TY - JOUR AB - The influence of structural modifications on the catalytic activity of carbon materials is poorly understood. A collection of carbonaceous materials with different pore networks and high nitrogen content was characterized and used to catalyze four reactions to deduce structure–activity relationships. The CO2 cycloaddition and Knoevenagel reaction depend on Lewis basic sites (electron-rich nitrogen species). The absence of large conjugated carbon domains resulting from the introduction of large amounts of nitrogen in the carbon network is responsible for poor redox activity, as observed through the catalytic reduction of nitrobenzene with hydrazine and the catalytic oxidation of 3,3′,5,5′-tetramethylbenzidine using hydroperoxide. The material with the highest activity towards Lewis acid catalysis (in the hydrolysis of (dimethoxymethyl)benzene to benzaldehyde) is the most effective for small molecule activation and presents the highest concentration of electron-poor nitrogen species. AU - Lepre, Enrico AU - Rat, Sylvain AU - Cavedon, Cristian AU - Seeberger, Peter H. AU - Pieber, Bartholomäus AU - Antonietti, Markus AU - López‐Salas, Nieves ID - 12922 IS - 2 JF - Angewandte Chemie International Edition KW - General Chemistry KW - Catalysis SN - 1433-7851 TI - Catalytic properties of high nitrogen content carbonaceous materials VL - 62 ER - TY - GEN AB - Cover Page AU - Becker, Lea Marie AU - Berbon, Mélanie AU - Vallet, Alicia AU - Grelard, Axelle AU - Morvan, Estelle AU - Bardiaux, Benjamin AU - Lichtenecker, Roman AU - Ernst, Matthias AU - Loquet, Antoine AU - Schanda, Paul ID - 14861 IS - 19 KW - General Chemistry KW - Catalysis SN - 1433-7851 T2 - Angewandte Chemie International Edition TI - Cover Picture: The rigid core and flexible surface of amyloid fibrils probed by Magic‐Angle‐Spinning NMR spectroscopy of aromatic residues VL - 62 ER - TY - JOUR AB - The short history of research on Li-O2 batteries has seen a remarkable number of mechanistic U-turns over the years. From the initial use of carbonate electrolytes, that were then found to be entirely unsuitable, to the belief that (su)peroxide was solely responsible for degradation, before the more reactive singlet oxygen was found to form, to the hypothesis that capacity depends on a competing surface/solution mechanism before a practically exclusive solution mechanism was identified. Herein, we argue for an ever-fresh look at the reported data without bias towards supposedly established explanations. We explain how the latest findings on rate and capacity limits, as well as the origin of side reactions, are connected via the disproportionation (DISP) step in the (dis)charge mechanism. Therefrom, directions emerge for the design of electrolytes and mediators on how to suppress side reactions and to enable high rate and high reversible capacity. AU - Jethwa, Rajesh B AU - Mondal, Soumyadip AU - Pant, Bhargavi AU - Freunberger, Stefan Alexander ID - 14687 JF - Angewandte Chemie International Edition KW - General Chemistry KW - Catalysis SN - 1433-7851 TI - To DISP or not? The far‐reaching reaction mechanisms underpinning Lithium‐air batteries ER - TY - JOUR AB - Aromatic side chains are important reporters of the plasticity of proteins, and often form important contacts in protein--protein interactions. By studying a pair of structurally homologous cross-β amyloid fibrils, HET-s and HELLF, with a specific isotope-labeling approach and magic-angle-spinning (MAS) NMR, we have characterized the dynamic behavior of Phe and Tyr aromatic rings to show that the hydrophobic amyloid core is rigid, without any sign of "breathing motions" over hundreds of milliseconds at least. Aromatic residues exposed at the fibril surface have a rigid ring axis but undergo ring flips, on a variety of time scales from ns to µs. Our approach provides direct insight into hydrophobic-core motions, enabling a better evaluation of the conformational heterogeneity generated from a NMR structural ensemble of such amyloid cross-β architecture. AU - Becker, Lea Marie AU - Berbon, Mélanie AU - Vallet, Alicia AU - Grelard, Axelle AU - Morvan, Estelle AU - Bardiaux, Benjamin AU - Lichtenecker, Roman AU - Ernst, Matthias AU - Loquet, Antoine AU - Schanda, Paul ID - 12675 IS - 19 JF - Angewandte Chemie International Edition KW - General Chemistry KW - Catalysis SN - 1433-7851 TI - The rigid core and flexible surface of amyloid fibrils probed by Magic‐Angle Spinning NMR of aromatic residues VL - 62 ER - TY - JOUR AB - Covalent organic frameworks (COFs) are structurally tuneable, porous and crystalline polymers constructed through the covalent attachment of small organic building blocks as elementary units. Using the myriad of such building blocks, a broad spectrum of functionalities has been applied for COF syntheses for broad applications, including heterogeneous catalysis. Herein, we report the synthesis of a new family of porous and crystalline COFs using a novel acridine linker and benzene-1,3,5-tricarbaldehyde derivatives bearing a variable number of hydroxy groups. With the broad absorption in the visible light region, the COFs were applied as photocatalysts in metallaphotocatalytic C−N cross-coupling. The fully β-ketoenamine linked COF showed the highest activity, due to the increased charge separation upon irradiation. The COF showed good to excellent yields for several aryl bromides, good recyclability and even catalyzed the organic transformation in presence of green light as energy source. AU - Traxler, Michael AU - Gisbertz, Sebastian AU - Pachfule, Pradip AU - Schmidt, Johannes AU - Roeser, Jérôme AU - Reischauer, Susanne AU - Rabeah, Jabor AU - Pieber, Bartholomäus AU - Thomas, Arne ID - 11955 IS - 21 JF - Angewandte Chemie International Edition SN - 1433-7851 TI - Acridine‐functionalized covalent organic frameworks (COFs) as photocatalysts for metallaphotocatalytic C−N cross‐coupling VL - 61 ER - TY - JOUR AB - We demonstrate that several visible-light-mediated carbon−heteroatom cross-coupling reactions can be carried out using a photoactive NiII precatalyst that forms in situ from a nickel salt and a bipyridine ligand decorated with two carbazole groups (Ni(Czbpy)Cl2). The activation of this precatalyst towards cross-coupling reactions follows a hitherto undisclosed mechanism that is different from previously reported light-responsive nickel complexes that undergo metal-to-ligand charge transfer. Theoretical and spectroscopic investigations revealed that irradiation of Ni(Czbpy)Cl2 with visible light causes an initial intraligand charge transfer event that triggers productive catalysis. Ligand polymerization affords a porous, recyclable organic polymer for heterogeneous nickel catalysis of cross-coupling reactions. The heterogeneous catalyst shows stable performance in a packed-bed flow reactor during a week of continuous operation. AU - Cavedon, Cristian AU - Gisbertz, Sebastian AU - Reischauer, Susanne AU - Vogl, Sarah AU - Sperlich, Eric AU - Burke, John H. AU - Wallick, Rachel F. AU - Schrottke, Stefanie AU - Hsu, Wei‐Hsin AU - Anghileri, Lucia AU - Pfeifer, Yannik AU - Richter, Noah AU - Teutloff, Christian AU - Müller‐Werkmeister, Henrike AU - Cambié, Dario AU - Seeberger, Peter H. AU - Vura‐Weis, Josh AU - van der Veen, Renske M. AU - Thomas, Arne AU - Pieber, Bartholomäus ID - 12924 IS - 46 JF - Angewandte Chemie International Edition KW - General Chemistry KW - Catalysis SN - 1433-7851 TI - Intraligand charge transfer enables visible‐light‐mediated Nickel‐catalyzed cross-coupling reactions VL - 61 ER - TY - JOUR AB - The precursor conversion chemistry and surface chemistry of Cu3N and Cu3PdN nanocrystals are unknown or contested. Here, we first obtain phase-pure, colloidally stable nanocubes. Second, we elucidate the pathway by which copper(II) nitrate and oleylamine form Cu3N. We find that oleylamine is both a reductant and a nitrogen source. Oleylamine is oxidized by nitrate to a primary aldimine, which reacts further with excess oleylamine to a secondary aldimine, eliminating ammonia. Ammonia reacts with CuI to form Cu3N. Third, we investigated the surface chemistry and find a mixed ligand shell of aliphatic amines and carboxylates (formed in situ). While the carboxylates appear tightly bound, the amines are easily desorbed from the surface. Finally, we show that doping with palladium decreases the band gap and the material becomes semi-metallic. These results bring insight into the chemistry of metal nitrides and might help the development of other metal nitride nanocrystals. AU - Parvizian, Mahsa AU - Duràn Balsa, Alejandra AU - Pokratath, Rohan AU - Kalha, Curran AU - Lee, Seungho AU - Van Den Eynden, Dietger AU - Ibáñez, Maria AU - Regoutz, Anna AU - De Roo, Jonathan ID - 11451 IS - 31 JF - Angewandte Chemie - International Edition SN - 1433-7851 TI - The chemistry of Cu₃N and Cu₃PdN nanocrystals VL - 61 ER - TY - JOUR AB - The broad implementation of thermoelectricity requires high-performance and low-cost materials. One possibility is employing surfactant-free solution synthesis to produce nanopowders. We propose the strategy of functionalizing “naked” particles’ surface by inorganic molecules to control the nanostructure and, consequently, thermoelectric performance. In particular, we use bismuth thiolates to functionalize surfactant-free SnTe particles’ surfaces. Upon thermal processing, bismuth thiolates decomposition renders SnTe-Bi2S3 nanocomposites with synergistic functions: 1) carrier concentration optimization by Bi doping; 2) Seebeck coefficient enhancement and bipolar effect suppression by energy filtering; and 3) lattice thermal conductivity reduction by small grain domains, grain boundaries and nanostructuration. Overall, the SnTe-Bi2S3 nanocomposites exhibit peak z T up to 1.3 at 873 K and an average z T of ≈0.6 at 300–873 K, which is among the highest reported for solution-processed SnTe. AU - Chang, Cheng AU - Liu, Yu AU - Lee, Seungho AU - Spadaro, Maria AU - Koskela, Kristopher M. AU - Kleinhanns, Tobias AU - Costanzo, Tommaso AU - Arbiol, Jordi AU - Brutchey, Richard L. AU - Ibáñez, Maria ID - 11705 IS - 35 JF - Angewandte Chemie - International Edition SN - 1433-7851 TI - Surface functionalization of surfactant-free particles: A strategy to tailor the properties of nanocomposites for enhanced thermoelectric performance VL - 61 ER - TY - JOUR AB - The question of how RNA, as the principal carrier of genetic information evolved is fundamentally important for our understanding of the origin of life. The RNA molecule is far too complex to have formed in one evolutionary step, suggesting that ancestral proto-RNAs (first ancestor of RNA) may have existed, which evolved over time into the RNA of today. Here we show that isoxazole nucleosides, which are quickly formed from hydroxylamine, cyanoacetylene, urea and ribose, are plausible precursors for RNA. The isoxazole nucleoside can rearrange within an RNA-strand to give cytidine, which leads to an increase of pairing stability. If the proto-RNA contains a canonical seed-nucleoside with defined stereochemistry, the seed-nucleoside can control the configuration of the anomeric center that forms during the in-RNA transformation. The results demonstrate that RNA could have emerged from evolutionarily primitive precursor isoxazole ribosides after strand formation. AU - Xu, Felix AU - Crisp, Antony AU - Schinkel, Thea AU - Dubini, Romeo C. A. AU - Hübner, Sarah AU - Becker, Sidney AU - Schelter, Florian AU - Rovo, Petra AU - Carell, Thomas ID - 12228 IS - 45 JF - Angewandte Chemie International Edition KW - General Chemistry KW - Catalysis SN - 1433-7851 TI - Isoxazole nucleosides as building blocks for a plausible proto‐RNA VL - 61 ER - TY - JOUR AB - Controlling the selectivity of a chemical reaction with external stimuli is common in thermal processes, but rare in visible-light photocatalysis. Here we show that the redox potential of a carbon nitride photocatalyst (CN-OA-m) can be tuned by changing the irradiation wavelength to generate electron holes with different oxidation potentials. This tuning was the key to realizing photo-chemo-enzymatic cascades that give either the (S)- or the (R)-enantiomer of phenylethanol. In combination with an unspecific peroxygenase from Agrocybe aegerita, green light irradiation of CN-OA-m led to the enantioselective hydroxylation of ethylbenzene to (R)-1-phenylethanol (99 % ee). In contrast, blue light irradiation triggered the photocatalytic oxidation of ethylbenzene to acetophenone, which in turn was enantioselectively reduced with an alcohol dehydrogenase from Rhodococcus ruber to form (S)-1-phenylethanol (93 % ee). AU - Schmermund, Luca AU - Reischauer, Susanne AU - Bierbaumer, Sarah AU - Winkler, Christoph K. AU - Diaz‐Rodriguez, Alba AU - Edwards, Lee J. AU - Kara, Selin AU - Mielke, Tamara AU - Cartwright, Jared AU - Grogan, Gideon AU - Pieber, Bartholomäus AU - Kroutil, Wolfgang ID - 11956 IS - 13 JF - Angewandte Chemie International Edition SN - 1433-7851 TI - Chromoselective photocatalysis enables stereocomplementary biocatalytic pathways VL - 60 ER - TY - JOUR AB - DNA nanotechnology offers a versatile toolbox for precise spatial and temporal manipulation of matter on the nanoscale. However, rendering DNA-based systems responsive to light has remained challenging. Herein, we describe the remote manipulation of native (non-photoresponsive) chiral plasmonic molecules (CPMs) using light. Our strategy is based on the use of a photoresponsive medium comprising a merocyanine-based photoacid. Upon exposure to visible light, the medium decreases its pH, inducing the formation of DNA triplex links, leading to a spatial reconfiguration of the CPMs. The process can be reversed simply by turning the light off and it can be repeated for multiple cycles. The degree of the overall chirality change in an ensemble of CPMs depends on the CPM fraction undergoing reconfiguration, which, remarkably, depends on and can be tuned by the intensity of incident light. Such a dynamic, remotely controlled system could aid in further advancing DNA-based devices and nanomaterials. AU - Ryssy, Joonas AU - Natarajan, Ashwin K. AU - Wang, Jinhua AU - Lehtonen, Arttu J. AU - Nguyen, Minh‐Kha AU - Klajn, Rafal AU - Kuzyk, Anton ID - 13358 IS - 11 JF - Angewandte Chemie International Edition KW - General Chemistry KW - Catalysis SN - 1433-7851 TI - Light‐responsive dynamic DNA‐origami‐based plasmonic assemblies VL - 60 ER - TY - JOUR AB - Water-in-salt electrolytes based on highly concentrated bis(trifluoromethyl)sulfonimide (TFSI) promise aqueous electrolytes with stabilities nearing 3 V. However, especially with an electrode approaching the cathodic (reductive) stability, cycling stability is insufficient. While stability critically relies on a solid electrolyte interphase (SEI), the mechanism behind the cathodic stability limit remains unclear. Here, we reveal two distinct reduction potentials for the chemical environments of 'free' and 'bound' water and that both contribute to SEI formation. Free-water is reduced ~1V above bound water in a hydrogen evolution reaction (HER) and responsible for SEI formation via reactive intermediates of the HER; concurrent LiTFSI precipitation/dissolution establishes a dynamic interface. The free-water population emerges, therefore, as the handle to extend the cathodic limit of aqueous electrolytes and the battery cycling stability. AU - Bouchal, Roza AU - Li, Zhujie AU - Bongu, Chandra AU - Le Vot, Steven AU - Berthelot, Romain AU - Rotenberg, Benjamin AU - Favier, Fréderic AU - Freunberger, Stefan Alexander AU - Salanne, Mathieu AU - Fontaine, Olivier ID - 7847 IS - 37 JF - Angewandte Chemie International Edition SN - 1433-7851 TI - Competitive salt precipitation/dissolution during free‐water reduction in water‐in‐salt electrolyte VL - 59 ER - TY - JOUR AB - We show the synthesis of a redox‐active quinone, 2‐methoxy‐1,4‐hydroquinone (MHQ), from a bio‐based feedstock and its suitability as electrolyte in aqueous redox flow batteries. We identified semiquinone intermediates at insufficiently low pH and quinoid radicals as responsible for decomposition of MHQ under electrochemical conditions. Both can be avoided and/or stabilized, respectively, using H 3 PO 4 electrolyte, allowing for reversible cycling in a redox flow battery for hundreds of cycles. AU - Schlemmer, Werner AU - Nothdurft, Philipp AU - Petzold, Alina AU - Frühwirt, Philipp AU - Schmallegger, Max AU - Gescheidt-Demner, Georg AU - Fischer, Roland AU - Freunberger, Stefan Alexander AU - Kern, Wolfgang AU - Spirk, Stefan ID - 8329 IS - 51 JF - Angewandte Chemie International Edition SN - 1433-7851 TI - 2‐methoxyhydroquinone from vanillin for aqueous redox‐flow batteries VL - 59 ER - TY - JOUR AB - Cross-coupling reactions mediated by dual nickel/photocatalysis are synthetically attractive but rely mainly on expensive, non-recyclable noble-metal complexes as photocatalysts. Heterogeneous semiconductors, which are commonly used for artificial photosynthesis and wastewater treatment, are a sustainable alternative. Graphitic carbon nitrides, a class of metal-free polymers that can be easily prepared from bulk chemicals, are heterogeneous semiconductors with high potential for photocatalytic organic transformations. Here, we demonstrate that graphitic carbon nitrides in combination with nickel catalysis can induce selective C−O cross-couplings of carboxylic acids with aryl halides, yielding the respective aryl esters in excellent yield and selectivity. The heterogeneous organic photocatalyst exhibits a broad substrate scope, is able to harvest green light, and can be recycled multiple times. In situ FTIR was used to track the reaction progress to study this transformation at different irradiation wavelengths and reaction scales. AU - Pieber, Bartholomäus AU - Malik, Jamal A. AU - Cavedon, Cristian AU - Gisbertz, Sebastian AU - Savateev, Aleksandr AU - Cruz, Daniel AU - Heil, Tobias AU - Zhang, Guigang AU - Seeberger, Peter H. ID - 11957 IS - 28 JF - Angewandte Chemie International Edition SN - 1433-7851 TI - Semi‐heterogeneous dual nickel/photocatalysis using carbon nitrides: Esterification of carboxylic acids with aryl halides VL - 58 ER - TY - JOUR AB - Singlet oxygen (1O2) causes a major fraction of the parasitic chemistry during the cycling of non‐aqueous alkali metal‐O2 batteries and also contributes to interfacial reactivity of transition‐metal oxide intercalation compounds. We introduce DABCOnium, the mono alkylated form of 1,4‐diazabicyclo[2.2.2]octane (DABCO), as an efficient 1O2 quencher with an unusually high oxidative stability of ca. 4.2 V vs. Li/Li+. Previous quenchers are strongly Lewis basic amines with too low oxidative stability. DABCOnium is an ionic liquid, non‐volatile, highly soluble in the electrolyte, stable against superoxide and peroxide, and compatible with lithium metal. The electrochemical stability covers the required range for metal–O2 batteries and greatly reduces 1O2 related parasitic chemistry as demonstrated for the Li–O2 cell. AU - Petit, Yann K. AU - Leypold, Christian AU - Mahne, Nika AU - Mourad, Eléonore AU - Schafzahl, Lukas AU - Slugovc, Christian AU - Borisov, Sergey M. AU - Freunberger, Stefan Alexander ID - 7276 IS - 20 JF - Angewandte Chemie International Edition SN - 1433-7851 TI - DABCOnium: An efficient and high-voltage stable singlet oxygen quencher for metal-O2 cells VL - 58 ER - TY - JOUR AB - Solid reagents, leaching catalysts, and heterogeneous photocatalysts are commonly employed in batch processes but are ill-suited for continuous-flow chemistry. Heterogeneous catalysts for thermal reactions are typically used in packed-bed reactors, which cannot be penetrated by light and thus are not suitable for photocatalytic reactions involving solids. We demonstrate that serial micro-batch reactors (SMBRs) allow for the continuous utilization of solid materials together with liquids and gases in flow. This technology was utilized to develop selective and efficient fluorination reactions using a modified graphitic carbon nitride heterogeneous catalyst instead of costly homogeneous metal polypyridyl complexes. The merger of this inexpensive, recyclable catalyst and the SMBR approach enables sustainable and scalable photocatalysis. AU - Pieber, Bartholomäus AU - Shalom, Menny AU - Antonietti, Markus AU - Seeberger, Peter H. AU - Gilmore, Kerry ID - 11958 IS - 31 JF - Angewandte Chemie International Edition SN - 1433-7851 TI - Continuous heterogeneous photocatalysis in serial micro-batch reactors VL - 57 ER - TY - JOUR AB - Solid alkali metal carbonates are universal passivation layer components of intercalation battery materials and common side products in metal‐O2 batteries, and are believed to form and decompose reversibly in metal‐O2/CO2 cells. In these cathodes, Li2CO3 decomposes to CO2 when exposed to potentials above 3.8 V vs. Li/Li+. However, O2 evolution, as would be expected according to the decomposition reaction 2 Li2CO3→4 Li++4 e−+2 CO2+O2, is not detected. O atoms are thus unaccounted for, which was previously ascribed to unidentified parasitic reactions. Here, we show that highly reactive singlet oxygen (1O2) forms upon oxidizing Li2CO3 in an aprotic electrolyte and therefore does not evolve as O2. These results have substantial implications for the long‐term cyclability of batteries: they underpin the importance of avoiding 1O2 in metal‐O2 batteries, question the possibility of a reversible metal‐O2/CO2 battery based on a carbonate discharge product, and help explain the interfacial reactivity of transition‐metal cathodes with residual Li2CO3. AU - Mahne, Nika AU - Renfrew, Sara E. AU - McCloskey, Bryan D. AU - Freunberger, Stefan Alexander ID - 7277 IS - 19 JF - Angewandte Chemie International Edition SN - 1433-7851 TI - Electrochemical oxidation of Lithium Carbonate generates singlet oxygen VL - 57 ER - TY - JOUR AB - Confining organic molecules to the surfaces of inorganic nanoparticles can induce intermolecular interactions between them, which can affect the composition of the mixed self-assembled monolayers obtained by co-adsorption from solution of two different molecules. Two thiolated ligands (a dialkylviologen and a zwitterionic sulfobetaine) that can interact with each other electrostatically were coadsorbed onto gold nanoparticles. The nanoparticles favor a narrow range of ratios of these two molecules that is largely independent of the molar ratio in solution. Changing the solution molar ratio of the two ligands by a factor of 5 000 affects the on-nanoparticle ratio of these ligands by only threefold. This behavior is reminiscent of the formation of insoluble inorganic salts (such as AgCl), which similarly compensate positive and negative charges upon crystallizing. Our results pave the way towards developing well-defined hybrid organic–inorganic nanostructures. AU - Chu, Zonglin AU - Han, Yanxiao AU - Král, Petr AU - Klajn, Rafal ID - 13377 IS - 24 JF - Angewandte Chemie International Edition KW - General Chemistry KW - Catalysis SN - 1433-7851 TI - “Precipitation on nanoparticles”: Attractive intermolecular interactions stabilize specific ligand ratios on the surfaces of nanoparticles VL - 57 ER - TY - JOUR AB - In the present work, we detail a fast and simple solution-based method to synthesize hexagonal SnSe2 nanoplates (NPLs) and their use to produce crystallographically textured SnSe2 nanomaterials. We also demonstrate that the same strategy can be used to produce orthorhombic SnSe nanostructures and nanomaterials. NPLs are grown through a screw dislocation-driven mechanism. This mechanism typically results in pyramidal structures, but we demonstrate here that the growth from multiple dislocations results in flower-like structures. Crystallographically textured SnSe2 bulk nanomaterials obtained from the hot pressing of these SnSe2 structures display highly anisotropic charge and heat transport properties and thermoelectric (TE) figures of merit limited by relatively low electrical conductivities. To improve this parameter, SnSe2 NPLs are blended here with metal nanoparticles. The electrical conductivities of the blends are significantly improved with respect to bare SnSe2 NPLs, what translates into a three-fold increase of the TE Figure of merit, reaching unprecedented ZT values up to 0.65. AU - Zhang, Yu AU - Liu, Yu AU - Lim, Khak Ho AU - Xing, Congcong AU - Li, Mengyao AU - Zhang, Ting AU - Tang, Pengyi AU - Arbiol, Jordi AU - Llorca, Jordi AU - Ng, Ka Ming AU - Ibáñez, Maria AU - Guardia, Pablo AU - Prato, Mirko AU - Cadavid, Doris AU - Cabot, Andreu ID - 5982 IS - 52 JF - Angewandte Chemie International Edition SN - 1433-7851 TI - Tin diselenide molecular precursor for solution-processable thermoelectric materials VL - 57 ER - TY - JOUR AB - Aprotic sodium–O2 batteries require the reversible formation/dissolution of sodium superoxide (NaO2) on cycling. Poor cycle life has been associated with parasitic chemistry caused by the reactivity of electrolyte and electrode with NaO2, a strong nucleophile and base. Its reactivity can, however, not consistently explain the side reactions and irreversibility. Herein we show that singlet oxygen (1O2) forms at all stages of cycling and that it is a main driver for parasitic chemistry. It was detected in‐ and ex‐situ via a 1O2 trap that selectively and rapidly forms a stable adduct with 1O2. The 1O2 formation mechanism involves proton‐mediated superoxide disproportionation on discharge, rest, and charge below ca. 3.3 V, and direct electrochemical 1O2 evolution above ca. 3.3 V. Trace water, which is needed for high capacities also drives parasitic chemistry. Controlling the highly reactive singlet oxygen is thus crucial for achieving highly reversible cell operation. AU - Schafzahl, Lukas AU - Mahne, Nika AU - Schafzahl, Bettina AU - Wilkening, Martin AU - Slugovc, Christian AU - Borisov, Sergey M. AU - Freunberger, Stefan Alexander ID - 7289 IS - 49 JF - Angewandte Chemie International Edition SN - 1433-7851 TI - Singlet oxygen during cycling of the aprotic sodium-O2 battery VL - 56 ER -