scholarly journals Molecular Cu(I)-Cu(II) Photosensitizer-Catalyst Photoelectrode for Water Oxidation

2020 ◽  
Author(s):  
Zujhar Singh ◽  
Pedro Donnarumma ◽  
Marek Majewski
Keyword(s):  
Aqueous Solution ◽  
Zinc Oxide ◽  
Water Oxidation ◽  
Light Harvesting ◽  
High Energy ◽  
Molecular Assembly ◽  
Oxidation Catalyst ◽  
Faradaic Efficiency ◽  
Nanowire Surface ◽  
A Charge

Photochemical splitting of H<sub>2</sub>O to H<sub>2</sub> and O<sub>2</sub> is one approach to generate "solar fuels." Cu(II)-based electrocatalysts for water oxidation in aqueous solution have been studied previously, but photodriving these systems still remains a challenge. Light harvesting units can be employed for this purpose, that upon photoexcitation generate a high energy excited state and give rise to a charge separated state. In this work, a bis-diimine Cu(I)-based donor-chromophore-acceptor (D-C-A) system is synthesized, characterized, and applied as the light harvesting component of a photoanode. Here, this molecular assembly was integrated onto a zinc oxide (ZnO) nanowire surface on a fluorine-doped tin oxide (FTO) glass slide. Upon photoexcitation, chronoamperometric studies reveal that the integrated triad can inject electrons directly into the conduction band of zinc oxide generating oxidizing equivalents that are then transferred to a Cu(II) water oxidation catalyst in aqueous solution yielding O<sub>2</sub> from H<sub>2</sub>O with a Faradaic efficiency of 76%. <br>

scholarly journals Molecular Cu(I)-Cu(II) Photosensitizer-Catalyst Photoelectrode for Water Oxidation

2020 ◽  
Author(s):  
Zujhar Singh ◽  
Pedro Donnarumma ◽  
Marek Majewski
Keyword(s):  
Aqueous Solution ◽  
Zinc Oxide ◽  
Water Oxidation ◽  
Light Harvesting ◽  
High Energy ◽  
Molecular Assembly ◽  
Oxidation Catalyst ◽  
Faradaic Efficiency ◽  
Nanowire Surface ◽  
A Charge

Photochemical splitting of H<sub>2</sub>O to H<sub>2</sub> and O<sub>2</sub> is one approach to generate "solar fuels." Cu(II)-based electrocatalysts for water oxidation in aqueous solution have been studied previously, but photodriving these systems still remains a challenge. Light harvesting units can be employed for this purpose, that upon photoexcitation generate a high energy excited state and give rise to a charge separated state. In this work, a bis-diimine Cu(I)-based donor-chromophore-acceptor (D-C-A) system is synthesized, characterized, and applied as the light harvesting component of a photoanode. Here, this molecular assembly was integrated onto a zinc oxide (ZnO) nanowire surface on a fluorine-doped tin oxide (FTO) glass slide. Upon photoexcitation, chronoamperometric studies reveal that the integrated triad can inject electrons directly into the conduction band of zinc oxide generating oxidizing equivalents that are then transferred to a Cu(II) water oxidation catalyst in aqueous solution yielding O<sub>2</sub> from H<sub>2</sub>O with a Faradaic efficiency of 76%. <br>

(Invited) Visible Light-Driven Water Oxidation with Porphyrin Sensitizers and Water Oxidation Catalysts

2018 ◽  
Vol MA2018-01 (31) ◽  
pp. 1852-1852
Author(s):  
Hiroshi Imahori
Keyword(s):  
Excited State ◽  
Visible Light ◽  
Water Oxidation ◽  
Light Harvesting ◽  
Visible Region ◽  
Oxidation Catalyst ◽  
Efficient Production ◽  
Oxidation Catalysts ◽  
Visible Light Driven ◽  
Artificial Photosynthetic

Exporing renewable energy sources is an important task in making our society sustainable. In this regard, use of sunlight as an infinite energy source is fascinating. Specifically, realizing artificial photosynthesis, i.e., integration of light-harvesting, multi-step electron and proton transfer, and water oxidation for the efficient production of solar fuels, is a great challenge in chemistry. For the purpose, dye-sensitized photoelectrosynthesis cells (DSPSC) have been investigated, as the heterogeneous water splitting on inorganic semiconductors is promising for the upcoming large scale device operation. In DSPSC a molecular sensitizer adsorbed on a semiconducting electrode harvests visible light and injects an electron from the excited-state of the sensitizer (S*) to a conduction band (CB) of the electrode. Then, the sensitizer radical cation (S• +) extracts an electron from a water oxidation catalyst (WOC) to regenerate the sensitizer and one-electron oxidized WOC. After reiterating the cycle, high oxidation states of the WOC are produced, eventually transforming two water molecules into four protons and one oxygen molecule. As the sensitizer bis(2,2’-bipyridine)(4,4’-diphosphonato-2,2’-bipyridine)ruthenium(II) (RuP) has been frequently employed for the construction of molecule-based artificial photosynthetic systems, owing to its sufficient first oxidation potential for water oxidation and a long lifetime of its excited state for electron injection. However, the light-harvesting ability of RuP is rather low in visible region beyond 500 nm. Considering that yellow to red photons mainly shower down on the earth from sun, use of photons in visible region is essential for efficient chemical conversion by sunlight. In this context, porphyrins are attractive as the sensitizer due to their excellent light-harvesting in visible region and facile tuning of their excited-states and redox properties by their chemical functionalization. Nevertheless, molecule-based artificial photosynthetic systems with porphyrins as the sensitizer have been very limited as the result of their poor performance. One plausible reason is the occurrence of fast charge recombination (CR) between the electron injected into the CB of TiO2 (denoted as TiO2(e−)) and S• +. CR from TiO2(e−) to the oxidized WOC would also take place within a few microsecond. Undesirable CR from TiO2(e−) to water is indicated. Thus, to overcome the disadvantages, it is crucial to optimize the electron transfer (ET) processes at the interfaces. In this talk, I will give an overview of our recent initiatives on visible light-driven water oxidation with novel porphyrin sensitizers and water oxidation catalysts. [1] M. Yamamoto, L. Wang, F. Li, T. Fukushima, K. Tanaka, L. Sun and H. Imahori, Chem. Sci., 7, 1430-1439 (2016). [2] M. Yamamoto, Y. Nishizawa, P. Chábera, F. Li, T. Pascher, V. Sundström, L. Sun, and H. Imahori, Chem. Commun., 52, 13702-13705 (2016). [3] M. Yamamoto, J. Föhlinger, J. Petersson, L. Hammarström, and H. Imahori, Angew. Chem. Int. Ed., 56, 3329-3333 (2017).

scholarly journals Efficient electrolyzer for CO2 splitting in neutral water using earth-abundant materials

2016 ◽  
Vol 113 (20) ◽  
pp. 5526-5529 ◽  
Author(s):  
Arnaud Tatin ◽  
Clément Comminges ◽  
Boniface Kokoh ◽  
Cyrille Costentin ◽  
Marc Robert ◽  
...  
Keyword(s):  
Energy Efficiency ◽  
Water Oxidation ◽  
High Efficiency ◽  
Low Voltage ◽  
High Energy ◽  
Nafion Membrane ◽  
Powder Layer ◽  
Carbon Powder ◽  
Faradaic Efficiency ◽  
Neutral Water

Low-cost, efficient CO2-to-CO+O2 electrochemical splitting is a key step for liquid-fuel production for renewable energy storage and use of CO2 as a feedstock for chemicals. Heterogeneous catalysts for cathodic CO2-to-CO associated with an O2-evolving anodic reaction in high-energy-efficiency cells are not yet available. An iron porphyrin immobilized into a conductive Nafion/carbon powder layer is a stable cathode producing CO in pH neutral water with 90% faradaic efficiency. It is coupled with a water oxidation phosphate cobalt oxide anode in a home-made electrolyzer by means of a Nafion membrane. Current densities of approximately 1 mA/cm2 over 30-h electrolysis are achieved at a 2.5-V cell voltage, splitting CO2 and H2O into CO and O2 with a 50% energy efficiency. Remarkably, CO2 reduction outweighs the concurrent water reduction. The setup does not prevent high-efficiency proton transport through the Nafion membrane separator: The ohmic drop loss is only 0.1 V and the pH remains stable. These results demonstrate the possibility to set up an efficient, low-voltage, electrochemical cell that converts CO2 into CO and O2 by associating a cathodic-supported molecular catalyst based on an abundant transition metal with a cheap, easy-to-prepare anodic catalyst oxidizing water into O2.

scholarly journals A Tetranuclear Cobalt (II) Phosphate Possessing a D4R Core: An Efficient Water Oxidation Catalyst

2019 ◽  
Author(s):  
Atanu Dey ◽  
Virendra Kumar ◽  
Shubhadeep Pal ◽  
Anku Guha ◽  
Sumit Bawari ◽  
...  
Keyword(s):  
Water Oxidation ◽  
Density Functional ◽  
Oxidation Catalyst ◽  
Phosphate Ester ◽  
Durability Test ◽  
Efficient Catalyst ◽  
Functional Theory ◽  
Faradaic Efficiency ◽  
Alkaline Conditions ◽  
Current Densities

<p>The reaction of Co(OAc)<sub>2</sub>·4H<sub>2</sub>O with the sterically hindered phosphate ester, LH<sub>2</sub>, afforded the tetranuclear complex, [Co<sup>II</sup>(L)(CH<sub>3</sub>CN)]<sub>4</sub>∙5CH<sub>3</sub>CN (<b>1</b>) [LH<sub>2</sub> = <a>2,6</a>‐(diphenylmethyl)‐4‐isopropyl‐phenyl phosphate]. The molecular structure of <b>1</b> reveals that it is a tetranuclear assembly where the Co(II) centers are present in the alternate corners of a cube. The four Co(II) centers are held together by four di-anionic [L]<sup>2-</sup> ligands. The fourth coordination site on Co(II) is taken by an acetonitrile ligand. Changing the Co(II) precursor from Co(OAc)<sub>2</sub>·4H<sub>2</sub>O to Co(NO<sub>3</sub>)<sub>2</sub>.6H<sub>2</sub>O afforded the mononuclear complex [Co<sup>II</sup>(LH)<sub>2</sub>(CH<sub>3</sub>CN)<sub>2</sub>(MeOH)<sub>2</sub>](MeOH)<sub>2 </sub>(<b>2). </b>In<b> 2, </b>the Co(II) is surrounded by two monoanionic [LH]<sup>‒</sup> ligands, and a pair of methanol and acetonitrile solvents in a six-coordinate arrangement. <b>1</b> has been found to be an efficient catalyst for the electrochemical water oxidation under high basic conditions while the mononuclear analogue, <b>2</b>, does not respond towards electrochemical water oxidation. The tetranuclear catalyst has excellent electrochemcial stability and longevity, as established by the chronoamperometry and >1000 cycles durability test in high alkaline conditions. Excellent current densities of 1 and 10 mAcm<sup>‒2</sup> were achieved with the overpotential of 354 and 452 mV respectively. The turnover frequency of this catalyst was calculated as 5.23 s<sup>−1 </sup>with excellent faradaic efficiency of 97%, indicating the selective oxygen evolution (OER) process happening with the aid of this catalyst. A mechanistic insight in to the higher activity of complex <b>1</b> towards OER compared to complex <b>2 </b>is also provided with the help of density functional theory based calculations.</p>

scholarly journals A Tetranuclear Cobalt (II) Phosphate Possessing a D4R Core: An Efficient Water Oxidation Catalyst

2019 ◽  
Author(s):  
Atanu Dey ◽  
Virendra Kumar ◽  
Shubhadeep Pal ◽  
Anku Guha ◽  
Sumit Bawari ◽  
...  
Keyword(s):  
Water Oxidation ◽  
Density Functional ◽  
Oxidation Catalyst ◽  
Phosphate Ester ◽  
Durability Test ◽  
Efficient Catalyst ◽  
Functional Theory ◽  
Faradaic Efficiency ◽  
Alkaline Conditions ◽  
Current Densities

<p>The reaction of Co(OAc)<sub>2</sub>·4H<sub>2</sub>O with the sterically hindered phosphate ester, LH<sub>2</sub>, afforded the tetranuclear complex, [Co<sup>II</sup>(L)(CH<sub>3</sub>CN)]<sub>4</sub>∙5CH<sub>3</sub>CN (<b>1</b>) [LH<sub>2</sub> = <a>2,6</a>‐(diphenylmethyl)‐4‐isopropyl‐phenyl phosphate]. The molecular structure of <b>1</b> reveals that it is a tetranuclear assembly where the Co(II) centers are present in the alternate corners of a cube. The four Co(II) centers are held together by four di-anionic [L]<sup>2-</sup> ligands. The fourth coordination site on Co(II) is taken by an acetonitrile ligand. Changing the Co(II) precursor from Co(OAc)<sub>2</sub>·4H<sub>2</sub>O to Co(NO<sub>3</sub>)<sub>2</sub>.6H<sub>2</sub>O afforded the mononuclear complex [Co<sup>II</sup>(LH)<sub>2</sub>(CH<sub>3</sub>CN)<sub>2</sub>(MeOH)<sub>2</sub>](MeOH)<sub>2 </sub>(<b>2). </b>In<b> 2, </b>the Co(II) is surrounded by two monoanionic [LH]<sup>‒</sup> ligands, and a pair of methanol and acetonitrile solvents in a six-coordinate arrangement. <b>1</b> has been found to be an efficient catalyst for the electrochemical water oxidation under high basic conditions while the mononuclear analogue, <b>2</b>, does not respond towards electrochemical water oxidation. The tetranuclear catalyst has excellent electrochemcial stability and longevity, as established by the chronoamperometry and >1000 cycles durability test in high alkaline conditions. Excellent current densities of 1 and 10 mAcm<sup>‒2</sup> were achieved with the overpotential of 354 and 452 mV respectively. The turnover frequency of this catalyst was calculated as 5.23 s<sup>−1 </sup>with excellent faradaic efficiency of 97%, indicating the selective oxygen evolution (OER) process happening with the aid of this catalyst. A mechanistic insight in to the higher activity of complex <b>1</b> towards OER compared to complex <b>2 </b>is also provided with the help of density functional theory based calculations.</p>

Photo-degradation of monoazo dye blue 13 using advanced oxidation process

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Aqueous Solution ◽  
Advanced Oxidation Process ◽  
Oxidation Process ◽  
High Energy ◽  
Uv Exposure ◽  
H2o2 Concentration ◽  
Oxidizing Agent ◽  
Photo Degradation ◽  
High Energy Radiation ◽  
Uv Lamp

The high energy radiation overcome the bonding of solute in a solution and H2O2 acts as an oxidizing agent and generates a free radical in the solution which results in photo-degradation by converting the solute in to simple form and resultantly, colored substance under the effect of photo-degradation becomes colorless. The photo-degradation of monoazo dye Blue 13 in an aqueous solution was investigated using a laboratory scale UV lamp in the presence of H2O2 and for maximum degradation of dye, the independent parameter UV power, UV exposure time, pH and H2O2 concentration were optimized. It was found that neither UV in the presence of H2O2 is able to degrade Blue 13 under optimum condition. The results revealed that the use of both UV and H2O2 have pronounced effect on the discoloration of dyes which could be used for management of textile effluents contain waste dyes.

Reactions in Activated Peroxide Systems and their Influences on Bleaching Performance

2020 ◽  
Vol 17 ◽  
Author(s):  
Xiaoyan Wang ◽  
Jinmei Du ◽  
Changhai Xu
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Peroxide ◽  
Energy Efficiency ◽  
Textile Industry ◽  
High Energy ◽  
Side Reactions ◽  
Competitive Reactions ◽  
High Energy Efficiency ◽  
Hydrolysis Of ◽  
Bleach Activators

Abstract:: Activated peroxide systems are formed by adding so-called bleach activators to aqueous solution of hydrogen peroxide, developed in the seventies of the last century for use in domestic laundry for their high energy efficiency and introduced at the beginning of the 21st century to the textile industry as an approach toward overcoming the extensive energy consumption in bleaching. In activated peroxide systems, bleach activators undergo perhydrolysis to generate more kinetically active peracids that enable bleaching under milder conditions while hydrolysis of bleach activators and decomposition of peracids may occur as side reactions to weaken the bleaching efficiency. This mini-review aims to summarize these competitive reactions in activated peroxide systems and their influence on bleaching performance.

scholarly journals Insights on forming N,O-coordinated Cu single-atom catalysts for electrochemical reduction CO2 to methane

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yanming Cai ◽  
Jiaju Fu ◽  
Yang Zhou ◽  
Yu-Chung Chang ◽  
Qianhao Min ◽  
...  
Keyword(s):  
Energy Barrier ◽  
Active Sites ◽  
Theoretical Calculations ◽  
High Energy ◽  
Single Atom ◽  
Faradaic Efficiency ◽  
High Energy Barrier ◽  
Catalytic Sites ◽  
Electron Reduction ◽  
First Time

AbstractSingle-atom catalysts (SACs) are promising candidates to catalyze electrochemical CO2 reduction (ECR) due to maximized atomic utilization. However, products are usually limited to CO instead of hydrocarbons or oxygenates due to unfavorable high energy barrier for further electron transfer on synthesized single atom catalytic sites. Here we report a novel partial-carbonization strategy to modify the electronic structures of center atoms on SACs for lowering the overall endothermic energy of key intermediates. A carbon-dots-based SAC margined with unique CuN2O2 sites was synthesized for the first time. The introduction of oxygen ligands brings remarkably high Faradaic efficiency (78%) and selectivity (99% of ECR products) for electrochemical converting CO2 to CH4 with current density of 40 mA·cm-2 in aqueous electrolytes, surpassing most reported SACs which stop at two-electron reduction. Theoretical calculations further revealed that the high selectivity and activity on CuN2O2 active sites are due to the proper elevated CH4 and H2 energy barrier and fine-tuned electronic structure of Cu active sites.

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