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Oxidative methane (CH

Atomically dispersed catalysts such as single-atom catalysts have been shown to be effective in selectively oxidizing methane, promising a direct synthetic route to value-added oxygenates such as acetic acid or methanol. However, an important challenge of this approach has been that the loading of active sites by single-atom catalysts is low, leading to a low overall yield of the products. Here, we report an approach that can address this issue. It utilizes a metal-organic framework built with porphyrin as the linker, which provides high concentrations of binding sites to support atomically dispersed rhodium. It is shown that up to 5 wt% rhodium loading can be achieved with excellent dispersity. When used for acetic acid synthesis by methane oxidation, a new benchmark performance of 23.62 mmol·gcat-1·h-1 was measured. Furthermore, the catalyst exhibits a unique sensitivity to light, producing acetic acid (under illumination, up to 66.4% selectivity) or methanol (in the dark, up to 65.0% selectivity) under otherwise identical reaction conditions.

Molecular catalysts are promising oxygen evolution promoters in conjunction with photoanodes for solar water splitting. Maintaining the stability of both photoabsorber and cocatalyst is still a prime challenge, with many efforts tackling this issue through sophisticated material designs. Such approaches often mask the importance of the electrode‐electrolyte interface and overlook easily tunable system parameters, such as the electrolyte environment, to improve efficiency. We provide a systematic study on the activity‐stability relationship of a prominent Fe2O3 photoanode modified with Ir molecular catalysts using in situ mass spectroscopy. After gaining detailed insights into the dissolution behavior of the Ir cocatalyst, a comprehensive pH study is conducted to probe the impact of the electrolyte on the performance. An inverse trend in Fe and Ir stability is found, with the best activity‐stability synergy obtained at pH 9.7. The results bring awareness to the overall photostability and electrolyte engineering when advancing catalysts for solar water splitting.

The accumulation of oxidative charges on atomically dispersed Ir catalytic sites shows dependence on the support. The impact of the hole redistribution on the rate of water oxidation leads to temperature-dependent kinetics of water oxidation.

Atomically dispersed catalysts have been shown highly active for preferential oxidation of carbon monoxide in the presence of excess hydrogen (PROX). However, their stability has been less than ideal. We show here that the introduction of a structural component to minimize diffusion of the active metal center can greatly improve the stability without compromising the activity. Using an Ir dinuclear heterogeneous catalyst (DHC) as a study platform, we identify two types of oxygen species, interfacial and bridge, that work in concert to enable both activity and stability. The work sheds important light on the synergistic effect between the active metal center and the supporting substrate and may find broad applications for the use of atomically dispersed catalysts.

The versatility of using electrodes to control catalytic reactions heralds a new paradigm in designing chemical transformations based on molecular compounds. Functionalization of molecular compounds on an electrically addressable surface offers an additional degree of freedom in controlling a catalyst’s reactivity and selectivity. Herein, we discuss the possibilities to harness electrode-supported molecular catalysts in electrocatalytic reactions and electrostatic effects observed in the surface-anchored systems recently reported. Furthermore, we summarize reported functionalization methods and outline how the proximate electrode asserts its influence on catalysis by a variety of avenues.

The utilization of carbon dioxide in polymer synthesis is an attractive strategy for sustainable materials. Electrochemical CO2 reduction would offer a natural starting point for producing monomers, but the conditions of electrocatalysis are often drastically different from the conditions of organometallic coordination-insertion polymerization. Reported here is a strategy for integrating electrochemical and organometallic catalysts that enables polyketone synthesis from CO2 and ethylene in a single multicompartment reactor. Polyketone materials that are up to 50% derived from CO2 can be prepared in this way. Potentiostatic control over the CO-producing catalyst enables the controlled generation of low-pressure CO, which in conjunction with a palladium phosphine sulfonate organometallic catalyst enables copolymerization to nonalternating polyketones with the CO content tuned based on the applied current density

Integrated catalysis is an emerging methodology that can streamline the multistep synthesis of complicated products in a single reaction vessel, achieving a high degree of control and reducing the waste and cost of the overall process. Integrated catalysis utilizes spatial and temporal control to couple different catalytic cycles in one pot. This primer discusses commonly employed spatial and temporal approaches and their underlying mechanisms, and elaborates on how the integration of spatially and temporally controlled catalysis in one pot can deliver the synthesis of complex products with high efficiency. We highlight recent advances, analyze current applications and limitations, and provide an outlook for the future development of integrated catalysis.

Summary O–O bond formation is a key elementary step of the water-oxidation reaction. However, it is still unclear how the mechanism of O–O coupling depends on the applied electrode potential. Herein, using water-in-salt electrolytes, we systematically altered the water activity, which enabled us to probe the O–O bond-forming mechanism on heterogeneous Co-based catalysts as a function of applied potential. We discovered that the water-oxidation mechanism is sensitive to the applied potential: At relatively low driving force, the reaction proceeds through an intramolecular oxygen coupling mechanism, whereas the water nucleophilic attack mechanism prevails at high driving force. The observed mechanistic switch has major implications for the understanding and control of the water-oxidation reaction on heterogeneous catalysts.

Metal-organic frameworks (MOF) are promising media for achieving solid-state Mg2+ conduction and developing a magnesium-based battery. To this end, the chemical behavior and transport properties of an Mg(TFSI)2/DME electrolyte system inside Mg-MOF-74 were studied by density functional theory (DFT). We found that inside the MOF chemical environment, solvent and anion molecules occupy the coordinatively unsaturated open metal sites of Mg-MOF-74, while Mg2+ ions adsorb directly onto the carboxylate group of the MOF organic linker. These predicted binding geometries were further corroborated by IR spectroscopy. We computed the free energies of desolvation of Mg2+ ions inside MOF to investigate the capacity of Mg-MOF-74 thin film to act as a separator for selective Mg2+ transport. We showed that Mg-MOF-74 could facilitate partial, but not full, desolvation of Mg2+. We found that the dominant minimum-energy pathway (MEP) for Mg2+ conduction inside Mg-MOF-74 corresponds to a "solvent hopping" mechanism, with an energy barrier of 4.4 kcal/mol. The molar conductivity of Mg2+ associated with the idealized solvent hopping mechanism along the MOF one-dimensional channel was predicted to be 2.4 × 10-3 S cm-1 M-1, which is one to two orders of magnitude greater than the experimentally measured value of 1.2 × 10-4 S cm-1 M-1 (with an estimated Mg2+ concentration). We have discussed several possible factors contributing to this apparent discrepancy. The current work demonstrates the validity of the computational strategies applied and the structural models constructed for the understanding of fast and selective Mg2+ transport in Mg-MOF-74, which serves as a cornerstone for studying transport of multivalent ions in MOFs. Furthermore, it provides detailed molecular-level insights that are not yet accessible experimentally.

Lithium metal anode holds great promises for next-generation battery technologies but is notoriously difficult to work with. The key to solving this challenge is believed to lie in the ability of forming stable solid-electrolyte interphase (SEI) layers. To further address potential safety issues, it is critical to achieve this goal in nonflammable electrolytes. Building upon previous successes in forming stable SEI in conventional carbonate-based electrolytes, here we report that reversible Li stripping/plating could be realized in triethyl phosphate (TEP), a known flame retardant. The critical enabling factor of our approach was the introduction of oxygen, which upon electrochemical reduction induces the initial decomposition of TEP and produces Li3 PO4 and poly-phosphates. Importantly, the reaction was self-limiting, and the resulting material regulated Li plating by limiting dendrite formation. In effect, we obtained a functional SEI on Li metal in a nonflammable electrolyte. When tested in a symmetric Li∥Li cell, more than 300 cycles of stripping/plating were measured at a current density of 0.5 mA cm-2 . Prototypical Li-O2 and Li-ion batteries were also fabricated and tested to further support the effectiveness of this strategy. The mechanism by which the SEI forms was studied by density functional theory (DFT), and the predictions were corroborated by the successful detection of the intermediates and products.

Water oxidation, an essential step in photosynthesis, has attracted intense research attention. Understanding the reaction pathways at the electrocatalyst/water interface is of great importance for the development of water oxidation catalysts. How the water is oxidized on the electrocatalyst surface by the positive charges is still an open question. This review summarizes current advances in studies on surface chemistry within the context of water oxidation, including the intermediates, reaction mechanisms, and their influences on the reaction kinetics. The Tafel analyses of some electrocatalysts and the rate-laws relative to charge consumption rates are also presented. Moreover, how the multiple charge transfer relies on the intermediate coverage and the accumulated charge numbers is outlined. Lastly, the intermediates and rate-determining steps on some water oxidation catalysts are discussed based on density functional theories.

Osteosarcoma is a bone tumor frequently diagnosed in children and young adults. Despite advances in chemotherapy and surgical resection, tumors metastasize in 30% of osteosarcoma patients. In addition, side effects caused by chemotherapeutic drugs, as well as the development of chemoresistance, highlight the need to identify the molecular mechanisms involved in the pathogenesis of osteosarcoma. We compared 65 osteosarcoma samples to their adjacent normal tissues, as well as commercially obtained osteosarcoma cell lines with normal osteoblast cell lines, and identified a role for the microRNA (miR)-140/ubiquitin-specific protease 22 (USP22)/lysine-specific demethylase 1 (LSD1)/p21 axis in the development of osteosarcoma. Osteosarcoma tissues and cells exhibited poor miR-140 and p21 expression, whereas the expression of USP22 and LSD1 was increased. Overexpression of miR-140 inhibited cell proliferation, migration, and invasion and promoted cell apoptosis by directly targeting USP22, resulting in its decreased expression. Overexpression of USP22 reversed the effects of miR-140 overexpression in osteosarcoma cells. Overexpression of miR-140 or USP22 knockdown led to the ubiquitination and degradation of LSD1. miR-140 overexpression also suppressed tumorigenesis in vivo. This study revealed a role for miR-140 in the restriction of osteosarcoma development and identified miR-140 as a potential target for therapeutic intervention., Graphical Abstract, This study reveals a role for miR-140 in the restriction of osteosarcoma development and identifies miR-140 as a potential target for therapeutic intervention.

In this work, we present an in situ method to probe the evolution of photoelectrochemically driven surface oxidation on photoanodes during active operation in aqueous solutions. A standard solution of K4Fe(CN)6-KPi was utilized to benchmark the photocurrent and assess progressive surface oxidation on Ta3N5 in various oxidizing solutions. In this manner, a proportional increase in the surface oxygen concentration was detected with respect to oxidation time and further correlated with a continuous decline in the photocurrent. To discern how surface oxidation alters the photocurrent, we experimentally and theoretically explored its impact on the surface carrier recombination and the interfacial hole transfer rates. Our results indicate that the sluggish photocurrent demonstrated by oxidized Ta3N5 arises because of changes in both rates. In particular, the results suggest that the N-O replacement present on the Ta3N5 surface primarily increases the carrier recombination rate near the surface and to a lesser degree reduces the interfacial hole transfer rate. More generally, this methodology is expected to further our understanding of surface oxidation atop other nonoxide semiconductor photoelectrodes and its impact on their operation.

This study aimed to expand the competing endogenous RNA network in osteosarcoma (OS) involving hsa_circ_0085539 and its downstream target miR-526b-5p. The expression levels of circ_0085539, miR-526b-5p, and stress-associated endoplasmic reticulum protein 1 (SERP1) mRNA in OS tissues and cells were detected and analyzed by qRT-PCR. After that, the interrelationships between these three genetic materials were validated with a luciferase reporter assay system. The effect of the circ_0085539/miR-526b-5p/SERP1 axis on OS cell malignancy phenotypes was further assessed using in vitro assays, including cell counting kit-8 (CCK-8) assays, colony foci formation assays, wound-healing migration assays, and transwell invasion assays. To determine the function of circ_0085539 on OS tumor growth in vivo, a xenograft formation assay was performed. In OS tissues and cells, the expression of circ_0085539 and SERP1 was upregulated, while that of miR-526b-5p was downregulated. After experimental analyses, it was found that silencing circ_0085539 inhibited the aggression of OS in vivo and in vitro. Mechanistic investigations also revealed that circ_0085539 could sponge miR-526b-5p and that miR526b-5p could directly target SERP1. The cytological experiments in vitro demonstrated that miR-526b-5p could restore the effect of circ_0085539 in terms of promoting OS malignancy phenotypes by suppressing SERP1. Overall, the present study validated that hsa_circ_0085539 could promote the progression of OS by regulating miR-526b-5p/SERP1., Graphical Abstract, This study is the first to investigate the effect of the interactions between circ_0085539, miR-526b-5p, and SERP1 in OS. The authors found that circ_0085539 accelerated OS progression by binding to and regulating miR-526b-5p, which suppressed SERP1. Their findings also revealed a novel molecular interactome of circ_0085539/miR-526b-5p/SERP1 in OS.

Summary Catalytic electrodes play an indispensable role in electrochemical devices. As the pursuit of high activity dominates the research focus, limited attention was paid to the recycling technologies. Existing methods often only allow for recovering specific metallic substance without restoring the functionality of the electrode. Herein, we report a general, non-destructive method based on high-temperature pulse annealing to enable direct reuse of catalytic electrodes. The high temperature ensures complete decomposition of byproducts; meanwhile, the rapid annealing maintains the original physiochemical property, and thus the performance of the catalyst. Using the Li-air battery as a model system, we can regenerate a Ru-loaded electrode for 10 times after each cycling operation, thus extending its lifetime by nearly 10 folds. Our method can be readily applied to other electrochemical systems where catalytic electrodes are prone to deactivation by byproducts. This study paves a new way toward highly sustainable operation of electrochemical devices.

Background: Nerve block shows some potential in alleviating pain after mammaplasty. This systematic review and meta-analysis aims to investigate the efficacy of nerve block for pain control after m...

One-step synthesis of β-carboxyl ketones from α, β-unsaturated ketones using CO2 as a feedstock by photoelectro-synergetic catalysis is reported herein. In this ambient system, silica nanowires (Si...

Ferroelectric semiconductors like BiFeO3 are increasingly being investigated for applications in solar energy conversion and storage due to their intrinsic ability to induce ferroelectric polarization-driven separation of the photogenerated charge carriers resulting in above-bandgap photovoltages. Nevertheless, the BiFeO3 has been commonly prepared using complex and expensive fabrication techniques, e.g., epitaxial growth, radio frequency sputtering and pulsed laser deposition, which are not economically viable for large-scale production. Herein, we report a facile and scalable method for the fabrication of porous perovskite BiFeO3 photoanodes, as well as sequential interfacial engineering methods to enhance their photoelectrochemical performance for water splitting. Upon atomic layer deposition of a TiO2 overlayer and photo-assisted electrodeposition of a cobalt oxide/oxyhydroxide co-catalyst, the photocurrent density of the engineered photoanode for oxygen evolution reaction (1 M NaOH) significantly increased from negligible photocurrent of the pristine BiFeO3 to 0.16 mA cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE) under simulated 1 sun irradiation (100 mW cm−2, AM1.5G spectrum). Furthermore, such functionalization of the BiFeO3 photoanodes shifts the photoelectrochemical oxidation onset potential by 0.7 V down to 0.6 V vs. RHE. The significantly enhanced photoelectro-oxidation activity is facilitated by the improved charge transfer and electrochemical kinetics.

Multi-elemental alloy (MEA) nanoparticles have recently received notable attention owing to their high activity and superior phase stability. Previous syntheses of MEA nanoparticles mainly used carbon as the support, owing to its high surface area, good electrical conductivity, and tunable defective sites. However, the interfacial stability issue, such as nanoparticle agglomeration, remains outstanding due to poor interfacial binding between MEA and carbon. Such a problem often causes performance decay when MEA nanoparticles are used as catalysts, hindering their practical applications. Herein, an interface engineering strategy is developed to synthesize MEA-oxide-carbon hierarchical catalysts, where the oxide on carbon helps disperse and stabilize the MEA nanoparticles toward superior thermal and electrochemical stability. Using several MEA compositions (PdRuRh, PtPdIrRuRh, and PdRuRhFeCoNi) and oxides (TiO

Water oxidation is an important first step in photosynthesis. It provides electrons and protons for reduction reactions such as hydrogen generation or carbon dioxide reduction. From a technological development perspective, it is critically important to carry out water oxidation on heterogeneous catalyst surfaces. However, this reaction is exceedingly difficult to study. Part of the reason for the challenge lies in the lack of clarity of the catalytically active centers for water oxidation. Another reason for the difficulty comes from the fact that the structures of the active center often evolve under reaction conditions. These issues have made water oxidation by heterogeneous catalysts poorly understood. In this talk, we present our recent efforts in addressing this challenge. Using cobalt oxide-based catalysts as a model system, we introduced a new approach of varying water activities. This was achieved through a "water-in-salt" electrolyte system. It was observed that such an electrolyte allows for discerning two competing mechanisms of water oxidation, namely water nucleophilic attack and intramolecular oxygen coupling. Moreover, it was found that the mechanisms are sensitive to the driving forces, demonstrating a preferences to water nucleophilic attack at high applied potentials and intramolecular oxygen coupling at low applied potentials. The results have major implications to the catalyst design for water oxidation reactions.

Metal-organic frameworks (MOF) are promising media for achieving solid-state Mg

The incompatibility between the anode and the cathode chemistry limits the used of Mg as an anode. This issue may be addressed by separating the anolyte and the catholyte with a membrane that only allows for Mg2+ transport. Mg-MOF-74 thin films were used as the separator for this purpose. It was shown to meet the needs of low-resistance, selective Mg2+ transport. The uniform MOF thin films supported on Au substrate with thicknesses down to ca. 202 nm showed an intrinsic resistance as low as 6.4 Ω cm2 , with the normalized room-temperature ionic conductivity of ca. 3.17×10-6 S cm-1 . When synthesized directly onto a porous anodized aluminum oxide (AAO) support, the resulting films were used as a standalone membrane to permit stable, low-overpotential Mg striping and plating for over 100 cycles at a current density of 0.05 mA cm-2 . The film was effective in blocking solvent molecules and counterions from crossing over for extended period of time.

Carbon dioxide (CO2) is regarded as a main contributor to the greenhouse effect. As a potential strategy to mitigate its negative impacts, the reduction of CO2 is environmentally critical, economically meaningful and scientifically challenging. Being both thermodynamically and kinetically unfavored, CO2 reduction requires catalysts as a crucial component irrespective of the reaction modes, be it electrocatalytic, photoelectrocatalytic or photocatalytic. In an effort to systematically review the types of catalysts that have been studied for CO2 reduction, we categorize them into two major groups: those being activated by external sources and those being photoexcited and activated themselves. Attention is focused on the detailed mechanisms for each group by which the reduction of CO2 proceeds, yielding a summary of the guiding principles for catalyst designs. This review highlights the importance of mechanistic studies, which permits us to discuss our perspectives on potential directions of catalyst investigation for future catalytic CO2 reduction research.

Nanostructured catalysts often face an important challenge: poor stability. Many factors contribute to catalytic degradation, including parasitic chemical reactions, phase separation, agglomeration, and dissolution, leading to activity loss especially during long-term catalytic reactions. This challenge is shared by a new family of catalysts, multimetallic nanoparticles, which have emerged owing to their broad tunability and high activity. While significant synthesis-based advances have been made, the stability of these nanostructured catalysts, especially during catalytic reactions, has not been well addressed. In this study, we reveal the critical influence of a synthetic method on the stability of nanostructured catalysts through aprotic oxygen catalysis (Li-O2 battery) demonstrations. In comparison to the conventional wet impregnation (WI) method, we show that the carbothermal shock (CTS) method dramatically improves the overall structural and chemical stability of the catalyst with the same elemental compositions. For multimetallic compositions (4- and 8-elements), the overall stability of the electrocatalysts as well as the battery lifetime can be further improved by incorporating additional noncatalytically active elements into the individual nanoparticles via CTS. The results offer a new synthetic path toward the stabilization of nanostructured catalysts, where additional reaction schemes beyond oxygen electrocatalysis are foreseeable.

CO2 electrochemical reduction is of great interest not only for its technological implications but also for the scientific challenges it represents. How to suppress the kinetically favored hydrogen evolution in the presence of H2O, for instance, has attracted significant attention. Here we report a new way of achieving such a goal. Our strategy involves a unique water-in-salt electrolyte system, where the H2O concentration can be greatly suppressed due to the strong solvation of the high-concentration salt. More importantly, the water-in-salt electrolyte offers an opportunity to tune the H2O concentration for electrokinetic studies of CO2 reduction, a parameter of critical importance to the understanding of the detailed mechanisms but difficult to vary previously. Using Au as a model catalyst platform, we observed a zeroth-order dependence of the reaction rate on the H2O concentration, strongly suggesting that electron transfer, rather than concerted proton electron transfer, from the electrode to the adsorbed CO2 is the rate-determining step. The results shed new light on the mechanistic understanding of CO2 electrochemical reduction. Our approach is expected to be applicable to other catalyst systems, as well, which will offer a new dimension to mechanistic studies by tuning H2O concentrations., A water-in-salt system was used to understand the role of H2O in CO2 electrochemical reduction. Improved CO selectivity was achieved owing to the suppressed hydrogen evolution reaction.

Solar hydrogen production by the photoelectrochemical method promises a means to store solar energy. While it is generally understood that the process is highly sensitive to the nature of the interface between the semiconductor and the electrolyte, a detailed understanding of this interface is still missing. For instance, few prior studies have established a clear relationship between the interface energetics and the catalyst loading amount. Here we aim to study this relationship on a prototypical Si-based photoelectrochemical system. Two types of interfaces were examined, one with GaN nanowires as a protection layer and one without. It was found that when GaN was present, higher Pt loading (> 0.1 μg/cm2) led to not only better water reduction (and, hence, hydrogen evolution) kinetics but also more favorable interface energetics for greater photovoltages. In the absence of the protection layer, by stark contrast, increased Pt loading exhibited no measurable influence on the interface energetics, and the main difference was observed only in the hydrogen evolution kinetics. The study sheds new light on the importance of interface engineering for further improvement of photoelectrochemical systems, especially concerning the role of catalysts and protection layers.

Photo-excited charge carrier dynamics in hematite (α-Fe2O3), ranging from 10–8 to 10–5 s, was investigated using the heterodyne transient grating technique in combination with the randomly interleaved pulse-train method. We observed four components in this time scale, and each component was successfully assigned by scavengers and the responses of oxygen-abundant and -deficient samples were compared. Particularly, we found components which have not been discussed so far with an aid of the combination method, and they were assigned to recombination arising from trapped electrons. In addition, the effect of an amorphous NiFeOx coating on the dynamics in this time scale was also investigated under the bias condition and demonstrated that the coated sample strongly depended on the applied bias voltage, while the bare sample did not, implying that the Fermi-level pinning effect in hematite was reduced by the amorphous NiFeOx coating.

Kinetic studies of photo- and photoelectro-catalysis fixation of CO2 are rare. Herein, a typical CO2 reduction addition to trans-stilbene is studied. Through Tafel analyses, the reaction rate-determining step (RDS) is identified as the first step of an anion free radical generation from the substrate, and the reaction order is 0.5.

Photoelectrochemical (PEC) water splitting has been intensively studied in the past decades as a promising method for large-scale solar energy storage. Among the various issues that limit the progress of this field, the lack of photoelectrode materials with suitable properties in all aspects of light absorption, charge separation and transport, and charge transfer is a key challenge, which has attracted tremendous research attention. A large variety of compositions, in different forms, have been tested. This review aims to summarize efforts in this area, with a focus on materials-related considerations. Issues discussed by this review include synthesis, optoelectronic properties, charge behaviors and catalysis. In the recognition that thin-film materials are representative model systems for the study of these issues, we elected to focus on this form, so as to provide a concise and coherent account on the different strategies that have been proposed and tested. Because practical implementation is of paramount importance to the eventual realization of using solar fuel for solar energy storage, we pay particular attention to strategies proposed to address the stability and catalytic issues, which are two key factors limiting the implementation of efficient photoelectrode materials. To keep the overall discussion focused, all discussions were presented within the context of water splitting reactions. How the thin-film systems may be applied for fundamental studies of the water splitting chemical mechanisms and how to use the model system to test device engineering design strategies are discussed.