Download Free Exploring New Applications Of Group 7 Complexes For Catalytic And Co2 Reduction Using Photons Or Electrochemistry Book in PDF and EPUB Free Download. You can read online Exploring New Applications Of Group 7 Complexes For Catalytic And Co2 Reduction Using Photons Or Electrochemistry and write the review.

This thesis focuses on the synthesis, characterization and reactivity of group VII transition metal complexes. It begins with exploring a new pincer geometry of Re(I) compounds and then examining both Re(I) and Mn(I) compound as homogenous catalysts for photocatalytic and electrocatalytic reduction of CO2. In the first chapter, I focus on some recently reported approaches to photocatalytic and electrocatalytic reduction of CO2 using homogenous catalysts of transition metal. The second chapter presents efforts to capture Re(I) in a neutral N,N,N pincer scaffold and the resulting enhanced absorption of visible light. Most of these results have appeared in a publication. In this thesis, I only present my work on rhenium compounds that are supported by the bis(imino)pyridine ligand and an examination of the differences in properties between the bidentate and tridentate ligand geometries. Later I examine both tridentate and bidentate complexes for the photocatalytic and electrocatalytic reduction of CO2 to CO. The failure of tridentate Re1 bis(imino)pyridine compounds to reduce CO2 to CO prompted a change in direction to rhenium compounds that are supported with diimine ligands. Thus, I choose 4,5-diazafluoren-9-one as supporting ligand for rhenium and manganese. This chapter explained the reasons behind choosing these particular ligand and metal combinations. ReI and Mn1 compounds of 4,5-diazafluoren-9-one have shown activity for the photocatalytic and electrocatalytic reduction of CO2 to CO. In the fourth chapter, as rhenium and manganese compounds of 4,5-diazafluoren-9-one have shown the great ability of CO2 reduction to CO, the focus here was to modify the ligand by attaching a photosensitizer to the ligand in order to prepare supramolecular complexes that may increase the efficiency and yield of reduction products. In this chapter, I examined two types of the photosensitizer; tris(bipyridine)ruthenium(II)chloride and osmium dichloro bis(4,​4'-​dimethyl-​2,​2'-​bipyridine).
The increase of the carbon dioxide concentration in the atmosphere provides a strong impetus to discover new catalysts that are able to reduce CO2. The reduction processes of this greenhouse gas CO2 have recently received enormous efforts in the research area. The objective of this thesis was the photocatalytic reduction of CO2 that is known as an artificial photosynthesis using visible light, and the objective of the thesis was to study the ability and efficiency of different new molecular catalysts towards CO2 reduction. The goals of the thesis are to design and characterize new catalysts that have high efficiency for the catalytic reduction of CO2. After a brief introduction in Chapter 1 about the photocatalytic reduction of CO2, a different catalyst is presented in each chapter with their characterization and examination for the photocatalytic reduction of CO2. In addition, these presented catalysts were also examined for the electrocatalytic reduction of CO2, but they show a good catalytic behavior in the photocatalytic reduction of CO2. The catalytic mechanisms were also suggested for each catalyst and tried to be confirmed by many different experiments. observed to be highly influenced by CO2 concentration. These newly discovered catalysts are based on transition metal complexes that are able to be good catalysts for the photocatalytic CO2 reduction. These new transition metal complexes have been synthesized, characterized and examined for their catalytic reactivity for CO2 reduction. As presented in Chapter 2, new manganese and rhenium ccomplexes bearing a phosphino-amino-pyridine ligand were synthesized, characterized and showed their photocatalytic ability for CO2 reduction. In addition, Chapter 3 presents new Ru catalysts supported by an unprecedented ligand array and documented their photocatalytic ability towards CO2 reduction. Moreover, Chapter 4 focuses on new Zn(II) complexes that are novel catalysts in the photocatalytic CO2 reduction area. Furthermore, Chapter 5 presents a new environment for Re photocatalyst that has the switch in product to formic acid compare to all other reported Re photocatalysts. On the other hand, Chapter 6 shows new dimers and monomers for a series of earth-abundant transition metal dibromide complexes supported by a neutral SNS ligand framework and reveals their applications in the catalysis. Finally, Chapter 7 presents a brief conclusion and a number of future directions. The attempts to explore and discover the new catalysts for CO2 reduction were exciting, successfully and resulted in the discovery of new catalysts. These catalysts show their good ability to reduce carbon dioxide (CO2) to more valuable products such as carbon monoxide (CO) and formic acid (HCOOH).
Filling the gap in the market for comprehensive coverage of this hot topic, this timely book covers a wide range of organic transformations, e. g. reductions of unsaturated compounds, oxidation reactions, Friedel-Crafts reactions, hydroamination reactions, depolymerizations, transformations of carbon dioxide, oxidative coupling reactions, as well as C-C, C-N, and C-O bond formation reactions. A chapter on the application of zinc catalysts in total synthesis is also included. With its aim of stimulating further research and discussion in the field, this is a valuable reference for professionals in academia and industry wishing to learn about the latest developments.
This book explores the modification of various synthesis processes to enhance the photocatalytic activity in varied applications in the fields of environmental remediation and energy production. It outlines the enhancement of photocatalytic activity via alloys synthesis, thin film coatings, electro-spun nanofibers and 3D printed photocatalysts. The book further states the diverse applications of materials for degrading organic pollutants and airborne pathogens, improving indoor air quality and as a potential antimicrobial agent. The application of photocatalysts in green organic synthesis, biomedical field and in hydrogen evolution are also presented in the book. It covers theoretical studies of photocatalytic material and conversion of CO2 to value added chemical feed stocks. The book is of relevance to researchers in academia and industry alike in the fields of material science, environmental science & technology, photocatalytic applications and in energy generation and conversion.
Explore green catalytic reactions with this reference from a renowned leader in the field Green reactions—like photo-, photoelectro-, and electro-catalytic reactions—offer viable technologies to solve difficult problems without significant damage to the environment. In particular, some gas-involved reactions are especially useful in the creation of liquid fuels and cost-effective products. In Photo- and Electro-Catalytic Processes: Water Splitting, N2 Fixing, CO2 Reduction, award-winning researcher Jianmin Ma delivers a comprehensive overview of photo-, electro-, and photoelectron-catalysts in a variety of processes, including O2 reduction, CO2 reduction, N2 reduction, H2 production, water oxidation, oxygen evolution, and hydrogen evolution. The book offers detailed information on the underlying mechanisms, costs, and synthetic methods of catalysts. Filled with authoritative and critical information on green catalytic processes that promise to answer many of our most pressing energy and environmental questions, this book also includes: Thorough introductions to electrocatalytic oxygen reduction and evolution reactions, as well as electrocatalytic hydrogen evolution reactions Comprehensive explorations of electrocatalytic water splitting, CO2 reduction, and N2 reduction Practical discussions of photoelectrocatalytic H2 production, water splitting, and CO2 reduction In-depth examinations of photoelectrochemical oxygen evolution and nitrogen reduction Perfect for catalytic chemists and photochemists, Photo- and Electro-Catalytic Processes: Water Splitting, N2 Fixing, CO2 Reduction also belongs in the libraries of materials scientists and inorganic chemists seeking a one-stop resource on the novel aspects of photo-, electro-, and photoelectro-catalytic reactions.
The oxygen reduction reaction (ORR) plays an important role in various life processes such as respiration and in energy conversion systems such as fuel cells and metal-air batteries. Achieving a selective and efficient ORR remains a significant challenge in energy conversion, where the sluggish kinetics of the ORR has also restricted its practical application. Platinum group metal (PGM) catalysts are currently the best-performing candidates for efficient reduction of O2 with overpotential less than 300 mV. However, scientists are exploring non-PGM ORR catalysts, due to their high abundance and low cost. Molecular first row transition-metal complexes, such as those macrocyclic ligands containing cobalt are the main representatives of non-precious ORR catalysts. This thesis details the comprehensive investigation of the selectivity, overpotential, mechanistic studies, and linear free energy relationship (LFER) analysis of homogeneous O2 reduction to H2O2 and H2O catalyzed by a series of monomeric cobalt complexes. Chapters 2-4 of this thesis depicts the homogeneous 2e[-]/2H+ O2 reduction catalyzed by a series of cobalt complexes bearing tetradentate N2O2-based ligands (Co(N2O2)). These studies show that H2O2 is directly produced from molecular O2 with an effective overpotential as low as 90 mV. A linear dependence of logarithm of turnover frequency (log(TOF)) is observed with respect to effective overpotential suggesting there exists a trade-off between the rate and overpotential for ORR with these Co(N2O2) complexes. However, the dependence is weaker compared with that of iron porphyrin (Fe(por)) complexes, which is rationalized by the different influence of effective overpotential on their turnover-limiting step. The subsequent mechanistic studies reveal that the protonation on the proximal oxygen atom of the CoIII(OOH) intermediate is the rate-limiting step in the ORR. Density functional theory (DFT) studies, in combination with kinetic and electrochemical studies, provide deeper mechanistic insights into the O2 reduction catalyzed by Co(N2O2) complexes. The small Brønsted coefficient and O2-independent rate law imply that the low-overpotential O2 reduction is achievable because the ORR rate is relatively insusceptible to the effective overpotential. The performance of monomeric cobalt ORR catalysts bearing N4-macrocyclic ligands reported in the literature is evaluated on the basis of their TOF and effective overpotential. It is shown for the first time that they all fall in the linear relationships between log(TOF) and effective overpotential. Chapters 5-7 of this thesis highlight the exploration of the homogeneous 4e[-]/4H+ reduction of O2 to H2O catalyzed by a series of cobalt porphyrin (Co(por)) complexes. The catalysis-initiating potential of the Co(por) complexes (half-wave potential, E1/2(CoIII/II)) is found to be independent of the pKa values of the acids, but the potential shift for O2/H2O redox couples is nearly 59 mV/pKa in organic media. This outcome suggests that the effective overpotential is correlated with the acid strength following Nernstian behavior of 59 mV/pKa unit. Thus, selective homogeneous 4e[-]/4H+ O2 reduction to H2O with effective overpotentials as low as 50 mV is achieved by using high-potential Co(por) complexes and modulating the O2/H2O redox couple with different acids. A second effect of this modulation is that the selective reduction of O2 to H2O is observed when the E1/2(CoIII/II) of the monomeric cobalt complexes are above the O2/H2O2 redox couple, implying that the ORR selectivity is tunable based on thermodynamic constraints. A crossover in the LFER of the O2 reduction mediated by the same Co(por) complex exhibits that the susceptibility of the log(TOF) to effective overpotential changes with the ORR selectivity (H2O vs. H2O2). The different slopes of the relationship between log(TOF) and effective overpotential for O2/H2O and O2/H2O2 is elucidated by their distinctive rate laws and catalytic mechanisms. Finally, the different LFERs for the O2 reduction catalyzed by monomeric cobalt and iron complexes between the log(TOF) and effective overpotential are attributed to their different Brønsted coefficients, rate laws, and catalytic mechanisms, and the performance of molecular cobalt and iron ORR catalysts are quantitatively evaluated with LFER analyses. Collectively, this thesis delineates the opportunities for the utilization of molecular cobalt catalysts for achieving selective 2e-/2H+ and 4e[-]/4H+ reduction of O2 with low overpotentials. The overpotential can be tuned using different cobalt catalysts and reaction media under homogeneous conditions, and this feature serves as the basis for switching the selectivity from H2O2 to H2O or vice versa based on thermodynamic restraints.
Electrocatalytic reduction of carbon dioxide (CO2) is a profoundly challenging problem that is of interest, not only as a means of counteracting unsustainable emissions of CO2, but also as a method for the development of renewable fuels. Rhenium and manganese bipyridine tricarbonyl complexes are among the most active and robust catalysts for proton-coupled CO2 reduction to carbon monoxide (CO). X-ray Absorption Spectroscopy studies are reported to reveal the electronic ground state of the Re catalysts, which help explain origins for high selectivity for CO2 reduction over proton reduction. Stopped-flow mixing in tandem with rapid-scan IR spectroscopy is utilized to probe the direct reaction of the Re catalysts with CO2, observing, for the first time, the binding of CO2 to these catalysts. Manganese bipyridine catalysts are desirable, in comparison with their Re analogs, due to the earth-abundance of Mn and the ability for these catalysts to operate at lower overpotentials. One distinct difference between these Mn catalysts and their Re counterparts is a high tendency for dimerization after one-electron reduction, which contributes to the potential necessary to access their active state and to limiting their catalytic activity. Synthetic modification of the bipyridine ligand (by adding bulky mesityl groups) is used to completely eliminate dimerization for these Mn complexes, allowing the active catalyst to be generated at a 300 mV more positive potential than in typically Mn bipyridine complexes. CO2 reactivities in the presence of weak Brønsted acids, strong Brønsted acids, and Lewis acids have been explored in order to encourage this bulky Mn catalyst to reduce CO2 at low overpotentials. Mechanistic tools, including IR-spectroelectrochemistry, are described to gain insight into these unique catalytic processes. In order to further enhance stability and facilitate product separation, the use of metal-organic frameworks (MOFs) is explored as a means of anchoring molecular catalysts on a heterogeneous platform. A Mn bipyridine catalyst attached to a highly robust Zr(IV)-based MOF is used to enhance photochemical CO2 reduction. By utilizing an iron porphyrin catalyst, anchored into the linkers of a MOF thin film, we demonstrate, in a proof of principle, electrochemical CO2 reduction by this heterogenized molecular catalyst.
The use of fossil fuels to meet our energy requirements has contributed significantly to increase the atmospheric carbon dioxide level causing global warming. This calls for the development of processes to reduce CO2 level and its conversion to other value-added products. In this regard, photocatalytic CO2 reduction using sunlight is a key reaction to achieve artificial photosynthesis to produce solar or renewable fuels. Designing efficient and robust catalysts for this reduction reaction is crucial and remains a challenging task. Recently, N-heterocyclic carbenes (NHCs) have emerged as strong donor ligands that are useful for forming transition metal-based catalysts. The combination of two NHCs with a central pyridyl ring in a symmetric fashion results in a tridentate CNC-pincer framework that can promote catalyst stability. Metal complexes containing such CNC-pincer ligands along with other co-ligands have been synthesized, characterized, and evaluated for photocatalytic CO2 reduction reaction (CO2-RR). We have shown that the use of a bidentate co-ligand (2,2ʣ-bipyiridine (bpy)) along with a CNC-pincer in ruthenium complexes ([(CNC)RuIIL(bpy)]n+, L is chloride or acetonitrile) resulted in the development of self-sensitized catalysts for photocatalytic CO2-RR under photosensitizer (PS) free conditions. The effect of various donor groups at the 4-position of the central pyridyl ring in CNC-pincer ligand has been evaluated via structure-activity relationships for sensitized photocatalytic CO2-RR in the presence of an external PS using [(CNC)RuIICl(MeCN)2]+ complexes. We have also compared the positional effect for one of the donor group. To further explore the structure-activity relationships, 11 novel ruthenium complexes with the general formula [(CNC)RuIIL(NN)]n+ (NN = diimine ligands, L = chloride or bromide or acetonitrile) were synthesized, characterized, and evaluated for sensitized and self-sensitized photocatalytic CO2-RR. The structures include two CNC-pincer ligands based on imidazole and benzimidazole derived NHCs and three diimine ligands including bpy, 4,4ʣ-dimethyl-2,2ʣ-bipyridine (dmb), and 1,10-phenanthroline. The development of heterogeneous catalysts has also been pursued. Two highly active homogeneous photocatalysts containing CNC-pincer and bpy co-ligand on ruthenium were considered for surface immobilization to develop heterogeneous catalysts with well-defined active sites. Syntheses of ruthenium complexes via bpy ligand modifications are described that can be immobilized onto an inert solid support for surface organometallic chemistry (SOMC). In addition, we have attempted to explore the use of first-row transition metals to develop catalysts for photocatalytic CO2-RR. The development of nickel CNC-pincer complexes for this reduction reaction has been described. We also aimed to synthesized iron-based catalysts and the efforts are described. The use of bulkier wing-tip groups on the CNC-pincer ligands and phosphine co-ligand resulted in the formation of miscellaneous ruthenium complexes.
This book explains the basic and fundamental aspects of nanotechnology and the potential use of nanostructured photocatalysts in various applications, especially in the context of the environment and energy harvesting. It describes the preparation and characterization of unique nanostructured photocatalysts and provides details of their catalytic action, and also discusses the design of new types of photocatalysts with controlled nanostructures. Given its broad scope, the book will appeal to academic and industrial researchers interested in heterogeneous photocatalysis, sustainable chemistry, energy conversion and storage, nanotechnology, chemical engineering, environmental protection, optoelectronics, sensors and surface and interface science.
One of the crucial challenges in the energy sector is the efficient capture and utilisation of CO2 generated from fossil fuels. Carbon capture and storage technologies can provide viable alternatives for energy intensive processes, although implementation of large-scale demonstrators remains challenging. Therefore, innovative technologies are needed that are capable of processing CO2 emission from a wide range of sources, ideally without additional fossil energy demand (e.g. solar driven or overcoming the limits of photosynthesis). This book covers the most recent developments in the field of electrochemical reduction of CO2, from first-principle mechanistic studies to technological perspectives. An introduction to basic concepts in electrochemistry and electrocatalysis is included to provide a background for newcomers to this field. This book provides a comprehensive overview for researchers and industrial chemists working in environmental science, electrochemistry and chemical engineering.