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Replacing fossil resources as the primary source of carbon‐based chemicals by alternative feedstocks, while implementing more sustainable production routes, has become imperative for environmental and resource sustainability. In this context, lignin, often treated as a biomass waste, emerges as an appealing candidate, considering the principles of circular economy. For this pursuit, depolymerization methods offer potential strategies to harness lignin to produce valuable organic chemicals, while electrocatalysis processes stand out especially in the context of sustainability, as they can be powered by electricity from renewable sources. This minireview article explores the pivotal role of various electrocatalysts in lignin depolymerization, investigating both oxidative and reductive pathways. Emphasizing recent advancements, the review delves into the diverse nature of electrocatalysts and their influence on lignin valorization. Highlighting current trends, the discussion encompasses the catalytic mechanisms and selectivity of electrochemical processes employed for lignin breakdown. Additionally, some insights into emerging technologies are also offered, emphasizing the need for sustainable and efficient strategies. By providing an overview of the field, this minireview aims to guide future research endeavors toward innovative electrocatalytic approaches for lignin depolymerization, paving the way for sustainable biorefinery processes. [ABSTRACT FROM AUTHOR]

Replacing crude oil as the primary industrial source of carbon‐based chemicals has become crucial for both environmental and resource sustainability reasons. In this scenario, wood arises as an excellent candidate, whilst depolymerization approaches have emerged as promising strategies to unlock the lignin potential as a resource in the production of high‐value organic chemicals. However, many drawbacks, such as toxic solvents, expensive catalysts, high energy inputs, and poor product selectivity have represented major challenges to this task. Herein, we present an unprecedented approach using electrocatalysis for the simultaneous depolymerization and dearomatization of lignin in aqueous medium under ambient conditions. By employing water/sodium carbonate as a solvent system, we demonstrated a pathway for selectively depolymerizing lignin under reductive electrochemical conditions using carbon as an electrocatalyst. After reductive electrocatalysis, the presence of aromatic compounds was no longer detected via nuclear magnetic resonance (NMR) spectroscopy. Further characterization by NMR, FTIR spectroscopy, and mass spectrometry revealed the major presences of sodium levulinate, sodium 4‐hydroxyvalerate, sodium formate, and sodium acetate as products. By achieving a complete dearomatization, valuable aliphatic intermediates with enhanced reactivity were selectively obtained, opening new avenues for further synthesis of many different organic chemicals, and contributing to a more sustainable and circular economy. [ABSTRACT FROM AUTHOR]

The development of sustainable valorization methods for lignin is a challenging task because the vast majority of the reported studies involve either harsh conditions or expensive transition metal catalysts. Inspired by the sunlight degradation of lignin compounds, known as lignin yellowing, the use of a commercially available cheap organic photoinitiator, namely, phenacyl bromide (PAB) is reported here, for the efficient cleavage of lignin model compound 2‐phenoxyacetophenone (2‐PAP) and for the depolymerization of soda pulped lignin (SL) under UV‐A irradiation and ambient conditions. Real‐time NMR investigations of the photoreaction between 2‐PAP and PAB shed light on the possible reaction mechanisms involving different radical species, HBr, and molecular oxygen. Interestingly, combined spectral, chromatographic, powder X‐ray diffraction, and thermal studies of the photoreaction between PAB and SL indicate the formation of guaiacyl alcohol as the main product. The unprecedented performance of PAB is attributed to the excess generation of phenacyl radicals, the generation of photolabile brominated species, and HBr playing key roles in the cleavage of β‐O‐4 linkages. This work represents a new edge for sustainable lignin valorization under mild reaction conditions and offers the opportunity for large‐scale production of valuable aromatics using technical lignins as feedstock. [ABSTRACT FROM AUTHOR]

The majority of sediment transported from rivers to the global oceans is moved in suspension as fine particles. Thereby, the transported sediment shapes the physical environment regarding erosive and accumulative processes. Temporal variations in sediment supply and transport lead to unquantified uncertainties in annual load estimates, requiring high‐resolution data sets and a sound understanding of site‐specific catchment characteristics. We investigate the temporal variability of suspended sediment transport in four catchments in Germany with highly different discharge regimes and catchment sizes (<1,000 km2 to >100,000 km2). The data set consists of high‐resolution 15‐min turbidity measurements with daily discharge and frequent manual sampling. Utilizing a bootstrap approach based on the 15‐min time series, we assessed the impact of the sampling interval on annual load estimates for less frequent data sets. We use the sediment load exceedance time (Ts80%) as a measure of variability and relate it to uncertainties in annual load estimates. Since low‐frequency data sets rely on sediment rating curves, we performed a sensitivity analysis of the rating parameters a, b, and ε. Our results indicate a negative exponential relationship between Ts80% and uncertainties in annual load estimates. Based on the Ts80%, we can derive the shortest sampling frequency necessary to obtain annual load estimates with an error of <20% over varying discharge regimes. Additionally, Ts80% is linked to rating exponent b, with low b‐values indicating high Ts80%‐values and lower variability, and high b‐values indicating higher variability. Plain Language Summary: On their way to the global oceans, rivers transport sediment. The transported sediment can be divided into two main fractions: fine particles and coarse sediment. Fine particles are distributed over the entire water column and represent most of the mass (sediment load) that is transported by rivers. The sediment load for rivers is not constant and varies significantly over time. Thereby, it is challenging to determine (annual) sediment loads with high accuracy. Through the combination of specialized sensors, which measure continuously, and manual water samples it is possible to reduce uncertainties in the calculation of sediment loads. First, we investigate how much data is necessary to calculate annual sediment loads with as little uncertainty as possible. Second, we investigate how much time is necessary to transport the majority (80%) of the annual sediment load. Third, we investigate how interpolation and extrapolation of small/infrequent data sets affects uncertainties in the calculation of annual sediment loads. Our results help planners and users of sediment transport data to refine (existing) sampling schemes and interpret low‐resolution data sets. Key Points: Negative exponential relationship between sediment load exceedance time and uncertainties in annual load estimatesOptimal sampling frequency can be derived from uncertainty‐sediment load exceedance time functionSediment rating exponent b is directly linked to sediment load exceedance time [ABSTRACT FROM AUTHOR]

The immobilization and structural analysis of platinum nanoparticles on a nitrogen‐rich, bipyridine‐containing covalent triazine framework (bpyCTF) having structural defects are disclosed by taking advantage of 15N solid‐state nuclear magnetic resonance measurements at natural 15N isotope abundance and X‐ray photoelectron spectroscopic analyses. The photocatalyst (Pt@bpyCTF) with structural defects reduces CO2 to formic acid (FA) at a rate of 152 µmol h−1g−1 and a selectivity higher than 95% over CO and H2 in water under simulated solar light. The presence of amine defects and the immobilization of Pt cause improvement in the photocurrent density and CO2 capture capacity (≈8% by weight) despite the moderate surface area (0.54 cm3 g−1)of the photocatalyst. Theoretical models and density functional theory calculations are employed to investigate the possible CO2 reduction reaction (CO2RR) mechanisms. Considering the exceptional CO2 capture capacity and high FA production using only CO2‐bubbled water, this work highlights the great potential of nitrogen‐rich CTFs for photocatalyzed CO2RRs under green conditions. [ABSTRACT FROM AUTHOR]

The low stability of the electrocatalysts at water oxidation (WO) conditions and the use of expensive noble metals have obstructed large‐scale H2 production from water. Herein, we report the electrocatalytic WO activity of a cobalt‐containing, water‐soluble molecular WO electrocatalyst [CoII(mcbp)(OH2)] (1) [mcbp2−=2,6‐bis(1‐methyl‐4‐(carboxylate)benzimidazol‐2‐yl)pyridine] in homogeneous conditions (overpotential of 510 mV at pH 7 phosphate buffer) and after anchoring it on pyridine‐modified fluorine‐doped carbon cloth (PFCC). The formation of cobalt phosphate was identified only after 4 h continuous oxygen evolution in homogeneous conditions. Interestingly, a significant enhancement of the stability and WO activity (current density of 5.4 mA/cm2 at 1.75 V) was observed for 1 after anchoring onto PFCC, resulting in a turnover (TO) of >3.6×103 and average TOF of 0.05 s−1 at 1.55 V (pH 7) over 20 h. A total TO of >21×103 over 8 days was calculated. The electrode allowed regeneration of∼ 85 % of the WO activity electrochemically after 36 h of continuous oxygen evolution. [ABSTRACT FROM AUTHOR]

Breaking down lignin into smaller units is the key to generate high value‐added products. Nevertheless, dissolving this complex plant polyphenol in an environment‐friendly way is often a challenge. Levulinic acid, which is formed during the hydrothermal processing of lignocellulosic biomass, has been shown to efficiently dissolve lignin. Herein, levulinic acid was evaluated as a medium for the reductive electrochemical depolymerization of the lignin macromolecule. Copper was chosen as the electrocatalyst due to the economic feasibility and low activity towards the hydrogen evolution reaction. After depolymerization, high‐resolution mass spectrometry and nuclear magnetic resonance spectroscopy revealed lignin‐derived monomers and dimers. A predominance of aryl ether and phenolic groups was observed. Depolymerized lignin was further evaluated as an anti‐corrosion coating, revealing enhancements on the electrochemical stability of the metal. Via a simple depolymerization process of biomass waste in a biomass‐based solvent, a straightforward approach to produce high value‐added compounds or tailored biobased materials was demonstrated. [ABSTRACT FROM AUTHOR]

The commercial breakthrough of Li‐ion batteries (LIBs) in the 1990s irrevocably shaped today's energy storage landscape, but the disposed batteries represent a growing hazard to the environment. One may initially assume that recycling processes are commendable technologies to ensure a counterbalance to LIBs manufacturing. However, the question remains whether current state‐of‐the‐art in LIBs recycling technologies can be considered as green. This problem is due to the application of toxic chemicals or the in situ generation of harmful substances during the recycling process. Besides the potential toxicity, current solutions are accompanied with intense energy consumption, causing carbon dioxide emissions, in disagreement with the circular economy principles. This review provides a critical assessment of both published research articles and patents to derive a broad picture on the sustainability of LIBs recycling technologies. Although the efficiency of industrially applied recycling technologies can exhibit a high overall efficiency, their general process design is generally based on waste reduction and downcycling. Contrariwise, sustainable recycling of LIBs should rely on circular processes ensuring upcycling of all materials toward zero waste and minimized energy utilization. Current solutions and expected development in LIBs recycling are presented, ranging from dismantling over components separation to application of bioderived materials. [ABSTRACT FROM AUTHOR]

Lignin nanoparticles (LNPs) are promising renewable nanomaterials with applications ranging from biomedicine to water purification. However, the instability of LNPs under acidic and basic conditions severely limits their functionalization for improved performance. Here, we show that controlling the degree of esterification can significantly improve the stability of lignin oleate nanoparticles (OLNPs) in acidic and basic aqueous dispersions. The high stability of OLNPs is attributed to the alkyl chains accumulated in the shell of the particle, which delays protonation/deprotonation of carboxylic acid and phenolic hydroxyl groups. Owing to the enhanced stability, acid‐ and base‐catalyzed functionalization of OLNPs at pH 2.0 and pH 12.0 via oxirane ring‐opening reactions were successfully performed. We also demonstrated these new functionalized particles as efficient pH‐switchable dye adsorbents and anticorrosive particulate coatings. [ABSTRACT FROM AUTHOR]

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The carbodiimide SnCN2 was prepared at low temperatures (400 °C–550 °C) by using a patented urea precursor route. The crystal structure of SnCN2 was determined from single‐crystal data in space group C2/c (no. 15) with a=9.1547(5), b=5.0209(3), c=6.0903(3) Å, β=117.672(3), V=247.92 Å3 and Z=4. As carbodiimide compounds display remarkably high thermal and chemical resistivity, SnCN2 has been doped with Eu and Tb to test it for its application in future phosphor‐converted LEDs. This doping of SnCN2 proved that a color tuning of the carbodiimide host with different activator ions and the combination of the latter ones is possible. Additionally, as the search for novel high‐performing electrode materials is essential for current battery technologies, this carbodiimide has been investigated concerning its use in lithium‐ion batteries. To further elucidate its application possibilities in materials science, several characterization steps and physical measurements (XRD, in situ XANES, Sn Mössbauer spectroscopy, thermal expansion, IR spectroscopy, Mott‐Schottky analysis) were carried out. The electronic structure of the n‐type semiconductor SnCN2 has been probed using X‐ray absorption spectroscopy and density functional theory (DFT) computations. [ABSTRACT FROM AUTHOR]

Lignin is one the most fascinating natural polymers due to its complex aromatic‐aliphatic structure. Phenolic hydroxyl and carboxyl groups along with other functional groups provide technical lignins with reactivity and amphiphilic character. Many different lignins have been used as functional agents to facilitate the synthesis and stabilization of inorganic materials. Herein, the use of lignin in the synthesis and chemistry of inorganic materials in selected applications with relevance to sustainable energy and environmental fields is reviewed. In essence, the combination of lignin and inorganic materials creates an interface between soft and hard materials. In many cases it is either this interface or the external lignin surface that provides functionality to the hybrid and composite materials. This Minireview closes with an overview on future directions for this research field that bridges inorganic and lignin materials for a more sustainable future. [ABSTRACT FROM AUTHOR]

Sunlight can be used to split water into hydrogen and oxygen by means of a photoelectrochemical (PEC) cell. Oxide nanostructures in heterojunction geometry, consisting of anisotropic WO3 nanostructures coated with a second semiconductor having a narrower band gap, such as α-Fe2O3, have emerged as prospective photoanodes. Herein, the integration of monodisperse CoPd nanocrystals (NCs) with α-Fe2O3 and WO3/α-Fe2O3 heterojunction semiconductor nanostructures for PEC water oxidation is reported. Depositing CoPd NCs on the surface of hematite leads to more stable photocurrent in comparison to the bare electrode, which indicates improved electron-hole separation at the semiconductor/electrolyte interface. Altering the surface of WO3/α-Fe2O3 photoanodes with CoPd NCs induces a cathodic shift of the onset potential and increases photocurrent density from 0.15 to 0.5 mA cm-2 during water oxidation at 1.23 V versus RHE under AM 1.5 G illumination (pH 7). [ABSTRACT FROM AUTHOR]

Coating, depolymerization, electrocatalysis, levulinic acid, lignin Front Cover: Electrochemical Depolymerization of Lignin in a Biomass-based Solvent (ChemSusChem 15/2022) Keywords: coating; depolymerization; electrocatalysis; levulinic acid; lignin EN coating depolymerization electrocatalysis levulinic acid lignin 1 1 1 08/11/22 20220805 NES 220805 B The Front Cover b shows tree trunks as potential sources of lignin, an underutilized industrial feedstock, which can undergo reductive electrochemical depolymerization. [Extracted from the article]

The ternary Zintl phase EuMgGe was synthesized from the elements, and its structure solved by single-crystal X-ray diffraction. Chemical bonding is discussed, by means of electronic structure calculations at the DFT level and its physical properties characterized with respect to electronic conductivity, magnetic susceptibility, specific heat capacity, and magnetoresistivity. The compound may be interpreted according to the Zintl-Klemm concept as (Eu2+)(Mg2+)(Ge4-) with isolated germanium anions. Resistivity measurements reveal a semimetallic character, which is consistent with the vanishing energy gap obtained from our calculations. The magnetic susceptibility and the specific heat indicate that two consecutive transitions take place, at 9 and 16 K, and they show evidence of magnetic frustration. A possible physical scenario for this magnetic behavior is discussed based on known models of partially frustrated magnets. [ABSTRACT FROM AUTHOR]

Zintl phases: The new lithium‐rich Zintl phase Li12Ag1−xSi4 (x=0.15) contains the highly charged 16‐electron anion [AgSi2]7−. Chemical bonding is discussed based on electronic band structure analysis (see figure). [ABSTRACT FROM AUTHOR]

Two new ternary compounds Eu5+ xMg18- xGe13 ( x = 0.1) and Eu8Mg16Ge12 were obtained by solid state synthesis and their crystal structures determined by single crystal X-ray diffraction. The two compounds crystallize in the hexagonal crystal system (space group P $\bar{6}$2 m). Eu5+ xMg18- xGe13 ( x = 0.1) is a Zintl phase with nine isolated Ge4- ions and a [Ge4]10- star, which is isoelectronic with PF3 but surprisingly almost planar. Eu8Mg16Ge12 contains a [ MGe3] ( M = Eu, Mg) unit, instead of the [Ge4]10-, and can be described as a salt-like compound, containing 12 'isolated' Ge4- anions. The structural similarity of these two compounds allows to analyze the chemical bonding of different Zintl anions, which belong to a structural greater isosteric unit. The metallic conductivity of Eu8Mg16Ge12 originates from the ecliptic stacking of the 'so-called isolated' anions along the c direction. In Eu5+ xMg18- xGe13 the deviation of the Zintl anion from the planarity causes a semi-metallic behavior. In both cases, the magnetic response is dominated by the local moments of the europium atoms, which are all found in a 2+ oxidation state. Deviations from the Curie-Weiss law are observed for T < 20 K in the cation-richer compound and at lower temperatures in the other. The behavior in the low-temperature range changes with the replacement of the [Ge4]10- star by the MGe3 unit. These studies show that metallic behavior through ecliptic stacking of planar anions can be achieved even with monatomic anions, up to 4.4 Å with germanium at least, and can be destroyed by small deviations from planarity in an extended anion. [ABSTRACT FROM AUTHOR]

Two new ternary compounds Eu5+ xMg18- xGe13 ( x = 0.1) and Eu8Mg16Ge12 were obtained by solid state synthesis and their crystal structures determined by single crystal X-ray diffraction. The two compounds crystallize in the hexagonal crystal system (space group P $\bar{6}$2 m). Eu5+ xMg18- xGe13 ( x = 0.1) is a Zintl phase with nine isolated Ge4- ions and a [Ge4]10- star, which is isoelectronic with PF3 but surprisingly almost planar. Eu8Mg16Ge12 contains a [ MGe3] ( M = Eu, Mg) unit, instead of the [Ge4]10-, and can be described as a salt-like compound, containing 12 'isolated' Ge4- anions. The structural similarity of these two compounds allows to analyze the chemical bonding of different Zintl anions, which belong to a structural greater isosteric unit. The metallic conductivity of Eu8Mg16Ge12 originates from the ecliptic stacking of the 'so-called isolated' anions along the c direction. In Eu5+ xMg18- xGe13 the deviation of the Zintl anion from the planarity causes a semi-metallic behavior. In both cases, the magnetic response is dominated by the local moments of the europium atoms, which are all found in a 2+ oxidation state. Deviations from the Curie-Weiss law are observed for T < 20 K in the cation-richer compound and at lower temperatures in the other. The behavior in the low-temperature range changes with the replacement of the [Ge4]10- star by the MGe3 unit. These studies show that metallic behavior through ecliptic stacking of planar anions can be achieved even with monatomic anions, up to 4.4 Å with germanium at least, and can be destroyed by small deviations from planarity in an extended anion. [ABSTRACT FROM AUTHOR]

The new ternary phase Eu2- xMg2- yGe3 ( x = 0.1, y = 0.5) was obtained by solid-state synthesis and the structure determined by means of Single Crystal X-ray Diffraction. The compound crystallizes with the orthorhombic space group Cmcm (no. 63) having structural features of the low-temperature modification of LaSi. The crystal structure contains two different types of germanium anions: isolated Ge4- and $\rm^{2}_{\infty}$[Ge2- x- y] chains. The cation substructure is partially disordered and is best represented assuming a split position. The chemical bonding is well represented by the Zintl-Klemm concept. Resistivity measurements reveal that the compound is metallic. DFT band structure calculations were carried out on the ideal stoichiometric compound Eu2Mg2Ge3, showing that this model ( x = 0; y = 0) would be also metallic as a consequence of the ecliptic stacking of anions. Susceptibility and specific heat measurements evidence the presence of weak, and probably frustrated, antiferromagnetic interactions between disordered europium atoms. [ABSTRACT FROM AUTHOR]

EuMgGe is prepared by melting and annealing the elements (Nb tube, 1. [ABSTRACT FROM AUTHOR]

The new Zintl phase of title is synthesized from the elements (Nb crucible, 650 °C, 8 d). [ABSTRACT FROM AUTHOR]

The new compounds Li7CuSi2 (I) and Li7.3CuSi3 (II) are synthesized from the elements (Nb ampule, 600 °C, 7 d) and characterized by XRD, magnetic measurements, and band structure calculations. [ABSTRACT FROM AUTHOR]

Eu5.1Mg17.9Ge13 (I) and Eu8Mg16Ge12 (II) are prepared by solid state reaction of the elements (Nb ampules, 890-1020 °C, 48 h-16 d). [ABSTRACT FROM AUTHOR]