Absorption Of Sunlight Research Articles

Enhanced photoelectrochemical water splitting performance of GaN nanowires on textured Si (100) platforms: The role of texturing in 3.69 % STH conversion efficiency

Nanostructured GaN semiconductors, including 0D quantum wells and 1D nanowires (NWs), as well as 3D nanoporous structures, have the potential to enhance the efficiency of photoelectrochemical (PEC) cells due to their shorter charge carrier transfer paths, accelerated separation of photogenerated carriers, and enhanced sunlight absorption. However, their practical applicability is limited due to poor stability and low solar-to-hydrogen conversion efficiency. To address these issues, one approach is to load a passivation layer and cocatalyst onto the GaN surfaces to protect against oxidation and corrosion and promote the oxidation of water, respectively. Another strategy is to design these structures on textured platforms to enhance light management, resulting in broader absorption of wavelengths and reduced sensitivity to incident angle and light polarization. In this study, we present a novel comparison of PEC-WS performance among 120 CdS/ZnO/GaN nanowires fabricated on different substrates, including planar Si (120 CdS/ZnO/GaN NWs-Si), textured 3D pyramids (120 CdS/ZnO/GaN-Si PNWs), and NWs Si (120 CdS/ZnO/GaN-Si HNWS). Compared to the other substrates, 120 CdS/ZnO/GaN-Si HNWS photoanode showed a 1.14 and 1.26-fold increase in photocurrent density and 3.69 % solar to hydrogen conversion efficiency under 1-Sun illumination. Our Si texturing approach, in-depth understanding of charge transportation, and demonstration of a co-catalyst-loaded core-shell passivated structure offer promising opportunities for achieving highly efficient PEC-WS performance in GaN-based photoanodes.

Interfacial modulation of α-Ag1.82Cu0.09WO4 with high active BiOClxI1−x for boosting photocatalytic activity and degradation of emerging contaminants under direct sunlight

Removal of organic contaminants in wastewater using sunlight-driven photocatalysts has received significant attention in recent years. However, the rational design of photocatalysts to attain high light absorption, lower charge carrier recombination with efficient photocatalytic activity and good recycling capability is crucial for the practical photocatalysis process. Herein, solid-state Z-scheme BiOCl0.6I0.4/α-Ag1.82Cu0.09WO4 heterojunction is synthesized by assembling hierarchical 3D-BiOCl0.6I0.4 nanoflowers on cube-like 3D-α-Ag1.82Cu0.09WO4 surface through a hydrothermal method. A wide range of characterization techniques confirms the successful synthesis of BiOClxI1−x (0 ≤ x ≤ 1.0), α-Ag1.82Cu0.09WO4 and BiOCl0.6I0.4/α-Ag1.82Cu0.09WO4 binary composites. The TC antibiotic removal efficiency of 30 wt% BiOCl0.6I0.4/α-Ag1.82Cu0.09WO4 binary composite reaches 95.91% within 120 min under natural sunlight irradiation and the rate constant is 1.81 and 3.33 times higher than the pristine BiOCl0.6I0.4 and α-Ag1.82Cu0.09WO4, respectively. The optimized binary heterojunction exhibits excellent photocatalytic performance for toxic pollutants like MB (η = 97.27%) and RhB (η = 95.75%) under direct sunlight irradiation. The favorable photocatalytic activity of binary heterojunction is ascribed to enhancing the sunlight absorption range, the tight contact interface and the effective separation of electron/hole pairs. Notably, 30 wt% BiOCl0.6I0.4/α-Ag1.82Cu0.09WO4 binary composite exhibits attractive recycling ability and good photostability for prolonged sunlight irradiation. Furthermore, the total organic carbon results also confirm that the 30 wt% BiOCl0.6I0.4/α-Ag1.82Cu0.09WO4 efficiently mineralized the model pollutants (TC antibiotic, MB and RhB) into other unharmful compounds under sunlight irradiation. In summary, this work offers an effective strategy to prepare solid-state Z-scheme heterojunction with favorable photocatalytic activity, which can increase wastewater purification efficiency.

MoS2 modified NiFe LDH hierarchical structure as efficient photoanode towards photoelectrochemical water splitting

Designing effective photo electrode for photo-electrochemical (PEC) water splitting is highly demanded yet challengeable because of the limited sunlight utilization and retarded redox reaction kinetics. This work introduces a feasible one-pot hydrothermal strategy of fabricating MoS2/NiFe LDH p-n heterojunctions on conductive porous nickel foam as an efficient photoanode for PEC water splitting. A great enhancement for PEC water oxidation is achieved because of the improved sunlight absorption and the increased photo-excited charge separation. The optimal 10% MoS2/Ni0.9Fe0.1 LDH/nickel foam photoanode demonstrates 3.8 times enhanced PEC activity than the Ni0.9Fe0.1 LDH/NF counterpart and a low Tafel plot of 54 mV dec−1. The bandgap modulation and the Z-scheme charge transfer dynamics due to the formation of MoS2/NiFe LDH p-n heterostructure, along with the high conductivity of porous nickel foam account for the increased photo-current conversion efficiency and the boosted charge transfer.

A mechanistic study on enhanced solar photocatalytic activity of SnWO4/BiMoO6 nanocomposites for degradation of tetracycline

Step-scheme band configuration is considered to be an excellent option for photocatalytic applications including degradation of organic pollutants. This phenomenon has been demonstrated here via sunlight mediated photocatalytic degradation of trace concentrations of antibiotics in water by SnWO4/BiMoO6 nanocomposites. The structural, morphological, textural, compositional and optical properties of the hydrothermally synthesized SnWO4/BiMoO6 nanocomposites are critical towards enhanced photocatalytic degradation kinetics of tetracycline, used here for mimicking antibiotic residue in water. The optimized batch of 0.10SnWO4/Bi2MoO6 photocatalyst exhibited step-type band position and accounted for 95 % sunlight mediated photocatalytic degradation of tetracycline solution at a rate constant of 0.031 min−1. The degradation rate is six times higher than that of pristine Bi2MoO6 and fifteen times higher than that of SnWO4 nanoparticles. The mechanism involved in the photocatalytic degradation of tetracycline hydrocloride has been addressed in the light of (a) enhanced absorption of sunlight by 0.10SnWO4/Bi2MoO6; (b) favourable type-II-like band position of Bi2MoO6 and SnWO4 leading to heterojunction formation, (c) electrochemical studies showing charge carrier mobility and photocurrent measurements showing inhibition of charge carrier recombination, and (d) in situ generation of hydroxyl radicals.

Enhancing solar steam generation in hydrogel evaporator by bio-based microfluidic component

The hydrogel-based evaporator exhibits exceptional water activation capabilities, enabling it to surpass the previously established upper limits of evaporation rates in interfacial solar steam generation (ISSG). Although hydrogels possess a pronounced affinity for water, this characteristic could result in temporary expansion and heat loss, which hinder their capacity to sustain rapid and efficient evaporation over prolonged durations. Herein, polyacrylamide-based photothermal hydrogel with customized microfluidic components achieved long-term operation. The photothermal hydrogel showed high sunlight absorbance (∼95.5%) and its surface temperature spontaneously could reach 44.1 °C under one sun simulated irradiation (1.0 kW/m2). The efficient regulation of water transport was accomplished by Nafion-modified corn straw, i.e., a microfluidic component. This hydrogel-based evaporator demonstrated an increasing evaporation rate from 2.03 to 2.42 kg/m2/h during 12 h of continuous solar illumination. Notably, the microfluidic component resulted in controlled water transport enabling programmable adjustment of the hydrogel evaporator, allowing it to be reused multiple times in practical applications around the clock. The daily potable freshwater production amount reached 7.84 kg/m2/h in outdoor seawater desalination experiments. This research provides a paradigm approach to address freshwater scarcity on a global scale by using waste biomass to fully compensate for the shortcomings of hydrogels in ISSG systems.

Engineering all-polymer planar photonic crystals as aegises against sunlight overheating

Reducing heating by sunlight is of paramount interest for sustainability and energy efficiency. Solar heating causes harmful CO2 emissions related to the cooling of buildings and vehicles cooling and causes a reduction in greenhouse crop yields during hot seasons. Therefore, reducing the absorption of sunlight with low-cost passive systems could play a major role in energy saving and human sustainability from an environmental standpoint. In this work, dielectric mirrors (aegises) are designed to reflect near-infrared radiation and fabricated out of different polymer pairs ranging from commodity to specialty polymers. Structurally similar tandem structures are designed using a quantitative rationale that allows for predicting thermal shielding efficiency that could be used to design optimized reflectors. As a proof-of-concept, structures are designed via the presented rationale and then fabricated out of different polymer pairs and tested. This allowed to study the influence of materials’ dielectric contrast on the efficiency in heat reduction. Thanks to the new rationale and the improved materials, although coming at the cost of an increase of reflectance of visible light, an efficiency of 27 % is achieved with the polymer pair providing the higher dielectric contrast, namely the Aquivion-poly(N-vinylcarbazole) one.

Effect of Co doping of (Ga, In) and 2N preferred orientation on the magnetic and optical properties of ZnO

Current research on the Zn1−xMxO1−yNy (M = Ga, In) system mainly focuses on the p-type property, where Ga–N or In–N has different preferred orientations for bonding. Studies on the magnetic, bandgap, and optical properties of ZnO co doped with N are also lacking. The generalized gradient approximation (GGA+U) plane wave ultrasoft pseudopotential method based on density functional theory is used to systematically investigate the effects of the magnetic, band gap, and optical properties of the system for addressing the aforementioned problems. Results show that the formation energy of the Zn1−xMxO1−yNy (M = Ga, In) system is negative, all doping is easy, and all doped systems are stable and magnetic. The magnetism comes from the double exchange effect of electron spin polarization. Research has found that the band gap in Ga–N or In–N bonding along the c-axis direction is narrower than that along the a-axis direction. In the low-energy region, the redshift of the absorption spectrum is more significant, and the absorption or reflection coefficient and the carrier polarization and activity are stronger. In particular, In–N forms bonds along the c-axis direction and is co doped with another N in ZnO, which results in the narrowest band gap and the most significant redshift in the absorption spectrum. The absorption of sunlight can also be achieved in the ultraviolet visible near-infrared region. The absorption or reflection coefficient and the carrier polarization and activity are relatively strongest. This work has certain reference value for the design and preparation of new solar cell light absorbing materials based on ZnO.

Synthesis of strontium oxide-zinc oxide nanocomposites by Co-precipitation method and its application for degradation of malachite green dye under direct sunlight

Photocatalysts workable under direct sunlight are the safe and cost-effective option for water purification. The nanocomposites of strontium oxide and zinc oxide (SZ NCs) were synthesized using coprecipitation method. The respective precursors of SZ NCs were subjected to alkaline hydrolysis and subsequently thermally treated to yield SZ NCs. The SZ NCs with different ZnO composition was synthesized by varying the concentration of ZnO precursor from 0.2 to 1 M. The structural properties of SZ NCs evaluated using X-Ray diffraction (XRD), Thermogravimetric analysis (TGA), and Differential thermal analysis DTA). The optical properties of SZ NCs studied using ultraviolet–visible (UV–Vis) spectroscopic study. The trend observed in the intensity of XRD peaks indicated the occurrence of Zn doping in the crystalline lattice of SrO and the formation of SrO–ZnO composite. Upon incorporation of 1 M of ZnO precursor, the grain size of the SrO was decreased from 49.3 to 27.6 nm. The weight loss in the thermal analysis indicates the removal of carbonates from the sample upon heating and shows the formation of an oxide structure. UV–Vis spectra confirmed that the presence of SrO enhanced the sunlight absorption of SZ NCs. The increase in the composition of ZnO precursors increased the bandgap of SrO (2.09 eV) to the level of ZnO (3.14 eV). SZ NCs exhibited heterostructure morphology, where the nanosized domains with varying shapes (layered and rod-like) were observed. Under direct sunlight conditions, SZ NCs prepared using 1 M/0.6 M of SrO/ZnO precursors exhibited 15–20 % higher photocatalytic efficiency than neat SrO and ZnO. In precise, 1 mg of this SZ NC was degraded 98 % of malachite green dye dissolved in water (10 ppm) under direct sunlight. Additionally, the thermal stability results showed that 18 % decomposition was obtained due to the degradation impurities in SrO/ZnO catalysts and the XRD results revealed that no structural change is obtained in SrO/ZnO photocatalysts after stability test. The SZ NCs can be effectively used as safe and economic sunlight photocatalysts for water purification in remote areas without the electricity.

Engineering High-Tortuosity 3D Gradient Structure and CFD-Assisted Multifield Analysis for Solar Interfacial Evaporation.

Solar interfacial evaporation is a promising method for solving the global shortage of fresh water. While 2D evaporators can efficiently localize solar-converted heat at the thin layer of the water-air interface, 3D solar evaporators can maximize energy reutilization while maintaining effective mass transport ability, few studies are conducted to explore the effect of gradient porosity on evaporation performance. In this study, a multifield assisted strategy based on a gradient 3D structure with high tortuosity is proposed, which creates a thermal field environment for efficient evaporation through high absorption of sunlight and excellent photothermal conversion and uses the gradient structure to optimize the internal pressure field to enhance water evaporation and transport. This hierarchically nanostructured solar absorber, with porosity inhomogeneity-induced pressure gradient and optimized temperature management, is a valuable design idea for manufacturing a more efficient 3D solar evaporator in the field of seawater desalination. Owing to the understanding of optimizing the dimension by various simulation parameters, the evaporation efficiencies of such structures are found to be 165.7%, suppressing the most evaporator. Moreover, it can provide new ideas and references for the fields of mass transfer and thermal management.

Superior solar water purification achieved by the excellent photothermal conversion and thermal management of porous plasmonic TiN nanoparticles

Solar photothermal steam generation promises decentralized water purification, but the lack of materials that have strong sunlight absorption in wide spectral range, superior thermal management, large specific surface area as well as good water wettability limits the overall solar water purification efficiency. Herein, porous TiN nanospheres are prepared for solar water purification. The monodispersed porous TiN nanospheres are prepared through the wet-chemistry synthesis of TiO2 and followed nitridation. The prepared porous TiN nanospheres have relatively large specific surface area and very good hydrophilicity. In comparison with solid TiN nanospheres, the porous counterparts have stronger light absorption and better thermal management. The optimum solar evaporation film prepared with the porous TiN nanospheres and filter membrane (TiN/FM) exhibits a reflectance smaller than ∼ 19% in the entire solar spectrum. All these merits of the porous TiN nanospheres give rise to a water evaporation rate of 1.68 kg m-2 h−1 and a solar-steam conversion efficiency of 93.4% under AM 1.5 irradiation. Both seawater and polluted water can be purified to potable water with TiN/FM. Our work not only provides a preparation approach for monodispersed porous TiN nanospheres but also demonstrates the great potential of porous plasmonic nanoparticles for the future development of solar water purification.

Hierarchical metal-organic framework-functionalized PVDF tree-like nanofiber membrane for high-efficient photothermal membrane distillation

The development of membrane with strong sunlight absorption and high energy efficiency is the key to improve the water production efficiency in photothermal membrane distillation (PMD). In this paper, a hierarchical Cu-based metal–organic framework-functionalized polyvinylidene fluoride (PVDF) tree-like nanofiber membrane (Cu-CAT@TLNM-TLNMs) was developed for high-efficient PMD. The Cu-CAT@TLNM-TLNM was prepared by in-situ growth of Cu-CAT on the surface of PVDF tree-like nanofiber membrane (TLNM) as photothermal layer and PVDF TLNM as support layer, which exhibited excellent photothermal conversion performance, high energy utilization and high permeate flux. The PVDF TLNM with high specific surface area provided more active sites for the growth of Cu-CAT, thus forming a uniform Cu-CAT nanoarray. The spinous structure of the Cu-CAT photothermal layer can increase the length of the light-matter interaction and improve light absorption. In addition, the tree-like structure of the support layer with high porosity and small pore size can improve the permeate flux and long-term stability. Under the illumination of 1 kW·m−2, the surface temperature of the Cu-CAT@TLNM-TLNMs reached about 80 °C within 50 s, with a permeate flux of 1.37 kg·m−2·h−1, a salt rejection of >99.99 %, and a photothermal conversion efficiency of 76 %. More importantly, the permeate flux of the Cu-CAT@TLNM-TLNMs was still stable at 0.79 kg·m−2·h−1 with a salt rejection of >99.99 % after 84 h of continuous operation. This photothermal nanofiber composite membrane can be applied to solve the problem of freshwater shortage in areas where freshwater and fuel resources are scarce and solar energy is abundant.

Cu2O-Electrodeposited TiO2 Photoelectrode for Integrated Solar Redox Flow Battery

TiO2 photoelectrode has become an attractive platform due to its excellent photoelectric performance and has been widely used in battery, photocatalysis, and other photoelectric fields. However, when the TiO2 photoelectrode is used in solar flow batteries, the small photo-charging current is a potential problem, which will extend the charging process and lower the battery utilization efficiency. To address this issue, Cu2O is introduced to the surface of the TiO2 photoelectrode, and Cu2O-TiO2 forms a heterojunction to improve battery performance in this work. The formation mechanism of Cu2O-TiO2 is revealed and utilized to deposit Cu2O on pre-treated FTO glass covered with TiO2 films using electrochemical deposition (ECD). The photoelectrochemical properties of Cu2O-TiO2 photoelectrodes are characterized using XRD, UV-vis diffuse reflectance spectroscopy, XPS, and electrochemical characterizations. The successful deposition of Cu2O on the surface of TiO2 photoelectrode is confirmed, and the UV-vis spectroscopic test results show that the incorporation of Cu2O enhances and broadens the absorption and utilization of sunlight in the UV range by the TiO2 photoelectrode. Furthermore, the electrochemical test results manifest that the Cu2O-TiO2 photoelectrode possesses a higher carrier concentration under illumination conditions due to the formation of a heterojunction. Finally, a 30 min unbiased photocharging test demonstrates that the Cu2O-TiO2 photoelectrode charges in a current density of 425.03 μA·cm−2, indicating an increased photogenerated carrier concentration and a decreased photogenerated carrier recombination rate, which results from the enlarged doping concentration and improved charge transfer process at the electrolyte/semiconductor interface due to the incorporation of Cu2O. Compared with the current density of 116.21 μA·cm−2 for the bare TiO2 photoelectrode, the performance can be improved by over 365%.

Conduction Band Tuning by Controlled Alloying of Fe into Cs2AgBiBr6 Double Perovskite Powders

AbstractHalide double perovskite semiconductors such as Cs2AgBiBr6 are widely investigated as a more stable, less toxic alternative to lead‐halide perovskites in light conversion applications including photovoltaics and photoredox catalysis. However, the relatively large and indirect bandgap of Cs2AgBiBr6 limits efficient sunlight absorption. Here, it is shown that controlled replacement of Bi3+ with Fe3+ via mechanochemical synthesis results in a remarkable tunable absorption onset between 2.1 and ≈1 eV. First‐principles density functional theory (DFT) calculations suggest that this bandgap reduction originates primarily from a lowering of the conduction band upon the introduction of Fe3+, and predict a direct bandgap when >50% of Bi3+ is replaced with Fe3+. The tunability of the conduction band energy is found and reflected in the photoredox activity of these semiconductors. These findings open new avenues for enhancing the sunlight absorption of double perovskite semiconductors and for harnessing their full potential in sustainable energy applications.

Lawn-inspired polypyrrole functionalized waste fabrics for chromium removal through a combination of adsorption and interface evaporation

Polypyrrole can effectively remove Cr(VI) from wastewater through electrostatic adsorption, ion exchange, and reduction. However, plenty of residual Cr(III) is still extremely harmful to the environment. In this work, waste fabrics are functionalized with polypyrrole (Fabric@PPy) for removing chromium ions by the combination of adsorption and solar-driven interfacial evaporation technologies. Fabric@PPy exhibited efficient removal of Cr(VI) (146.78 mg g−1) and ultra-high economic benefit (1725.14 mg USD−1). The same treatment method was applied to different fabrics and the removal of Cr(VI) remained consistently at nearly 100 %, which proves the universality of the proposed method in recycled waste fabrics. Based on the plenty of pores and surface hairiness between the waste fabric yarns, the evaporation rate was increased to 1.47 kg h−1 m−2 by enhancing sunlight absorption and water vapor escaping outward. In addition, Cr(VI) and Cr(III) concentrations after evaporative cooling were 0 mg/L and 0.016 mg/L, respectively. More critically, the evaporation rate per unit cost reached 2263.28 g h−1 USD−1. This strategy has the advantages of simplicity, low cost, and easy industrial production, whether it is reducing heavy metal pollution or reusing waste fabrics, it is of great significance.

PDI-Based Organic Small Molecule Regulated by Inter/Intramolecular Interactions for Efficient Solar Vapor Generation.

Organic small molecules with processing feasibility, structural diversity, and fine-tuned properties have the potential applications in solar vapor generation. However, the common defects of narrow solar absorption, low photothermal conversion efficiency, and photobleaching result in limited materials available and unsatisfactory evaporation performance. Herein, the perylene diimide (PDI) derivatives are exploited as stable sunlight absorbers for solar vapor generation. Particularly, the N,N'-bis(3,4,5-trimethoxyphenyl)-3,4,9,10-perylenetetracarboxylic diimide (PDI-DTMA) is well-designed with donor-acceptor-donor configuration based on plane rigid PDI core. The efficient photothermal conversion is enabled through strong intermolecular π-π stacking and intramolecular charge transfer, as revealed by experimental demonstration and theoretical calculation. The PDI-DTMA with a narrow band gap of 1.17eV exhibits expanded absorption spectrum and enhanced nonradiative transition capability. The 3Dhybrid hydrogels (PPHs) combining PDI-DTMA and polyvinyl alcohol are constructed. With the synergistic effect of solar-to-heat conversion, thermal localization management, water activation, and unobstructed water transmission of PPHs, the high water evaporation rates can reach 3.61-10.07kg m-2 h-1 under one sun. The hydrogels also possess great potential in seawater desalination and sewage treatment. Overall, this work provides valuable insights into the design of photothermal organic small molecules and demonstrates their potentials in solar water evaporation.

Photothermal superhydrophobic copper nanowire assemblies: fabrication and deicing/defrosting applications

Ice and frost buildup continuously pose significant challenges to multiple fields. As a promising de-icing/defrosting alternative, designing photothermal coatings that leverage on the abundant sunlight source on the earth to facilitate ice/frost melting has attracted tremendous attention recently. However, previous designs suffered from either localized surface heating owing to the limited thermal conductivity or unsatisfied meltwater removal rate due to strong water/substrate interaction. Herein, we developed a facile approach to fabricate surfaces that combine photothermal, heat-conducting, and superhydrophobic properties into one to achieve efficient de-icing and defrosting. Featuring copper nanowire assemblies, such surfaces were fabricated via the simple template-assisted electrodeposition method, allowing us to tune the nanowire assembly geometry by adjusting the template dimensions and electrodeposition time. The highly ordered copper nanowire assemblies facilitated efficient sunlight absorption and lateral heat spreading, resulting in a fast overall temperature rise to enable the thawing of ice and frost. Further promoted by the excellent water repellency of the surface, the thawed ice and frost could be spontaneously and promptly removed. In this way, the all-in-one design enabled highly enhanced de-icing and defrosting performance compared to other nanostructured surfaces merely with superhydrophobicity, photothermal effect, or the combination of both. In particular, the defrosting efficiency could approach ∼100%, which was the highest compared to previous studies. Overall, our approach demonstrates a promising path toward designing highly effective artificial deicing/defrosting surfaces.

Two-dimensional anisotropic monolayers NbOX2 (X = Cl, Br, I): Promising candidates for photocatalytic water splitting with high solar-to-hydrogen efficiency

Motivated by the recent experimental synthesis of two-dimensional (2D) NbOI2 which possesses a moderate bandgap and outstanding absorption of sunlight, using the first-principles calculations, we conduct a thorough study of the geometric configuration, electronic structures, and photocatalytic properties for NbOX2 (X = Cl, Br, I) monolayers. These NbOX2 monolayers have been demonstrated to be dynamically, thermally, and mechanically stable. The significant anisotropic mechanical properties of NbOX2 monolayers are reflected by the calculated Young's modulus and Poisson's ratio. Our results indicate that these NbOX2 materials unfold semiconductor characters with indirect bandgaps of 1.886, 1.909, and 1.813 eV, respectively. Among these monolayers, it is found that the NbOBr2 system exhibits a favorable photocatalytic activity in an acidic condition (pH = 0), and the NbOI2 monolayer can act as a potential photocatalyst for spontaneous photocatalytic water splitting under a neutral environment (pH = 7). Furthermore, the response of bandgap and band edge positions of NbOX2 monolayers to the exerting in-plane strain (–6% to 6%) are investigated. These NbOX2 monolayers also show strong light absorption from the visible to ultraviolet region and anisotropic high carrier transport. Particularly, the high solar-to-hydrogen efficiency of the NbOCl2 (1% tensile strain), NbOBr2, and NbOI2 monolayers are predicted to be 14.11% (pH = 0), 16.34% (pH = 0), and 17.05% (pH = 7), respectively. Therefore, we expect the NbOX2 monolayers to be promising candidates for highly efficient photocatalytic water splitting.

Antibacterial activity of SnO2 in visible light enhanced by erbium–cobalt co-doping

In this work, a series of SnO2 samples with systematically varied doping amounts of Er and Co were prepared via a precipitation–hydrothermal method. The results show that after Er doping, the 4I15/2 ground state of Er3+ jumps to the 4H11/2 higher-energy level, and the Er-doped SnO2 samples can efficiently convert low-energy light into high-energy light. Thus, Er doping is beneficial for improving the visible and near-infrared light response of SnO2 and thus enhances its photocatalytic performance. Furthermore, doping SnO2 with Co leads to a distortion of the SnO2 lattice. A proportion of the SnO2 lattice is replaced by Co atoms, which can effectively lower the bandgap of SnO2, widen its optical response range, and enhance its sunlight absorption efficiency. The photocatalytic antibacterial activities of pure SnO2, as well as SnO2 co-doped with Er and Co in visible light, were investigated under visible light using Escherichia coli. SnO2 shows the best antibacterial activity and electron–hole separation efficiency when co-doped with 1.5 mol. % Er and 1.5 mol. % Co (Er1.5Co1.5-SnO2). Gradient experiments reveal that mainly the reactive oxygen species affect the antibacterial activity of pure SnO2. The improved antibacterial performance of Er1.5Co1.5-SnO2 is attributed to the increased generation of·O2− and·OH. In addition, scavenger experiments reveal that·O2− is the key contributor to the enhanced antibacterial activity of SnO2.

Manipulating Nucleation and Crystal Growth of Inorganic Perovskite Solar Cells.

Inorganic metal halide perovskite materials as sunlight absorbers for solar cells exhibit better thermal stability than organic-inorganic hybrid counterparts. Pure cesium lead triiodide (CsPbI3), with the most suitable band gap, suffers phase instability under an ambient environment. Nucleation and crystal growth are two crucial steps in fabricating a solution-processed perovskite film. A high-quality perovskite film with good morphology makes a significant impact on the efficiency and stability of perovskite solar cells. Dimethylformamide (DMF) is a commonly used aprotic solvent. However, it is difficult to obtain a high-quality inorganic perovskite film using DMF as a single solvent due to its slow evaporation and strong coordination with Pb2+. Here, we investigate dimethylacetamide (DMAc)/DMF as a cosolvent to prompt nucleation during the spin-coating process, leading to higher nucleation density and better surface coverage. In addition, we introduce CsBr in dimethylammonium lead triiodide (DMAPbI3)/CsI precursors to slow down the crystal growth process. CsBr does not increase the film band gap but leads to a pinhole-free film with better crystallinity. Through nucleation and crystal growth engineering, the power conversion efficiency of inorganic perovskite devices is improved to 17.67%, and ambient environment stability is significantly enhanced.

Global modeling of lake-water indirect photochemistry based on the equivalent monochromatic wavelength approximation: The case of the triplet states of chromophoric dissolved organic matter.

Chromophoric dissolved organic matter (CDOM) plays key role as photosensitizer in sunlit surface-water environments, and it is deeply involved in the photodegradation of contaminants. It has recently been shown that sunlight absorption by CDOM can be conveniently approximated based on its monochromatic absorption at 560nm. Here we show that such an approximation allows for the assessment of CDOM photoreactions on a wide global scale and, particularly, in the latitude belt between 60°S and 60°N. Global lake databases are currently incomplete as far as water chemistry is concerned, but estimates of the content of organic matter are available. With such data it is possible to assess global steady-state concentrations of CDOM triplet states (3CDOM*), which are predicted to reach particularly high values at Nordic latitudes during summer, due to a combination of high sunlight irradiance and elevated content of organic matter. For the first time to our knowledge, we are able to model an indirect photochemistry process in inland waters around the globe. Implications are discussed for the phototransformation of a contaminant that is mainly degraded by reaction with 3CDOM* (clofibric acid, lipid regulator metabolite), and for the formation of known products on a wide geographic scale.