discussed.

Boosting the photo-induced charge transfer in melon by lengthening the melon chains through a facile regrowth approach

Melon-derived carbon nitride photocatalysts are a kind of star layered materials applied in solar energy conversion.With in-planeπorbitals of the heptazine subunits and their overlap along the melon chains being the most distinctive feature,the condition of melon chains is of great importance for the atomic and energy band structures of carbon nitride photocatalysts as well as their photo-activities.In principle,fragmentized melon chains in practical carbon nitride would lead to unfavorable structure disorder both in longitudinal and vertical directions,thus inhibiting the efficient transfer for photo-induced electrons and holes,respectively.Here,with a facile regrowth approach,that is to treat carbon nitride under the atmosphere containing C/N species,the melon chains in carbon nitride were experimentally lengthened,which was reflected by the regularly fraction variation of different nitrogen species derived from X-ray photoelectron spectroscopy(XPS)analysis.The prolonged melon chains led to dramatically improved in-plane structure order and boosted transfer of photo-induced electrons and holes,which were confirmed by the spontaneous photo-deposition of oxidants and reductants.The combination of this regrowth approach with homogenously distributed nitrogen vacancies resulted in much enhanced visible-light-responsive photoactivities.Besides,control experiments using nitrogen-vacancy-free carbon nitride and different C/N-contained precursors showed the compatibility as well as the critical factors for the lengthening effects of the regrowth approach.We hope that the facile but efficient regrowth approach could be widely adopted in melon-derived carbon nitride photocatalysts used for various applications.

Secondary Aggregation Induced by Volatile Additive for Improved Exciton Diffusion and Charge Separation in High Efficiency Organic Photovoltaic Devices

Comprehensive Summary The morphology of the active layer plays a crucial role in the performance of organic photovoltaics.Although volatile additives are commonly used to manipulate the morphology,their mechanism of action remains poorly understood.In this study,we conducted a systematic exploration of the mechanism of the traditional volatile additive 1-CN in film formation kinetics of typical PM6:Y6 system.We found that 1-CN induces a secondary aggregation effect,improving film morphology and promoting face-on crystalline orientation.Through elucidating its impact on exciton dynamics,we established a link between morphology optimization and increased exciton diffusion length and accelerated charge separation.Our findings unveil the unique mechanism of action of volatile additive,providing a new perspective for improving the morphology and enhancing the performance of organic photovoltaic devices.

Construction of charge transfer chain in Bi_(12)TiO_(20)-Bi_(4)Ti_(3)O_(12)/α-Bi_(2)O_(3)composites to accelerate photogenerated charge separation

Photogenerated charge separation and transfer is one of the bottleneck steps in photocatalysis,and efficient charge separation strategies are strongly desired.Here,mimicking the electron transport chain in natural photosynthesis,we report the design and fabrication of a charge transfer chain using bismuth-based semiconductor as a proof-of-concept.In view of the thermodynamic energy band positions and structural similarity based on the density functional theory(DFT)analysis,heterostructured combination ofα-Bi_(2)O_(3),perovskite-like Bi_(4)Ti_(3)O_(12),and sillenite Bi12TiO20 was designed for fabrication of charge transfer chain.By tuning the molar ratio of Bi and Ti precursors,the Bi_(4)Ti_(3)O_(12)and Bi12TiO20 particles were formed on the surface ofα-Bi_(2)O_(3)by an insitu transformation process,giving rise to Bi_(12)TiO_(20)-Bi_(4)Ti_(3)O_(12)/α-Bi_(2)O_(3)composites with charge transfer chain.We propose that the effective charge transfer is accomplished amongα-Bi_(2)O_(3),Bi12TiO20,and Bi_(4)Ti_(3)O_(12),which significantly improves the photogenerated charge separation and transfer,as indicated by photoluminescene,time-resolved photoluminescene,and electrochemical impedance spectra results.As expected,the Bi_(12)TiO_(20)-Bi_(4)Ti_(3)O_(12)/α-Bi_(2)O_(3)shows the superior photocatalytic activity for the degradation of environmental pollutants with high concentration.Even for the refractory pollutants like 4-chlorophenol,the optimal Bi_(12)TiO_(20)-Bi_(4)Ti_(3)O_(12)/α-Bi_(2)O_(3)composite shows 28 times higher than that ofα-Bi_(2)O_(3)for photocatalytic degradation,verifying the superiority of photogenerated charge transfer chain in photocatalysis.This work demonstrates the feasibility of the charge transfer chain strategy to boost the photogenerated charge separation,which is of great significance for designing energy and environmental-related materials in heterogonous photocatalysis.

Fast charge transfer kinetics in Sv-ZnIn_(2)S_(4)/Sb_(2)S_(3)S-scheme heterojunction photocatalyst for enhanced photocatalytic hydrogen evolution

Constructing a S-scheme heterojunction with tight interface contact and fast charge transfer is beneficial to improving the photocatalytic hydrogen evolution performance.Herein,a unique one-dimensional(1D)/two-dimensional(2D)S-scheme heterojunction containing 1D Sb_(2)S_(3) nanorods and 2D ZnIn_(2)S_(4) with affluent sulfur vacancies(denoted as Sv-ZnIn_(2)S_(4)@Sb_(2)S_(3)) was designed.The introduced sulfur vacancy can promote the effective adsorption of H+for the following interfacial hydrogen-evolution reaction.Furthermore,the larger contact area and stronger electron interaction between Sb_(2)S_(3) and ZnIn_(2)S_(4) effectively inhibits the recombination of photo-generated electron–hole pairs and abridges the migration distance of charges.As a result,the optimal Sv-ZnIn_(2)S_(4)@Sb_(2)S_(3) sample achieves H_(2) evolution activity of 2741.3 mol·h^(−1)·g^(−1),which is 8.6 times that of pristine ZnIn_(2)S_(4) and 3.0 times that of the Sv-ZnIn_(2)S_(4) samples.Based on the experimental result,the photo-reactivity S-scheme mechanism of hydrogen evolution from water splitting with Sv-ZnIn_(2)S_(4)@Sb_(2)S_(3) is proposed.This work provides an effective method for developing S-scheme heterojunction composites of transition metal sulfide with high hydrogen evolution performance.

Photo-induced Charge Separation of p-Tricyanovinyl-N,N-Dialkylanilines

In this paper,p-tricyanovinyl-N,N-dialkylanilines were synthesized as model compounds and through their spectroscopic behavior,the photo-induced electron transfer,charge separation were discussed and the aggregation in DMSO-H_2O system was investigated.

A new semiconductor-based SERS substrate with enhanced charge collection and improved carrier separation: CuO/TiO_(2) p-n heterojunction

In this paper, CuO/TiO_(2) p-n heterojunction was developed as a new surface enhanced Raman scattering(SERS) substrate to magnify Raman signal of 4-mercaptobenzoic acid(4-MBA) molecule. In the heterojunction-molecule system, CuO as an “electron capsule” can not only offer more electrons to inject into the surface state energy level of TiO_(2) and consequently bring additional charge transfer, but also improve photogenerated carrier separation efficiency itself due to strong interfacial coupling in the interface of heterojunction, which together boost SERS performance of the heterojunction substrate. As expected,owing to the enhanced charge collection capacity and the improvement of photogenerated carrier separation efficiency derived from internal electric field and strong interface coupling provided in the interface of heterojunction, this substrate exhibits excellent SERS detection sensitivity towards 4-MBA, with a detection limit as low as 1 × 10^(-10)mol/L and an enhancement factor of 8.87 × 10~6.

Kinetics of charge separation and energy transfer in photosystem Ⅱ reaction center

THE primary photochemical reaction occurring in the photosynthetic reaction center is one of the key processes for photosynthesis. The detailed mechanism of the primary reaction in the photosystenl Ⅱ(PS Ⅱ) has been an important topic of current interest during the recent years. Since the preparation of the reaction center of PS Ⅱ D1/D2/Cyt b559 complex

Activation of hematite photoanode synthesized at low temperature by W doping

1.Introduction Solar water splitting offers a promising approach for green hydrogen production[1].There are many ways to achieve solar water splitting,such as photocatalytic(PC)water splitting,photoelectrochemical(PEC)water splitting,and photovoltaicelectrocatalytic(PV-EC)water splitting[2].

Ferroelectrically modulate the Fermi level of graphene oxide to enhance SERS response

Surface-enhanced Raman scattering(SERS)substrates based on chemical mechanism(CM)have received widespread attentions for the stable and repeatable signal output due to their excellent chemical stability,uniform molecular adsorption and controllable molecular orientation.However,it remains huge challenges to achieve the optimal SERS signal for diverse molecules with different band structures on the same substrate.Herein,we demonstrate a graphene oxide(GO)energy band regulation strategy through ferroelectric polarization to facilitate the charge transfer process for improving SERS activity.The Fermi level(Ef)of GO can be flexibly manipulated by adjusting the ferroelectric polarization direction or the temperature of the ferroelectric substrate.Experimentally,kelvin probe force microscopy(KPFM)is employed to quantitatively analyze the Ef of GO.Theoretically,the density functional theory calculations are also performed to verify the proposed modulation mechanism.Consequently,the SERS response of probe molecules with different band structures(R6G,CV,MB,PNTP)can be improved through polarization direction or temperature changes without the necessity to redesign the SERS substrate.This work provides a novel insight into the SERS substrate design based on CM and is expected to be applied to other two-dimensional materials.

利用飞秒宽带荧光光谱仪揭示光合细菌反应中心原初过程

本文为深入了解光合细菌反应中心内的高效能量转换机制,采用飞秒宽带荧光光谱技术,研究了室温下光合细菌反应中心中光诱导能量转移和电荷分离的动力学过程.得益于此技术的宽带光谱测量能力,直接确认了与细菌叶绿素B和P相关的两种不同的瞬态荧光组分,其Stokes位移分别确定为约197和450cm^(-1).通过对荧光发射动力学的拟合,揭示了从细菌脱镁叶绿素H到细菌叶绿素B(98 fs)和从细菌叶绿素B到细菌叶绿素P(170 fs)的超快能量转移过程.值得注意的是,预期亚200 fs的细菌叶绿素B荧光寿命被显著延长至约400 fs,表明B的电子激发态与P的电子振动态之间可能存在一-定的耦合,并对能量转移过程有潜在的促进作用.上述发现将有助于人们进一步理解电子振动耦合动力学对光合反应中心内光诱导原初过程的影响机制.

An Inorganic-Organic Hybrid Polymer Cocatalyst for Photoelectrochemical Water Oxidation with Dual Functions of Accelerating Kinetics and Improving Charge Transfer

Oxygen evolution cocatalysts(OECs)play important roles in improving the efficiency of photocatalysts in solar water splitting.Inorganic–organic hybrid polymers(IOHPs),which have good electrolyte accessibility and evenly distributed active sites,are expected to be promising OECs.Here,a novel IOHP[Co(Bpn)_(2)(SCN)_(2)]n(1,Bpn=2,6-bis(4-pyridyl)-naphthalene,SCN=thiocyanate ion)exhibited a two-dimensional(2D)layer structure with(4,4)topology,was constructed by Bpn ligands connecting Co(II)ions,and was decorated on BiVO_(4) photoanodes for photoelectrochemical(PEC)water oxidation.The 1/BiVO_(4) hybrid electrode showed significantly negative onset potential and approximately 3.7 times higher photocurrent density at 1.23 V versus reversible hydrogen electrode(RHE)compared with the bare BiVO_(4).The mechanisms for the improved PEC efficiency were investigated and mainly ascribed to enhanced water oxidation kinetics and increased charge separation and transfer properties.This work provides a promising OEC candidate for PEC water oxidation and sheds light on the attractive application prospect of IOHPs for solar water splitting.

电荷转移器件检测器及其在分析化学中的应用

本文介绍了电荷转移器件检测器的原理、类型和特征,评述了它们在分子光谱、原子光谱、拉曼光谱、分离科学、图象分析等分析化学领域中的应用研究概况.引用文献74篇.

苝四羧酸多联体化合物的合成及其光谱特性研究

本文合成了８个四羧酸多联体化合物；测定了这些化合物的吸收光谱、荧光光谱．研究了由供电子分子键连的多联体分子的光谱特性及其分子体系内稳态荧光猝灭机理．首次从吸收光谱和荧光光谱上分析和考察了四羧酸多联体化合物分子体系内的光致电子转移反应．

不同位置取代的三氰基乙烯基蒽的光谱行为的研究

本文设计合成了两个典型的共轭的电子给体与电子受体（Ｄ－Ａ）化合物：２－三氰基乙烯基蒽（２－ＴＣＶＡ）与９－三氰基乙烯基蒽（９－ＴＣＶＡ），通过极性效应，温度效应对它们基态与激发态的光谱行为进行了表征。研究表明：这两个化合物均表现出显著的电荷转移（ＣＴ）吸收峰，分子受光激发后，９－ＴＣＶＡ只能在非极性溶剂中产生分子内电荷转移（ＩＣＴ）态荧光，而２－ＴＣＶＡ在极性与非极性溶剂中都能从ＩＣＴ态发光．另外，温度效应显示冻结态下，２－ＴＣＶＡ只发射ＩＣＴ态荧光，而９－ＴＣＶＡ既发射类蒽（ａｎｔｈｒａｃｅｎｅ－ｌｉｋｅ）荧光又发射ＩＣＴ态荧光，造成这一现象的主要原因可能是２－ＴＣＶＡ与９－ＴＣＶＡ分子平面性上的差异而引起分子内电荷转移相互作用不同所致。文中还利用了Ｂｉｌｏｔ－Ｋａｗｓｋｉ公式估算了化合物２－ＴＣＶＡ在激发态与基态时偶极矩的差值为１８．８Ｄ。

铁酸锌纳米半导体电极制备及其光电化学性质研究

本文首次制备并表征ＺｎＦｅ２Ｏ４纳米晶光伏电池。研究发现，ＺｎＦｅ２Ｏ４纳米晶光伏电池具有对可见光敏感、不发生光腐蚀及较好的光电转换特性等优点。探讨了各种因素对其光电化学性质的影响。

g-C_3N_4/g-C_3N_4异质结结构的制备及其光催化性能

采用简单的热分解法,分别以硫脲、尿素及硫脲和尿素混合物等为原料,制备了三种具有不同能带结构的石墨相氮化碳(g-C_3N_4),并使用XRD、AFM、SEM、UV-vis等测试方法对所制备样品的晶相结构、形貌、以及光吸收能力等进行了表征,同时研究了不同能带结构的样品对甲基橙的光降解性能.结果表明:制备出的三种样品均是以三嗪环为基本结构单元的片层状化合物.其中,以硫脲和尿素混合物为原料制备出的g-C_3N_4/g-C_3N_4异质结厚度为1.05nm,禁带宽度为2.75eV,其对甲基橙的降解效率高于分别以硫脲、尿素为原料制备的gC_3N_4,这是因为制备出的g-C_3N_4/g-C_3N_4异质结结构,促进了电荷的有效分离和传输,提高了可见光光催化活性.