Defect Engineering Simultaneously Regulating Exciton Dissociation in Carbon Nitride and Local Electron Density in Pt Single Atoms Toward Highly Efficient Photocatalytic Hydrogen Production.

The high exciton binding energy (Eb) and sluggish surface reaction kinetics have severely limited the photocatalytic hydrogen production activity of carbon nitride (CN). Herein, a hybrid system consisting of nitrogen defects and Pt single atoms is constructed through a facile self-assembly and photodeposition strategy. Due to the acceleration of exciton dissociation and regulation of local electron density of Pt single atoms along with the introduction of nitrogen defects, the optimized Pt-MCT-3 exhibits a hydrogen production rate of 172.0 µmol h-1 (λ ≥ 420 nm), ≈41 times higher than pristine CN. The apparent quantum yield for the hydrogen production is determined to be 27.1% at 420 nm. The experimental characterizations and theoretical calculations demonstrate that the nitrogen defects act as the electron traps for the exciton dissociation, resulting in a decrease of Eb from 86.92 to 43.20 meV. Simultaneously, the stronger interaction between neighboring nitrogen defects and Pt single atoms directionally drives free electrons to aggregate around Pt single atoms, and tailors the d-band electrons of Pt, forming a moderate binding strength between Pt atoms and H* intermediates.

Accelerating the Design of High-Energy-Density Hydrocarbon Fuels by Learning from the Data.

In the ZINC20 database, with the aid of maximum substructure searches, common substructures were obtained from molecules with high-strain-energy and combustion heat values, and further provided domain knowledge on how to design high-energy-density hydrocarbon (HEDH) fuels. Notably, quadricyclane and syntin could be topologically assembled through these substructures, and the corresponding assembled schemes guided the design of 20 fuel molecules (ZD-1 to ZD-20). The fuel properties of the molecules were evaluated by using group-contribution methods and density functional theory (DFT) calculations, where ZD-6 stood out due to the high volumetric net heat of combustion, high specific impulse, low melting point, and acceptable flash point. Based on the neural network model for evaluating the synthetic complexity (SCScore), the estimated value of ZD-6 was close to that of syntin, indicating that the synthetic complexity of ZD-6 was comparable to that of syntin. This work not only provides ZD-6 as a potential HEDH fuel, but also illustrates the superiority of learning design strategies from the data in increasing the understanding of structure and performance relationships and accelerating the development of novel HEDH fuels.

Photoelectrochemical oxygen evolution with interdigitated array electrodes: the example of TiO2.

The catalytic reactions of photoelectrochemical water splitting attracts tremendous attention as a promising strategy for clean energy production. And the research on reaction mechanism is particularly important in design and developing new catalysts. In this work, the special electrochemical tool of interdigitated array (IDA) electrodes was utilized in investigating the photoelectrochemical oxygen evolution reaction process and detecting the reaction productin situwith the generation-collection mode. TiO2was taken as a model catalyst and was decorated onto the IDA generator electrode through an electrophoresis method, so that the photoelectrochemical water splitting can take place on the IDA generator and the reaction product can be detected directly with the IDA collector in real time. It is found that TiO2can be successfully decorated onto the surface of IDA electrode with the expected photoelectrochemical activity, and the generation-collection mode reveals and distinguishes the production of O2from the overall photoelectrochemical current on TiO2generator. The mass transfer process of O2from the TiO2generator to the collector could be observed as well. Large overall current at high potential range indicates the possible increasing production of the byproducts or nonfaradaic current.

WO3/g-C3N4 composites: one-pot preparation and enhanced photocatalytic H2 production under visible-light irradiation.

A series of WO3/g-C3N4 composites with different WO3 contents were prepared via a facile one-pot pyrolysis method, and showed notably enhanced visible-light-driven photocatalytic H2-evolution activities, with the highest rate of 400 µmol h-1 gcat-1 that was 15.0 times of that for pristine g-C3N4. Contents and sizes of WO3 crystallites in the composites were easily adjusted by changing the molar ratios of (NH4)2WS4 to C3H6N6 in the feed reagents, thereby successfully optimizing the Z-scheme system constructed by WO3 and g-C3N4 and thus effectively reducing the recombination of photogenerated charge carriers in g-C3N4. Moreover, pore volumes and surface areas of the composites were gradually enlarged by introducing WO3 into g-C3N4 via the one-pot preparation strategy, therefore promoting the redox reactions to evolve H2. This work presented an effective route to simultaneously optimize the phase compositions and textural structures of photocatalysts for enhanced H2 evolution.

Specific interactions of leucine with disaccharides by electrospray ionization mass spectrometry: application to rapid differentiation of disaccharide isomers in combination with statistical analysis.

The identification of carbohydrate isomers, including mono units, linkage positions and anomeric configurations, remains an arduous subject. In this study, the natural amino acid leucine (Leu) was found to specifically interact with cellobiose (Cello) to form a series of potassium adducts as [Cello + Leu + K](+), [Cello + 2Leu + K](+), and [2Cello + Leu + K](+) in the gas phase using mass spectrometry. By using CID-MS/MS, these complexes produced specific fragmentation patterns from the sugar backbone cleavage instead of non-covalent interactions. Moreover, their fragment distributions were dependent on the ratios of Cello-to-Leu in the complexes and the fragmentation pathways of potassium-cationized disaccharides (Dis) were remarkably changed with leucine binding. It should be pointed out that the ternary complex [2Cello + AA + K](+) was unique for leucine among all the twenty natural amino acids. The [2Dis + Leu + K](+) complex produced the most informative fragments by tandem mass spectrometry, which was successfully applied for rapid and efficient discrimination of twelve glucose-containing disaccharide isomers in combination with statistical analyses including PCA and OPLS-DA. The methodology developed here not only provides a novel analytical approach for the differentiation of disaccharide isomers, but also brings new sight towards the interactions of amino acids with disaccharides.

A cocatalyst-free Eosin Y-sensitized p-type of Co3O4 quantum dot for highly efficient and stable visible-light-driven water reduction and hydrogen production.

Owing to the effect of energy band bending, p-type Co3O4 quantum dots sensitized by Eosin Y showed a high and stable photocatalytic activity (∼13,440 µmol h(-1) g(-1)(cat)) for water reduction and hydrogen production under visible-light irradiation without any cocatalyst.

A first-principles investigation on microscopic atom distribution and configuration-averaged properties in Cd(1-x)Zn(x)S solid solutions.

The structural, energetic, and electronic properties of zincblende and wurtzite phase Cd(1-x)Zn(x)S (0≤x≤1) solid solutions were investigated by first-principles calculations. It was revealed that the trend of atom distribution in configurations with the same x value can be quantitatively characterized by the average length of the Zn-S bonds. The origin of this trend was attributed to the strong interaction of the Zn-S bonds, which acted against the aggregation of Zn atoms in this solid solution. By using a configuration-averaged method, structural and energetic properties were estimated as a function of Zn content at the level of the generalized gradient approximation, whereas electronic properties were corrected by using a hybrid functional. Phase diagrams of both solid solutions were established. An optimal x value of approximately 0.5 for photocatalytic hydrogen production was determined by taking both the band edges and band gaps into consideration; this conclusion was supported by the results of a variety of experiments.

Supercritical CH3OH-Triggered Isotype Heterojunction and Groups in g-C3N4 for Enhanced Photocatalytic H2 Evolution.

The structure tuning of bulk graphitic carbon nitride (g-C3N4) is a critical way to promote the charge carriers dynamics for enhancing photocatalytic H2-evolution activity. Exploring feasible post-treatment strategies can lead to effective structure tuning, but it still remains a great challenge. Herein, a supercritical CH3OH (ScMeOH) post-treatment strategy (250-300 °C, 8.1-11.8 MPa) is developed for the structure tuning of bulk g-C3N4. This strategy presented advantages of time-saving (less than 10 min), high yield (over 80%), and scalability due to the enhanced mass transfer and high reactivity of ScMeOH. During the ScMeOH post-treatment process, CH3OH molecules diffused into the interlayers of g-C3N4 and subsequently participated in N-methylation and hydroxylation reactions with the intralayers, resulting in a partial phase transformation from g-C3N4 into carbon nitride with a poly(heptazine imide)-like structure (Q-PHI) as well as abundant methyl and hydroxyl groups. The modified g-C3N4 showed enhanced photocatalytic activity with an H2-evolution rate 7.2 times that of pristine g-C3N4, which was attributed to the synergistic effects of the g-C3N4/Q-PHI isotype heterojunction construction, group modulation, and surface area increase. This work presents a post-treatment strategy for structure tuning of bulk g-C3N4 and serves as a case for the application of supercritical fluid technology in photocatalyst synthesis.

A new rainfall prediction model based on ICEEMDAN-WSD-BiLSTM and ESN.

Precipitation, as an important indicator describing the evolution of the regional climate system, plays an important role in understanding the spatial and temporal distribution characteristics of regional precipitation. Scientific and accurate prediction of regional precipitation is helpful to provide theoretical basis for relevant departments to guide flood and drought control. To address the uncertainty and nonlinear characteristics of precipitation series, this paper uses the established improved complete ensemble empirical mode decomposition with adaptive noise (ICEEMDAN)-wavelet signal denoising (WSD)-bi-directional long short-term memory (BiLSTM), and echo state network (ESN) models to predict precipitation of four cities in southern Anhui Province. The BiLSTM is used to predict the high-frequency components and the ESN to predict the low-frequency components, thus avoiding the influence between the two neural network predictions. The results show that the ICEEMDAN-WSD-BiLSTM and ESN models are more accurate. The average relative error reached 2.64% and the NSE (Nash-Sutcliffe efficiency coefficient) was 0.91, which was significantly better than the other four models. The model reveals the temporal change pattern and evolution characteristics of future precipitation, guides flood prevention and mitigation, and has certain theoretical significance and application value for promoting regional sustainable development.

Base- or acid-assisted polystyrene plastic degradation in supercritical CO2.

Plastic has caused serious "white pollution" to the environment, and the highly inert characteristics of plastic bring a major challenge for degradation. Supercritical fluids have unique physical properties and have been widely used in various fields. In this work, supercritical CO2 (Sc-CO2) with mild conditions was selected and assisted by NaOH/HCl solution to degrade polystyrene (PS) plastic, and the reaction model was designed using response surface methodology (RSM). It was found that, regardless of the types of assistance solutions, the factors affecting PS degradation efficiencies were reaction temperature, reaction time, and NaOH/HCl concentration. At the temperature of 400 °C, time of 120 min, and base/acid concentration of 5% (in weight), 0.15 g PS produced 126.88/116.99±5 mL of gases with 74.18/62.78±5 mL of H2, and consumed 81.2/71.5±5 mL of CO2. Sc-CO2 created a homogeneous environment, which made PS highly dispersed and uniformly heated, thus promoting the degradation of PS. Moreover, Sc-CO2 also reacted with the degradation products to produce new CO and more CH4 and C2Hx (x=4, 6). Adding NaOH/HCl solution not only improved the solubility of PS in Sc-CO2, but also provided a base/acid environment that reduced the activation energy of the reaction, and effectively improved the degradation efficiencies of PS. In short, degrading PS in Sc-CO2 is feasible, and better results are obtained with the assistance of base/acid solution, which can provide a reference for the disposal of waste plastics in the future. Supplementary Information: The online version contains supplementary material available at 10.1007/s42768-023-00139-1.

Rational design of covalent heptazine framework photocatalysts with high oxidation ability through reaction-dependent strategy.

Due to structural tunability, high surface area, abundant pore structures, and abundant active sites, covalent heptazine frameworks (CHFs) constructed from heptazine and other molecular blocks are especially prominent. Here, we proposed a reaction-dependent strategy for designing two dimensional CHFs including high-throughput precursors screening, structure generation, and performance evaluation. Assuming that oxamide-like precursors can undergo the same thermal polymerization reaction as producing C6N7, seven precursors were screened from more than 109 molecules in the ZINC20 database in terms of molecular weight, number of substructures, shape index, and symmetry. Furthermore, CHF-L1 to CHF-L7 were constructed from urea and the seven precursors according to the topologically assembling scheme in thermal polymerization. The designed CHFs had band gaps ranging from 1.89 to 3.10 eV. Among them, CHF-L3 assembled structurally by urea and 1,2,4,5-tetrazine-3,6-dicarboxamide with the smallest bandgap and an oxidative potential bias of 1.38 V for oxygen evolution reaction was screened as the candidate with high oxidative ability. The negative formation energy based on the synthesis route indicated the synthetic feasibility of CHF-L3, and negative cohesive energy as well as the stable structure under ab initio molecular dynamics simulations confirmed the stability of CHF-L3. The present work is expected to provide a powerful design strategy for two-dimensional CHFs design and is broadly applicable to various computational covalent organic framework design systems and experimental studies.

Construction of a transition-metal sulfide heterojunction photocatalyst driven by a built-in electric field for efficient hydrogen evolution under visible light.

Photocatalytic H2 evolution is of prime importance in the energy crisis and in lessening environmental pollution. Adopting a single semiconductor as a photocatalyst remains a formidable challenge. However, the construction of an S-scheme heterojunction is a promising method for efficient water splitting. In this work, CdS nanoparticles were loaded onto NiS nanosheets to form CdS/NiS nanocomposites using hollow Ni(OH)2 as a precursor. The differences in the Fermi energy levels between the two components of CdS and NiS resulted in the formation of a built-in electric field in the nanocomposite. Density functional theory (DFT) calculations reveal that the S-scheme charge transfer driven by the built-in electric field can accelerate the effective separation of photogenerated carriers, which is conducive to efficient photocatalytic hydrogen evolution. The hydrogen evolution rate of the optimized photocatalyst is 39.68 mmol·g-1 h-1, which is 6.69 times that of CdS under visible light. This work provides a novel strategy to construct effective photocatalysts to relieve the environmental and energy crisis.

Ultrathin porous graphitic carbon nitride from recrystallized precursor toward significantly enhanced photocatalytic water splitting.

Structure regulation (including electronic structure and morphology) for graphitic carbon nitride (g-C3N4) is an effective way to promote the photocatalytic activity. Herein, an ultrathin porous g-C3N4 (BCN-HT100) was synthesized by calcination of biuret hydrate. Hydrothermal treatment induced biuret recrystallization to form biuret hydrate precursor with regular morphology and large crystal size, thus promoting the polymerization of melem to form g-C3N4 network. Accordingly, BCN-HT100 possessed ultrathin nanosheet structure, higher polymerization degree, larger surface area and more pores than biuret-derived g-C3N4. BCN-HT100 behaved high-efficiency photocatalytic H2-productin activity with an apparent quantum yield (AQY) of 58.7% at 405 nm due to the enhanced utilization efficiency for photo-generated charge carriers and abundant reactive sites. Furthermore, Pt-NiCo2O4 dual cocatalysts were employed on BCN-HT100 for achieving photocatalytic overall water splitting, and the AQY reached 4.9% at 405 nm. This work provides a meaningful reference to designing g-C3N4 to achieve efficient solar energy conversion into hydrogen.

Visible light-driven photocatalysis of doped SrTiO3 tubular structure.

SrTiO3 tubular structures co-doped with Cr and Ta were synthesized through a combination of solvothermal-hydrothermal processes. X-ray photoelectron spectroscopy (XPS) measurements of the oxidation state of Cr ions reveal that the formation of Cr6+ ions, which would serve as the non-radiative recombination centers for photogenerated electrons and holes, was suppressed without the process of high temperature hydrogen reduction. Compared to similar co-doped materials synthesized by solid-state reaction, (Cr, Ta) co-doped SrTiO3 tubular structures have significantly higher photocatalytic activity for hydrogen evolution as measured in an aqueous methanol solution under visible light irradiation.

Site-selected doping of upconversion luminescent Er3+ into SrTiO3 for visible-light-driven photocatalytic H2 or O2 evolution.

A series of upconversion luminescent erbium-doped SrTiO(3) (ABO(3)-type) photocatalysts with different initial molar ratios of Sr/Ti have been prepared by a facile polymerized complex method. Er(3+) ions, which were gradually transferred from the A to the B site with increasing Sr/Ti, enabled the absorption of visible light and the generation of high-energy excited states populated by upconversion processes. The local internal fields arising from the dipole moments of the distorted BO(6) octahedra promoted energy transfer from the high-energy excited states of Er(3+) with B-site occupancy to the host SrTiO(3) and thus enhanced the band-to-band transition of the host SrTiO(3). Consequently, the erbium-doped SrTiO(3) species with B-site occupancy showed higher photocatalytic activity than those with A-site occupancy for visible-light-driven H(2) or O(2) evolution in the presence of the corresponding sacrificial reagents. The results generally suggest that the introduction of upconversion luminescent agents into host semiconductors is a promising approach to simultaneously harnessing low-energy photons and maintaining redox ability for photocatalytic H(2) and O(2) evolution and that the site occupancy of doped elements in ABO(3)-type perovskite oxides greatly determines the photocatalytic activity.

Significantly enhanced photothermal catalytic hydrogen evolution over Cu2O-rGO/TiO2 composite with full spectrum solar light.

Reduced graphene oxide (rGO) has conspicuous photothermal characteristics in photothermal applications. Thus in our previous work, we used reduced graphene oxide (rGO) supported titanium dioxide (TiO2) nanocomposite (rGO/TiO2) to absorb the ultraviolet and infrared light in the photothermal hydrogen evolution process. In order to make use of the full spectrum solar energy into other clear energy, the visible light should be also considered in following research. Herein, we report a cuprous oxide (Cu2O) decorated reduced graphene oxide (rGO) supported titanium dioxide (TiO2) (Cu2O-rGO/TiO2) catalysts, which can absorb full spectrum solar light in an innovative way. The Cu2O-rGO/TiO2 catalyst is synthesized through a one-step hydrothermal method. The rates of hydrogen evolution are 17800 µmol·g-1h-1 under photothermal condition (90°C), 3800 µmol·g-1h-1 under photocatalysis condition only (25°C) and 0 µmol·g-1h-1 under thermal catalysis condition only. The result of photothermal catalytic hydrogen evolution rate is about 4.7 times that of the sum of the photocatalytic and thermal reactions. The photothermal synergetic effect promotes the photo-generated electron-holes separation through the rGO due to the temperature rising, and accelerates the reaction rates on the catalyst surface in hydrogen evolution process simultaneously. This work could provide us a new promising way for the conversion of full spectrum solar energy to hydrogen energy.

Photocatalytic overall water splitting without noble-metal: Decorating CoP on Al-doped SrTiO3.

CoP, a noble-metal-free cocatalyst, was first introduced onto the surface of Al-doped SrTiO3 (Al:STO) via an in situ photodeposition-phosphorization method for photocatalytic overall water splitting (POWS) into stoichiometric H2 and O2. Compared with pure Al:STO, the POWS activity was enhanced by a factor of ~ 421 over 1.0%CoP/Al:STO, with the highest evolution rates of 2106 and 1002 µmol h-1 g-1 for H2 and O2, respectively. The mechanism for the remarkably boosted POWS activity was systematically analyzed based on the comprehensive characterization. On the one hand, benefiting from the in situ photodeposition process, CoP with metallic character were intimately decorated onto the surface of Al:STO and accelerated the separation and migration of photoinduced charge carriers. On the other hand, CoP, serving as reactive sites for H2 evolution reaction, lowered the overpotential and facilitated the surface reduction reaction, thereby enhancing the POWS activity. Furthermore, Cr2O3 was photodeposited on the surface of 1.0%CoP/Al:STO composite to suppress the undesired reverse reaction and the POWS activity was further enhanced up to 3558 and 1722 µmol h-1 g-1 for H2 and O2, respectively, with apparent quantum yield of 7.1% at 350 ± 10 nm. This work presents a new avenue for designing POWS system without noble-metal cocatalyst.

Ultrafast Electron Transfer in InP/ZnSe/ZnS Quantum Dots for Photocatalytic Hydrogen Evolution.

InP/ZnS core/shell quantum dots have shown extraordinary application potential in photocatalysis. In this work, we demonstrated by ultrafast spectroscopy that the electron transfer ability of InP/ZnSe/ZnS core/shell/shell quantum dots was better than that of InP/ZnS quantum dots, because the introduction of ZnSe midshell resulted in improved passivation and greater exciton delocalization. The temperature-dependent PL spectra indicate that the exciton-phonon coupling strength and exciton binding energy of InP/ZnSe/ZnS quantum dots are smaller than those of InP/ZnS quantum dots. Further photocatalytic hydrogen evolution testing revealed that the photocatalytic activity of InP/ZnSe/ZnS quantum dots was significantly higher than that of InP/ZnS quantum dots, and InP/ZnSe/ZnS quantum dots even demonstrated improved stability. This research deepened our understanding of carrier dynamics and charge separation of InP/ZnSe/ZnS quantum dots, especially highlighting the application potential of InP/ZnSe/ZnS quantum dots in photocatalytic hydrogen evolution.

EDTA-dominated hollow tube-like porous graphitic carbon nitride towards enhanced photocatalytic hydrogen evolution.

Graphite carbon nitride (g-C3N4) as metal-free photocatalyst has been widely studied recently in photocatalytic water reduction, which is considered as one of the promising routes to realizing the hydrogen energy-based society in the future. The generally used preparation process based on thermal polymerization of precursors easily brought the formation of aggregated nanosheets morphology, severely limiting its photocatalytic activity. Herein, the hollow tube-like morphology with porous surface was elaborately obtained by ethylene diamine tetraacetic acid (EDTA)-involved hydrothermal treatment of melamine precursor. The hollow and porous features shortened the migration distance of photo-generated carriers, trapped the incident lights, and provided more photocatalytic reactive sites, then realizing the enhanced photocatalytic H2-evolution activity up to 7.1 times that of pristine g-C3N4. The presence of EDTA acted as the pivotal role to control the recrystallization process of melamine and its derivative, cyanuric acid, and thus to determine the framework formation of the hollow tube-like microstructure. Moreover, complete thermal decomposition of cyanuric acid during the thermal polymerization of precursors was responsible for the hollow and porous features. This work extends the morphology regulation cognition of g-C3N4 based on hydrothermal treatment of precursors, and is expected to bring deep understanding and feasible strategies to design morphology-dominated highly-efficient g-C3N4 photocatalysts.

A urinary proteomic landscape of COVID-19 progression identifies signaling pathways and therapeutic options.

Signaling pathway alterations in COVID-19 of living humans as well as therapeutic targets of the host proteins are not clear. We analyzed 317 urine proteomes, including 86 COVID-19, 55 pneumonia and 176 healthy controls, and identified specific RNA virus detector protein DDX58/RIG-I only in COVID-19 samples. Comparison of the COVID-19 urinary proteomes with controls revealed major pathway alterations in immunity, metabolism and protein localization. Biomarkers that may stratify severe symptoms from moderate ones suggested that macrophage induced inflammation and thrombolysis may play a critical role in worsening the disease. Hyper activation of the TCA cycle is evident and a macrophage enriched enzyme CLYBL is up regulated in COVID-19 patients. As CLYBL converts the immune modulatory TCA cycle metabolite itaconate through the citramalyl-CoA intermediate to acetyl-CoA, an increase in CLYBL may lead to the depletion of itaconate, limiting its anti-inflammatory function. These observations suggest that supplementation of itaconate and inhibition of CLYBL are possible therapeutic options for treating COVID-19, opening an avenue of modulating host defense as a means of combating SARS-CoV-2 viruses.