Wide Light Absorption Range Research Articles

Nickel and indium core-shell co-catalysts loaded silicon nanowire arrays for efficient photoelectrocatalytic reduction of CO2 to formate

Abstract Developing an efficient artificial photosynthetic system for transforming carbon dioxide and storing solar energy in the form of chemical bonds is one of the greatest challenges in modern chemistry. However, the limited choice of catalysts with wide light absorption range, long-term stability and excellent selectivity for CO2 reduction makes the process sluggish. Here, a core-shell-structured non-noble-metal Ni@In co-catalyst loaded p-type silicon nanowire arrays (SiNWs) for efficient CO2 reduction to formate is demonstrated. The formation rate and Faradaic efficiency of formate over the Ni@In/SiNWs catalyst reach 58 μmol h−1 cm−2 and 87% under the irradiation of one simulated sunlight (AM 1.5G, 100 mW cm−2), respectively, which are about 24 and 12 times those over the pristine SiNWs. The enhanced photoelectrocatalytic performance for CO2 reduction is attributed to the rational combination of Ni capable of effectively extracting the photogenerated electrons and In responsible for the selective activation of CO2.

Porous visible light-responsive Fe3+-doped carbon nitride for efficient degradation of sulfadiazine.

The development of efficient solar driven catalyst for the degradation of antibiotics has become increasingly important in environmental protection. However, the reported efficient photocatalysts for antibiotic degradation are limited. In this work, porous Fe3+-doped graphitic carbon nitride (g-C3N4) with outstanding photocatalytic ability is synthesized and then used as the photocatalyst for the efficient degradation of sulfadiazine (SDZ) under visible light. A series of characterization results indicate that Fe3+ is successfully doped into the interlayer of g-C3N4 and is stabilized in g-C3N4 by Fe-N coordination bond. The SEM, DRS and ESI and transient photocurrent results demonstrated that Fe3+-doped g-C3N4 has a porous structure, a low band gap, improved separation efficiency of photogenerated electron and holes as well as a wider light absorption range. Such improved physical and chemical properties greatly enhanced the photocatalytic ability. Using Fe3+-doped g-C3N4 for photocatalytic degradation of SDZ under white light, almost complete degradation of SDZ was achieved with a degradation efficiency as high as 99.8% (whereas only 52.1% for bulk g-C3N4) within 90min. The degradation was mainly ascribe to 1O2 during the irradiation, and also a small amount of •O2-, OH• and h+ are involved in the degradation process. The Fe3+-doped g-C3N4 was applicable for the degradation of a wide range of antibiotic pollutants.

WO3–ZnO and CuO–ZnO nanocomposites as highly efficient photoanodes under visible light illumination

We prepared ZnO nanocomposites with WO3 or CuO nanostructures to improve the photocatalytic performance of ZnO nanostructures. Characterization of the nanocomposites using scanning electron microscopy, x-ray diffraction, UV–vis spectrometry and photoluminescence revealed the morphologies and wide light absorption range of the materials. The highest current densities of WO3/ZnO and CuO/ZnO nanocomposites were 1.28 mA cm−2 and 2.49 mA cm−2 at 1.23 V (versus a reversible hydrogen electrode) under AM 1.5 100 mW cm−2, which are ~1.2- and 3.5-fold greater than those of bare ZnO nanostructures, respectively. The easy fabrication process suggests that nanocomposites with narrow bandgap materials, such as WO3 and CuO, will improve the performance of electrochemical and optoelectrical devices such as dye-sensitized solar cells and biosensors.

Two-dimensional gersiloxenes with tunable bandgap for photocatalytic H2 evolution and CO2 photoreduction to CO

The discovery of graphene and graphene-like two-dimensional materials has brought fresh vitality to the field of photocatalysis. Bandgap engineering has always been an effective way to make semiconductors more suitable for specific applications such as photocatalysis and optoelectronics. Achieving control over the bandgap helps to improve the light absorption capacity of the semiconductor materials, thereby improving the photocatalytic performance. This work reports two-dimensional −H/−OH terminal-substituted siligenes (gersiloxenes) with tunable bandgap. All gersiloxenes are direct-gap semiconductors and have wide range of light absorption and suitable band positions for light driven water reduction into H2, and CO2 reduction to CO under mild conditions. The gersiloxene with the best performance can provide a maximum CO production of 6.91 mmol g−1 h−1, and a high apparent quantum efficiency (AQE) of 5.95% at 420 nm. This work may open up new insights into the discovery, research and application of new two-dimensional materials in photocatalysis.

Functional Block Copolymers Carrying One Double-Stranded Ladderphane and One Single-Stranded Block in a Facile Metathesis Cyclopolymerization Procedure.

In order to improve the poor film-forming ability of polymeric ladderphane, di-block copolymers containing perylene diimide (PDI)-linked double-stranded poly(1,6–heptadiyne) ladderphane and branched alkyl side chains modified single-stranded poly(1,6–heptadiyne) were synthesized by metathesis cyclopolymerization (MCP) using Grubbs third-generation catalyst (Ru–III) in tetrahydrofuran solvent. The first block containing the ladderphane structure leads to higher thermal-stability, wider UV–vis absorption, lower LUMO level and ladderphane-induced rigidity and poor film-forming ability. The second block containing long alkyl chains is crucial for the guarantee of excellent film-forming ability. By comparing the effect of ladderphane structure on the resulted copolymers, single-stranded poly(1,6–heptadiyne) derivatives with PDI pedant were also processed. The structures of copolymers were proved by 1H NMR and gel permeation chromatography, electrochemical, photophysical, and thermal-stability performance were achieved by cyclic voltammetry (CV), UV-visible spectroscopy and thermogravimetric analysis (TGA) measurements. According to the experiment results, both copolymers possessed outstanding film-forming ability, which cannot be realized by small PDI molecules and oligomers. And they can serve as a superior candidate as for n-type materials, especially for their relatively wide range of light absorption (λ = 200~800 nm), and lower LUMO level (−4.3 and −4.0 eV).

Facile RbBr interface modification improves perovskite solar cell efficiency

High-performance hybrid perovskite solar cell (PSC) is an emerging generation of energy material by virtue of its excellent properties such as wide light absorption range, large electron diffusion length, and small exciting energy. However, to date, methods of perovskite deposition generally do not offer desired film coverage, resulting in the direct interfacial contact, which seriously deteriorates the photovoltaic performance of devices. To improve the interfacial functions of the perovskite layer (PL)/electron transport layer (ETL) of the PSC devices, rubidium bromide (RbBr) is applied as a facile interfacial modifier. It is sandwiched between ETL tin oxide (SnO2) and PL [Cs0.05(MA0.17FA0.83)0.95Pb(I0·83Br0.17)3] to a fabricate a planar PSC. The RbBr modification of the PSC fluorine-doped tin oxide/SnO2/(RbBr)/PL/spiro-OMeTAD/Au (2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spiro-bifluorene) can reduce the energy barrier at the ETL/PL interface, improve the electronic contact between PL and ETL, and accelerate the electron extraction process. The RbBr modification thus leads to a higher power conversion efficiency of 18.29% for the PSC, as compared with 16.03% without RbBr modification. The facile RbBr modification procedure and significant performance advancement pave the way for future energy studies.

The effect of Mn-doped ZnSe passivation layer on the performance of CdS/CdSe quantum dot-sensitized solar cells**Project supported by the National Natural Science Foundation of China (Grant Nos. 61376011, 61704114, 51402141, and 61604086), the Gansu Provincial Natural Science Foundation, China (Grant No. 17JR5RA198), the Fundamental Research Funds for the Central Universities, China (Grant Nos. lzujbky-2018-119 and lzujbky-2018-ct08), and the Fund from

ZnSe as a surface passivation layer in quantum dot-sensitized solar cells plays an important role in preventing charge recombination and thus improves the power conversion efficiency (PCE). However, as a wide bandgap semiconductor, ZnSe cannot efficiently absorb and convert long-wavelength light. Doping transition metal ions into ZnSe semiconductors is an effective way to adjust the band gap, such as manganese ions. In this paper, it is found by the method of density functional theory calculation that the valence band of ZnSe moves upward with manganese ions doping, which leads to acceleration of charge separation, wider light absorption range, and enhancing light harvesting. Finally, by using ZnSe doped with manganese ions as the passivation layer, the TiO2/CdS/CdSe co-sensitized solar cell has a PCE of 6.12%, and the PCE of the solar cell increases by 9% compared with the undoped one (5.62%).

Porous Organic Polymers Containing a Sulfur Skeleton for Visible Light Degradation of Organic Dyes.

Three novel chemically stable porous organic polymers (POPs) were synthesized by the hydrothermal method; the POPs contain sulfone bonds (TpSD), no sulfur atoms (TpMD), or thioether bonds (TpTD). The catalytic mechanism of the POP with sulfone bonds was studied, and it was found that the wide visible light absorption range, high specific surface area, and the hydrophilicity of the material significantly promoted the catalytic efficiency of TpSD. The presence of O=S=O gives TpSD a higher degree of conjugation than TpMD and TpTD, so TpSD shows the strongest UV/Visible absorption and faster transmission of electrons. The photocatalytic degradation of Rhodamine B (RhB) molecules is approximately 100 % with TpSD and its pseudo-first-order rate constant is 0.0770 min-1 , which is the highest among all reported non-metallic photocatalysts. Moreover, it is also the first time that sulfur-containing polymer have been used in photocatalytic degradation of dyes.

Plasmon-Enhanced Fluorescence of Carbon Nanodots in Gold Nanoslit Cavities.

Carbon nanodots (CNDs) are featured with a wide range of light absorption and excitation-dependent fluorescence. The emission enhancement of CNDs is of great interest for the development of nanophotonics. Although the phenomenon of plasmon-enhanced fluorescence for quantum dots and molecular dyes has been well investigated, rarely has it been reported for CNDs. In this work, a series of plasmonic nanoslit designs were fabricated and utilized for immobilization of CNDs in nanoslits and examination of the best match for plasmonic fluorescence enhancement of CNDs. In concert, to better understand the plasmonic effect on the enhancement, the surface optical field is measured with or without CND immobilization using a hyperspectral imaging system as a comparison, and a semianalytical model is conducted for a quantitative analysis of surface plasmon generation under the plane-wave illumination. Both the fluorescence and surface reflection light intensity enhancement are demonstrated as a function of nanoslit width and are maximized at the 100 nm nanoslit width. The analysis of surface plasmon-exciton coupling of CNDs in the nanoslit area suggests that the enhancement is primarily due to plasmonic light trapping for increased electromagnetic field and plasmon-induced resonance energy transfer. This study suggests that incorporating CNDs in the plasmonic nanoslits may provide a largely enhanced CND-based photoemission system for optical applications.

Hydroxylated carbon nanotube/carbon nitride nanobelt composites with enhanced photooxidation and H2 evolution efficiency

Hydroxylated multi-walled carbon nanotubes modified with a carbon nitride nanobelt (HCNT/CNN) were successfully fabricated by using combined solvothermal and ultrasonic methods to improve both tetracycline hydrochloride (TC) degradation and H2 evolution. The well-designed photocatalysts exhibited a wide light absorption range, low photoluminescence (PL) intensity, high photocurrent, and small electrochemical impedance spectroscopy (EIS) arc; these properties significantly enhanced the overall photocatalytic efficiency. At the optimal loading of HCNT (0.05 wt%), the resulting HCNT/CNN exhibited the highest TC photocatalytic degradation rate, and the H2 production rate reached 175.5 μmol g−1 h−1. Compared to the multi-walled carbon nanotube modified carbon nitride nanobelt, the TC photocatalytic degradation rate and H2 production rate of HCNT/CNN increased by factors of 3 and 4.2, respectively. This significantly enhanced performance can be ascribed to the formation of hydrogen bonds between HCNT and CNN, which facilitates the electron transfer from the CNN to the HCNT surface, thereby accelerating the separation of photogenerated charge carriers. Moreover, the possible mechanism of the improved photocatalytic performance for the HCNT/CNN composites was proposed. This study provides the guidance for the design of novel carbon nitride nanobelt-based photocatalysts for wastewater purification and H2 evolution.

CdSe Quantum Dots Doped WS2 Nanoflowers for Enhanced Solar Hydrogen Production

In this paper, a facile method for synthesizing WS2 nanoflowers (NFs) and CdSe quantum dots (QDs) using hydrothermal and hot injection methods, are reported, respectively. Additionally, the photocatalytic activity of a CdSe QDs/WS2 NF nanocomposite is analyzed in a typical three‐electrode electrochemical cell. It is found that the CdSe QDs/WS2 NF hybrid exhibits a current density of −1.12 mA at 0 V and a Tafel slope of 82 mV dec−1, which are superior to the values of bare WS2 NFs (current density of −0.25 mA and Tafel slope of 150 mV dec−1). This improvement of photocatalytic performance is attributed to the wide range of light absorption for e−/h+ generation provided by the CdSe QDs, as well as the large surface area and numerous active sites for hydrogen production provided by WS2 NFs. Therefore, the CdSe QDs/WS2 NF hybrid structure is a promising candidate for highly effective and stable photocatalytic performance under solar light illumination for hydrogen production.

Effect of atom adsorption on the electronic, magnetic, and optical properties of the GeP monolayer: A first-principle study

First-principles calculations have been carried out to explore the effect of atom surface adsorption on the electronic, magnetic, and optical properties of the germanium phosphide (GeP) monolayer. It is shown that the GeP monolayer exhibits good adsorption capability to all the selected adatoms and can preserve the structural integrity upon the adsorption of most adatoms. The adatoms can bring out diverse electronic properties to the GeP monolayer. The H, Li, Na, K, and Al adatoms donate electrons to the GeP monolayer and result in its metallization. The other adatoms do not change the semiconducting nature of the GeP monolayer and will induce midgap states (Mg, Ca, Si, Ge, Ag, and Au) or reduce the bandgaps (Ni, Pd, and Pt). The B, N, P, As, V, Cr, Mn, Fe, and Co adatoms induce spin magnetic moments into the GeP monolayer. Especially, the spin magnetic moments are mainly located on the adatoms for the GeP decorated with the V, Cr, Mn, Fe, and Co atoms. As a result, the dilute magnetic semiconductor can be obtained. In addition, all the adatoms decrease the work function, except O. Thus, some effects on the optical properties are highly expected. The GeP monolayer exhibits a wide range of light absorption and the Mg, Si, Ge, Cu, Ag, Au, and Pt adatoms can further redshift the absorption edge of the GeP monolayer along the x and y directions. Our calculations provide an effective method to modulate the electronic, magnetic, and optical properties of the GeP monolayer for device applications.

The impact of the reaction atmosphere on the additive-free growth of Mg2B2O5 nanorods

Although many routes for the production of magnesium borates (Mg2B2O5, Mg3B2O6 and MgB4O7) are well known, the synthesis of single phases is still a challenge. Secondary phases such as other magnesium borates and MgO are commonly observed in the final product. In order to produce high quality Mg2B2O5 nanorods, we developed a study analyzing the influence of different reaction atmospheres on the synthesis of magnesium borate in a tubular furnace. Through this investigation, a strong correlation between the produced borate phases and the composition of the atmospheres was verified. The sample produced under Ar presented Mg2B2O5, Mg3B2O6 and MgO in molar percentages of 36.82%, 35.34% and 27.84% respectively, while the sample synthesized under H2 is composed of 18.9 mol% of Mg3B2O6 and 81.1 mol% of MgO. Mg2B2O5 nanorods with elevated structural homogeneity were successfully produced under hydrogen and acetonitrile. Under this atmosphere only Mg2B2O5 and Mg3B2O6 were produced, with the formation of Mg2B2O5 nanorods representing 87.5 mol% of the sample. The nanorods growth followed a solution-solid-solid (SSS) self-catalyzed mechanism. This synthesis was performed without the assistance of external agents such as catalysts or surfactants, guaranteeing elevated chemical purity for applications in the optical and electronic field. Reflectance and impedance analyses presented a wide range of light absorption and a dielectric character for the nanorods. The produced structure would be very interesting for theranostic applications.

Construction of urchin-like ZnIn2S4-Au-TiO2 heterostructure with enhanced activity for photocatalytic hydrogen evolution

The ternary ZnIn2S4-Au-TiO2 Z-scheme heterostructure photocatalysts has been fabricated by selecting effectiveness Au NPs as a solid electron mediator, via a chemical-deposition process for water splitting under simulated solar light irradiation. The designed photocatalysts exhibit high surface area and wide light absorption range, which significantly enhance photocatalytic efficiency. At an optimal ratio of 24 wt% Au NPs and 60 wt% ZnIn2S4, the obtained ZnIn2S4-Au-TiO2 photocatalysts achieve the highest H2 production with the rate of 186.3 μmol g−1 h−1, and the O2 production rate is reached to 66.3 μmol g−1 h−1. It showed that the ZnIn2S4-Au-TiO2 composite structures exhibit significantly better photocatalytic activity than ZnIn2S4-TiO2 and Au-ZnIn2S4-TiO2 structure. Such an excellent performance should be attributed to the Au NPs in the Z-scheme system structure which favor to enhance the transfer rate of the photogenerated electrons and holes and remain strong redox ability of the photocatalysts. It is worth pointing out that the unique Z-scheme ZnIn2S4-Au-TiO2 heterostructure shows great solar activity toward water splitting into renewable hydrocarbon fuel.

De novo synthetic biliprotein design, assembly and excitation energy transfer.

Bilins are linear tetrapyrrole chromophores with a wide range of visible and near-visible light absorption and emission properties. These properties are tuned upon binding to natural proteins and exploited in photosynthetic light-harvesting and non-photosynthetic light-sensitive signalling. These pigmented proteins are now being manipulated to develop fluorescent experimental tools. To engineer the optical properties of bound bilins for specific applications more flexibly, we have used first principles of protein folding to design novel, stable and highly adaptable bilin-binding four-α-helix bundle protein frames, called maquettes, and explored the minimal requirements underlying covalent bilin ligation and conformational restriction responsible for the strong and variable absorption, fluorescence and excitation energy transfer of these proteins. Biliverdin, phycocyanobilin and phycoerythrobilin bind covalently to maquette Cys in vitro A blue-shifted tripyrrole formed from maquette-bound phycocyanobilin displays a quantum yield of 26%. Although unrelated in fold and sequence to natural phycobiliproteins, bilin lyases nevertheless interact with maquettes during co-expression in Escherichia coli to improve the efficiency of bilin binding and influence bilin structure. Bilins bind in vitro and in vivo to Cys residues placed in loops, towards the amino end or in the middle of helices but bind poorly at the carboxyl end of helices. Bilin-binding efficiency and fluorescence yield are improved by Arg and Asp residues adjacent to the ligating Cys on the same helix and by His residues on adjacent helices.

D-A-π-A dye-sensitizers with Cd (Ⅱ) or Cu (Ⅱ) complex as auxiliary electron acceptor

In the process of structure modification for dye-sensitizers, D-A-π-A motif sensitizers stood out from various structures of dyes owing to their high efficiencies and long lifetimes. In this work, four novel polymeric metal complex dyes in D-A-π-A pattern (PCZ-QCd, PCZ-QCu, PIDT-QCd and PIDT-QCu), which use Cd (Ⅱ) or Cu (Ⅱ) complexes as auxiliary electron acceptors, indacenodithiophene (IDT) and carbazole (CZ) derivatives as donors and 8-quinolinol derivative as π bridge and acceptors (A) were designed, synthesized and applied to dye-sensitized solar cells (DSSCs). Polymers using different donors and coordination ions are discussed by testing their thermal, optical, electrochemical properties and photovoltaic performance in dye-sensitized solar cells (DSSCs). All polymers show good terminal stability with decomposition temperatures (Td) higher than 300 °C. There is a wide light absorption range in the near ultraviolet and visible region for the polymer (PIDT-QCd) with Cd (Ⅱ) as coordination ion and IDT as donor. As a result, a highest power conversion efficiency of 6.55% was achieved by PIDT-QCd-based DSSC device. This work provides a distinctive perspective for the designing of sensitizers in DSSCs.

Perylene Bisimide In-chain Polyethylene with Unique Self-assembly Nanostructure through Acyclic Diene Metathesis (ADMET) Polymerization

A novel perylene tetracarboxylic acid bisimide (PTCBI) in-chain polyethylene (PE) was first prepared via acyclic diene metathesis (ADMET) polymerization of PTCBI-functionalized α,ω-diene monomer. The polymers could spontaneously self-assemble into hollow cylindrical structures in which the π-π interaction between adjacent PTCBI moieties was enhanced and the electron mobility was possibly promoted. The hydrogenation of as-obtained polymer was readily accomplished, affording the desired precision PTCBI in-chain PE with a saturated backbone, which showed high glass transition temperature (Tg = 63 °C), relatively wide range of light absorption (λ = 200−575 nm), and higher LUMO level (−3.62 eV). It can therefore serve as a superior model for facile construction of functional polyolefin and soluble PTCBI polymer with ordered architecture.

Cosensitized Quantum Dot Solar Cells with Conversion Efficiency over 12.

The improvement of sunlight utilization is a fundamental approach for the construction of high-efficiency quantum-dot-based solar cells (QDSCs). To boost light harvesting, cosensitized photoanodes are fabricated in this work by a sequential deposition of presynthesized Zn-Cu-In-Se (ZCISe) and CdSe quantum dots (QDs) on mesoporous TiO2 films via the control of the interactions between QDs and TiO2 films using 3-mercaptopropionic acid bifunctional linkers. By the synergistic effect of ZCISe-alloyed QDs with a wide light absorption range and CdSe QDs with a high extinction coefficient, the incident photon-to-electron conversion efficiency is significantly improved over single QD-based QDSCs. It is found that the performance of cosensitized photoanodes can be optimized by adjusting the size of CdSe QDs introduced. In combination with titanium mesh supported mesoporous carbon as a counterelectrode and a modified polysulfide solution as an electrolyte, a champion power conversion efficiency up to 12.75% (Voc = 0.752 V, Jsc = 27.39 mA cm-2 , FF = 0.619) is achieved, which is, as far as it is known, the highest efficiency for liquid-junction QD-based solar cells reported.

A new approach to preparing Bi2Zr2O7 photocatalysts for dye degradation

A new synthetic route is presented to prepared pure Bi2Zr2O7 material, in which a NaNO3/KNO3 molten salt is used to obtain the resulting Bi2Zr2O7 at a relatively low temperature of 400 °C under atmospheric pressure. Powder x-ray diffraction confirmed the structure type and purity of the as-prepared sample, and further revealed that a single-source Bi(OH)3 · Zr(OH)4 · nH2O complex precursor plays a crucial role to synthesize Bi2Zr2O7 nanocrystals. Scanning electron microscope and transmission electron microscope show the morphologies and sizes of Bi2Zr2O7 crystal in detail, and UV–vis diffuse reflectance measurements evidenced the wide light absorption range. Furthermore, the as-synthesized Bi2Zr2O7 with smaller particle size and larger specific surface area exhibit superior photocatalytic activities compared with the sample obtained without adding molten salts.

Integration of Plasmonic Effects and Schottky Junctions into Metal-Organic Framework Composites: Steering Charge Flow for Enhanced Visible-Light Photocatalysis.

A wide range of light absorption and rapid electron-hole separation are desired for efficient photocatalysis. Herein, on the basis of a semiconductor-like metal-organic framework (MOF), a Pt@MOF/Au catalyst with two types of metal-MOF interfaces integrates the surface plasmon resonance excitation of Au nanorods with a Pt-MOF Schottky junction, which not only extends the light absorption of the MOF from the UV to the visible region but also greatly accelerates charge transfer. The spatial separation of Pt and Au particles by the MOF further steers the formation of charge flow and expedites the charge migration. As a result, the Pt@MOF/Au presents an exceptionally high photocatalytic H2 production rate by water splitting under visible light irradiation, far superior to Pt/MOF/Au, MOF/Au and other counterparts with similar Pt or Au contents, highlighting the important role of each component and the Pt location in the catalyst.