Solar hydrogen production using carbon quantum dots and a molecular nickel catalyst.

Carbon quantum dots (CQDs) are established as excellent photosensitizers in combination with a molecular catalyst for solar light driven hydrogen production in aqueous solution. The inexpensive CQDs can be prepared by straightforward thermolysis of citric acid in a simple one-pot, multigram synthesis and are therefore scalable. The CQDs produced reducing equivalents under solar irradiation in a homogeneous photocatalytic system with a Ni-bis(diphosphine) catalyst, giving an activity of 398 μmolH2 (gCQD)(-1) h(-1) and a "per Ni catalyst" turnover frequency of 41 h(-1). The CQDs displayed activity in the visible region beyond λ > 455 nm and maintained their full photocatalytic activity for at least 1 day under full solar spectrum irradiation. A high quantum efficiency of 1.4% was recorded for the noble- and toxic-metal free photocatalytic system. Thus, CQDs are shown to be a highly sustainable light-absorbing material for photocatalytic schemes, which are not limited by cost, toxicity, or lack of scalability. The photocatalytic hybrid system was limited by the lifetime of the molecular catalyst, and intriguingly, no photocatalytic activity was observed using the CQDs and 3d transition metal salts or platinum precursors. This observation highlights the advantage of using a molecular catalyst over commonly used heterogeneous catalysts in this photocatalytic system.This work was supported by an Oppenheimer PhD scholarship (to B.C.M.M.), a Poynton PhD scholarship (to G.A.M.H.), a Marie Curie postdoctoral fellowship (GAN 624997 to C.C.), an EPSRC Career Acceleration Fellowship (EP/H00338X/2 to E.R.), the Christian Doppler Research Association (Austrian Federal Ministry of Science, Research, and Economy and the National Foundation for Research, Technology and Development), and the OMV Group.This is the final version of the article. It first appeared from ACS via http://dx.doi.org/10.1021/jacs.5b01650

Efficient photosynthesis of carbon monoxide from CO2 using perovskite photovoltaics

Artificial photosynthesis, mimicking nature in its efforts to store solar energy, has received considerable attention from the research community. Most of these attempts target the production of H2 as a fuel and our group recently demonstrated solar-to-hydrogen conversion at 12.3% efficiency. Here, in an effort to take this approach closer to real photosynthesis, which is based on the conversion of CO2, we demonstrate the efficient reduction of CO2 to carbon monoxide driven solely by simulated sunlight using water as the electron source. Employing series-connected perovskite photovoltaics and high-performance catalyst electrodes, we reach a solar-to-CO efficiency exceeding 6.5%, which represents a new benchmark in sunlight-driven CO2 conversion. Considering hydrogen as a secondary product, an efficiency exceeding 7% is observed. Furthermore, this study represents one of the first demonstrations of extended, stable operation of perovskite photovoltaics, whose large open-circuit voltage is shown to be particularly suited for this process

Identifying the structure of Zn-N-2 active sites and structural activation

Identification of active sites is one of the main obstacles to rational design of catalysts for diverse applications. Fundamental insight into the identification of the structure of active sites and structural contributions for catalytic performance are still lacking. Recently, X-ray absorption spectroscopy (XAS) and density functional theory (DFT) provide important tools to disclose the electronic, geometric and catalytic natures of active sites. Herein, we demonstrate the structural identification of Zn-N-2 active sites with both experimental/theoretical X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra. Further DFT calculations reveal that the oxygen species activation on Zn-N-2 active sites is significantly enhanced, which can accelerate the reduction of oxygen with high selectivity, according well with the experimental results. This work highlights the identification and investigation of Zn-N-2 active sites, providing a regular principle to obtain deep insight into the nature of catalysts for various catalytic applications

Influence of Intermetallic Particles on the Corrosion Properties of Extruded ZK60 Mg Alloy Containing Cu

The microstructure and corrosion behavior of the extruded ZK60 Mg alloys with different Cu content were comparatively investigated. The ZK60 alloy had a microstructure consisting of ??-Mg grains with intermetallic MgZn2 and Zn2Zr3 particles. The addition of 1 wt % Cu resulted in the additional presence of CuMgZn particles. In a 0.6 M NaCl solution at 25 ??C, the corrosion rate of the alloy with the added Cu appeared to be about 16% faster than that of the alloy without the addition of Cu. The factors affecting the degraded corrosion resistance of the Cu-added ZK60 alloy are discussed

A novel route to Pt-Bi2O3 composite thin films and their application in photo-reduction of water

A novel homoleptic bismuth(III) β-diketonate (dibenzoylmethane – dbm) complex [Bi(dbm)3]2 has been used as a precursor to thin films of crystalline β-Bi2O3, and hexachloroplatinic acid (H2PtCl6·6H2O) has been demonstrated as a suitable precursor for deposition of platinum nanoparticles, both deposited via aerosol-assisted chemical vapour deposition (AACVD). Thin films of Pt–Bi2O3 were co-deposited from a mixture of [Bi(dbm)3]2 and H2PtCl6·6H2O; the introduction of Pt particles into β-Bi2O3 causes hydrogen to be evolved during photolysis of water over the composite material, a property not found for Pt particles or β-Bi2O3 alone

Investigation of the cobalt (ІІ) hydroxide precipitation process

Гідроксиди перехідних металів широко використовуються у якості пігментів, адсорбентів, каталізаторів. Особливе місце займають кобальт(II) і кобальт(III) гідроксиди. Дуже часто їх використовують як сировину для отримання сполук складної структури. Оксиди, гідроксиди, оксігідроксиди кобальту є перспективною сировиною для отримання магнітоносіїв, хемосорбентов, каталізаторів, джерел струму, спеціальної кераміки, ІЧ-детекторів, магніторезісторів, лазерних матеріалів. Важливою задачею є встановлення механізму осадження кобальт(II) гідроксиду на основі використання комплексу методів аналізу: потенціометричного титрування, залишкових концентрацій, вимірювання електропровідності, уявного об'єму осаду, циклічної вольтамперометрії, чисельного диференціювання. Криві потенціометричного титрування для системи Со2+-NaOH-H2O показують, що при співвідношенні [OH-/Со2 +] = 1,8 спостерігається невелике плато, яке відповідає утворенню основної солі, при стехіометричному співвідношенні [OH- /Со2 +] = 2 відбувається повне осадження у вигляді гідроксиду кобальту Со(OH)2. Крива залежності уявного об'єму в системі СоSO4-NаОH-Н2О складається з двох частин, які відповідають кривій потенціометричного титрування. Криві залежності електропровідності мають чіткий перегин в точці, що відповідає утворенню основної солі та гідроксиду. ЦВА для кобальтвмісних розчинів мають характерні піки на катодній хвилі, відповідні відновленню кобальт (III) в кобальт (II) і кобальт (II) в кобальт (0), анодна хвиля має додатковий пік в інтервалі потенціалів +0,19 - +0,20 В. Поступове вивільнення катіонів від циклу 1 до циклу 5 свідчить про утворення стійких полігідроксокомплексів кобальту, які поступово руйнуються. Таким чином, встановлено, що реакція взаємодії між СоSO4 і NaOH протікає в кілька стадій з утворенням спочатку основної солі і потім полігідроксокомплексів. У розчинах з концентрацією ССоSO4 = 0,4-0,5 моль / л утворюється основна сіль складу Со(OH)1,8(SO4)0,1, в більш розведених розчинах утворюється основна сіль складу Со (OH)1,9(SO4)0,05.Hydroxides of transition metals are widely used as pigments, adsorbents, catalysts. A special place is occupied by cobalt (II) and cobalt (III) hydroxides. Very often they are used as raw materials to obtain compounds of complex structure. Cobalt oxides, hydroxides, oxyhydroxides is a promising raw material for the production of magnetocarriers, chemisorbents, catalysts, current sources, special ceramics, IR detectors, magnetoresistors, and laser materials. The main task is to study a cobalt (II) hydroxide deposition mechanism based on a set of analysis methods such as potentiometric titration, residual concentrations, conductivity measurements, apparent volume of precipitation, cyclic voltammetry, and numerical differentiation. Potentiometric titration curves for the Co2+-NaOH-H2O system show that with a ratio of [OH-/Cо2 +] = 1.8 a small plateau is observed that corresponds to the formation of the basic salt, with a stoichiometric ratio of [OH-/Cо2 +] = 2 complete deposition in the form of cobalt hydroxide Co(OH)2 occurs. The apparent volume dependence curve in the CoSO4-NaOH-H2O system consists of two parts corresponding to a potentiometric titration curve. Conductivity curves have a clear kink at the point corresponding to the formation of the base salt and hydroxide. CVA for cobalt-containing solutions have characteristic peaks on the cathode wave, corresponding to the reduction of cobalt (III) to cobalt (II) and cobalt (II) to cobalt (0), the anode wave has an additional peak in the range of potentials +0.19 - +0.20 V. The gradual release of cations from cycle 1 to cycle 5 indicates the formation of stable cobalt polyhydroxocomplexes, which are gradually destroyed. Thus, it was found that the reaction between CoSO4 and NaOH proceeds in several stages with the formation of first the basic salt and then polyhydroxocomplexes. In solutions with a concentration of ССoSO4 = 0.4-0.5 mol/L, a basic salt of the composition Co(OH)1.8(SO4)0.1 is formed. In more dilute solutions a basic salt of the composition Cо(OH)1.9(SO4)0.05 is formed

Ti(3)C(2) MXene co-catalyst on metal sulfide photo-absorbers for enhanced visible-light photocatalytic hydrogen production

Scalable and sustainable solar hydrogen production through photocatalytic water splitting requires highly active and stable earth-abundant co-catalysts to replace expensive and rare platinum. Here we employ density functional theory calculations to direct atomic-level exploration, design and fabrication of a MXene material, Ti3C2 nanoparticles, as a highly efficient co-catalyst. Ti3C2 nanoparticles are rationally integrated with cadmium sulfide via a hydrothermal strategy to induce a super high visible-light photocatalytic hydrogen production activity of 14,342 μmol h-1 g-1 and an apparent quantum efficiency of 40.1% at 420 nm. This high performance arises from the favourable Fermi level position, electrical conductivity and hydrogen evolution capacity of Ti3C2 nanoparticles. Furthermore, Ti3C2 nanoparticles also serve as an efficient co-catalyst on ZnS or ZnxCd1-xS. This work demonstrates the potential of earth-abundant MXene family materials to construct numerous high performance and low-cost photocatalysts/photoelectrodes.Jingrun Ran, Guoping Gao, Fa-Tang Li, Tian-Yi Ma, Aijun Du and Shi-Zhang Qia

Catalytic dehydrocoupling of amine-boranes and amines into diaminoboranes: isolation of a Pt(II), Shimoi-type, η1-BH complex

The platinum complex [Pt(IBu′)(IBu)][BAr] is a very efficient catalyst in the synthesis of diaminoboranes through dehydrocoupling of amine-boranes and amines. Shimoi-type, η-BH complexes are key intermediates in the process.Financial support (FEDER contribution) from the MINECO (Projects CTQ2013-45011-P and CTQ2014-51912-REDC) and the Junta de Andalucía (Project FQM-2126) is gratefully acknowledged.We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).Peer Reviewe

Oxygen-tolerant proton reduction catalysis: Much O<inf>2</inf> about nothing?

This perspective summarises strategies for avoiding adverse effects of O2 on H2-evolving enzymatic systems, molecular synthetic catalysts and catalytic surfaces.Financial support from the EPSRC (EP/H00338X/2), the Christian Doppler Research Association (Austrian Federal Ministry of Science, Research and Economy and National Foundation for Research, Technology and Development), and the OMV Group is gratefully acknowledged.This is the final version of the article. It first appeared from the Royal Society of Chemistry via http://dx.doi.org/10.1039/C5EE01167

Nickel as a co-catalyst for photocatalytic hydrogen evolution on graphitic-carbon nitride (sg-CN): what is the nature of the active species?

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The nature of a nickel-based co-catalyst deposited on a sol-gel prepared porous graphitic-carbon nitride (sg-CN), for photocatalytic H-2 production from water, has been investigated. The formation of the active catalytic species, charge separation and recombination of the photogenerated electrons and holes during photochemical H-2 evolution has been determined for the first time using in situ EPR spectroscopy.DFG, EXC 314, Unifying Concepts in CatalysisBMBF, 03IS2071D, Light2Hydroge