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The self-doping of oxygen vacancy and Ti.sup.3+ by electrochemical reduction (ER) method has been proved to be an effective means to improve the PEC performance of TiO.sub.2. However, the effect of the surface structure on ER treatment remains ambiguous. In this work, three kinds of nanostructured rutile TiO.sub.2 (nanowire arrays (TNWs), etched nanowire arrays (E-TNWs) and nanorod arrays (TNRs)) were reduced electrochemically to explore the factors influencing the ER process of rutile TiO.sub.2. The experimental results show that alkaline environment (1 M NaOH) is more conducive to the occurrence of ER reaction. And the reduced three kinds of nanostructured TiO.sub.2 photoanodes show a significantly higher photocurrent density of about 1.46, 1.65 and 1.45 mA cm.sup.-2 at 1.23 V vs. relative hydrogen electrode (RHE), respectively, which are 15, 16 and 1.1 times that of pristine TiO.sub.2. The different degrees of photocurrent density enhancement can be ascribed to the different degrees of electrochemical reduction of TiO.sub.2 with different crystallinity and exposed crystal facets as well as specific surface area. This study provides new insights into the mechanism of electrochemical reduction method.

In this work, two series of Au(III) and Pt(II) alkynylphosphonium complexes of composition [M(CNC)(C[sub.2]−L−P(CH[sub.3])Ph[sub.2])][sup.n+] Pt1–Pt3 (n = 0) and Au1–Au3 (n = 1), (CNC = 2,6-diphenylpyridine; L = phenyl, biphenyl, naphthyl) were synthesized and characterized to discover the similarities and differences in photophysical properties between isoelectronic metallocentres. It is shown that Au(III) and Pt(II) complexes obtained demonstrate different photophysical properties despite isoelectronic metal centres, and some reasons for that are discussed based on experimental data and quantum-chemical calculation results. Complex Pt1 also demonstrated the first example of room-temperature solution phosphorescence in the family of [Pt(CNC)(alkynyl)] complexes. It has been found that the crystal packing of Pt1 contains a Pt–H interaction, qualified by quantum-chemical calculations as a unique hydrogen bond.

Cu.sub.2O has been successfully synthesized in different morphologies/sizes (nanoparticles and octahedrons) via a low-temperature chemical reduction method. Trapping metal ions in an ice cube and letting them slowly melt in a reducing agent solution is the simplest way to control the nanostructure. Enhancement of charge transfer and transportation of ions by Cu.sub.2O nanoparticles was shown by cyclic voltammetry and electrochemical impedance spectroscopy measurements. In addition, nanoparticles exhibited higher current densities, the lowest onset potential, and the Tafel slope than others. The Cu.sub.2O electrocatalyst (nanoparticles) demonstrated the Faraday efficiencies (FEs) of CO, CH.sub.4, and C.sub.2H.sub.6 up to 11.90, 76.61, and 1.87%, respectively, at -0.30 V versus reference hydrogen electrode, which was relatively higher FEs than other morphologies/sizes. It is mainly attributed to nano-sized, more active sites and oxygen vacancy. In addition, it demonstrated stability over 11 h without any decay of current density. The mechanism related to morphology tuning and electrochemical CO.sub.2 reduction reaction was explained. This work provides a possible way to fabricate the different morphologies/sizes of Cu.sub.2O at low-temperature chemical reduction methods for obtaining the CO, CH.sub.4, and C.sub.2H.sub.6 products from CO.sub.2

This study is based on the strategies of composite and element doping. Herein, P-MoS[sub.2]/rGO materials were synthesized using a solvent-assisted hydrothermal method. The MoS[sub.2] nanosheets were uniformly and vertically grown on rGO; meanwhile, the optimized structure of MoS[sub.2] was achieved by P doping, resulting in improved catalytic performance and structural stability. Under alkaline conditions, the P-MoS[sub.2]/rGO catalyst exhibits good electrocatalytic activity, demonstrating a Tafel slope of 70.7 mV dec[sup.−1] and an overpotential of 172.8 mV at 10 mA/cm[sup.2]. Notably, even after 3000 consecutive LSV tests, the curves still show a high degree of overlap, indicating exceptional stability.

Harnessing solar energy to produce hydrogen through semiconductor-mediated photocatalytic water splitting is a promising avenue to address the challenges of energy scarcity and environmental degradation. Ever since Fujishima and Honda’s groundbreaking work in photocatalytic water splitting, titanium dioxide (TiO[sub.2]) has garnered significant interest as a semiconductor photocatalyst, prized for its non-toxicity, affordability, superior photocatalytic activity, and robust chemical stability. Nonetheless, the efficacy of solar energy conversion is hampered by TiO[sub.2]’s wide bandgap and the swift recombination of photogenerated carriers. In pursuit of enhancing TiO[sub.2]’s photocatalytic prowess, a panoply of modification techniques has been explored over recent years. This work provides an extensive review of the strategies employed to augment TiO[sub.2]’s performance in photocatalytic hydrogen production, with a special emphasis on foreign dopant incorporation. Firstly, we delve into metal doping as a key tactic to boost TiO[sub.2]’s capacity for efficient hydrogen generation via water splitting. We elaborate on the premise that metal doping introduces discrete energy states within TiO[sub.2]’s bandgap, thereby elevating its visible light photocatalytic activity. Following that, we evaluate the role of metal nanoparticles in modifying TiO[sub.2], hailed as one of the most effective strategies. Metal nanoparticles, serving as both photosensitizers and co-catalysts, display a pronounced affinity for visible light absorption and enhance the segregation and conveyance of photogenerated charge carriers, leading to remarkable photocatalytic outcomes. Furthermore, we consolidate perspectives on the nonmetal doping of TiO[sub.2], which tailors the material to harness visible light more efficiently and bolsters the separation and transfer of photogenerated carriers. The incorporation of various anions is summarized for their potential to propel TiO[sub.2]’s photocatalytic capabilities. This review aspires to compile contemporary insights on ion-doped TiO[sub.2], propelling the efficacy of photocatalytic hydrogen evolution and anticipating forthcoming advancements. Our work aims to furnish an informative scaffold for crafting advanced TiO[sub.2]-based photocatalysts tailored for water-splitting applications.

The introduction of hydrogen in the yttrium aluminum garnet, Y [Formula omitted]Al [Formula omitted]O [Formula omitted] (YAG), has been known to affect the optical and luminescence properties of this material. This makes it imperative to examine the nature of hydrogen impurities in YAG and also to understand how hydrogen interacts with native defects. Recent studies based on positron-annihilation lifetime spectroscopy (PALS) provided strong evidence on the presence of hydrogen inside the YAG lattice that eventually led to strong reduction of the positron lifetimes attributed to cation-vacancy defects. The present study reports first-principles calculations that determine the character of isolated hydrogen states in the YAG solid as well as the interaction and binding of hydrogen to the aluminum monovacancies. A hybrid functional approach that incorporates exact electron-exchange interactions is employed to determine the defect association of aluminum vacancies with hydrogen and the charge-transition levels of the resulting vacancy-hydrogen complexes. The effects of hydrogen towards passivation were studied by means of two-component density-functional theory where the positron trapping and corresponding lifetimes of the vacancy defects were calculated as a function of the number hydrogen atoms bound to each vacancy. The final results are also discussed in connection with the experimental PALS data.

Hydrogen energy from solar water-splitting is known as an ideal method with which to address the energy crisis and global environmental pollution. Herein, the first-principles calculations are carried out to study the photocatalytic water-splitting performance of single-layer GaInSe[sub.3] under biaxial strains from −2% to +2%. Calculations reveal that single-layer GaInSe[sub.3] under various biaxial strains has electronic bandgaps ranging from 1.11 to 1.28 eV under biaxial strain from −2% to +2%, as well as a completely separated valence band maximum and conduction band minimum. Meanwhile, the appropriate band edges for water-splitting and visible optical absorption up to ~3 × 10[sup.5] cm[sup.−1] are obtained under biaxial strains from −2% to 0%. More impressively, the solar conversion efficiency of single-layer GaInSe[sub.3] under biaxial strains from −2% to 0% reaches over 30%. The OER of unstrained single-layer GaInSe[sub.3] can proceed without co-catalysts. These demonstrate that single-layer GaInSe[sub.3] is a viable material for solar water-splitting.

A novel and efficient technique has been designed for the creation of oxygen vacancies on La[sub.2]Ti[sub.2]O[sub.7] (LTO) nanosheets. This is achieved via a controlled solid-state reaction between NaBH[sub.4] and LTO nanosheets. Transmission electron microscopy (TEM) analyses expose that these processed LTO specimens possess a unique crystalline core/amorphous shell structure, represented as La[sub.2]Ti[sub.2]O[sub.7]@La[sub.2]Ti[sub.2]O[sub.7-x]. According to X-ray photoelectron spectroscopy (XPS) observations, there is a notable correlation between the reaction time, temperature, and the concentration of oxygen vacancies. The concentration of these vacancies tends to increase along with the reaction time and temperature. Concurrently, UV-Visible spectra and photocatalytic tests reveal a significant impact of oxygen vacancies on the LTO surface on both light absorption and photocatalytic functionality. Most notably, the LTO nanosheets with engineered oxygen vacancies have demonstrated an exceptional photocatalytic capacity for hydrogen production under visible light. The maximal activity recorded was an impressive 149 μmol g[sup.−1] h[sup.−1], which is noticeably superior to the performance of the pristine La[sub.2]Ti[sub.2]O[sub.7].

Cucumber is a warm climate vegetable that is sensitive to chilling reactions. Chilling can occur at any period of cucumber growth and development and seriously affects the yield and quality of cucumber. Hydrogen (H[sub.2]) is a type of antioxidant that plays a critical role in plant development and the response to stress. Hydrogen-rich water (HRW) is the main way to use exogenous hydrogen. This study explored the role and mechanism of HRW in the cucumber defense response to chilling stress. The research results showed that applying 50% saturated HRW to the roots of cucumber seedlings relieved the damage caused by chilling stress. The growth and development indicators, such as plant height, stem diameter, leaf area, dry weight, fresh weight, and root length, increased under the HRW treatment. Photosynthetic efficiency, chlorophyll content, and Fv/Fm also improved and reduced energy dissipation. In addition, after HRW treatment, the REC and MDA content were decreased, and membrane lipid damage was reduced. NBT and DAB staining results showed that the color was lighter, and the area was smaller under HRW treatment. Additionally, the contents of O[sub.2] [sup.−] and H[sub.2]O[sub.2] also decreased. Under chilling stress, the application of HRW increased the activity of the antioxidases SOD, CAT, POD, GR, and APX and improved the expression of the SOD, CAT, POD, GR, and APX antioxidase genes. The GSSG content was reduced, and the GSH content was increased. In addition, the ASA content also increased. Therefore, exogenous HRW is an effective measure for cucumber to respond to chilling stress.