Defect and Donor Manipulated Highly Efficient Electron-Hole Separation in a 3D Nanoporous Schottky Heterojunction.

Given the rapid recombination of photogenerated charge carriers and photocorrosion, transition metal sulfide photocatalysts usually suffer from modest photocatalytic performance. Herein, S-vacancy-rich ZnIn2S4 (VS-ZIS) nanosheets are integrated on 3D bicontinuous nitrogen-doped nanoporous graphene (N-npG), forming 3D heterostructures with well-fitted geometric configuration (VS-ZIS/N-npG) for highly efficient photocatalytic hydrogen production. The VS-ZIS/N-npG presents ultrafast interfacial photogenerated electrons captured by the S vacancies in VS-ZIS and holes neutralization behaviors by the extra free electrons in N-npG during photocatalysis, which are demonstrated by in situ XPS, femtosecond transient absorption (fs-TA) spectroscopy, and transient-state surface photovoltage (TS-SPV) spectra. The simulated interfacial charge rearrangement behaviors from DFT calculations also verify the separation tendency of photogenerated charge carriers. Thus, the optimized VS-ZIS/N-npG 3D hierarchical heterojunction with 1.0 wt % N-npG exhibits a comparably high hydrogen generation rate of 4222.4 µmol g-1 h-1, which is 5.6-fold higher than the bare VS-ZIS and 12.7-fold higher than the ZIS without S vacancies. This work sheds light on the rational design of photogenerated carrier transfer paths to facilitate charge separation and provides further hints for the design of hierarchical heterostructure photocatalysts.

Visible-light-driven AgI/Bi4O5I2 S-scheme heterojunction for efficient tetracycline hydrochloride removal: Mechanism and degradation pathway.

The existence of excessive tetracycline hydrochloride (TCH) in the ecological environment has seriously threatened human health, so there is an urgent need to develop a high-performance photocatalyst that can efficiently and greenly remove TCH. Currently, most photocatalysts have the problems of fast recombination of photogenerated charge carriers and low degradation efficiency. Herein, S-scheme AgI/Bi4O5I2 (AB) heterojunctions was constructed for TCH removal. Compared with the single component, the apparent kinetic constant of the 0.7AB is 5.6 and 10.2 time as high as the AgI and Bi4O5I2, and the photocatalytic activity only decreases by 3.0% after four recycle runs. In addition, to verify the potential practical application of the fabricated AgI/Bi4O5I2 nanocomposite, the photocatalytic degradation of TCH was performed under different conditions by regulating the dosage of photocatalyst, the TCH concentration, pH, and the existence of various anions. Systematical characterizations are conducted to investigate the intrinsic physical and chemical properties of the constructed AgI/Bi4O5I2 composites. Based on the synergetic characterizations by in situ X-ray photoelectron spectroscopy, band edge measurements, as well as reactive oxygen species (ROS) detections, the S-scheme photocatalytic mechanism is proved. This work provides a valuable reference for developing efficient and stable S-scheme AgI/Bi4O5I2 photocatalyst for TCH removal.

Facile Synthesis of P-Doped ZnIn2S4 with Enhanced Visible-Light-Driven Photocatalytic Hydrogen Production.

ZnIn2S4 (ZIS) is widely used in the field of photocatalytic hydrogen production due to its unique photoelectric properties. Nonetheless, the photocatalytic performance of ZIS usually faces problems of poor conductivity and rapid recombination of charge carriers. Heteroatom doping is often regarded as one of the effective strategies for improving the catalytic activity of photocatalysts. Herein, phosphorus (P)-doped ZIS was prepared by hydrothermal method, whose photocatalytic hydrogen production performance and energy band structure were fully studied. The band gap of P-doped ZIS is about 2.51 eV, which is slightly smaller than that of pure ZIS. Moreover, due to the upward shift of its energy band, the reduction ability of P-doped ZIS is enhanced, and P-doped ZIS also exhibits stronger catalytic activity than pure ZIS. The optimized P-doped ZIS exhibits a hydrogen production rate of 1566.6 µmol g-1 h-1, which is 3.8 times that of the pristine ZIS (411.1 µmol g-1 h-1). This work provides a broad platform for the design and synthesis of phosphorus-doped sulfide-based photocatalysts for hydrogen evolution.

Highly efficient and recyclable Z-scheme heterojunction of Ag3PO4/g-C3N4 floating foam for photocatalytic inactivation of harmful algae under visible light.

Harmful algal blooms (HABs) have frequently occurred worldwide, causing marine ecosystems and human health risks. As an advanced and green oxidation technology, photocatalysis has potential to remove red tide algae using solar energy. Herein, in this work, Z-scheme photocatalysts of Ag3PO4/g-C3N4 (APCN) floating foam with different mass ratios were fabricated for the algae inactivation. Under visible light irradiation, the 0.10APCN (0.10 mM AgNO3) composite photocatalyst could cause 91.8% of the loss in Karenia mikimotoi (K. mikimotoi) cell viability following 24 h and the removal rate of algae could reach to 86% after five successive cycles. The underlying mechanism of photocatalytic inactivation of harmful algae is proposed in this system. The photosynthetic efficiency of harmful algae is inhibited with the decrease of photosynthetic pigments, which are inactivated by the high levels of reactive oxygen species (ROS) (superoxide radical •O2- and hydroxyl radical •OH) produced in Z-scheme photocatalytic system of the Ag3PO4/g-C3N4 heterojunction under visible light. Meanwhile, the activities of antioxidant enzymes (i.e. POD, APX and SOD) are up-regulating with the overproduction of ROS going into the algae, causing the cytotoxicity and apoptosis of algae. This work not only reveals the mechanisms of photocatalytic inactivation of harmful algae, but also guides the design the construction of high active composite photocatalysts, and thus provides theoretical and practical significance for highly efficient and recyclable prospect of controlling of harmful algae.

Efficient Charge Transfer and Effective Active Sites in Lead-Free Halide Double Perovskite S-Scheme Heterojunctions for Photocatalytic H2 Evolution.

The practical application of lead-free double perovskite Cs2 AgBiBr6 in photocatalytic H2 evolution is still restricted due to the low activity and poor stability. The rational design of lead-free halide double perovskites heterojunctions with efficient charge transfer and effective active sites is a potential route to achieve the ideal prospect. Herein, in this work an S-scheme heterojunction of Cs2 AgBiBr6 with enriched Br-vacancies and WO3 nanorods (VBr -Cs2 AgBiBr6 /WO3 ) obtaining excellent visible-light responsive photocatalytic H2 evolution performance and durable stability is reported. The S-scheme heterojunction driven by the unaligned Fermi levels of these two semiconductors ensures the efficient charge transfer at the interface, and density functional theory calculations reveal the enriched Br vacancies on Cs2 AgBiBr6 (022) surfaces introduced by atom thermal vibration provide effective active sites for hydrogen evolution. The optimized VBr -Cs2 AgBiBr6 /WO3 S-scheme photocatalyst exhibits the photocatalytic hydrogen evolution rate of 364.89 µmol g-1 h-1 which is 4.9-fold of bare VBr -Cs2 AgBiBr6 (74.44 µmol g-1 h-1 ) and presents long-term stability of 12 h continuous photocatalytic reaction. This work provides deep insights into the photocatalytic mechanism of VBr -Cs2 AgBiBr6 /WO3 S-scheme heterojunctions, which emerges a new strategy in the applications of perovskite-based photocatalysts.

Stochastic behaviors of an improved Gompertz tumor growth model with coupled two types noise.

In this work, an improved Gompertz tumor growth model has been introduced. The expressions of steady probability distributions (SPD) of stochastic Gompertz tumor growth models are studied by using the technique of Fokker-Planck equation (FPE), and their dynamic behaviors are also further investigated. Moreover, the expressions for mean, variance, skewness, as well as the mean first-passage time (MFPT) also have been derived. And the influence of noise intensity, correlation coefficient, and noise correlation time of SPD are further analyzed. It is worthy noting that the colored noise intensity has an important impact on SPD. Furthermore, adjusting birth and death parameters also significantly impact SPD, MFPT, mean, variance as well as skewness.

Construction of Electrostatic Self-Assembled 2D/2D CdIn2S4/g-C3N4 Heterojunctions for Efficient Visible-Light-Responsive Molecular Oxygen Activation.

Molecular oxygen activated by visible light to generate radicals with high oxidation ability exhibits great potential in environmental remediation The efficacy of molecular oxygen activation mainly depends on the separation and migration efficiency of the photoinduced charge carriers. In this work, 2D/2D CdIn2S4/g-C3N4 heterojunctions with different weight ratios were successfully fabricated by a simple electrostatic self-assembled route. The optimized sample with a weight ratio of 5:2 between CdIn2S4 and g-C3N4 showed the highest photocatalytic activity for tetracycline hydrochloride (TCH) degradation, which also displayed good photostability. The enhancement of the photocatalytic performance could be ascribed to the 2D/2D heterostructure; this unique 2D/2D structure could promote the separation and migration of the photoinduced charge carriers, which was beneficial for molecular oxygen activation, leading to an enhancement in photocatalytic activity. This work may possibly provide a scalable way for molecular oxygen activation in photocatalysis.