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 (TiOsub.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 TiOsub.2’s wide bandgap and the swift recombination of photogenerated carriers. In pursuit of enhancing TiOsub.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 TiOsub.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 TiOsub.2’s capacity for efficient hydrogen generation via water splitting. We elaborate on the premise that metal doping introduces discrete energy states within TiOsub.2’s bandgap, thereby elevating its visible light photocatalytic activity. Following that, we evaluate the role of metal nanoparticles in modifying TiOsub.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 TiOsub.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 TiOsub.2’s photocatalytic capabilities. This review aspires to compile contemporary insights on ion-doped TiOsub.2, propelling the efficacy of photocatalytic hydrogen evolution and anticipating forthcoming advancements. Our work aims to furnish an informative scaffold for crafting advanced TiOsub.2-based photocatalysts tailored for water-splitting applications.
The introduction of hydrogen in the yttrium aluminum garnet, Y Formula omittedAl Formula omittedO 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 GaInSesub.3 under biaxial strains from −2% to +2%. Calculations reveal that single-layer GaInSesub.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 × 10sup.5 cmsup.−1 are obtained under biaxial strains from −2% to 0%. More impressively, the solar conversion efficiency of single-layer GaInSesub.3 under biaxial strains from −2% to 0% reaches over 30%. The OER of unstrained single-layer GaInSesub.3 can proceed without co-catalysts. These demonstrate that single-layer GaInSesub.3 is a viable material for solar water-splitting.
Using first-principles calculations, this paper reports a systematic research on HER performance enhancing of LNS-TiO.sub.2 by passivated codoping. Six codoping systems, Ti.sub.17O.sub.35CrC, ...Ti.sub.17O.sub.35MoC, Ti.sub.17O.sub.35WC, Ti.sub.17O.sub.35VN, Ti.sub.17O.sub.35NbN and Ti.sub.17O.sub.35TaN are studied. Results show that the energy band can be tuned by the codoping donor-acceptor pairs. The energy band performance of Ti.sub.17O.sub.35WC should be the best in HER process for its tiny CBM change and small band gap. Besides, the hydrogen adsorption ability of LNS-TiO.sub.2 in HER process can also be tuned by the codoping pairs. The hydrogen adsorption performance of Ti.sub.17O.sub.35TaN should be the best for its âG.sub.H* is close to zero. In a word, Ti.sub.17O.sub.35WC and Ti.sub.17O.sub.35TaN have their own advantages as catalysts in HER process, and their exact HER efficiency is waiting to be obtained in the future experiments. In general, this passivated codoping LNS-TiO.sub.2 represents a novel kind of material. Research in this paper can enrich the theoretical knowledge of HER field.
A novel and efficient technique has been designed for the creation of oxygen vacancies on Lasub.2Tisub.2Osub.7 (LTO) nanosheets. This is achieved via a controlled solid-state reaction between ...NaBHsub.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 Lasub.2Tisub.2Osub.7@Lasub.2Tisub.2Osub.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 gsup.−1 hsup.−1, which is noticeably superior to the performance of the pristine Lasub.2Tisub.2Osub.7.
Room temperature gas-sensitive metal oxides have received growing concern over their long-term stability in recent years. Presently, Pt-SnO.sub.2 composite nanoceramics of 1 wt% Pt have been ...prepared, and the time dependence of their room temperature hydrogen sensing capability has been carefully studied. A strong variation with time was observed, with the room temperature response to 1% H.sub.2- 20% O.sub.2-N2 decreased by a factor of several dozen after only one week. Heat treatments were found highly effective to activate those aged samples. Their room temperature hydrogen sensing capability was almost completely restored through 10 min heat treatments at temperatures as low as 130 °C. It is proposed that impurity gases in air slowly deposit on Pt in Pt-SnO.sub.2 composite nanoceramics, and the catalytic role of Pt is deactivated by the deposition and then activated after their desorption through heat treatments. These results suggest that periodic mild heat treatments can be a simple and feasible way for some room temperature gas-sensitive metal oxides to maintain a high long-term stability.
The geometries and energetics of the n-vertex polyhedral dicobaltadithiaboranes and dicobaltadiselenaboranes Cpsub.2Cosub.2Esub.2Bnsub.−4Hnsub.−4 (E = S, Se; n = 8 to 12) have been investigated via ...the density functional theory. Most of the lowest-energy structures in these systems are generated from the (n + 1)-vertex most spherical closo deltahedra by removal of a single vertex, leading to a tetragonal, pentagonal, or hexagonal face depending on the degree of the vertex removed. In all of these low-energy structures, the chalcogen atoms are located at the vertices of the non-triangular face. Alternatively, the central polyhedron in most of the 12-vertex structures can be derived from a Cosub.2Esub.2Bsub.8 icosahedron with adjacent chalcogen (E) vertices by breaking the E-E edge and 1 or more E-B edges to create a hexagonal face. Examples of the arachno polyhedra with two tetragonal and/or pentagonal faces derived from the removal of two vertices from isocloso deltahedra were found among the set of lowest-energy Cpsub.2Cosub.2Esub.2Bnsub.−4Hnsub.−4 (E = S, Se; n = 8 and 12) structures.
Molybdenum-based cocatalyst being used to construct heterojunctions for efficient photocatalytic Hsub.2 production is a promising research hotspot. In this work, CdInsub.2Ssub.4 was successfully ...closely supported on bulk Mosub.2C via the hydrothermal method. Based on their matching band structures, they formed a Type Ⅰ heterojunction after the combination of Mosub.2C (1.1 eV, −0.27 V, 0.83 V) and CdInsub.2Ssub.4 (2.3 eV, −0.74 V, 1.56 V). A series of characterizations proved that the heterojunction composite had higher charge separation efficiency compared to a single compound. Meanwhile, Mosub.2C in heterojunction could act as an active site for hydrogen production. The photocatalytic Hsub.2 production activity of the heterojunction composites was significantly improved, and the maximum activity was up to 1178.32 μmmol hsup.−1 gsup.−1 for 5Mosub.2C/CdInsub.2Ssub.4 composites. 5Mosub.2C/CdInsub.2Ssub.4 heterojunction composites possess excellent durability in three cycles (loss of 6%). Additionally, the mechanism of increased activity for composites was also investigated. This study provides a guide to designing noble-metal-free photocatalyst for highly efficient photocatalytic Hsub.2 evolution.
For hydrogen and oxygen evolution reactions, the price of precious metals and their long-time testing stability limit their range of use and increase the difficulty of commercialization. Thus, it is ...necessary to use non-noble metal materials with excellent activity and stability to replace noble metal materials as electrocatalysts. Herein, an efficient and durable electrocatalyst consisting of Cu.sub.3P@NiFe-MOF is synthesized by hydrothermal method. Specially, the as-prepared Cu.sub.3P@NiFe-MOF-4 delivery an overpotential of 226 mV at a current density of 10 mA cm.sup.-2, and it also has a very low Tafel slope and a high double layer capacitance.
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 (Hsub.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 Osub.2 sup.− and Hsub.2Osub.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.
