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oxygen evolution

Xiaolei Kang, Wei Sun, Limei Cao, Ji Yang
A novel cryptomelane-Ir (cry-Ir) electrode is prepared for Ir to enter into the cryptomelane (named as cry-Mn) structure and used for aspirin degradation. This catalyst can efficiently reduce the Ir usage from 85 to 34%. Also, the onset potential of cry-Ir is about 1.40 V and the over potential is about 0.34 V at 10 mA cm(-2), indicating that cry-Ir has an excellent oxygen evolution reaction (OER) activity to produce oxidizing species and can decrease electrolytic voltage during the electro-oxidation process...
September 22, 2017: Environmental Science and Pollution Research International
D Wrana, C Rodenbücher, M Krawiec, B R Jany, J Rysz, M Ermrich, K Szot, F Krok
We report on the systematic exploration of electronic and structural changes of Nb-doped rutile TiO2(110) single crystal surfaces due to the thermoreduction under ultra-high vacuum conditions (without sputtering), with comparison to undoped TiO2(110) crystals. It has been found that the surface of the doped sample undergoes a previously unknown transition during reduction above 850 °C, as provided by LEED, STM and LC-AFM. This transition involves a change from heterogeneous conductivity (due to the presence of conducting filaments) to homogeneous conductivity, connected with a new (4 × 2) reconstruction of rows parallel to the [001] direction...
September 22, 2017: Physical Chemistry Chemical Physics: PCCP
Ting-Ting Li, Jinjie Qian, Qianqian Zhou, Jian-Li Lin, Yue-Qing Zheng
Immobilization of earth-abundant water oxidation catalysts (WOCs) on carbon supports to produce functional electrodes for electrochemical water splitting is a crucial approach for future clean energy production. Herein we report the non-covalent immobilization of a pyrene-bearing cobalt(ii) Schiff base complex (2) on the surface of multiwalled carbon nanotubes (MWCNTs) to form a hybrid anode for electrocatalytic water oxidation. The 2/MWCNT anode displayed excellent catalytic activity and durability in neutral aqueous solution, and a catalytic current density of 1...
September 22, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Peiyao Wang, Mengyu Yan, Jiashen Meng, Gengping Jiang, Longbing Qu, Xuelei Pan, Jefferson Zhe Liu, Liqiang Mai
The oxygen evolution reaction involves complex interplay among electrolyte, solid catalyst, and gas-phase and liquid-phase reactants and products. Monitoring catalysis interfaces between catalyst and electrolyte can provide valuable insights into catalytic ability. But it is a challenging task due to the additive solid supports in traditional measurement. Here we design a nanodevice platform and combine on-chip electrochemical impedance spectroscopy measurement, temporary I-V measurement of an individual nanosheet, and molecular dynamic calculations to provide a direct way for nanoscale catalytic diagnosis...
September 21, 2017: Nature Communications
Matthias Steimecke, Gerda Seiffarth, Michael Bron
We present a spectroelectrochemical setup, in which Raman microscopy is combined with scanning electrochemical microscopy (SECM) in order to provide both spectroscopic and electrochemical information of the very same location of an electrode at the same time. The setup is applied to a subject of high academic and practical interest, namely the oxygen evolution reaction at Ni and Ni/Fe electrodes. It comprises a transparent substrate electrode, onto which Ni and Ni/Fe thin films are deposited. An ultramicroelectrode (UME) is placed closely above the substrate to obtain electrochemical information, while a Raman microscope probes the same sample spot from below...
September 21, 2017: Analytical Chemistry
Yudi Tu, Toru Utsunomiya, Sho Kokufu, Masahiro Soga, Takashi Ichii, Hiroyuki Sugimura
Silicon is a promising electrode material for photoelectrochemical and photocatalytic reaction. However, the chemically active surface of silicon will be easily oxidized when exposed to the oxidation environment. We immobilized graphene oxide (GO) onto hydrogen-terminated silicon (H-Si) and reduced it through ultraviolet (UV) and vacuum-ultraviolet (VUV) irradiation. This acted as an ultrathin conductive layer to protect H-Si from oxidation. The elemental evolution of GO was studied by X-ray photoelectron spectroscopy and it was found that GO was partially reduced soon after the deposition onto H-Si and further reduced after UV or VUV light irradiation...
September 20, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
B Öztaş, D Akyüz, A Koca
Peripherally and non-peripherally terminal alkynyl substituted manganese phthalocyanines (MnPc) were synthesized and characterized and then used as functional materials in modified electrodes. MnPcs were substituted with alkynyl groups, which are reactive moieties in click electrochemistry (CEC) reactions. Mn(iii) cations were incorporated into the cavity of the Pc ring in order to increase the redox activity of the complexes. Electrochemical characterizations of the complexes were determined by voltammetric and in situ spectroelectrochemical measurements in order to determine their possible technological applications...
September 20, 2017: Physical Chemistry Chemical Physics: PCCP
Ming Liu, Xiaoqing Lu, Chen Guo, Zhaojie Wang, Yanpeng Li, Yan Lin, Yan Zhou, Shutao Wang, Jun Zhang
To improve the efficiency of cobalt-based catalysts for water electrolysis, tremendous efforts have been dedicated to tuning the composition, morphology, size and structure of the materials. We report here the facile preparation of orthorhombic CoTe2 nanocrystals embedded in N-doped graphitic carbon matrix to form a 3D architecture with a size of ~500 nm and abundant mesopores of ~4 nm for the oxygen evolution reaction. The hybrid electrocatalyst delivers a small overpotential of 300 mV at 10 mA cm-2, which is much lower than that for pristine CoTe2 powder...
September 19, 2017: ACS Applied Materials & Interfaces
An-Liang Wang, Yu-Tao Dong, Mei Li, Chaolun Liang, Gao-Ren Li
Herein, NixFe1-xOOH/NiFe/NixFe1-xOOH sandwich-structured nanotube arrays (SNTAs) supported on carbon fiber cloth (CFC) (NixFe1-xOOH/NiFe/NixFe1-xOOH SNTAs-CFC) have been developed as flexible high-performance OER catalysts by a facile in-situ electrochemical oxidation of NiFe metallic alloy nanotube arrays (ANTAs) during oxygen evolution process. Benefiting from the advantages of high conductivity, hollow nanotube array and porous strucuture, NixFe1-xOOH/NiFe/NixFe1-xOOH SNTAs-CFC exhibited a low overpotential of ~220 mV at the current density of 10 mA cm-2 and a small Tafel slope of 52 mV dec-1 in alkaline solution, which both are smaller than those of most OER electrocatalysts...
September 19, 2017: ACS Applied Materials & Interfaces
Dong Jiang, Zeyu Zhao, Shenglong Mu, Vincent Phaneuf, Jianhua Tong
Mayenite (12CaO·7Al2O3, C12A7) electride with an anti-zeolite nanoporous structure has attracted intense attention due to its versatile promising application potentials. However, the synthesis difficulty because of extremely harsh conditions (e.g., reduction in sealed calcium or titanium vapor) significantly obstructs its realistic applications. In this work, we employed a simple, efficient, and cost-effective route for synthesizing mayenite electrides (C12A7:e(-)) in both powder and dense ceramic. C12A7:e(-) powders with efficient electron doping (3...
September 19, 2017: Inorganic Chemistry
Ethan M Cunningham, Alexander S Gentleman, Peter M Beardsmore, Andreas Iskra, Stuart R Mackenzie
Gas-phase metal ion-ligand complexes offer model environments to study molecular interactions which are key to many catalytic processes. Here, we present a combined experimental and computational study of M+(N2O)n [M= Cu, Ag, Au; n = 2-7] complexes. The spectra provide clear evidence for both nitrogen- and oxygen- bound ligands giving rise to a wide range of structural isomers for each complex studied. The evolution of the complex structures observed as well as spectral trends for each metal center are interpreted in terms of a molecular orbital binding picture and resulting calculated ligand binding energies...
September 19, 2017: Journal of Physical Chemistry. A
Rosely Almeida, Amitava Banerjee, Sudip Chakraborty, Jailton Almeida, Rajeev Ahuja
First principles electronic structure calculations based on density functional theory (DFT) framework are performed to investigate hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) on two-dimensional Al2C monolayer. The monolayer is functionalized with several dopants and four prominent doping elements are nitrogen (N), phosphorous (P), boron (B) and sulphur (S). After determining the individual adsorption energy of hydrogen and oxygen on different functionalized Al2C monolayer, the adsorption free energies are predicted subsequently for each of the functionalized cases in order to predict which case of functionalization serves better for HER or OER...
September 19, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Jie Fu, Sara Elizabeth Skrabalak
There are few methods yielding oxynitride crystals with defined shape, yet shape-controlled crystals often render enhanced photoactivity. Here, single-crystalline SrTaO2N nanoplates and polyhedra are achieved selectively. Central to these synthetic advances is the crystallization pathways used, where single-crystalline SrTaO2N nanoplates form by topotactic nitridation of aerosol-prepared Sr2Ta2O7 nanoplates and SrTaO2N polyhedra form by flux-assisted nitridation of the nanoplates. Evaluation of these materials for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) showed improved performance for the SrTaO2N nanoplates, with a record apparent quantum efficiency (AQE) of 6...
September 18, 2017: Angewandte Chemie
Patrick M Shih, Lewis M Ward, Woodward W Fischer
Various lines of evidence from both comparative biology and the geologic record make it clear that the biochemical machinery for anoxygenic photosynthesis was present on early Earth and provided the evolutionary stock from which oxygenic photosynthesis evolved ca. 2.3 billion years ago. However, the taxonomic identity of these early anoxygenic phototrophs is uncertain, including whether or not they remain extant. Several phototrophic bacterial clades are thought to have evolved before oxygenic photosynthesis emerged, including the Chloroflexi, a phylum common across a wide range of modern environments...
September 18, 2017: Proceedings of the National Academy of Sciences of the United States of America
Simon Geiger, Olga Kasian, Andrea M Mingers, Shannon S Nicley, Ken Haenen, Karl J J Mayrhofer, Serhiy Cherevko
In searching for alternative oxygen evolution reaction (OER) catalysts for acidic water splitting, fast screening of materials intrinsic activity and stability in half-cell tests is of vital importance. It significantly accelerates the discovery of new promising materials without the need of time-consuming real cell analysis. In commonly employed tests, a conclusion on the catalyst stability is drawn solely on the basis of pure electrochemical information, e.g. by evaluating potential vs. time profiles. In this work we demonstrate important limitations of such approaches, which are related to the degradation of the backing electrode material...
September 18, 2017: ChemSusChem
Bin Liu, Hui-Qing Peng, Cheuk-Nam Ho, Hongtao Xue, Shuilin Wu, Tsz-Wai Ng, Chun-Sing Lee, Wenjun Zhang
A novel mesoporous nanosheet networked hybrid comprising Co3 O4 and Co3 (PO4 )2 is successfully synthesized using a facile and scalable method through calcinating the carbon, cobalt hydroxy carbonate, and cobalt phosphate composite precursor. Electron transfer from Co3 O4 to Co3 (PO4 )2 , together with the special networked structure and the porous nature of the nanosheets enable the Co3 (PO4 )2 -Co3 O4 hybrid to have a high oxygen evolution reaction (OER) activity and outstanding stability in alkaline electrolyte, e...
September 18, 2017: Small
Kevin Huang
A hierarchically functionalized hybrid electrode for Zn-air batteries is discussed that requires no carbon. Instead, an oxygen evolution reaction (OER)-active, porous, conductive, and corrosion-resistant nitride Ni3 FeN is used as a support for oxygen reduction reaction (ORR)-active ordered intermetallic Fe3 Pt NPs. The porosity in the Ni3 FeN substrate is an important enabling factor for the high OER activity.
September 18, 2017: Angewandte Chemie
Jianwei Nai, Yan Lu, Le Yu, Xin Wang, Xiong Wen David Lou
Exploring effective electrocatalysts is a crucial requirement for boosting the efficiency of water splitting to obtain clean fuels. Here, a self-templating strategy is reported to synthesize Ni-Fe mixed diselenide cubic nanocages for the electrocatalytic oxygen evolution reaction (OER). The diselenide nanocages are derived from corresponding Prussian-blue analog nanocages, which are first obtained by treating the nanocube precursor with a site-selective ammonia etchant. The resulting Ni-Fe mixed diselenide nanocages perform as a superior OER electrocatalyst, which affords a current density of 10 mA cm(-2) at a small overpotential of 240 mV; a high current density, mass activity, and turnover frequency of 100 mA cm(-2) , 1000 A g(-1) , and 0...
September 18, 2017: Advanced Materials
Thomas Lohmiller, Vera Krewald, Arezki Sedoud, A William Rutherford, Frank Neese, Wolfgang Lubitz, Dimitrios A Pantazis, Nicholas Cox
Nature's water splitting catalyst, an oxygen-bridged tetra-manganese calcium (Mn4O5Ca) complex, sequentially activates two substrate water molecules generating molecular O2. Its reaction cycle is composed of five intermediate (Si) states, where the index i indicates the number of oxidizing equivalents stored by the cofactor. After formation of the S4 state, the product dioxygen is released and the cofactor returns to its lowest oxidation state, S0. Membrane-inlet mass spectrometry measurements suggest that at least one substrate is bound throughout the catalytic cycle, as the rate of (18)O-labeled water incorporation into the product O2 is slow, on a millisecond to second timescale depending on the S state...
September 18, 2017: Journal of the American Chemical Society
Lennart Köhler, Majid Ebrahimizadeh Abrishami, Vladimir Roddatis, Janis Geppert, Marcel Risch
Targeted improvement of the low efficiency of water oxidation during the oxygen evolution reaction (OER) is severely hindered by insufficient knowledge of the electrocatalytic mechanism on heterogeneous surfaces. We chose LiMn2O4 as a model system for mechanistic investigations as it shares the cubane structure with the active site of photosystem II and the valence of Mn3.5+ with the dark-stable S1 state in the mechanism of natural photosynthesis. The investigated LiMn2O4 nanoparticles are electrochemically stable in NaOH electrolytes and show respectable activity in any of the main metrics...
September 18, 2017: ChemSusChem
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