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water splitting

Daniel J O'Brien, Gabriel O Sawakuchi
PURPOSE: The aim of this study was to examine the effect of sub-millimeter air gaps that may exist between an ionization chamber and solid phantoms when measurements are performed in a magnetic field. METHODS: Geant4 Monte Carlo simulations were performed using a model of a PTW 30013 Farmer chamber in a water phantom. Symmetrical and asymmetrical air gaps of various thicknesses were modeled surrounding the chamber, and the dose to the air cavity of the chamber was scored in each case...
April 22, 2017: Medical Physics
Ibrahim Khan, Akram A M Ibrahim, Manzar Sohail, Ahsanulhaq Qurashi
This article presented the synthesis of a hybrid nanoarchitecture material composed of reduced graphene oxide (RGO) multiple sheets and ZnO nanowire arrays (NWAs) formed on an arbitrary ZnO coated fluorine doped tin oxide (FTO) substrates via pulse sonication and hydrothermal approach. The NWAs have high aspect-ratio, high density, apt positioning and well-ordered formation. FESEM images demonstrated that RGO layers have been effectively intercalated between and on the accessible surfaces of the ZnO NWAs. The diameter of ZnO nanowires is 80-150nm and length about 1-2μm...
July 2017: Ultrasonics Sonochemistry
Rojiar Akbari Sene, G R Moradi, S Sharifnia
Hydrogen evolution via water splitting was investigated over the sonochemically synthesized TiO2-clinoptilolite photocomposites. To this aim, a series of photocatalysts containing 10wt% titania were prepared by impregnation and solid state dispersion (SSD) methods in the presence and absence of ultrasound irradiation. The samples were characterized by XRD, FESEM, EDX, BET, FTIR, PL and UV-vis techniques and tested for the water splitting. The characterization results indicated that ultrasound irradiation endowed the photocatalysts with uniform morphology, higher surface area and more homogenous dispersion...
July 2017: Ultrasonics Sonochemistry
Wan Li, Shilin Zhang, Qining Fan, Fazhi Zhang, Sailong Xu
Transition metal phosphide (TMP) nanostructures have stimulated increasing interest for use in water splitting owing to their abundant natural sources and high activity for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Typically, the preparation of hierarchical TMPs involves the utilization of expensive or dangerous phosphorus sources, and, in particular, the understanding of topotactic transformations of the precursors to crystalline phases-which could be utilized to enhance electrocatalytic performance-remains very limited...
April 20, 2017: Nanoscale
Xiang Chen, Huanlin Chen, Jian Guan, Jieming Zhen, Zijun Sun, Pingwu Du, Yalin Lu, Shangfeng Yang
Graphitic carbon nitride (g-C3N4) as an emerging two-dimensional (2D) nanomaterial has been commonly used as a metal-free photocatalyst with potential applications in visible light photocatalytic water-splitting. However, the photocatalytic activity of g-C3N4 is quite low due to its relatively large band gap and the existence of contact resistance between the nanosheets. Herein we report for the first time the facile synthesis of a covalently bonded g-C3N4/C60 hybrid via a solid-state mechanochemical route and its application in photocatalytic hydrogen production under visible light...
April 19, 2017: Nanoscale
Ruixiang Ge, Hongbin Du, Kai Tao, Qiuju Zhang, Liang Chen
The development of non-noble metal oxygen evolution electrocatalysts working efficiently under benign conditions is still urgent and challenging. Herein we report the electrochemical generation of novel cobalt-borate (Co-Bi) nanoarray on carbon cloth (Co-Bi NA/CC) from CoS2 nanoarray precursor. As an integrated three-dimensional electrode, such Co-Bi NA/CC exhibits excellent catalytic performance for oxygen evolution with 10 mA cm-2 at an overpotential of 411 mV. Notably, this electrode also demonstrates outstanding long-term electrochemical durability for at least 20 hours, implying the great potential for water splitting applications at near-neutral pH...
April 18, 2017: ACS Applied Materials & Interfaces
Anton Litke, Yaqiong Su, Ionut Tranca, Thomas Weber, Emiel J M Hensen, Jan P Hofmann
Overall photocatalytic water splitting is one of the most sought after processes for sustainable solar-to-chemical energy conversion. The efficiency of this process strongly depends on charge carrier recombination and interaction with surface adsorbates at different time scales. Here, we investigated how hydration of TiO2 P25 affects dynamics of photogenerated electrons at the millisecond to minute time scale characteristic for chemical reactions. We used rapid scan diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS)...
April 6, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Angel T Garcia-Esparza, Tatsuya Shinagawa, Samy Ould-Chikh, Muhammad Qureshi, Xuyuan Peng, Nini Wei, Dalaver H Anjum, Alain Clo, Tsu-Chien Weng, Dennis Nordlund, Dimosthenis Sokaras, Jun Kubota, Kazunari Domen, Kazuhiro Takanabe
For overall water-splitting systems, it is essential to establish O2 -insensitive cathodes that allow cogeneration of H2 and O2 . An acid-tolerant electrocatalyst is described, which employs a Mo-coating on a metal surface to achieve selective H2 evolution in the presence of O2 . In operando X-ray absorption spectroscopy identified reduced Pt covered with an amorphous molybdenum oxyhydroxide hydrate with a local structural order composed of polyanionic trimeric units of molybdenum(IV). The Mo layer likely hinders O2 gas permeation, impeding contact with active Pt...
April 13, 2017: Angewandte Chemie
Jomana Al-Nu'airat, Mohammednoor K Altarawneh, Xiangpeng Gao, Phillip R Westmoreland, Bogdan Z Dlugogorski
Dissolved organic matter (DOM) acts as an effective photochemical sensitiser that produces the singlet delta state of molecular oxygen (O2 1Δg), a powerful oxidiser that removes aniline from aqueous solutions. However, the exact mode of this reaction, the para to ortho-iminobenzoquinone ratio, and the selectivity of one over the other remain largely speculative. This contribution resolves these uncertainties. We report, for the first time, a comprehensive mechanistic and kinetic account of the oxidation of aniline with the singlet delta oxygen using B3LYP and M06 functionals in both gas and aqueous phases...
April 13, 2017: Journal of Physical Chemistry. A
Stefan Iglauer
Carbon geosequestration (CGS) has been identified as a key technology to reduce anthropogenic greenhouse gas emissions and thus significantly mitigate climate change. In CGS, CO2 is captured from large point-source emitters (e.g., coal fired power stations), purified, and injected deep underground into geological formations for disposal. However, the CO2 has a lower density than the resident formation brine and thus migrates upward due to buoyancy forces. To prevent the CO2 from leaking back to the surface, four trapping mechanisms are used: (1) structural trapping (where a tight caprock acts as a seal barrier through which the CO2 cannot percolate), (2) residual trapping (where the CO2 plume is split into many micrometer-sized bubbles, which are immobilized by capillary forces in the pore network of the rock), (3) dissolution trapping (where CO2 dissolves in the formation brine and sinks deep into the reservoir due to a slight increase in brine density), and (4) mineral trapping (where the CO2 introduced into the subsurface chemically reacts with the formation brine or reservoir rock or both to form solid precipitates)...
April 13, 2017: Accounts of Chemical Research
Kai Han, Tomas Kreuger, Bastian Mei, Guido Mul
Transients in the composition of Ni@NiO x core-shell co-catalysts deposited on SrTiO3 are discussed on the basis of state-of-the-art continuous analysis of photocatalytic water splitting, and post-XPS and TEM analyses. The formation of excessive hydrogen (H2:O2 ≫ 2) in the initial stages of illumination demonstrates oxidation of Ni(OH)2 to NiOOH (nickel oxyhydroxide), with the latter catalyzing water oxidation. A disproportionation reaction of Ni and NiOOH, yielding Ni(OH)2 with residual embedded Ni, occurs when illumination is discontinued, which explains repetitive transients in (excess) hydrogen and oxygen formation when illumination is reinitiated...
March 3, 2017: ACS Catalysis
Jiao Deng, Haobo Li, Suheng Wang, Ding Ding, Mingshu Chen, Chuan Liu, Zhongqun Tian, K S Novoselov, Chao Ma, Dehui Deng, Xinhe Bao
Hydrogen production through water splitting has been considered as a green, pure and high-efficient technique. As an important half-reaction involved, hydrogen evolution reaction is a complex electrochemical process involving liquid-solid-gas three-phase interface behaviour. Therefore, new concepts and strategies of material design are needed to smooth each pivotal step. Here we report a multiscale structural and electronic control of molybdenum disulfide foam to synergistically promote the hydrogen evolution process...
April 12, 2017: Nature Communications
Stepan Kment, Francesca Riboni, Sarka Pausova, Lei Wang, Lingyun Wang, Hyungkyu Han, Zdenek Hubicka, Josef Krysa, Patrik Schmuki, Radek Zboril
Solar driven photoelectrochemical water splitting (PEC-WS) using semiconductor photoelectrodes represents a promising approach for a sustainable and environmentally friendly production of renewable energy vectors and fuel sources, such as dihydrogen (H2). In this context, titanium dioxide (TiO2) and iron oxide (hematite, α-Fe2O3) are among the most investigated candidates as photoanode materials, mainly owing to their resistance to photocorrosion, non-toxicity, natural abundance, and low production cost. Major drawbacks are, however, an inherently low electrical conductivity and a limited hole diffusion length that significantly affect the performance of TiO2 and α-Fe2O3 in PEC devices...
April 11, 2017: Chemical Society Reviews
Xiao-Yuan Liu, Hao Chen, Ruili Wang, Yuequn Shang, Qiong Zhang, Wei Li, Guozhen Zhang, Juan Su, Cao Thang Dinh, F Pelayo García de Arquer, Jie Li, Jun Jiang, Qixi Mi, Rui Si, Xiaopeng Li, Yuhan Sun, Yi-Tao Long, He Tian, Edward H Sargent, Zhijun Ning
Hydrogen generation via photocatalysis-driven water splitting provides a convenient approach to turn solar energy into chemical fuel. The development of photocatalysis system that can effectively harvest visible light for hydrogen generation is an essential task in order to utilize this technology. Herein, a kind of cadmium free Zn-Ag-In-S (ZAIS) colloidal quantum dots (CQDs) that shows remarkably photocatalytic efficiency in the visible region is developed. More importantly, a nanocomposite based on the combination of 0D ZAIS CQDs and 2D MoS2 nanosheet is developed...
April 11, 2017: Advanced Materials
Hongjie An, Beng Hau Tan, James Guo Sheng Moo, Sheng Liu, Martin Pumera, Claus-Dieter Ohl
Graphene nanobubbles are of significant interest due to their ability to trap mesoscopic volumes of gas for various applications in nanoscale engineering. However, conventional protocols to produce such bubbles are relatively elaborate and require specialized equipment to subject graphite samples to high temperatures or pressures. Here, we demonstrate the formation of graphene nanobubbles between layers of highly oriented pyrolytic graphite (HOPG) with electrolysis. Although this process can also lead to the formation of gaseous surface nanobubbles on top of the substrate, the two types of bubbles can easily be distinguished using atomic force microscopy...
April 10, 2017: Nano Letters
Baocang Liu, Lili Huo, Zhiqing Gao, Guolei Zhi, Geng Zhang, Jun Zhang
Developing high-performance but low-cost hydrogen evolution reaction (HER) electrocatalysts with superior activity and stability for future sustainable energy conversion technologies is highly desired. Tuning of microstructure, configuration, and chemical composition are paramount to developing effective non-noble electrocatalysts for HER. Herein, a universal "nanocasting" method is reported to construct graphene decorated with uniform ternary (CoP)x -(FeP)1-x (0 ≤ x ≤ 1) nanorods hybrids with different chemical compositions [(CoP)x -(FeP)1-x -NRs/G] as a highly active and durable nonprecious-metal electrocatalyst for the HER...
April 10, 2017: Small
Yujin Ji, Mingye Yang, Huilong Dong, Tingjun Hou, Lu Wang, Youyong Li
Full utilization of solar energy to split water into hydrogen and oxygen is an efficient way to solve the current energy problem. Graphene-like germanium monochalcogenides (GeS or GeSe) are proposed here as efficient photocatalysts for water splitting under a broad range from ultraviolet, visible to near-infrared light dependent on their thickness. Compared to traditional photocatalysts, GeS and GeSe possess a large intrinsic dipole and introduce an internal electric field directing from Ge surface to S/Se surface, which causes notable band bending...
April 10, 2017: Nanoscale
Yunjung Oh, Wooseok Yang, Jimin Kim, Sunho Jeong, Jooho Moon
Efficient sunlight-driven water-splitting devices can be achieved by using an optically and energetically well-matched pair of photoelectrodes in a tandem configuration. The key for maximizing the photoelectrochemical efficiency is the use of a highly transparent front photoelectrode with a band gap below 2.0 eV. Herein, we propose two-dimensional (2D) photonic crystal (PC) structures consisting of a CuFeO2-decorated microsphere monolayer, which serve as self-light-harvesting architectures allowing for amplified light absorption and high transparency...
April 13, 2017: ACS Applied Materials & Interfaces
A S Schenk, S Eiben, M Goll, L Reith, A N Kulak, F C Meldrum, H Jeske, C Wege, S Ludwigs
Spinel-type Co3O4 finds applications in a wide range of fields, including clean energy conversion, where nanostructured Co3O4 may provide a cost-efficient alternative to platinum- and iridium-based catalysts for electrocatalytic water-splitting. We here describe a novel strategy in which basic cobalt carbonate - a precursor to Co3O4 - is precipitated as sheet-like structures and microspheres covered with fine surface protrusions, via ammonium carbonate decomposition at room temperature. Importantly, these mild reaction conditions enable us to employ bio-inspired templating approaches to further control the mineral structure...
April 7, 2017: Nanoscale
Alena A Volgusheva, Martina Jokel, Yagut Allahverdiyeva, Galina P Kukarskikh, Eugeni P Lukashev, Maya D Lambreva, Tatayana E Krendeleva, Taras K Antal
Magnesium (Mg)-deprived Chlamydomonas reinhardtii cells are capable to sustain hydrogen (H2 ) photoproduction at relatively high PSII activity levels for an extended time period as compared with sulfur (S)-deprived cells. Herein, we present a comparative study of H2 photoproduction induced by Mg and S shortage to unravel the specific rearrangements of photosynthetic machinery and cell metabolism occurring under the two deprivation protocols. The exhaustive analysis of photosynthetic activity and regulatory pathways, respiration, and starch metabolism revealed the specific rearrangements of photosynthetic machinery and cellular metabolism, which occur under the two deprivation conditions...
April 7, 2017: Physiologia Plantarum
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