Failure Mechanism of Fiber-Reinforced Prestressed Concrete Containments under Internal Pressure Considering Different Fiber Types

Current investigations of performance improvement in prestressed concrete containment vessels (PCCVs) with fiber reinforcement are scarce, and the type of fiber to select for PCCVs is not explicitly stated. The failure mechanism of PCCVs with fiber reinforcement under internal pressure is investigated in this paper. The effects of different fiber types, including rigid fiber, flexible fiber, and hybrid fiber, are considered for the creation of fiber-reinforced PCCVs. The mechanical behavior between conventional and fiber-reinforced PCCVs is scientifically compared and identified. The results demonstrate that to achieve the aim of inhibiting early cracking of the concrete, any type of fiber can be taken into account. The performance of the ultimate pressure capacity and yielding of the liner can be promoted, respectively, by introducing steel, steel-PP, and steel-PVA fiber-reinforced concrete. Additionally, the failure regions can be controlled to a certain extent under ultimate internal pressure via the appropriate use of FRC

Switching the O-O Bond Formation Pathways of Ru-pda Water Oxidation Catalyst by Third Coordination Sphere Engineering

Water oxidation is a vital anodic reaction for renewable fuel generation via electrochemical- and photoelectrochemical-driven water splitting or CO2 reduction. Ruthenium complexes, such as Ru-bda family, have been shown as highly efficient water-oxidation catalysts (WOCs), particularly when they undergo a bimolecular O-O bond formation pathway. In this study, a novel Ru(pda)-type (pda2– =1,10-phenanthroline-2,9-dicarboxylate) molecular WOC with 4-vinylpyridine axial ligands was immobilized on the glassy carbon electrode surface by electrochemical polymerization. Electrochemical kinetic studies revealed that this homocoupling polymer catalyzes water oxidation through a bimolecular radical coupling pathway, where interaction between two Ru(pda)–oxyl moieties (I2M) forms the O-O bond. The calculated barrier of the I2M pathway by density-functional theory (DFT) is significantly lower than the barrier of a water nucleophilic attack (WNA) pathway. By using this polymerization strategy, the Ru centers are brought closer in the distance, and the O-O bond formation pathway by the Ru (pda) catalyst is switched from WNA in a homogeneous molecular catalytic system to I2M in the polymerized film, providing some deep insights into the importance of third coordination sphere engineering of the water oxidation catalyst

Catalytic Water Oxidation by Mononuclear Ru Complexes with an Anionic Ancillary Ligand

Mononuclear Ru-based water oxidation catalysts containing anionic ancillary ligands have shown promising catalytic efficiency and intriguing properties. However, their insolubility in water restricts a detailed mechanism investigation. In order to overcome this disadvantage, complexes [Ru^II(bpc)­(bpy)­OH₂]⁺ (<b>1</b>⁺, bpc = 2,2′-bipyridine-6-carboxylate, bpy = 2,2′-bipyridine) and [Ru^II(bpc)­(pic)₃]⁺ (<b>2</b>⁺, pic = 4-picoline) were prepared and fully characterized, which features an anionic tridentate ligand and has enough solubility for spectroscopic study in water. Using Ce^IV as an electron acceptor, both complexes are able to catalyze O₂-evolving reaction with an impressive rate constant. On the basis of the electrochemical and kinetic studies, a water nucleophilic attack pathway was proposed as the dominant catalytic cycle of the catalytic water oxidation by <b>1</b>⁺, within which several intermediates were detected by MS. Meanwhile, an auxiliary pathway that is related to the concentration of Ce^IV was also revealed. The effect of anionic ligand regarding catalytic water oxidation was discussed explicitly in comparison with previously reported mononuclear Ru catalysts carrying neutral tridentate ligands, for example, 2,2′:6′,2″-terpyridine (tpy). When <b>2</b>⁺ was oxidized to the trivalent state, one of its picoline ligands dissociated from the Ru center. The rate constant of picoline dissociation was evaluated from time-resolved UV–vis spectra

Catalytic Water Oxidation by Mononuclear Ru Complexes with an Anionic Ancillary Ligand

Mononuclear Ru-based water oxidation catalysts containing anionic ancillary ligands have shown promising catalytic efficiency and intriguing properties. However, their insolubility in water restricts a detailed mechanism investigation. In order to overcome this disadvantage, complexes [Ru^II(bpc)­(bpy)­OH₂]⁺ (<b>1</b>⁺, bpc = 2,2′-bipyridine-6-carboxylate, bpy = 2,2′-bipyridine) and [Ru^II(bpc)­(pic)₃]⁺ (<b>2</b>⁺, pic = 4-picoline) were prepared and fully characterized, which features an anionic tridentate ligand and has enough solubility for spectroscopic study in water. Using Ce^IV as an electron acceptor, both complexes are able to catalyze O₂-evolving reaction with an impressive rate constant. On the basis of the electrochemical and kinetic studies, a water nucleophilic attack pathway was proposed as the dominant catalytic cycle of the catalytic water oxidation by <b>1</b>⁺, within which several intermediates were detected by MS. Meanwhile, an auxiliary pathway that is related to the concentration of Ce^IV was also revealed. The effect of anionic ligand regarding catalytic water oxidation was discussed explicitly in comparison with previously reported mononuclear Ru catalysts carrying neutral tridentate ligands, for example, 2,2′:6′,2″-terpyridine (tpy). When <b>2</b>⁺ was oxidized to the trivalent state, one of its picoline ligands dissociated from the Ru center. The rate constant of picoline dissociation was evaluated from time-resolved UV–vis spectra

Water Oxidation Catalysis: Influence of Anionic Ligands upon the Redox Properties and Catalytic Performance of Mononuclear Ruthenium Complexes

Aiming at highly efficient molecular catalysts for water oxidation, a mononuclear ruthenium complex Ru^II(hqc)­(pic)₃ (<b>1</b>; H₂hqc = 8-hydroxyquinoline-2-carboxylic acid and pic = 4-picoline) containing negatively charged carboxylate and phenolate donor groups has been designed and synthesized. As a comparison, two reference complexes, Ru^II(pdc)­(pic)₃ (<b>2</b>; H₂pdc = 2,6-pyridine-dicarboxylic acid) and Ru^II(tpy)­(pic)₃ (<b>3</b>; tpy = 2,2′:6′,2″-terpyridine), have also been prepared. All three complexes are fully characterized by NMR, mass spectrometry (MS), and X-ray crystallography. Complex <b>1</b> showed a high efficiency toward catalytic water oxidation either driven by chemical oxidant (Ce^IV in a pH 1 solution) with a initial turnover number of 0.32 s^–1, which is several orders of magnitude higher than that of related mononuclear ruthenium catalysts reported in the literature, or driven by visible light in a three-component system with [Ru­(bpy)₃]²⁺ types of photosensitizers. Electrospray ionization MS results revealed that at the Ru^III state complex <b>1</b> undergoes ligand exchange of 4-picoline with water, forming the authentic water oxidation catalyst in situ. Density functional theory (DFT) was employed to explain how anionic ligands (hqc and pdc) facilitate the 4-picoline dissociation compared with a neutral ligand (tpy). Electrochemical measurements show that complex <b>1</b> has a much lower <i>E</i>(Ru^III/Ru^II) than that of reference complex <b>2</b> because of the introduction of a phenolate ligand. DFT was further used to study the influence of anionic ligands upon the redox properties of mononuclear aquaruthenium species, which are postulated to be involved in the catalysis cycle of water oxidation

Water Oxidation Catalyzed by Mononuclear Ruthenium Complexes with a 2,2′-Bipyridine-6,6′-dicarboxylate (bda) Ligand: How Ligand Environment Influences the Catalytic Behavior

A new water oxidation catalyst [Ru^III(bda)­(mmi)­(OH₂)]­(CF₃SO₃) (<b>2</b>, H₂bda = 2,2′-bipyridine-6,6′-dicarboxylic acid; mmi = 1,3-dimethylimidazolium-2-ylidene) containing an axial N-heterocyclic carbene ligand and one aqua ligand was synthesized and fully characterized. The kinetics of catalytic water oxidation by <b>2</b> were measured using stopped-flow technique, and key intermediates in the catalytic cycle were probed by density functional theory calculations. While analogous Ru-bda water oxidation catalysts [Ru­(bda)­L₂] (L = pyridyl ligands) are supposed to catalyze water oxidation through a bimolecular coupling pathway, our study points out that <b>2</b>, surprisingly, undergoes a single-site water nucleophilic attack (acid–base) pathway. The diversion of catalytic mechanisms is mainly ascribed to the different ligand environments, from nonaqua ligands to an aqua ligand. Findings in this work provide some critical proof for our previous hypothesis about how alternation of ancillary ligands of water oxidation catalysts influences their catalytic efficiency