Photoexcited Charge Separation Research Articles

Construction of Hexagonal Prism-like Defective BiOCL Hierarchitecture for Photocatalytic Degradation of Tetracycline Hydrochloride.

Oxygen vacancy manipulation and hierarchical morphology construction in oxygen-containing semiconductors have been demonstrated to be effective strategies for developing high efficiency photocatalysts. In most studies of bismuth-based photocatalysts, hierarchical morphology and crystal defects are achieved separately, so the catalysts are not able to benefit from both features. Herein, using boiling ethylene glycol as the treatment solution, we developed an etching-recrystallization method for the fabrication of 3D hierarchical defective BiOCl at ambient pressure. The target hierarchical 3D-BiOCl is composed of self-assembled BiOCl nanosheets, which exhibit a hexagonal prism-like morphology on a micron scale, while simultaneously containing numerous oxygen vacancies within the crystal structure. Consequently, the target catalyst was endowed with a higher specific surface area, greater light harvesting capability, as well as more efficient separation and transfer of photo-excited charges than pristine BiOCl. As a result, 3D-BiOCl presented an impressive photocatalytic activity for the degradation of tetracycline hydrochloride in both visible light and natural white light emitting diode (LED) irradiation. Moreover, an extraordinary recycling property was demonstrated for the target photocatalyst thanks to its hierarchical structure. This study outlines a simple and energy-efficient approach for producing high-performance hierarchically defective BiOCl, which may also open up new possibilities for the morphological and crystal structural defect regulation of other Bi-based photocatalysts.

Efficient porous carbon nitride/Ag3PO4 photocatalyst for selective oxidation of amines to imines: Z-scheme heterojunction and interfacial adsorption

The Ag3PO4-loaded porous carbon nitride (PCN)-based composite (PCN/Ag3PO4) was synthesized by a simple method as a photocatalyst for the efficient oxidation of benzylamine to N-benzylidenebenzylamine under simulated sunlight. The PCN in the composite had abundant amino groups, which can form stable complexes with benzylamine through hydrogen bonding, demonstrating by FTIR and 1H NMR titrations. DFT further confirmed that these complexes were more favorable to form at the PCN edge. Based on the experimental results, the catalyst was successfully modified by adding functional groups to promote the contact between the reaction substrate and the active center, thereby improving the catalytic activity. The transfer pathway of photo-excited charge separation in heterojunction photocatalyst and the possible mechanism for catalyzing the oxidative coupling reaction of benzylamine was proposed. This study explained the mechanism of amine-rich PCN promoting the oxidative coupling reaction of benzylamine, which provided an important idea for the design of efficient catalyst.

Controllable interface engineering of g-C3N4/CuS nanocomposite photocatalysts

The rational fabrication of an efficient photocatalyst with optimal interface engineering remains a huge challenge for the enhancement of photocatalytic perpformance. Herein, a sequence of multidimensional nanocomposites with different spatial interfaces, including point, and line or face-contact surface are controllable designed by horizontal growing diverse dimensional (0D, 1D,2D and 3D) copper sulfide (CuS) on 2D graphitic-carbon nitride (g-C 3 N 4 ) nanosheets. Physical and photochemical measurements demonstrate that the formation of an extraordinary 2D/2D face-to-face contact interface can not only enhance the specific surface area, visible light utilization, and photo-excited charge separation efficiency, but also elevate the density and lifetime of photo-generated carriers. The results of ultraviolet photoemission spectroscopy (UPS) and density functional theory (DFT) calculation also confirm that charge transfer tends to occur in face-to-face contact. Among the types of nanocomposites considered, 2D/2D g-C 3 N 4 /CuS has the smallest electron transfer barrier (Ф Be ) between active species, thereby displaying the maximum photocatalytic apparent rate constant, which is about 12 times larger than that of pristine g-C 3 N 4 . Most importantly, this work systematically investigates the relationship between microscopic interface structure and photocatalytic activity from the perspective of the optical, and electrical and energy levels, providing a new insight on the rational design of desired interface engineering towards efficient photocatalysts. • 2D/xD g-C3N4/CuS nanocomposites with different spatial interfaces were fabricated. • 2D/2D g-C3N4/CuS nanocomposite displays the optimal photocatalytic performance. • The concentration, lifetime and separation-efficiency of photogenerated carriers were tested. • The energy barrier between active species and catalysts was analyzed by UPS and DFT. • The photocatalytic mechanism of 2D/2D g-C3N4/CuS nanocomposites is proposed.

Cu–Ni core–shell bimetallic cocatalyst decorated polymeric carbon nitride for highly efficient and selective methane production from photocatalytic CO2 reduction

The development of non-noble bimetallic cocatalysts for the efficient and selective CO2 photoreduction is extremely desirable yet challenging. Herein, we rationally synthesized a series of non-noble Cu–Ni bimetallic cocatalysts by varying the Cu and Ni molar ratios, and then, we decorated these cocatalysts on polymeric carbon nitride (CN) for photocatalytic CO2 reduction. Elemental distribution maps demonstrated that the Cu–Ni-11 bimetallic cocatalyst with a Cu:Ni molar ratio of 1:1 has a perfect core–shell configuration. Notably, this Cu–Ni-11 core–shell cocatalyst-decorated CN (Cu–Ni-11@CN) exhibited remarkable CO2 photoreduction activity for selective CH4 production, outperforming bare CN, Cu@CN, Ni@CN, and Cu–Ni-13@CN and Cu–Ni-31@CN catalysts with different metal proportions. Additionally, the Cu–Ni-11@CN catalyst was remarkably stable and durable over multiple test runs. The remarkable CO2 conversion activity and stability of the developed catalyst are predominantly due to the synergistic effect of the Cu–Ni-11 core–shell cocatalyst and CN, which affords significantly improved optical absorption, CO2 adsorption, and photoexcited charge separation. Therefore, the study results elucidate the rational design and development of non-noble bimetallic cocatalysts for photocatalytic CO2 conversion.

Simultaneously tailor band structure and accelerate charge separation by constructing novel In(OH)3-TiO2 heterojunction for enhanced photocatalytic water reduction

The convenient modification of transition metal and the simultaneous adjustment of energy band are effective measures to improve the photocatalytic activity of titanium dioxide but remains challenging in photocatalytic hydrogen evolution field. Herein, In(OH)3-TiO2 heterostructures were constructed by solid-state synthetic strategy under room temperature for tuning the band structure and accelerating the photoexcited charge separation to enhance the photocatalytic activity for hydrogen evolution. By the quantified modification of In(OH)3, the obtained In(OH)3-TiO2 delivers an appreciable photocatalytic activity and stability for hydrogen evolution, which is 15.7 folds superior to commercial P25. Due to the narrowed band gap, the increased charge carrier density, the restrained recombination rate of photoexcited electron-hole pairs and the accelerated photogenerated charge separation, the In(OH)3-TiO2 heterostructures thereby achieve the boosted photocatalytic hydrogen evolution performance. This work provides a feasible strategy to enhance the photocatalytic hydrogen evolution of TiO2 via tuning the band gap and accelerating the photoinduced charge separation.

All-Solid-State Z-scheme Ta3N5/Bi/CaTaO2N photocatalyst transformed from perovskite CaBi2Ta2O9 for efficient overall water splitting

Building up of all-solid-state Z-scheme system is vital to enhance the photoexcited charge separation and avoid the backward reactions for photocatalytic water splitting. However, coupling two individual photocatalysts with an electron mediator by a one-pot strategy is still a challenge. Here, an all-solid-state Z-scheme Ta3N5/Bi/CaTaO2N photocatalyst is successfully fabricated for the first time through a simple one-step nitridation approach. Density functional theory calculation and experimental results prove that CaTaO2N and Ta3N5 are employed as a H2-evolving and an O2-evolving photocatalyst, respectively. In-situ formed metallic Bi acts as an electron mediator for charge transfer between Ta3N5 and CaTaO2N, facilitating an improvement of the photogenerated charge separation efficiency. Therefore, in the absence of a sacrificial agent, Ta3N5/Bi/CaTaO2N exhibits an excellent photocatalytic overall water splitting performance under visible light irradiation. Meanwhile, an apparent quantum efficiency as high as 0.42% at 420 ± 15 nm is achieved, which surpasses most of the reported tantalum-based (oxy) nitrides photocatalysts. This work provides a new strategy for fabricating highly efficient and stable all-solid-state Z-scheme photocatalyst for solar energy conversion.

Insight into the activation of persulfate with Cu2O/visible-light: Cu(I) based photo-Fenton and Cu2O surface mediated free radical mechanism

In this research, persulfate (PS) was applied to enhance the photo-excited charge separation of Cu2O, which could simultaneously promote the activation of persulfate for wastewater decontamination. The results showed that Cu2O/PS/visible-light system exhibited excellent degradation performance. Cu(I) based photo-Fenton was demonstrated that Cu(I) in aqueous media could effectively activate PS and recycled by the photo-reduction. Besides, Cu2O surface mediated free radical mechanism was proposed that the metastable surface mediated SO4•- and O2•- were more active than that in aqueous media. Both homogeneous and.heterogeneous activation process towards PS were accountable for the generating of active free radicals. This work not only provides a facile effective photocatalytic system for removing contaminants, but also gives further insights about the complicated mechanisms of semiconductor-based photocatalytic activation of PS.

Simultaneously Optimizing the Number and Efficiency of Active Se Sites in Se‐Rich a‐MoSex Nanodot Cocatalysts for Efficient Photocatalytic H2 Evolution

MoSe2 as a cost‐effective cocatalyst is of huge interest for photocatalytic water splitting. However, the H2‐production activity of the bulk MoSe2 is still unsatisfactory because its interfacial H2‐generation rate is dominantly hindered by its insufficient and low‐efficiency Se sites. Herein, Se‐rich amorphous MoSex nanodots (a‐MoSex) as a novel H2‐evolution cocatalyst are fabricated onto TiO2 via a lactic acid‐induced hydrolysis pathway. The as‐synthesized a‐MoSex cocatalyst displays an ultrasmall and amorphous structure, especially Se‐rich property, which distinctly maximizes the number of active Se sites and optimizes H2‐production efficiency of Se atoms. Ultimately, the optimized a‐MoSex/TiO2(1 mL) photocatalyst delivers a superior H2‐evolution rate of 86.28 μmol h−1, which is about 76.4‐ and 2.5‐fold of the pure TiO2 and the crystalline MoSe2 modified‐TiO2 samples, respectively. Combined with the experimental investigations and density functional theory (DFT) calculations, the Se‐rich amorphous MoSex nanodots can not only effectively promote the photoexcited charge separation, but also achieve the simultaneous optimization of the number and H2‐evolution efficiency of active Se sites, thus actually improving photocatalytic H2‐production activity of TiO2. This work offers a new paradigm to simultaneously optimizing the number and efficiency of active Se sites for interfacial H2 evolution, which delivers an inspiration on constructing highly efficient cocatalysts for solar‐energy conversion.

Constructing Pd/ferroelectric Bi4Ti3O12 nanoflake interfaces for O2 activation and boosting NO photo-oxidation

Photo-oxidative NOx removal often encountered with sluggish charge carrier separation kinetics and poor selectivity. Herein, Pd/ferroelectric Bi4Ti3O12 nanoflakes (Pd/BTO NF) were constructed to investigate the photo-excited charge separation, O2 activation and the generated reactive oxygen species (ROS) in dictating NO removal. Results showed that the depolarization field of ferroelectric BTO NF significantly promoted bulk charge separation, leading to boosted NO removal reaction kinetics (10 times higher) for Pd/BTO NF comparing with Pd/TiO2. Revealed by electronic paramagnetic resonance and radical scavenging tests, it is observed that the primary O2 activation species differed among Pd, Ag and Pt supported BTO NF photocatalysts, which resulted in different selectivity. The underlying mechanism of NO photo-oxidative conversion pathway was studied by in situ diffuse reflectance infrared Fourier transform spectroscopy. This work illustrate that metal/ferroelectric interfaces can be tuned to obtain differing O2 activation species, and notable selectivity changes in photocatalysis mediated environmental remediation reactions.

A 3D flower-like WC with large capacitance as efficient co-catalyst in photocatalytic H2 evolution

Non-noble metal co-catalysts can promote photo-excited charge separation of semiconductor and act as active sites for proton catalytic H2 evolution. However, how to judge which function non-noble metal co-catalyst has is not clear. Here, we reported a 3D flower-like WC (WC–F) which shows outstanding activity (24502 μmol/h/g) on CdS in photocatalytic H2 evolution. WC–F has the largest specific capacitance (12.07 F/g), which contributes to the largest electron storage capability. The integration of noble metal Pd and WC tests demonstrated WC–F has the largest proton reduction catalysis ability. Significantly, composite co-catalyst Pd/WC–F on CdS shows slightly higher (1.16 times) activity than WC–F/CdS, which means most of photoexcited electrons on WC–F have been consumed and reaction with protons to produce hydrogen. Thus, two judgement methods for both charges storage and protons catalysis were put forward.

Constructing electrostatic self-assembled ultrathin porous red 2D g-C3N4/Fe2N Schottky catalyst for high-efficiency tetracycline removal in photo-Fenton-like processes

The traditional heterogeneous photo-Fenton reaction was mainly restricted by the fewer surface-active sites, low Fe3+/Fe2+ transformation and H2O2 activation efficiency of catalyst. This work designed and fabricated the efficient photo-Fenton Schottky catalysts via a facile electrostatic self-assembly of metallic Fe2N nanoparticles scattering on the surface of red g-C3N4 (ultrathin porous oxygen-doped 2D g-C3N4 nanosheets). The porous morphology and exceptional electrical structure of red g-C3N4 endowed more active sites and facilitated the photoexcited charge separation. Benefitting from the Schottky effect and unique dimensional coupling structure, the strong visible light absorption and fast spatial charge transfer were realized in the Schottky junction system. More strikingly, Fe2N as an efficient co-catalyst was in favor of the trap and export of e-, leading to the Fe3+/Fe2+ transformation and H2O2 activation during the photo-Fenton process. Accordingly, the as-prepared catalysts revealed outstanding activity in photo-Fenton like degradation of tetracycline (TC) although under 5 W white LED light irradiation. Furthermore, the reasonable degradation pathway of TC and corresponding toxicity of the intermediates, as well as the photo-Fenton catalytic mechanism were interpreted and discussed in detail. This study would be a great aid in the development of various Schottky catalysts for heterogeneous photo-Fenton-based environmental remediation systems.

Photocatalytic degradation of tetracycline antibiotic by a novel Bi2Sn2O7/Bi2MoO6 S-scheme heterojunction: Performance, mechanism insight and toxicity assessment

The fabrication of step-scheme (S-scheme) heterojunction with superior redox capability has been emerging as a prospective strategy for environmental remediation. Herein, novel Bi2Sn2O7/Bi2MoO6 S-scheme heterojunctions have been fabricated via in-situ anchoring Bi2Sn2O7 nanoparticles on Bi2MoO6 microspheres. The optimized Bi2Sn2O7/Bi2MoO6 (BSO/BMO-6%) attains the highest reaction rate constant (k) in the degradation of tetracycline hydrochloride (TC, k = 0.0397 min−1), which is 3.62 folds higher than that of pristine Bi2MoO6. Such an improvement is originated from more exposed active sites, higher photo-excited charge separation efficiency, superior redox ability, and efficient production of reactive h+, •OH and •O2–. Besides, Bi2Sn2O7/Bi2MoO6 could efficiently degrade the TC antibiotic in actual water matrix. Significantly, the toxicity evaluation verifies the nontoxicity of Bi2Sn2O7/Bi2MoO6. Moreover, the degradation pathways of TC are determined and the toxicity of degradation intermediates is appraised by using HPLC-MS spectra and QSAR prediction. A possible photocatalytic mechanism over S-scheme Bi2Sn2O7/Bi2MoO6 has been elucidated based on experimental studies combined with density functional theory (DFT) calculations. This work offers new insights for the design of high-performance S-scheme heterojunctions for environmental remediation.

Facile construction of novel ZnO and TiO2 combined g-C3N4 nanocomposite for superior visible-light photocatalytic organic pollutant degradation

ABSTRACT A novel g-C3N4/ZnO-TiO2 nanocomposite was prepared by facile calcination and hydrothermal assisted route to boost the photocatalytic efficiency of g-C3N4. The structural, morphology and optical properties of as-obtained nanocomposites (NCs) were examined by various physicochemical methods such as XRD, FT-IR, FESEM-EDX, HR-TEM, UV-DRS and PL spectra relatively. The as-obtained g-C3N4/ZnO-TiO2 heterojunction NCs displays an optimum efficiency (93.6%) and high photo-degradation rate constant towards the photo-degradation of RhB dye in 75 min under visible-light exposure. Likewise, the synergistic effects on heterostructure strong-coupling interfaces assembly of g-C3N4 and TiO2/ZnO NPs, which facilitates the excellent photo-excited charge separation efficiency, suppressing the recombination rate and also widening the visible-light fascination ability. Hence, the resulting in a prolonged lifetime leading to continuous generation of h+ and •OH− species which were eventually improved the photo-degradation process. Also, the as-obtained hybrid g-C3N4/ZnO-TiO2 photocatalysts (PCs) revealed superior recycling stability. Moreover, a probable photocatalytic reaction mechanism of the novel PCs was also suggested.

Investigation on novel Cu2O modified g-C3N4/ZnO heterostructures for efficient photocatalytic dye degradation performance under visible-light exposure

Highly efficient recyclable photocatalysts of ternary g-C3N4-ZnO/Cu2O nanocomposite were designed for photo-degradation of RhB dye. The structural, morphological, surface structure and optical properties of the as-prepared nanocomposites (NCs) were characterized by XRD, FT-IR, FE-SEM with EDS, HRTEM, XPS, BET, UV–Vis DRS and PL spectra analysis respectively. The photo-degradation efficiencies of RhB dye over the g-C3N4, g-C3N4/ZnO, g-C3N4/Cu2O and g-C3N4-ZnO/Cu2O photocatalysts (PCs) were 36.4%, 53% and 66%, and 91.4% in 100 min under visible-light. The as-obtained g-C3N4-ZnO/Cu2O PCs was remarkably upgraded the photo-degradation efficiency rate than to other samples. Also, the heterojunction formation among the g-C3N4 and ZnO/Cu2O interfaces due to the development of visible-light absorption capability and photo-excited charge separation efficiency which was improved the photocatalytic performance. Besides, the g-C3N4-ZnO/Cu2O PCs exhibit a greater photo-degradation performance after five successive reuses. Hence, the eco-friendly PCs might be widely useful for the application of dye polluted wastewater treatment.

Insight into the significantly enhanced photocatalytic CO2 reduction performance of Pt/MnOx dual cocatalysts on sea-urchin-like anatase TiO2 microspheres

Solar-driven CO2 reduction reaction (CO2RR) for producing chemical fuels over semiconductors is considered to be a potential way to ameliorate the global warming and energy shortage. Herein, we report a facile and robust method by co-decorating Pt/MnOx dual cocatalysts on sea-urchin-like anatase TiO2 microspheres (AMS) to significantly improve the CO2RR activity and CH4 product selectivity. The xPt-yMn-AMS composite with optimal contents of dual cocatalysts manifests compelling CO/CH4 yields of 16.5/125.3 μmol g−1h−1 with a total photoactivity of 1035.4 μmol g−1h−1, 13 times higher than that of AMS alone. The Pt nanoparticles on AMS mainly improve the photoexcited charge separation and CO2RR efficiency, while the MnOx cocatalyst mainly promotes the adsorption/activation of reactants and the CH4 product selectivity by varying the surface chemistry. The synergistic effect of dual cocatalysts on AMS renders the significantly improved CO2RR performance, and thus provides a simple yet general strategy for fabricating high-performing CO2RR TiO2-based photocatalyst.

Gold modified TiO2/g-C3N4 for enhanced photocatalytic activities to evolved H2 fuel

Plasmonic Au/TiO2/g-C3N4 nanocomposites have been successfully prepared by simple hydrothermal method. It is demonstrated that the as-synthesized nanocomposites show significant co-catalyst-free photocatalytic activities for H2 evolution under visible-light. The amount-optimized 1Au/4TiO2/g-C3N4 nanocomposite evolved 250-µmol.g-1h−1 H2 at λ > 400 light illumination. The improved photocatalytic activities for H2 evolution is attributed to the greatly-enhanced photoexcited charge separation by electron transfer from Au surface plasmon (~520 nm) and CN (470 nm > λ > 400) to TiO2. Based on the surface photovoltage spectra, photoelectrochemical I-V curves, hydroxyl radical amounts related spectra, and photocurrent action spectra, it is suggested that the fabricated Au/TiO2/g-C3N4 nanocomposite provide a proper energy platform for the photocatalytic H2 production. Moreover, TiO2 is much superior as compare to other wide-band gap metal oxides as energy platforms, like SnO2 and ZrO2. This work would provide a feasible strategy to synthesize an efficient plasmonic-assisted CN-based nanophotocatalyst for solar fuel production.

Surface engineering of CdS with ternary Bi/Bi2MoO6-MoS2 heterojunctions for enhanced photoexcited charge separation in solar-driven hydrogen evolution reaction

Solar driven hydrogen (H2) evolution reaction based on transition metal chalcogenides still suffers great challenges, which should realize strong visible light harvesting, photoinduced charge carriers generation and separation and the abundant reactive sites. Here, we report a proficient and scalable single-step growth of Bi/Bi2MoO6-MoS2 ternary heterojunctions on CdS nanorods using ethylene glycol mediated solvothermal growth for the first time and their application in solar energy conversion reactions. The obtained CdS-Bi/Bi2MoO6-MoS2 quaternary heteronanostructures resulted from the integration of multiple components into a single nanoarchitecture, which can precisely offer efficient charge carriers separation via different heterojunctions, enhanced visible light harvesting and suppressed electron-hole recombination. Thus, CdS-Bi/Bi2MoO6-MoS2 shows excellent H2-evolution activity of 2185 μmol/g/h, which is ten and fifteen times greater than CdS and Bi2MoO6 alone respectively. Moreover, CdS-Bi/Bi2MoO6-MoS2 photocatalyst displays good stability and recycle capability, demonstrating a promising photocatalyst for efficient H2 evolution reactions.

Matrix phase induced boosting photoactive performance of ZnO nanowire turf‐coated Bi2O3 plate composites

AbstractA new nanocomposite consisting of ZnO nanowire turf‐coated Bi2O3 plates was synthesized using a method combining a chemical bath and hydrothermal crystal growth through sputtering ZnO seed layer‐assisted growth. Structural analysis revealed that highly crystalline, high‐density, one‐dimensional (1D) ZnO crystals were uniformly coated on the organized two‐dimensional (2D) Bi2O3 plates with a single β phase or dual α/β polymorphic phases. The Bi2O3–ZnO composites exhibited enhanced absorption properties in the ultraviolet and visible regions compared with pristine Bi2O3 and ZnO. Furthermore, the Bi2O3–ZnO composites exhibited higher photoactive performance than that of the pristine Bi2O3 and ZnO because of the low recombination rate of photoinduced electron−hole pairs caused by the vectorial transfer of electrons and holes between ZnO and Bi2O3 and the substantially increased surface area of the unique composite morphology. The ZnO nanowire turf‐coated Bi2O3 plates with a α/β‐Bi2O3 matrix exhibited photoelectrochemical and photocatalytic properties superior to those of the composite with a single β‐Bi2O3 matrix. The coexistence of α/β homojunction in the Bi2O3 matrix and the abundant heterojunctions between the ZnO nanowires and Bi2O3 plates substantially enhanced photoexcited charge separation efficiency. Growing high‐density 1D ZnO on 2D Bi2O3 via a combination methodology and crystallographic phase control provided a promising material design route for nanocomposite systems with high photoactivity for photoexcited device applications.

Improved third-order optical nonlinearities in Ag/MoS2 Schottky-type nano/hetero-junctions

Molybdenum disulfide (MoS2) nanostructures have been prepared by a hydrothermal treatment and were decorated with metallic silver (Ag) using the conventional wet incipient impregnation process to form Ag/MoS2 nano/hetero-junctions. The physiochemical functionalities were characterized using X-ray diffraction, Fourier transfer infrared spectroscopy, Raman spectroscopy, field emission scanning electron microscopy, energy dispersive spectroscopy and transmission electron microscopy. UV–Vis (ultraviolet–visible) spectroscopy shows an improved light absorption in visible region for Ag/MoS2 nano/hetero-junctions due to the surface plasmon resonance absorption. Photoluminescence (PL) studies suggest efficient photoexcited charge separation to occur in Ag/MoS2 nano/hetero-junctions due to an internal electric field formed across Schottky interface. The nonlinear responses of as-prepared samples to intense laser fields were examined using standard single-beam Z-scan technique under a 532 nm CW second-harmonic Nd:YAG laser irradiation wherein demonstrated reverse saturable absorption behaviors and self-defocusing responses due to negative lens effects were observed. The third-order nonlinear refractive index and absorption coefficient for Ag/MoS2 nano/hetero-junctions were found to be 6.5 × 10-7 cm2/W and 3.5 × 10-4 cm/W, respectively, showing 1.44 and 1.5 times enhancement than in MoS2 nanostructures.

Efficient Photoexcited Charge Separation at the Interface of a Novel 0D/2D Heterojunction: A Time-Dependent Ultrafast Dynamic Study.

To achieve efficient conversion and avoid loss of solar energy, ultrafast charge separation and slow electron-hole recombination are desired. Combining time-dependent density functional theory (TD-DFT) with nonadiabatic molecular dynamics, Au9(PH3)8/MoS2, as a prototype for zero-dimensional/two-dimensional (0D/2D) heterojunction, has been demonstrated to present excellent light absorption capacity and effective charge separation characteristics. In the heterojunction, photoexcitation of the Au9(PH3)8 nanocluster drives an ultrafast electron transfer from Au9(PH3)8 to MoS2 within 20 fs, whereas photoexcitation of the MoS2 nanosheet leads to hole transfer from MoS2 to Au9(PH3)8 within 680 fs. The strong nonadiabatic coupling and prominent density overlap are responsible for the faster electron separation relative to hole separation. In competition with the charge separation, electron-hole recombination requires 205 ns, ensuring an effective carrier separation. Our atomistic TD-DFT simulation provides valuable insights into the photocarrier dynamics at the Au9(PH3)8/MoS2 interface, which would stimulate the exploration of 0D/2D hybrid materials for photovoltaic and optoelectronic devices.