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Showing papers in "Chemistry: A European Journal in 2018"


Journal ArticleDOI
TL;DR: The problem of mercury pollution in ASGM is reviewed with a discussion on how the chemistry community can contribute solutions, including portable and low‐cost mercury sensors, inexpensive and scalable remediation technologies, novel methods to prevent mercury uptake in fish and food crops, and efficient and easy‐to‐use mercury‐free mining techniques are all ways in which the Chemistry community can help.
Abstract: Mercury-dependent artisanal and small-scale gold mining (ASGM) is the largest source of mercury pollution on Earth. In this practice, elemental mercury is used to extract gold from ore as an amalgam. The amalgam is typically isolated by hand and then heated-often with a torch or over a stove-to distill the mercury and isolate the gold. Mercury release from tailings and vaporized mercury exceed 1000 tonnes each year from ASGM. The health effects on the miners are dire, with inhaled mercury leading to neurological damage and other health issues. The communities near these mines are also affected due to mercury contamination of water and soil and subsequent accumulation in food staples, such as fish-a major source of dietary protein in many ASGM regions. The risks to children are also substantial, with mercury emissions from ASGM resulting in both physical and mental disabilities and compromised development. Between 10 and 19 million people use mercury to mine for gold in more than 70 countries, making mercury pollution from ASGM a global issue. With the Minamata Convention on Mercury entering force this year, there is political motivation to help overcome the problem of mercury in ASGM. In this effort, chemists can play a central role. Here, the problem of mercury in ASGM is reviewed with a discussion on how the chemistry community can contribute solutions. Introducing portable and low-cost mercury sensors, inexpensive and scalable remediation technologies, novel methods to prevent mercury uptake in fish and food crops, and efficient and easy-to-use mercury-free mining techniques are all ways in which the chemistry community can help. To meet these challenges, it is critical that new technologies or techniques are low-cost and adaptable to the remote and under-resourced areas in which ASGM is most common. The problem of mercury pollution in ASGM is inherently a chemistry problem. We therefore encourage the chemistry community to consider and address this issue that affects the health of millions of people.

253 citations


Journal ArticleDOI
TL;DR: This review summarizes the advances made with photoactive CrIII, FeII, CuI, ZnII, ZrIV, Mo0, and UVI complexes in the context of synthetic organic photoredox chemistry using visible light as an energy input.
Abstract: Photoredox chemistry with metal complexes as sensitizers and catalysts frequently relies on precious elements such as ruthenium or iridium. Over the past 5 years, important progress towards the use of complexes made from earth-abundant elements in photoredox catalysis has been made. This review summarizes the advances made with photoactive Cr(III), Fe(II), Cu(I), Zn(II), Zr(IV), Mo(0) and U(VI) complexes in the context of synthetic organic photoredox chemistry using visible light as an energy input. Mechanistic considerations are combined with discussions of reaction types and scopes. Perspectives for the future of the field are discussed against the background of recent significant developments of new photoactive metal complexes made from earth-abundant elements.

241 citations


Journal ArticleDOI
TL;DR: In this review, the developments of SIMs with different metal centres are summarized, as well as the possible strategies of ligand field design.
Abstract: Single-ion magnets (SIMs), exhibiting slow magnetization relaxation in the absence of the magnetic field, originate from their single spin-carrier centre. In pursuit of high-performance magnetic properties, such as high spin-reversal barrier and high blocking temperature, various metal centres were investigated to establish SIMs, including 3d and 5d transition metal ions, 4f lanthanide ions, and 5f actinide ions, which possess unique zero-field splitting and magnetic properties. Therefore, proper ligand field is of great importance to different types of metals. In the given great breakthroughs since the first SIM, [Pc2 Tb]- (Pc=dianion of phthalocyanine), was reported, strategies of ligand field design have emerged. In this review, the developments of SIMs with different metal centres are summarized, as well as the possible strategies.

236 citations


Journal ArticleDOI
TL;DR: Recent developments over the past few years in aqueous micellar catalysis are discussed, and applications to problems in synthesis are highlighted, enabled by the use of surfactants that self-aggregate in water into micelles as nanoreactors.
Abstract: Recent developments over the past few years in aqueous micellar catalysis are discussed. Applications to problems in synthesis are highlighted, enabled by the use of surfactants that self-aggregate in water into micelles as nanoreactors. These include amphiphiles that have been available for some time, as well as those that have been newly designed. Reactions catalyzed by transition metals, including Pd, Cu, Rh, and Au, are of particular focus.

223 citations


Journal ArticleDOI
TL;DR: A new, stable covalent organic framework (COF) is reported as a porous platform for removing iodine vapor-a major radioactive fission waste, and the great potential of COFs as a designable porous material for challenging world-threatening pollution issues is suggested.
Abstract: Using porous materials to cope with environmental issues is promising but remains a challenge especially for removing the radioactive vapor wastes in fission because of harsh adsorption conditions. Here we report a new, stable covalent organic framework (COF) as a porous platform for removing iodine vapor-a major radioactive fission waste. The three-dimensional COF consists of a diamond topology knotted by adamantane units, creates ordered one-dimensional pores and are highly porous. The COF enables the removal of iodine vapor via charge transfer complex formation with the pore walls to achieve exceptional capacity. Moreover, the 3D COF is "soft" to trigger structural fitting to iodine while retaining connectivity and enables cycle use for many times while retaining high uptake capacity. These results set a new benchmark for fission waste removal and suggest the great potential of COFs as a designable porous material for challenging world-threatening pollution issues.

212 citations


Journal ArticleDOI
TL;DR: In this paper, the main limitation of aqueous supercapacitors lies in their narrow operating voltages, especially when compared with organic SCs, and strategies applied to expand the operating voltage are summarized and discussed from the aspects of electrolyte, electrode, and asymmetric structure.
Abstract: The main limitation of aqueous supercapacitors (SCs) lies in their narrow operating voltages, especially when compared with organic SCs. Fundamental understanding of factors relevant to the operating voltage helps providing guidance for the assembly of high-voltage aqueous SCs. In this regard, this concept analyzes the deciding factors for the operating voltage of aqueous SCs. Strategies applied to expand the operating voltage are summarized and discussed from the aspects of electrolyte, electrode, and asymmetric structure. Dynamic factors associated with water electrolysis and maximally using the available potential ranges of electrodes are particularly emphasized. Finally, other promising approaches that have not been explored and their challenges are also elaborated, hoping to provide more insights for the design of high-voltage aqueous SCs.

197 citations


Journal ArticleDOI
TL;DR: This short review highlights recent advances in the use of sulfur dioxide in radical reactions and covers the historical background, which forms the basis for these current progresses.
Abstract: Molecules containing a sulfonyl functionality, such as sulfones, sulfonyl chlorides or sulfonamides play an important role in organic chemistry and have found widespread application, especially in the construction of biologically active compounds. Recently, methods for the synthesis of the sulfonyl moiety utilizing sulfur dioxide as a key building block have received considerable attention. In this context, radical-based transformations with sulfur dioxide have emerged as a new and attractive approach for the construction of the sulfonyl functional group. This short review highlights recent advances in the use of sulfur dioxide in radical reactions and covers the historical background, which forms the basis for these current progresses. Limitations of the existing methods and potential further developments will be discussed.

197 citations


Journal ArticleDOI
TL;DR: Porous ternary metal sulfide integrated electrode materials with abundant electroactive sites and redox reactions are very promising for supercapacitors and thus as-synthesized Zn-Co-S/NF has great potential for practical applications.
Abstract: Porous ternary metal sulfide integrated electrode materials with abundant electroactive sites and redox reactions are very promising for supercapacitors. Herein, a porous zinc cobalt sulfide nanosheet array on Ni foam (Zn-Co-S/NF) was constructed by facile growth of 2D bimetallic zinc/cobalt-based metal-organic framework (Zn/Co-MOF) nanosheets with leaf-like morphology on NF, followed by additional sulfurization. The Zn-Co-S/NF nanosheet array acted directly as a supercapacitor electrode showing much better electrochemical performance (2354.3 F g-1 and 88.6 % retention over 1000 cycles) when compared with zinc cobalt sulfide powder (355.3 F g-1 and 75.8 % retention over 1000 cycles), which originates from good electrical conductivity and mechanical stability, abundant electroactive sites, and facilitated transportation of electrons and electrolyte ions due to the unique nanosheet array structure. An asymmetric supercapacitor (ASC) device assembled from Zn-Co-S/NF and activated carbon electrodes can deliver a highest energy density of 31.9 Wh kg-1 and a maximum power density of 8.5 kW kg-1 . Most importantly, this ASC also shows good cycling stability (71.0 % retention over 10000 cycles). Furthermore, a red LED can be powered by two connected ASCs, and thus as-synthesized Zn-Co-S/NF has great potential for practical applications.

196 citations



Journal ArticleDOI
TL;DR: This review provides a comprehensive overview of conductive-hydrogel-based flexible electronics, ranging from conductive hydrogels synthesis to several important flexible devices applications, including touch panels, sensors and energy storage.
Abstract: Flexible conductive materials have gained considerable research interest in recent years because of their potential applications in flexible energy storage devices, sensors, touch panels, electronic skins, etc. With excellent flexibility, outstanding electric properties and tunable mechanical properties, conductive hydrogels as conductive materials offer plentiful insights and opportunities for flexible electronic devices. Numerous synthetic strategies have been developed to obtain various conductive hydrogels, and high-performance flexible electronic devices based on these conductive hydrogels have been realized. This review provides a comprehensive overview of conductive-hydrogel-based flexible electronics, ranging from conductive hydrogels synthesis to several important flexible devices applications, including touch panels, sensors and energy storage. Finally, we provide new future research directions and perspectives for conductive-hydrogel-based flexible and portable electronic devices.

185 citations


Journal ArticleDOI
TL;DR: Fundamental mechanistic aspects as well as the importance in the preparation of nitrogen-containing molecules will be highlighted.
Abstract: In recent years, hydroxylamines derivatives have been exploited as nitrogen-radical precursors in visible-light photochemistry. Their ability to serve as electrophores in redox chemistry has propelled the development of many novel transformations. Fundamental mechanistic aspects as well as the importance in the preparation of nitrogen-containing molecules will be highlighted.

Journal ArticleDOI
TL;DR: A deaminative strategy for the borylation of aliphatic primary amines is described and the synthetic potential of this mild protocol was demonstrated through the late-stage functionalization of natural products and drug molecules.
Abstract: A deaminative strategy for the borylation of aliphatic primary amines is described. Alkyl radicals derived from the single-electron reduction of redox-active pyridinium salts, which can be isolated or generated in situ, were borylated in a visible light-mediated reaction with bis(catecholato)diboron. No catalyst or further additives were required. The key electron donor–acceptor complex was characterized in detail by both experimental and computational investigations. The synthetic potential of this mild protocol was demonstrated through the late-stage functionalization of natural products and drug molecules.

Journal ArticleDOI
TL;DR: Fundamentals of water electrolysis, and recent research progress and trends in the development of earth-abundant first-row transition-metal and hydrogen evolution electrocatalysts working in acidic, alkaline, or neutral conditions are reviewed.
Abstract: Fundamentals of water electrolysis, and recent research progress and trends in the development of earth-abundant first-row transition-metal (Mn, Fe, Co, Ni, Cu)-based oxygen evolution reaction (OER) and hydrogen evolution (HER) electrocatalysts working in acidic, alkaline, or neutral conditions are reviewed The HER catalysts include mainly metal chalcogenides, metal phosphides, metal nitrides, and metal carbides As for the OER catalysts, the basic principles of the OER catalysts in alkaline, acidic, and neutral media are introduced, followed by the review and discussion of the Ni, Co, Fe, Mn, and perovskite-type OER catalysts developed so far The different design principles of the OER catalysts in photoelectrocatalysis and photocatalysis systems are also presented Finally, the future research directions of electrocatalysts for water splitting, and coupling of photovoltaic (PV) panel with a water electrolyzer, so called PV-E, are given as perspectives

Journal ArticleDOI
TL;DR: Results suggest NUM-5 to be a highly selective and recyclable luminescent sensing material for the quantitative detection of CrVI anions in aqueous solution.
Abstract: A new luminescent ZnII -MOF with 1D triangular channels along the b axis, namely NUM-5, has been successfully assembled and well characterized, which features good stability, especially in aqueous solution. Interestingly, this compound exhibits a fast, sensitive and selective luminescence quenching response towards CrVI (Cr2 O72- /CrO42- ) in aqueous solution. The detection limits towards Cr2 O72- and CrO42- ions are estimated to be 0.7 and 0.3 ppm, respectively, which are among the lowest detection limits reported for the MOF-based fluorescent probes that can simultaneously detect Cr2 O72- and CrO42- in aqueous environment. The possible detection mechanism has been discussed in detail. Moreover, it can be easily regenerated after detection experiments, indicative of excellent recyclability. All these results suggest NUM-5 to be a highly selective and recyclable luminescent sensing material for the quantitative detection of CrVI anions in aqueous solution.

Journal ArticleDOI
TL;DR: Recently developed FMRs including push-pull type π-conjugated chromophores, meso-phenyl (borondipyrromethene) (BODIPY) derivatives, dioxaborine derivatives, cyanine derivatives and porphyrin derivatives whose FL mechanism is viscosity-responsive are described.
Abstract: Fluorescent molecular rotors (FMRs) can act as viscosity sensors in various media including subcellular organelles and microfluidic channels. In FMRs, the rotation of rotators connected to a fluorescent π-conjugated bridge is suppressed by increasing environmental viscosity, resulting in increasing fluorescence (FL) intensity. In this minireview, we describe recently developed FMRs including push-pull type π-conjugated chromophores, meso-phenyl (borondipyrromethene) (BODIPY) derivatives, dioxaborine derivatives, cyanine derivatives, and porphyrin derivatives whose FL mechanism is viscosity-responsive. In addition, FMR design strategies for addressing various issues (e.g., obtaining high FL contrast, internal FL references, and FL intensity-contrast trade-off) and their biological and microfluidic applications are also discussed.

Journal ArticleDOI
Lutz Greb1
TL;DR: The present review deals with strong Lewis acids and critically discusses Lewis acidity scaling methods and suggests an extended definition for Lewis superacidity, and summarizes the properties and applications of the strongest currently known Lewis acids, indexed by the fluoride ion affinity.
Abstract: Lewis acids play a major role in all areas of chemistry. For a long time, toxic, corrosive and oxidizing SbF5 was considered as the strongest Lewis acid known. Lately, species significantly exceeding the Lewis acidity of SbF5 have been realized and were termed Lewis superacids (LSA). Prospective new candidates emerge steadily, which not only outperform SbF5 by their strength, but also in terms of their accessibility and ease of handling. In principle, Lewis superacids allow us to combine the outstanding activity of Bronsted superacids with the excellent selectivity of a common Lewis acid. However, the broad application of Lewis superacids in synthesis is all but popular. The present review deals with strong Lewis acids. First, it critically discusses Lewis acidity scaling methods and suggests an extended definition for Lewis superacidity. It then summarizes the properties and applications of the strongest currently known Lewis acids, indexed by the fluoride ion affinity (FIA). The supporting information contains a comprehensive list of experimentally and theoretically derived FIA data as a guide for the choice of Lewis acidic reagents/catalyst. This contribution shall encourage the search for new Lewis superacids and promote their application in non-specialized laboratories.

Journal ArticleDOI
TL;DR: A novel supramolecular organic framework (SOF-THBP) was constructed by bis-thioacetylhydrazine functionalized pillar[5]arenes that shows a fluorescent response for Fe3+, Cr3+ , Hg2+ and Cu2+ ions and a series of metal-ion-coordinated SOFs (MSOFs) could selectively sense F-, Br- , and l-Cys, respectively.
Abstract: The selective detection and separation of target ions or molecules is an intriguing issue. Herein, a novel supramolecular organic framework (SOF-THBP) was constructed by bis-thioacetylhydrazine functionalized pillar[5]arenes. The SOF-THBP shows a fluorescent response for Fe3+ , Cr3+ , Hg2+ and Cu2+ ions. The xerogel of SOF-THBP shows excellent recyclable separation properties for these metal ions and the absorption rates were up to 99.29 %. More interestingly, by rationally introducing these metal ions into the SOF-THBP, a series of metal-ion-coordinated SOFs (MSOFs) such as MSOF-Fe, MSOF-Hg and MSOF-Cu were constructed. These metal ions coordinated MSOFs could selectively sense F- , Br- , and l-Cys, respectively. The detection limits of these MSOFs for F- , Br- and l-Cys were about 10-8 m.

Journal ArticleDOI
TL;DR: This Minireview will summarize recent synthetic examples of (chemo)enzymatic cascade reactions and outline promising methods for their spatial control either by using bio-derived or synthetic systems.
Abstract: Multi-catalytic cascade reactions bear a great potential to minimize downstream and purification steps, leading to a drastic reduction of the produced waste. In many examples, the compatibility of chemo- and biocatalytic steps could be easily achieved. Problems associated with the incompatibility of the catalysts and their reactions, however, are very frequent. Cascade-like reactions can hardly occur in this way. One possible solution to combine, in principle, incompatible chemo- and biocatalytic reactions is the defined control of the microenvironment by compartmentalization or scaffolding. Current methods for the control of the microenvironment of biocatalysts go far beyond classical enzyme immobilization and are thus believed to be very promising tools to overcome incompatibility issues and to facilitate the synthetic application of cascade reactions. In this Minireview, we will summarize recent synthetic examples of (chemo)enzymatic cascade reactions and outline promising methods for their spatial control either by using bio-derived or synthetic systems.

Journal ArticleDOI
TL;DR: A TYRP1-based homology model of TYR provides a high-quality platform to map and analyze albinism-related mutations, as well as the design of specific antimelanogenic compounds.
Abstract: Melanin is the main pigment responsible for the color of human skin, hair and eye. Its biosynthesis requires three melanogenic enzymes, tyrosinase (TYR), and the tyrosinase-related proteins TYRP1 and TYRP2. The difficulty of isolating pure and homogeneous proteins from endogenous sources has hampered their study, and resulted in many contradictory findings regarding their physiological functions. In this review, we summarize recent advances on the structure and function of TYR and TYRPs by virtue of the crystal structure of human TYRP1, which is the first available structure of a mammalian melanogenic enzyme. This structure, combined with tyrosinase structures from other lower eukaryotes and mutagenesis studies of key active site residues, sheds light on the mechanism of TYR and TYRPs. Furthermore, a TYRP1-based homology model of TYR provides a high-quality platform to map and analyze albinism-related mutations, as well as the design of specific antimelanogenic compounds. Finally, we provide perspectives for future structure/function studies of TYR and TYRPs.

Journal ArticleDOI
TL;DR: A concise summary of rutile TiO2 -based photocatalysts for water-splitting systems is provided.
Abstract: Water splitting using a semiconductor photocatalyst with sunlight has long been viewed as a potential means of large-scale H2 production from renewable resources. Different from anatase TiO2 , rutile enables preferential water oxidation, which is useful for the construction of a Z-scheme water-splitting system. The combination of rutile TiO2 with a suitable H2 -evolution photocatalyst such as a Pt-loaded BaZrO3 -BaTaO2 N solid solution enables solar-driven water splitting into H2 and O2 . While rutile TiO2 is a wide-gap semiconductor with a bandgap of 3.0 eV, co-doping of rutile TiO2 with certain metal ions and/or nitrogen produces visible-light-driven photocatalysts, which are also useful as a component for water oxidation in visible-light-driven Z-scheme water splitting. The key to achieving highly efficient water oxidation is to maintain a charge balance of dopants in the rutile, because single doping typically produces trap states that capture photogenerated electrons and/or holes. Here we provide a concise summary of rutile TiO2 -based photocatalysts for water-splitting systems.

Journal ArticleDOI
TL;DR: A comprehensive review of one of the key reagents for the synthesis of metal nanocrystals via chemical reduction: the reductants, including their major properties, reduction mechanisms, and additional effects on the final products.
Abstract: There is a growing interest in controlling the synthesis of colloidal metal nanocrystals and thus tailoring their properties toward various applications. In this context, choosing an appropriate combination of reagents (e.g., salt precursor, reductant, capping agent, and stabilizer) plays a pivotal role in enabling the synthesis of metal nanocrystals with diversified sizes, shapes, and structures. Here we present a comprehensive review that highlights one of the key reagents for the synthesis of metal nanocrystals via chemical reduction: the reductants. We start with a brief introduction to the compounds commonly employed as reductants in the colloidal synthesis of metal nanocrystals by showing their oxidation half-reactions and the corresponding oxidation potentials. Then we offer specific examples pertaining to the controlled synthesis of metal nanocrystals, followed by some fundamental aspects covering the general mechanisms of metal ion reduction based on the Marcus Theory. Afterwards, we present a case-by-case discussion on a wide variety of reductants, including their major properties, reduction mechanisms, and additional effects on the final products. We illustrate these aspects by selecting key examples from the literature and paying close attention to the underlying mechanism in each case. At the end, we conclude by summarizing the highlights of the review and providing some perspectives on future directions.

Journal ArticleDOI
TL;DR: It is discussed why this confusing terminology needs to be changed and reemphasized that (3,-1) CPs should be called "line" critical points (LCPs), and detaches the topological properties of molecular electron densities from any a priori chemical interpretation.
Abstract: Equating (3,-1) critical points (CPs), derived from the topological analysis of the electron densities, to chemical bonds has triggered a lot of confusion in recent years. Part of this confusion stems from calling these CPs "bond" CPs (BCPs). While the origin of this terminology is traceable to the late seventies and beginning of eighties, when it sounded reasonable, new computational studies conducted on molecular electron densities cast serious doubt on the supposed universal equivalence between the chemical bonds and (3,-1) CPs. Herein, recent computational studies are briefly reviewed to demonstrate why (3,-1) CPs are not indicators of chemical bonds. It is discussed why this confusing terminology needs to be changed and reemphasized that (3,-1) CPs should be called "line" critical points (LCPs). The proposed terminology detaches the topological properties of molecular electron densities from any a priori chemical interpretation. Such detachment, if adopted by other authors, will hopefully prevent further misinterpretation of the data emerging from the quantum theory of atoms in molecules (QTAIM).

Journal ArticleDOI
TL;DR: This Review offers a 360-degree overview on how caesium can strongly tune the properties and performance of perovskites and relative perovkite-based devices.
Abstract: Perovskite solar cells have the potential to revolutionize the world of photovoltaics, and their efficiency close to 23 % on a lab-scale recently certified this novel technology as the one with the most rapidly raising performance per year in the whole story of solar cells. With the aim of improving stability, reproducibility and spectral properties of the devices, in the last three years the scientific community strongly focused on Cs-doping for hybrid (typically, organolead) perovskites. In parallel, to further contrast hygroscopicity and reach thermal stability, research has also been carried out to achieve the development of all-inorganic perovskites based on caesium, the performances of which are rapidly increasing. The potential of caesium is further strengthened when it is used as a modifying agent of charge-carrier layers in solar cells, but also for the preparation of perovskites with peculiar optoelectronic properties for unconventional applications (e.g., in LEDs, photodetectors, sensors, etc.). This Review offers a 360-degree overview on how caesium can strongly tune the properties and performance of perovskites and relative perovskite-based devices.

Journal ArticleDOI
TL;DR: This Minireview draws a systematic parallel between methods and retrosynthetic analysis of enantioselective total or formal syntheses designed around Brønsted acid-catalyzed transformations to demonstrate the versatility of the reactions promoted and the diversity of the accessible motifs.
Abstract: Synthesis of biologically active molecules (whether at laboratory or industrial scale) remains a highly appealing area of modern organic chemistry. Nowadays, the need to access original bioactive scaffolds goes together with the desire to improve synthetic efficiency, while reducing the environmental footprint of chemical activities. Long neglected in the field of total synthesis, enantioselective organocatalysis has recently emerged as an environmentally friendly and indispensable tool for the construction of relevant bioactive molecules. Notably, enantioselective Bronsted acid catalysis has offered new opportunities in terms of both retrosynthetic disconnections and controlling stereoselectivity. The present report attempts to provide an overview of enantioselective total or formal syntheses designed around Bronsted acid-catalyzed transformations. To demonstrate the versatility of the reactions promoted and the diversity of the accessible motifs, this Minireview draws a systematic parallel between methods and retrosynthetic analysis. The manuscript is organized according to the main reaction types and the nature of newly-formed bonds.

Journal ArticleDOI
Xiaoyang Cui1, Cheng Tang1, Xiao-Meng Liu1, Chen Wang1, Wenjun Ma1, Qiang Zhang1 
TL;DR: In this paper, the NH3 yield and faradaic efficiency were improved by modifying the hematite nanostructure surface, leading to an average NH3 production rate of 0.46 and 6.04% respectively.
Abstract: The catalytic conversion of dinitrogen (N2 ) into ammonia under ambient conditions represents one of the Holy Grails in sustainable chemistry. As a potential alternative to the Haber-Bosch process, the electrochemical reduction of N2 to NH3 is attractive owing to its renewability and flexibility, as well as its sustainability for producing and storing value-added chemicals from the abundant feedstock of water and nitrogen on earth. However, owing to the kinetically complex and energetically challenging N2 reduction reaction (NRR) process, NRR electrocatalysts with high catalytic activity and high selectivity are rare. In this contribution, as a proof-of-concept, we demonstrate that both the NH3 yield and faradaic efficiency (FE) under ambient conditions can be improved by modification of the hematite nanostructure surface. Introducing more oxygen vacancies to the hematite surface renders an improved performance in NRR, which leads to an average NH3 production rate of 0.46 μg h-1 cm-2 and an NH3 FE of 6.04 % at -0.9 V vs. Ag/AgCl in 0.10 m KOH electrolyte. The durability of the electrochemical system was also investigated. A surprisingly high average NH3 production rate of 1.45 μg h-1 cm-2 and a NH3 FE of 8.28 % were achieved after the first 1 h chronoamperometry test. This is among the highest FEs reported so far for non-precious-metal catalysts that use a polymer-electrolyte-membrane cell and is much higher than the FE of precious-metal catalysts (e.g., Ru/C) under comparable reaction conditions. However, the NH3 yield and the FE dropped to 0.29 μg h-1 cm-2 and 2.74 %, respectively, after 16 h of chronoamperometry tests, which indicates poor durability of the system. Our results demonstrate the important role that the surface states of transition-metal oxides have in promoting electrocatalytic NRR under ambient conditions. This work may spur interest towards the rational design of electrocatalysts as well as electrochemical systems for NRR, with emphasis on the issue of stability.

Journal ArticleDOI
TL;DR: The design principle of each type of HSSEs are discussed, as well as their ionic conducting mechanism, electrochemical performance and effects of compositional/structural control, and challenges and perspectives are provided for the future development ofHSSEs and solid-state lithium batteries.
Abstract: Conventional liquid electrolytes for lithium batteries usually suffer from irreversible decomposition and safety concerns Solid state electrolytes (SSEs) have been considered as the key for advanced lithium batteries with improved energy density and safety, whereas challenges remain for polymer and inorganic SSEs Recently, hybrid solid-state electrolytes (HSSEs) that integrate the merits of different electrolyte systems have been under intensive study Herein, we summarize the recent progress of HSSEs with different compositions and structures The design principle of each type of HSSEs are discussed, as well as their ionic conducting mechanism, electrochemical performance and effects of compositional/structural control Finally, challenges and perspectives are provided for the future development of HSSEs and solid-state lithium batteries

Journal ArticleDOI
TL;DR: The experimental basis for the proposed modes of activation for iodine catalysis is summarized and typical iodine-catalyzed reactions are analyzed to gain more insights into the underlying reaction mechanisms.
Abstract: Molecular iodine has been used for more than 100 years as a remarkable catalyst for many organic transformations such as cycloadditions, Michael and aldol reactions, or esterifications. Different explanations for the origin of its catalytic effect have been proposed in the last decades including a "hidden" Bronsted acid catalysis by HI, a Lewis-acid (or halogen-bond) activation, or catalysis by an iodonium(I) species. Recently, iodine catalysis again gained more interest due to the latest developments in halogen-bond catalysis. In this Minireview, we first summarize the experimental basis for the proposed modes of activation. Subsequently, we analyze typical iodine-catalyzed reactions to gain more insights into the underlying reaction mechanisms.

Journal ArticleDOI
TL;DR: This Minireview showcases several electrocatalytic systems for both reductive and oxidative upgrading of representative biomass-derived intermediate compounds, including 5-hydroxymethylfurfural, furFural, levulinic acid, glycerol, and sorbitol to different value-added products.
Abstract: The continuous advance in exploring renewable energy resources such as solar and wind will certainly alleviate our reliance on limited fossil reserves. However, the sustainable development of mankind demands not only energy but also carbon-based chemical goods. Unfortunately, exploitation of renewable energy resources like solar and wind will not lead to any carbon-based chemicals. The only sustainable and green carbon source is biomass, the scale of annual production of which has an immense potential to complement that of fossil-derived carbons. To utilize biomass in economically effective ways, many catalytic processes have been investigated. Among various strategies of biomass refinery, electrocatalytic upgrading stands out as an attractive option because of its benign operation conditions, high energy efficiency, and convenient control on production rate and selectivity using electrochemical parameters. This Minireview showcases several electrocatalytic systems for both reductive and oxidative upgrading of representative biomass-derived intermediate compounds, including 5-hydroxymethylfurfural, furfural, levulinic acid, glycerol, and sorbitol to different value-added products. The catalytic routes and mechanisms of each biomass-derived platform compound are discussed and compared. In order to be feasible for large-scale applications, low-cost composition and preparation of electrocatalysts are mandatory and will be emphasized. Finally, our personal perspective on the current challenges and future directions of electrocatalytic biomass upgrading is presented.

Journal ArticleDOI
TL;DR: The synthesis of novel zinc electrodes has been successfully implemented by using the electroplating method with the aid of inorganic additives in the Electroplating solution, and the capacity retention is up to 15 % higher than the performance of battery containing commercial Zn after 1000 cycles of charge-discharge.
Abstract: The synthesis of novel zinc electrodes has been successfully implemented by the electroplating method with the aid of inorganic additives in the electroplating solution. The selected inorganic additives are indium sulfate, tin oxide, and boric acid. From X-ray diffraction results, the synthesized zinc electrodes prefer (002) and/or (103) crystallographic orientations, representing basal morphology and high resistance to dendrite growth. The corrosion rates of these electroplated zinc samples decrease as much as 11 times smaller than the rate of a zinc foil when the zinc materials are in contact with the aqueous electrolyte of a rechargeable hybrid aqueous battery (ReHAB). The ReHAB employing these anodes exhibits up to threefold decrease in float charge current density after a seven-day constant-voltage charging at 2.1 V vs. Zn2+/Zn. Furthermore, the capacity retentions are up to 15% higher than the performance of battery containing commercial Zn after 1000 cycles of charge-discharge. The significant advancements are attributed to the careful preparation of the anode, which contains appropriate crystallographic orientation and morphology.

Journal ArticleDOI
TL;DR: The critical points that currently limit the industrial production of PSCs are highlighted and what strategies are emerging to make these solar cells the leaders in the photovoltaic field are highlighted.
Abstract: Despite the fact that perovskite solar cells (PSCs) have a strong potential as a next-generation photovoltaic technology due to continuous efficiency improvements and the tunable properties, some important obstacles remain before industrialization is feasible. For example, the selection of low-cost or easy-to-prepare materials is essential for back-contacts and hole-transporting layers. Likewise, the choice of conductive substrates, the identification of large-scale manufacturing techniques as well as the development of appropriate aging protocols are key objectives currently under investigation by the international scientific community. This Review analyses the above aspects and highlights the critical points that currently limit the industrial production of PSCs and what strategies are emerging to make these solar cells the leaders in the photovoltaic field.