Intensive Light Absorption Research Articles

A C-modified engineering strategy of porous In2O3 catalysts for point-concentrated solar-driven photothermal CO2 hydrogenation

The solar-driven photothermal CO2 conversion serves as an effective approach for addressing the substantial challenges of energy crises and global environmental issues. In this work, various forms of In2O3 catalysts, including In2O3-c, In2O3-r, In2O3-s, and porous spherical In2O3, along with a C-modified porous spherical In2O3 catalyst (C-In2O3), were successfully synthesized through a hydrothermal method. An in-depth analysis was conducted to evaluate the performance of these catalysts in the point-concentrated solar-driven photothermal CO2 hydrogenation. As a result, the porous C-In2O3 catalyst exhibited a superior CO2 conversion rate of approximately 13.2 % under simulated sunlight irradiation, with a light intensity of 44.6 mW/cm2. Notably, all catalysts demonstrated nearly 100 % selectivity towards CO (CO production rate of around 8.51 mmol gcat−1h−1) during the photothermal catalytic reaction, without any formation of CH4. The outstanding performance of the C-In2O3 catalyst was attributed to the modification of In2O3 band structure by the incorporation of C, which significantly enhanced the intensive solar light absorption of the catalyst. Furthermore, incorporating C into In2O3 substantially augments its basic strength and significantly elevates the quantity of basic sites, thereby endowing it with outstanding CO2 adsorption and conversion capabilities. This work provides a C-modified engineering strategy to design efficient photothermal catalysts for boosting point-concentrated photothermal CO2 hydrogenation.

Steering charge flow in hierarchical ZnIn2S4/TiO2/Ti3C2 heterojunction for noble-metal-free photocatalytic hydrogen production

The construction of effective photogenerated charge transfer channels through interface engineering is the key to achieving the highly efficient of photocatalysts. Herein, sandwich-like ZnIn2S4/TiO2/Ti3C2 nanosheets integrated type-II heterostructure with Schottky junction are reasonably fabricated by low temperature in-situ growth method. Benefitting from the intensive visible light absorption of ZnIn2S4, the fast electron transport of TiO2, the rich active sites in Ti3C2, as well as the intimate interface coupling and the matched band alignment among ternary components, enhanced hydrogen production can be achieved with ZnIn2S4/TiO2/Ti3C2 hierarchical photocatalyst under visible light irradiation in the absence of noble metal co-catalysts. The concept of coupling type-II heterostructure with the Schottky barrier can steer the charge flow and boost the charge carrier separation and transfer across the interfacial domain, which may spark new ensemble design for efficient solar energy harvesting and conversion.

Construction of branched SnS2/Te heterostructure film for self-powered high-performance photodetector application

Effective design and construction of heterostructure can conduce to charges transportation/separation and simultaneously improve light absorption ability of photoelectrochemical (PEC) photoelectrode. In this work, the p-type Te nanorods were directly grown on the surface of ultra-thin SnS2 nanoflakes via a facile and low-cost electrochemical deposition (ED) method. The PEC performance of mixed-dimensional branched SnS2/Te nanoflakes/nanorods (NFRs) heterostructure composites film was optimized by varying the ED time. Under simulated light illumination of 40 mW/cm2, the optimal photocurrent density of the SnS2/Te NFRs photoanode significantly reached up to 0.95 mA/cm2, approximately 5.2 times and 3.5 times larger than those of bare SnS2 and Te film, respectively. The improved performance was attributed to appropriate energy band matching and intensive light absorption property. In particular, it presented good stability and high light on/off ratio of about 4.1 ×106 at the 0 bias voltages, suggesting an excellent self-powered characteristic of the device. Furthermore, the SnS2/Te NFRs photodetector exhibited photoresponsivity of 127 mA/W at 0.8 V bias and photodetectivity of 1.33 ×1011 Jones, respectively. This study presents a rational strategy to improve the photodetection performance of SnS2-based PEC-type photodetector and opens a new avenue for designing high-efficiency photoelectronics device.

Synthesis and spectroscopic properties of novel dipyrrole and tetrapyrrole-based photosensitizers with various biphenylyl substituents

Two series of novel pyrrole-based photosensitizers - sulfanyl porphyrazines, and BODIPY derivatives with different biphenylyl substituents such as fluorine atoms, cyano, or alkyloxycarbonyl groups, were synthesized, characterized, and subjected to broad spectroscopic studies. All tested compounds showed intensive light absorption, but only BODYPY derivatives exhibited emission properties. Moreover, iodinated BODIPYs revealed a significant heavy atom effect manifested by a red-shift of the absorption band by about 30 nm, about a 20-fold reduction in fluorescence intensity, and singlet oxygen generation efficiency increased 30–60 times compared to non-iodinated analogs. There was no correlation between the presence of peripheral fluorine atoms, cyano, or alkyloxycarbonyl groups and the absorption or emission properties. However, in both porphyrazines and BODIPYs, singlet oxygen formation was influenced by the substituents in the biphenylyl group. The compounds with cyano groups had the highest singlet oxygen generation ability and fluorine-analogs the lowest. Photodegradation studies revealed low or moderate decomposition of porphyrazines and non-iodinated BODIPYs with 5.9–18.8% of dyes degraded after 20 min of irradiation. However, the iodinated BODIPYs decomposed much faster, with the percentage of degradation in the range of 40.5–65.5%.

Bismuth-doped g-C3N4/ZIF-8 heterojunction photocatalysts with enhanced photocatalytic performance under visible light illumination

ABSTRACT In this work, g-C3N4/ZIF-8 heterojunction photocatalysts were synthesised by the process by which the metal-organic framework ZIF-8 nanoparticles were grown onto the g-C3N4 layer in situ. Bismuth element was doped into the as-prepared g-C3N4/ZIF-8 material and a new type of Bi@g-C3N4/ZIF-8 composite photocatalysts was manufactured, in which the doping element acts in adjusting the bandgap in the photocatalysts. The prepared photocatalysts were characterised by XRD, FESEM, TEM, FTIR, XPS, UV–VIS DRS, photoluminescence and photo-electrochemical experiments. The results show that the ZIF-8 nanoparticles grown in situ were well-formed onto the g-C3N4 layer, and bismuth was evenly doped into the gaps of the g-C3N4/ZIF-8 framework. The degradation rate of methylene blue by CNZ-1.5(Bi)-12, which was a photocatalyst composed of 12% Bi-doped with g-C3N4/ZIF-8 material (the mass ratio of g-C3N4: ZIF-8 = 1:1.5), reached 86.6% under visible light irradiation within 60 min. The free radical scavenging experiment and electron spin resonance spectroscopy showed that was the main active substance. Bismuth doping into the photocatalytic system promotes the excitation of electrons from the valence band to the conduction band and provides a good channel for the transmission of photogenerated carriers as well. It is achieved that intensive visible light absorption, the enhanced separation efficiency of photogenerated carriers, and excellent thermal stability and high recyclability in the novel composite photocatalyst, owing to the synergistic effect of the introduced bismuth with the heterostructure of g-C3N4/ZIF-8. Therefore, the synthesised Bi@g-C3N4/ZIF-8 heterojunction photocatalysts may be used as a good photocatalyst for purifying and degrading organic matter in sewage.

Fabrication of Z-scheme rod-like Ag2Mo2O7/g-C3N4 for phenol degradation under IO4¯/visible light system

A Z-scheme rod-like Ag2Mo2O7/g-C3N4 (AMO/BCN) was synthesized via a simple hydrothermal method. The physicochemical and optical properties of prepared catalysts were characterized by field emission scanning electron microscopy, X-ray diffraction, transmission electron microscopy, UV–vis absorption spectroscopy, photoluminescence and photocurrent response analyses. Morphology analysis showed that the surface of BCN was decorated by rod-like structure of AMO. Compared to BCN catalyst, AMO/BCN exhibited intensive visible light absorption and high separation rate of charge carriers. The photocatalytic assessment revealed 20 wt% AMO/BCN exhibited higher photodegradation of phenol compared to other samples. The enhanced photocatalytic performance was ascribed to the efficient charge transfer through a Z-scheme mechanism of rod-like AMO and BCN, improved visible light absorption, and high formation of hydroxyl radicals (•OH).

Fabrication of Black In2O3 with Dense Oxygen Vacancy through Dual Functional Carbon Doping for Enhancing Photothermal CO2 Hydrogenation

AbstractPhotothermocatalytic CO2 reduction as the channel of the energy and environmental issues resolution has captured persistent attention in recent years. In2O3 has been prompted to be a potential photothermal catalyst in this sector on account of its unique physicochemical properties. However, different from the metal‐based photothermal catalyst with the nature of efficient light‐to‐thermal conversion and H2 dissociation, the wide‐bandgap semiconductor needs to be modified to possess wide‐wavelength‐range absorption and the active surface. It remains a challenge to achieve the two aims simultaneously via a single material modulation approach. In this study, one strategy of carbon doping can empower In2O3 with two advantageous modifications. Carbon doping can reduce the formation energy of oxygen vacancy, which induces the generation of oxygen‐vacancy‐riched material. The introduction of oxygen defect levels and carbon doping levels in the bandgap of In2O3 significantly reduces this bandgap, which endows it full‐spectral and intensive solar light absorption. Therefore, the carbon doped In2O3 achieves effective light‐to‐thermal conversion and delivers a 123.6 mmol g–1 h–1 of CO generation rate with near‐unity selectivity, as well as prominent stability in photothermocatalytic CO2 reduction.

Donor-Acceptor Conjugated Macrocycles with Polyradical Character and Global Aromaticity.

SummaryPolyradical character and global aromaticity are fundamental concepts that govern the rational design of cyclic conjugated macromolecules for optoelectronic applications. Here, we report donor-acceptor (D−A) conjugated macromolecules with and without π-spacer derivatives to tune the antiferromagnetic couplings between the unpaired electrons. The macromolecules without π-spacer have a closed-shell electronic configuration and show global nonaromatic character in the singlet and lowest triplet states. However, the derivatives with π-spacer develop a nearly pure open-shell diradical and a very high polyradical character, not reported for D−A type macromolecules. Furthermore, the π-spacer derivatives display global nonaromaticity in the singlet ground state, but global aromaticity in the lowest triplet state, according to Baird's rule. The absorption spectra of the open-shell macromolecules calculated with time-dependent density functional theory indicate intensive light absorption in the near-infrared region and broadening to 2,500 nm, making these materials suitable for numerous optoelectronic applications.

Designing Donor-Acceptor Conjugated Macrocycles with Polyradical Character and Global (Anti)Aromaticity

Polyradical character and global (anti)aromaticity are fundamental concepts that govern rational design of cyclic conjugated macromolecules for optoelectronic applications. Here, we have designed donor-acceptor (D-A) macromolecules with ring topology along with their pi-spacer derivatives, and analyzed their unique electronic properties with density functional theory (DFT). The macromolecules with n = 8 and 16 repeat D-A units display similar singlet-triplet energy gap and have closed-shell electronic configuration with no diradical character (y0 = 0). These macromolecules also display global nonaromatic character, which is supported by NICS(0), AICD, and 2D-ICSS analysis. However, the derivatives with pi-spacer (n = 8-pi) develop near pure open-shell character (y0=1) with increased singlet-triplet gap. Furthermore, these derivatives display global antiaromaticity in the singlet ground-state according to Huckel's rule, and global aromaticity in the lowest triplet state following Baird's rule, and have a very high polyradical character, which is not reported for D-A type macromolecules. The calculated absorption spectra with time-dependent DFT (TDDFT) indicates intensive light absorption in the near-infrared (NIR) region broadening to 2500 nm. These macrocycles also display a size-dependent absorption maxima when the number of repeat units increased from n = 8 to 16. Furthermore, due to the development of open-shell character in the pi-spacer derivatives, a significant red-shift in the absorbance wavelength is observed.

Construction of S-scheme g-C3N4/ZrO2 heterostructures for enhancing photocatalytic disposals of pollutants and electrocatalytic hydrogen evolution

In consideration of environmental protection and energy conversion, the development of semiconductor photocatalytic technology is as first choice. But the photocatalytic performance of typical ZrO2 catalyst is seriously inhibited since it can only been driven by ultraviolet light. Herein, constructing S-scheme g–C3N4–modified ZrO2 heterostructures can be conducive to enhance photocatalytic performance by separating rapidly the photogenerated carriers. In this work, a series of S-scheme g-C3N4/ZrO2 heterostructures were constructed via the simple calcination, and their photocatalytic performances were evaluated by degradating Rhodamine B (RhB), Methyl orange (MO) and Acid orange II (AO II) under visible light irradiation. Importantly, 15% g-C3N4/ZrO2 heterostructures exhibited superior photocatalytic activities (degradating 82% RhB, 50% MO and 98% AO II in 150 min) and electrocatalytic performance (possessing lower overpotential, Tafel slope as well as more exposed active sites). The enhanced performances were ascribed to the intensive light absorption, the larger specific surface area, more exposed active sites as well as the higher separation of photogenerated electrons/holes pairs, which were confirmed by UV–vis diffuse reflectance spectra (DRS), photoluminescence (PL) spectra, electrochemical and radicals trapping experiments. This research provides the platform for the application in environmental protection and energy conversion via constructing S-scheme heterostructures.

Synthesis of nano titanium oxide with controlled oxygen content using pulsed discharge in water

Different titanium oxide nanoparticles were formed through pulsed discharge of Ti wires in distilled water and H2O2 solution. The recovered samples were characterized by various techniques, such as XRD, SEM and TEM. The results confirm the presence of various titanium oxide nanoparticles including TiO2 phases (anatase and rutile) and various nonstoichiometric TiO2−x in recovered samples owing to the oxygen deficient circumstance through pulsed discharge. The titanium oxide nanoparticles exhibit a spherical shape with a size of 10–300 nm. The results show that the energy input adjusted by charging voltage is one major factor to control the phases of titanium oxide and the overall oxygen content of recovered samples. In addition, the H2O2 content in distilled water also affects the oxygen content of recovered samples. The sample recovered from 10% H2O2 solution is pure TiO2 consisting of anatase and rutile without nonstoichiometric TiO2−x. Moreover, the UV–Vis absorption spectra of recovered samples show their intensive visible light absorption and the correlation between the visible light absorption and the experimental conditions (charging voltage and H2O2 content).

Determining the dispersion stability of black phosphorus colloids by 3D light scattering

Understanding the dispersion state of 2D black phosphorus (BP) nanosheets is of great significance for the application of BP based materials. However, the dispersion state of BP colloids cannot be analyzed by the conventional methods based on the optical signal detecting due to the intensive light absorption of BP in the ultraviolet-visible region and the high turbidity caused by the aggregation of pristine BP nanosheets. In this work, 3D light scattering has been proven to be an effective technique to characterize the dispersion characteristics of nanocolloids with intensive light absorption and limited dispersity by suppressing multiple scattering. The effect of the concentration, the temperature and the solvent on the dispersion stability of BP nanosheets has been systematically studied by modulated 3D cross-correlation. It has been shown that measurements at smaller angles can obtain better autocorrelation functions. The BP colloids exhibit excellent colloidal stability when the concentration is below 250 μgmL−1, above which aggregation tends to form. Increasing the temperature has shown to result in the formation of aggregation in the colloids. BP nanosheets possess better dispersion state in polar solvents than in nonpolar solvents, and the aggregation process in nonpolar solvents can be monitored by the slow relaxation mode of 3D light scattering. This study indicates that 3D light scattering paves way to analyze the dispersion dynamics of various 2D nanoparticle colloids with intensive light absorption and poor dispensability.

Improving the optical properties of [14] and [18] annulenes sandwiched between electron donor-acceptor groups

In the present research, an electron donor-acceptor compound (called push-pull systems) were studied using DFT methods in the vacuum space. We used [14] annulene and [18] annulene as π conjugated system and connected methoxy diphenylamine group as an electron donor and cyanoacrylic acid as an electron acceptor group. It was shown that the donor and acceptor groups narrowed the Eg of structure which is the result of hyperconjugation. Pristine annulenes had intensive light absorption in the ultraviolet region in electromagnetic radiation. After both molecules sandwiched between electron donor-acceptor groups, a significant redshift from the UV region to the visible and IR region was observed. Also in NMR calculation, it was observed the amount of aromaticity has increased after sandwiching. In all IR and Raman spectrum, it was shown the amount and intensity of light absorption increased after placing annulenes in electron donor-acceptor groups. The results of this research may be useful in designing new materials applicable as photosensitizers and photodynamic therapy.

Optical and photoelectrochemical properties of transparent NiO quantum dots

Intrinsic p-type NiO quantum dots were applied to study the thickness-dependent optical properties and photoelectrochemical performances. The reactive sputtering method was applied to grow quality NiO quantum dots (size of 5–7 nm) at a room-temperature for large-scale production. By controlling the NiO film thickness, the optical and photoelectrochemical features can be modulated, which are for the blue shift of band gap value (from 3.6 eV to 3.9 eV, Burstein-Moss shift), enhanced optical absorption, electrical conductivity, and a shift of flat band potential. A thin NiO film (50 nm) exhibited the same amount of photocurrent that of the 200 nm-thick NiO film. This strongly suggests the intensive light absorption property of the NiO film to illuminate of possibility of thin film uses. The transparent optical property and degenerate nature of NiO quantum dots will be a great interest to integrate them with low bandgap materials for the advantage of high light absorption and heterojunction for the water-splitting and hydrogen production.

ZnO nanosheets with atomically thin ZnS overlayers for photocatalytic water splitting

ZnO nanosheets with atomically thin ZnS overlayers were engineered for highly-efficient water splitting, and the ZnS/ZnO/ZnS sandwich nanostructure demonstrates intensive light absorption, fast charge separation, long electron lifetime, and eventually the highest hydrogen production rate reported for oxide catalysts so far.

Hollow cobalt ferrite–polyaniline nanofibers as magnetically separable visible-light photocatalyst for photodegradation of methyl orange

Abstract Hollow cobalt ferrite–polyaniline nanofibers (CoFe 2 O 4 –PANI) functioning as a photocatalyst were prepared by using electrospinning technique, followed by calcination and in-situ chemical oxidative polymerization. The hollow CoFe 2 O 4 –PANI nanofibers with one dimensional (1D) structure provide well-developed mesoporous structure and enhanced electrical conductivity. The hollow CoFe 2 O 4 –PANI nanofibers consisted of hollow core-double shell nanostructure, which has CoFe 2 O 4 as inner shell and PANI as outer shell. The hollow CoFe 2 O 4 –PANI nanofibers coated with PANI nanograins facilitate the optical properties by easily capturing visible light. The intensive visible light absorption and effective charge separation lead to a remarkable improvement of visible light photocatalysis owing to the heterojunction built between CoFe 2 O 4 and PANI. The pseudo-first-order kinetic constant of photocatalytic degradation of the methyl orange (MO) dye under visible light irradiation with CoFe 2 O 4 –PANI was 80 times greater than CoFe 2 O 4 . This evidence shows the advantage of the unique core–shell mesoporous structure in the CoFe 2 O 4 –PANI for efficient photocatalysis. The recovery ratio is almost the same after three cycles under visible light irradiation, displaying the excellent characteristics of magnetic separation for CoFe 2 O 4 –PANI hollow nanofibers.

Morphology controlled syntheses of Cu-doped ZnO, tubular Zn(Cu)O and Ag decorated tubular Zn(Cu)O microcrystals for photocatalysis

Without any assistance of surfactant and/or template the hexagonal prism-shaped Cu2+-doped ZnO (Zn(Cu)O) microcrystals with twinned structures were easily synthesized by one-step co-precipitating under atmospheric pressure and moderate temperature, in which Cu2+ ion was used as the dopant and the morphology controller. Because Cu2+ ions can be adsorbed on the (0001) and {101¯1} planes the growth on these planes was restrained, resulting in the formation of Zn(Cu)O microcrystals with stubby hexagonal prism shape. Meanwhile, the twinned structure Zn(Cu)O microcrystals were obtained via the electrostatic interaction between adsorbed Cu2+ ion and two (0001¯) negative planes. When twinned structure Zn(Cu)O sample was etched by NaOH solution the (0001) polar planes at two ends of Zn(Cu)O crystal were dissolved via forming Zn(OH)42− complex ion, but the non-polar {0110} planes did not. As a result, the tubular structure Zn(Cu)O microcrystals (T-Zn(Cu)O) were obtained in the absence of template and/or specific protective agent. The metallic Ag decorated tubular Zn(Cu)O (T-Zn(Cu)O/Ag) samples were prepared by auto-catalyzed deposition reaction. The morphological, structural, photoluminescence, as well as photocatalytic properties of Zn(Cu)O, T-Zn(Cu)O and T-Zn(Cu)O/Ag samples were investigated and the results indicated that the Zn(Cu)O sample with a very small amount of doped Cu2+ ion showed higher photocatalytic activity than ZnO. Tubular structure Zn(Cu)O samples showed moderately enhanced photocatalytic activities compared to corresponding Zn(Cu)O samples. By decorating metallic Ag on the surfaces the T-Zn(Cu)O/Ag samples exhibited distinctly enhanced photocatalytic activities due to the contribution of Schottky barrier and intensive light absorption in Vis and NIR regions.

Synthesis and Activity of Plasmonic Photocatalysts

AbstractPlasmonic photocatalysts, which have intensive light absorption and high charge‐separation efficiencies, are regarded as promising candidates to solve energy and environmental issues in the future. In this Review, we summarize recent developments in the synthesis, activity, and mechanism of plasmonic photocatalysts, with the aim of stimulating improvements in photocatalytic activities and promoting the development of photocatalysis. The materials systems, energy‐transfer mechanisms, and factors that influence the photocatalytic activities of plasmonic photocatalysts are discussed. Some perspectives for the future development of the design of highly efficient plasmonic photocatalysts are proposed.

Remarkable improvement of visible light photocatalysis with PANI modified core–shell mesoporous TiO2 microspheres

PANI modified core–shell mesoporous TiO2 (PANI/M-TiO2) with efficient photocatalytic capability under visible light irradiation was fabricated by hydrothermal method and chemisorption approach. The nitrogen adsorption–desorption characterization indicated that the specific surface area of mesoporous M-TiO2 was 2.8 times as great as that of P25, which resulted in the increased uptake of PANI molecule on the surface of M-TiO2. Environmental scanning electron microscopy and transmission electron microscopy images demonstrated that the PANI/M-TiO2 possessed a unique core–shell structure, which allowed multiple reflection or scattering of light in the photocatalyst and led to the increase of optical path length subsequently. Both the increased uptake of PANI molecules and optical path length in photocatalyst contributed to enhance the visible light absorption. The UV–vis diffuse reflectance spectra confirmed that the optical absorption for PANI/M-TiO2 was more intensive than that for PANI modified TiO2 nanoparticle (PANI/NP-TiO2) in the visible light region. The intensive visible light absorption and effective charge separation owing to the heterojunction built between TiO2 and PANI lead to remarkable improvement of visible light photocatalysis. The pseudo-first-order kinetic constant of photocatalytic degradation of rhodamine B and 4-chlorophenol under visible light irradiation with 6% PANI/M-TiO2 was 5.04 and 2.03 times as great as that with PANI/NP-TiO2 respectively, showing the advantage of the unique core–shell mesoporous structure in the PANI/M-TiO2 for efficient photocatalysis.

Visible light active pristine and [formula omitted] doped [formula omitted] spinel photocatalysts for solar hydrogen production

Spinel metal oxide photocatalysts, a rarely studied group in visible light driven photocatalytic decomposition of H 2 S and solar H 2 production, have been investigated in the present work. d 10 p-block element, Ga containing spinel CuGa 2 O 4 in pristine and Fe 3 + doped ( CuGa 2 - x Fe x O 4 , x = 0.6 ) states, was prepared by ceramic route without/with noble metal oxide, NiO / RuO 2 loading to the extent of 1 wt%. XRD analysis reveals a single-phase cubic spinel crystalline structure for all the catalysts. FESEM displays an irregular-shaped grain morphology for CuGa 2 O 4 and smaller size almost cubic particles for CuGa 2 - x Fe x O 4 . Energy dispersive X-ray spectroscopy suggests a chemical composition consistent with the stoichiometric molecular formula. Optically, the catalysts display an intensive light absorption in UV and visible regions with an onset at about 900 nm in the near IR region. Fe 3 + doping constructively influences the morphology and optical properties of pristine CuGa 2 O 4 . All these physico-chemical and material characteristics infuse a facile catalytic function into the prepared spinel oxides such that the naked CuGa 2 O 4 and CuGa 2 - x Fe x O 4 spinels exhibit a moderate to fairly good photocatalytic activity while the co-catalyst-loaded CuGa 2 - x Fe x O 4 spinel performs an exceedingly good photocatalytic activity with 15% quantum efficiency. Thus, the present work leads to the emergence of functionally high performance, stable and visible active ( λ ⩾ 420 nm ) photocatalysts in the spinel group for the production of solar hydrogen from H 2 S .