Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

2.3. Evaluation of Photocatalytic Water Splitting 6507 2.3.1. Photocatalytic Activity 6507 2.3.2. Photocatalytic Stability 6507 3. UV-Active Photocatalysts for Water Splitting 6507 3.1. d0 Metal Oxide Photocatalyts 6507 3.1.1. Ti-, Zr-Based Oxides 6507 3.1.2. Nb-, Ta-Based Oxides 6514 3.1.3. W-, Mo-Based Oxides 6517 3.1.4. Other d0 Metal Oxides 6518 3.2. d10 Metal Oxide Photocatalyts 6518 3.3. f0 Metal Oxide Photocatalysts 6518 3.4. Nonoxide Photocatalysts 6518 4. Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting 6519

Semiconductor-based Photocatalytic Hydrogen Generation

A fundamental aim in the field of catalysis is the development of new modes of small molecule activation. One approach toward the catalytic activation of organic molecules that has received much attention recently is visible light photoredox catalysis. In a general sense, this approach relies on the ability of metal complexes and organic dyes to engage in single-electron-transfer (SET) processes with organic substrates upon photoexcitation with visible light.

Many of the most commonly employed visible light photocatalysts are polypyridyl complexes of ruthenium and iridium, and are typified by the complex tris(2,2′-bipyridine) ruthenium(II), or Ru(bpy)32+ (Figure 1). These complexes absorb light in the visible region of the electromagnetic spectrum to give stable, long-lived photoexcited states.1,2 The lifetime of the excited species is sufficiently long (1100 ns for Ru(bpy)32+) that it may engage in bimolecular electron-transfer reactions in competition with deactivation pathways.3 Although these species are poor single-electron oxidants and reductants in the ground state, excitation of an electron affords excited states that are very potent single-electron-transfer reagents. Importantly, the conversion of these bench stable, benign catalysts to redox-active species upon irradiation with simple household lightbulbs represents a remarkably chemoselective trigger to induce unique and valuable catalytic processes.






Open in a separate window


Figure 1


Ruthenium polypyridyl complexes: versatile visible light photocatalysts.

/pdf/visible-light-photoredox-catalysis-with-transition-metal-5d1oxrsczo.pdf

Visible Light Photoredox Catalysis with Transition Metal Complexes: Applications in Organic Synthesis

As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

Overall water splitting with a semiconductor photocatalyst under visible-light irradiation is considered as a "dream reaction" in chemistry. The development of a 600 nm photocatalyst for solar water splitting highlighted here is not only an important milestone towards sustainable hydrogen production, but also a new starting point for artificial photosynthesis. STH=solar-to-hydrogen energy conversion efficiency.

Solar Water Splitting at λ=600 nm: A Step Closer to Sustainable Hydrogen Production.

Photocatalysis, which is the catalyzation of redox reactions via the use of energy obtained from light sources, is a topic that has garnered a lot of attention in recent years as a means of addressing the environmental and economic issues plaguing society today. Of particular interest are photosynthesis can potentially mimic a variety of vital reactions, many of which hold the key to develop sustainable energy economy. In light of this, many of the technological and procedural advancements that have recently occurred in the field are discussed in this review, namely those linked to: (1) photocatalysts made from metal oxides, nitride, and sulfides; (2) photocatalysis via polymeric carbon nitride (PCN); and (3) general advances and mechanistic insights related to TiO2-based catalysts. The challenges and opportunities that have arisen over the past few years are discussed in detail. Basic concepts and experimental procedures which could be useful for eventually overcoming the problems associated with photocatalysis are presented herein.

Photocatalysis: an overview of recent developments and technological advancements

Covalent Organic Framework Hosting Metalloporphyrin-Based Carbon Dots for Visible-Light-Driven Selective CO2 Reduction

Zn 2 GeO 4 nanorods were prepared by a surfactant-assisted hydrothermal method and used as photocatalysts for the decomposition of organic pollutants in water. The physicochemical properties of the Zn 2 GeO 4 photocatalysts were characterized by several techniques, and their photocatalytic activity was evaluated by the decomposition of methyl orange, salicylic acid, and 4-chlorophenol in aqueous solution. The results revealed that the Zn 2 GeO 4 nanorods have a much higher photocatalytic activity for decomposing organic pollutants in aqueous solution than both Zn 2 GeO 4 prepared by a conventional solid-state reaction and widely used TiO 2 (Degussa P25). There is no obvious deactivation of Zn 2 GeO 4 nanorods in the photocatalytic reactions. The intermediates of the photocatalytic reactions were monitored by LC-MS, and possible photocatalytic reaction pathways as to how Zn 2 GeO 4 nanorods degrade organic dyes were proposed.

Synthesis and Photocatalytic Activity of Zn2GeO4 Nanorods for the Degradation of Organic Pollutants in Water

The reduction of CO2 with visible light is a highly sustainable method for producing valuable chemicals. The function-led design of organic conjugated semiconductors with more chemical variety than that of inorganic semiconductors has emerged as a method for achieving carbon photofixation chemistry. Here, we report the molecular engineering of triazine-based conjugated microporous polymers to capture, activate and reduce CO2 to CO with visible light. The optical band gap of the CMPs is engineered by varying the organic electron-withdrawing (benzothiadiazole) and electron-donating units (thiophene) on the skeleton of the triazine rings while creating organic donor-acceptor junctions to promote the charge separation. This engineering also provides control of the texture, surface functionality and redox potentials of CMPs for achieving the light-induced conversion of CO2 to CO ambient conditions.

Xinchen Wang

Papers

Solar Water Splitting at λ=600 nm: A Step Closer to Sustainable Hydrogen Production.

Photocatalysis: an overview of recent developments and technological advancements

Covalent Organic Framework Hosting Metalloporphyrin-Based Carbon Dots for Visible-Light-Driven Selective CO2 Reduction

Synthesis and Photocatalytic Activity of Zn2GeO4 Nanorods for the Degradation of Organic Pollutants in Water

Functional Conjugated Polymers for CO2 Reduction Using Visible Light