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Cyriac Massué, Verena Pfeifer, Maurice Van Gastel, Johannes Noack, Gerardo Algara-Siller, Sebastien Cap, Robert Schlögl
Although quasi-amorphous Ir-oxohydroxides have repeatedly been identified as superior oxygen evolution reaction (OER) electrocatalysts, an exact description of the performance relevant species has so far remained a challenge. In this context, we report on the characterization of hydrothermally prepared IrIII/IV oxohydroxides exhibiting exceptional OER-performance. It was found that holes in the O2p states of IrIII/IV-oxohydroxides result in reactive OI--species identified by characteristic NEXAFS-features. A prototypical titration reaction based on CO as a probe molecule shows that these OI--species are highly susceptible to nucleophilic attack at room temperature...
September 21, 2017: ChemSusChem
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
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
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
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
Xuping Sun
In this communication, we report our recent finding that the generation of amorphous Co-Bi layer on Co3O4 nanowire arrays supported on Ti mesh (Co3O4@Co-Bi NA/TM) leads to significantly boosted OER activity. The as-prepared Co3O4@Co-Bi NA/TM demands overpotential of 304 mV to drive a ge-ometrical current density of 20 mA cm-2 in 1.0 M KOH, which is 109 mV less than that for Co3O4 NA/TM, with its catalytic activity being preserved for at least 20 h. It suggests that the existence of amorphous Co-Bi layer promotes more CoOx(OH)y generation on Co3O4 surface...
September 19, 2017: Chemistry: a European Journal
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
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
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
Areum Yu, Chongmok Lee, Myung Hwa Kim, Youngmi Lee
We report the unique transformation of one-dimensional tubular mixed oxide nanocomposites of iridium (Ir) and cobalt (Co) denoted as IrxCo1-xOy, where x is the relative Ir atomic content to the overall metal content. The formation of a variety of IrxCo1-xOy (0 ≤ x ≤ 1) crystalline tubular nanocomposites was readily achieved by electrospinning and subsequent calcination process. Structural characterizations clearly confirmed that IrxCo1-xOy polycrystalline nanocomposites had a tubular morphology consisting of Ir/IrO2 and Co3O4; and Ir, Co and O were homogeneously distributed throughout the entire nanostructures...
September 18, 2017: ACS Applied Materials & Interfaces
Nivedita Sikdar, Bharathi Konkena, Justus Masa, Wolfgang Schuhmann, Tapas Kumar Maji
There has been growing interest in the synthesis of efficient reversible oxygen electrodes for both the oxygen reduction reaction (ORR) and the oxygen evolution reactions (OER) for their potential use in a variety of renewable energy technologies such as regenerative fuel cells and metal-air batteries. Here, we report a bi-functional electrocatalyst derived from a novel dicyanamide based nitrogen rich MOF {[Co(bpe)2(N(CN)2)](N(CN)2)(5H2O)}n [Co-MOF-1, bpe = 1,2-bis(4-pyridyl)ethane, N(CN)2- = dicyanamide] under different pyrolysis conditions...
September 15, 2017: Chemistry: a European Journal
Martin Pumera
The natural occurring Palaeoproterozoic carbon mineral shungite is a complex raw carbon microporous matrix, loaded with a wide range of elements. Shungite.exhibits disordered and amorphous structure with highly irregular building blocks. Shungite incorporates metals in its structure, typically catalytic elements such Fe and Ni are also present, as well as, the toxic elements Pb and As at mg/g level. We show here that incorporation of the metals in the carbon matrix of shungite leads into synergiustic catalytic effect...
September 15, 2017: Chemistry: a European Journal
Xue Bai, Qin Wang, Feng He, Zhi-Jian Wu, Guangran Xu, Keke Huang, Yunkun Ning, Jun Zhang
Electrocatalytic splitting of water is becoming increasingly crucial for renewable energy and device technologies. As one of the most important half-reactions for water splitting reaction, oxygen evolution reaction (OER) is a kinetically sluggish process that will greatly affect the energy conversion efficiency. Therefore, exploring a highly efficient, and durable catalyst to boost the OER is of great urgency. In this work, we develop a facile strategy for synthesis of well-defined phosphorus, fluorine co-doped Ni1...
September 14, 2017: Chemistry: a European Journal
Hatem M A Amin, Helmut Baltruschat
Understanding the mechanism underlying the oxygen evolution reaction (OER) on oxides is crucial for the development of many energy storage systems. Here, the mechanism of OER on a Co3O4 spinel catalyst is investigated in alkaline media using (18)O-labeling combined with differential electrochemical mass spectrometry (DEMS). This work unravels the role of surface oxygen of the oxide in the OER. It is shown that in H2(18)O-containing electrolyte the amount of (18)O(16)O evolved increases from cycle to cycle together with a concomitant decrease of the amount of (16)O2 with each cycle before reaching a steady-state value...
September 13, 2017: Physical Chemistry Chemical Physics: PCCP
Yanmei Xin, Xiang Kan, Li-Yong Gan, Zhonghai Zhang
Solar-driven overall water splitting is highly desirable for hydrogen generation with sustainable energy sources, which need efficient, earth-abundant, robust, and bifunctional electrocatalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, we propose a heterogeneous bimetallic phosphide/sulfide nanocomposite electrocatalyst of NiFeSP on nickel foam (NiFeSP/NF), which shows superior electrocatalytic activity of low overpotentials of 91 mV at -10 mA cm(-2) for HER and of 240 mV at 50 mA cm(-2) for OER in 1 M KOH solution...
September 14, 2017: ACS Nano
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