Electrochemical water splitting requires efficient water oxidation catalysts to accelerate the sluggish kinetics of water oxidation reaction. Here, we report a promisingly dendritic core-shell ...nickel-iron-copper metal/metal oxide electrode, prepared via dealloying with an electrodeposited nickel-iron-copper alloy as a precursor, as the catalyst for water oxidation. The as-prepared core-shell nickel-iron-copper electrode is characterized with porous oxide shells and metallic cores. This tri-metal-based core-shell nickel-iron-copper electrode exhibits a remarkable activity toward water oxidation in alkaline medium with an overpotential of only 180 mV at a current density of 10 mA cm
. The core-shell NiFeCu electrode exhibits pH-dependent oxygen evolution reaction activity on the reversible hydrogen electrode scale, suggesting that non-concerted proton-electron transfers participate in catalyzing the oxygen evolution reaction. To the best of our knowledge, the as-fabricated core-shell nickel-iron-copper is one of the most promising oxygen evolution catalysts.
Highly active and low-cost electrocatalysts for water oxidation are required due to the demands on sustainable solar fuels; however, developing highly efficient catalysts to meet industrial ...requirements remains a challenge. Herein, we report a monolayer of nickel-vanadium-layered double hydroxide that shows a current density of 27 mA cm(-2) (57 mA cm(-2) after ohmic-drop correction) at an overpotential of 350 mV for water oxidation. Such performance is comparable to those of the best-performing nickel-iron-layered double hydroxides for water oxidation in alkaline media. Mechanistic studies indicate that the nickel-vanadium-layered double hydroxides can provide high intrinsic catalytic activity, mainly due to enhanced conductivity, facile electron transfer and abundant active sites. This work may expand the scope of cost-effective electrocatalysts for water splitting.
Noble‐metal‐free bimetal‐based electrocatalysts have shown high efficiency for water oxidation. Ni and/or Co in these electrocatalysts are essential to provide a conductive, high‐surface area and a ...chemically stable host. However, the necessity of Ni or Co limits the scope of low‐cost electrocatalysts. Herein, we report a hierarchical hollow FeV composite, which is Ni‐ and Co‐free and highly efficient for electrocatalytic water oxidation with low overpotential 390 mV (10 mA cm−2 catalytic current density), low Tafel slope of 36.7 mV dec−1, and a considerable durability. This work provides a novel and efficient catalyst, and greatly expands the scope of low‐cost Fe‐based electrocatalysts for water splitting without need of Ni or Co.
Missing, but not missed: Vanadium‐doped FeOOH is a low‐cost, highly efficient iron‐based electrocatalyst for water oxidation without Ni or Co participation. It exhibits a low overpotential 390 mV (10 mA cm−2 catalytic current density), low Tafel slope of 36.7 mV dec−1, and a considerable durability.
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A Ni-PY5 PY5=2,6-bis(1,1-bis(2-pyridyl)ethyl)pyridine) complex has been found to act as an electrocatalyst for oxidizing water to dioxygen in aqueous phosphate buffer solutions. The ...rate of water oxidation catalyzed by the Ni-PY5 is remarkably enhanced by the proton acceptor base HPO42−, with rate constant of 1820M−1s−1. Controlled potential bulk electrolysis with Ni-PY5 at pH 10.8 under an applied potential of 1.5V vs. normal hydrogen electrode (NHE) resulted in dioxygen formation with a high faradaic efficiency over 90%. A detailed mechanistic study identifies the water nucleophilic attack pathway for water oxidation catalysis.
Among the many gifted African American authors who emerged in the 1970s and 80s, John Edgar Wideman is one of the most challenging and innovative. His analytical mind can turn almost any topic into ...an intellectual adventure, whether it is playground basketball, the blues, the prison experience, father-son relationships, or the stories he lived or heard growing up in the impoverished section of Pittsburgh known as Homewood. In Understanding John Edgar Wideman, D. Quentin Miller offers a comprehensive overview of Wideman’s writings, which range from the critically acclaimed books of the Homewood Trilogy to lesser known writings such as the early novels A Glance Away and The Lynchers. Notably Miller includes the first scholarly analysis of Writing to Save a Life, Wideman’s recently published meditation on the military trial and execution of the father of civil rights martyr Emmett Till. In his fiction, nonfiction, and works that artfully combine both forms, Wideman has employed a multilayered and often difficult writing style in order to explore a wide range of topics. Miller tackles such topics as African American folk history, the intersection of personal and public history, the confluence of oral and written traditions, and the quest for meaning in nihilistic urban settings where black families struggle against crime, poverty, and despair. Miller also shows how Wideman’s singular personal history is interwoven into his writings. His impressive accomplishments, including an Ivy League education and numerous literary honors, have come alongside family tragedies. By the time his sixth novel was published, both his brother and son were serving life sentences for murder, a source of anguish that he wrestled with in Brothers and Keepers and Fatheralong. Wideman writes with such authority on so many subjects that readers frequently have no idea what to expect with a new publication. Understanding John Edgar Wideman is thus a necessary guide to a prolific, varied, and essential oeuvre.
The molecular water oxidation catalyst 1 was electrochemically polymerized on a dye-sensitized TiO2 electrode and an Fe2O3 nanorod electrode. High photocurrent densities of ca. 1.4 mA cm–2 for ...poly-1+RuP@TiO2 and ca. 0.4 mA cm–2 for poly-1@Fe2O3 were achieved under pH-neutral conditions. A kinetic isotope effect (KIE) study on poly-1+RuP@TiO2 shows that poly-1 catalyzes water oxidation on the surface of TiO2 via a radical coupling mechanism.
Photoelectrochemical (PEC) cells for light‐driven water splitting are prepared using hematite nanorod arrays on conductive glass as the photoanode. These devices improve the photocurrent of the ...hematite‐based photoanode for water splitting, owing to fewer surface traps and decreased electron recombination resulting from the one‐dimensional structure. By employing a molecular ruthenium co‐catalyst, which contains a strong 2,6‐pyridine‐dicarboxylic acid anchoring group at the hematite photoanode, the photocurrent of the PEC cell is enhanced with high stability for over 10 000 s in a 1 m KOH solution. This approach can pave a route for combining one‐dimensional nanomaterials and molecular catalysts to split water with high efficiency and stability.
Hold on tight! A molecular ruthenium catalyst containing a strong 2,6‐pyridine‐dicarboxylic acid anchoring group is successfully demonstrated as a co‐catalyst for the hematite photoanode. By combining a hematite nanorod array with this molecular ruthenium catalyst, the photocurrent of the photoelectrochemical device for water oxidation is not only enhanced, but also shows high stability.
Two molecular assemblies with one Ru(II)-polypyridine photosensitizer covalently linked to one Ru(II)(bda)L2 catalyst (1) (bda = 2,2′-bipyridine-6,6′-dicarboxylate) and two photosensitizers ...covalently linked to one catalyst (2) have been prepared using a simple C–C bond as the linkage. In the presence of sodium persulfate as a sacrificial electron acceptor, both of them show high activity for catalytic water oxidation driven by visible light, with a turnover number up to 200 for 2. The linked photocatalysts show a lower initial yield for light driven oxygen evolution but a much better photostability compared to the three component system with separate sensitizer, catalyst and acceptor, leading to a much greater turnover number. Photocatalytic experiments and time-resolved spectroscopy were carried out to probe the mechanism of this catalysis. The linked catalyst in its Ru(II) state rapidly quenches the sensitizer, predominantly by energy transfer. However, a higher stability under photocatalytic condition is shown for the linked sensitizer compared to the three component system, which is attributed to kinetic stabilization by rapid photosensitizer regeneration. Strategies for employment of the sensitizer-catalyst molecules in more efficient photocatalytic systems are discussed.
The use of cobalt porphyrin complexes as efficient and cost-effective molecular catalysts for water oxidation has been investigated previously. However, by combining a set of analytical techniques ...(electrochemistry, ultraviolet–visible spectroscopy (UV–vis), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and synchrotron-based photoelectron spectroscopy (SOXPES and HAXPES)), we have demonstrated that three different cobalt porphyrins, deposited on FTO glasses, decompose promptly into a thin film of CoOx on the surface of the electrode during water oxidation under certain conditions (borate buffer pH 9.2). It is presumed that the film is composed of CoO, only detectable by SOXPES, as conventional techniques are ineffective. This newly formed film has a high turnover frequency (TOF), while the high transparency of the CoOx-based electrode is very promising for future application in photoelectrochemical cells.
A series of molecularly engineered and novel dyes WS1, WS2, WS3, and WS4, based on the D35 donor, 1-(4-hexylphenyl)-2,5-di(thiophen-2-yl)-1H-pyrrole and ...4-(4-hexylphenyl)-4H-dithieno3,2-b:2′,3′-dpyrrole as π-conjugating linkers, were synthesized and compared to the well-known LEG4 dye. The performance of the dyes was investigated in combination with an electrolyte based on Co(II/III) complexes as redox shuttles. The electron recombination between the redox mediators in the electrolyte and the TiO2 interface decreases upon the introduction of 4-hexylybenzene entities on the 2,5-di(thiophen-2-yl)-1H-pyrrole and 4H-dithieno3,2-b:2′,3′-dpyrrole linker units, probably because of steric hindrance. The open circuit photovoltage of WS1-, WS2-, WS3-, and WS4-based devices in combination with the Co(II/III)-based electrolyte are consistently higher than those based on a I–/I3 – electrolyte by 105, 147, 167, and 75 mV, respectively. The WS3-based devices show the highest power conversion efficiency of 7.4% at AM 1.5 G 100 mW/cm2 illumination mainly attributable to the high open-circuit voltage (V OC).
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