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A bright future? Ammonia is of utmost importance for fertilizer production and recently gained interest as a future hydrogen storage material. However, photocatalytic production of ammonia suffers from stagnating materials development and unstandardized reaction conditions. This Review reports on recent materials and reaction engineering results, emphasizing the need to connect the activity of reported materials together with detailed reaction conditions and efficiencies. Research will strongly benefit from joint efforts between chemists, physicists and chemical engineers already at a fundamental level. Ammonia is not only the most important chemical for fertilizer production, it has also gained much interest as a future hydrogen storage material. Besides the well‐known Haber–Bosch process to generate ammonia from elemental sources, new ways to convert nitrogen into ammonia have been investigated in the last decade for a decentralized production, including electrocatalytic and photocatalytic approaches. However, photocatalysis in particular suffers from stagnating materials development and unstandardized reaction conditions. In this Review, we shine light on recent materials and reaction engineering results for photocatalytic nitrogen reduction, putting an emphasis on the need to connect the activity of reported materials together with detailed reaction conditions and efficiencies. Photocatalytic nitrogen reduction is an emerging field that will certainly gain significant interest in the future as a sustainable pathway to generate green hydrogen and ammonia. The field will certainly strongly benefit from joint efforts with strong interactions between chemists, physicists and chemical engineers at a fundamental level., publishedVersion

Photocatalytic nitrogen fixation under ambient conditions is currently widely explored in an attempt to develop a sustainable alternative for the Haber-Bosch process. Still, a lack of fundamental understanding of reaction pathways and nitrogen activation mechanisms result in the slow development in this field. In this work we combine defect-rich C3N4, one of the most investigated photocatalysts reported in literature for ammonia generation, with earth abundant and bioinspired FeS2 to improve the activity for photocatalytic ammonia production. By this approach, an activity enhancement of approx. 300 % compared to unmodified C3N4 was achieved. The optimal FeS2 loading was established to be 5 wt.%, with ammonia yields of up to 800 µg L-1 after irradiation for 7 hours. By detailed characterization of the electronic properties of the composites, we deduce that NH3 generation occurs via a novel mechanism involving mainly the reduction of the =N-CN group adjacent to nitrogen vacancies on defect-rich C3N4. FeS2 acts similar to a co-catalyst, improving the activity by π-back-donation from Fe-centers to the imine nitrogen of the defect-rich C3N4, reducing the activation barrier for terminal cyano group reduction upon illumination.

Many state-of-the-art photocatalyst systems suffer from high charge recombination rates that limit the number of charge carriers available for photocatalytic reactions on the surface. Additionally, the overpotential for the desired conversion reactions is often relatively high, likewise having an impeding effect on the activity. To overcome these limitations, the catalyst surface can be decorated with a cocatalyst that improves charge separation and lowers the overpotential. Noble metals have been especially promising in this regard.[1] However, the use of noble metals significantly increases the material costs and requires rare resources, thus compromising their sustainability. Molecular cocatalysts can be used alternatively, but suffer from stability issues, especially in aqueous media.[2] Recently, earth-abundant cocatalyst systems have emerged as alternative materials to improve photocatalytic hydrogen or oxygen generation.[3] Among the elements used, iron is one of the most abundant elements in the earth crust, and non-toxic. The use of iron-based cocatalysts can therefore significantly decrease photocatalyst production costs and minimize the creation of hazardous waste. Furthermore, iron is a core constituent of many active centers in enzymes, such as hydrogenase, nitrogenase or CO dehydrogenase, that are active in natural reduction and oxidation reactions.[4] This implies, that the development of efficient iron-based cocatalysts should generally be achievable. Interestingly, iron-based materials have only rarely been used as cocatalysts in photocatalysis. However, very prominent examples for photoelectrochemistry are FeOOH or Fe-based layered double hydroxides (LDH).[5] [6] On the other hand, ternary iron oxides and sulphides are promising electrocatalysts for water splitting and CO2 reduction, exhibiting low overpotentials for the respective reaction.[7] [8] E.g. we recently showed the first microwave-synthesis of phase-pure violarite Ni2FeS4 in only 30 minutes, and its application for electrocatalytic CO2 reduction and hydrogen generation.[8] The observed activity underlines the potential of these materials for the application in photocatalysis as well. Additionally, some of the known iron-based chalcogenides possess near metallic conductivity that should facilitate charge transfer. However, apart from the reduction of the overpotential, an efficient charge transfer from photocatalyst to cocatalyst is required, which necessitates a suitable band alignment, something, that is frequently overlooked in literature. In this contribution, novel ternary iron-based chalcogenides will be presented as efficient cocatalysts on TiO2 and C3N4, leading to a significant activity increase in hydrogen evolution, oxygen evolution and nitrogen reduction for both absorbers, even upon addition of relatively low amounts of 1 wt.-%. The influence of cocatalyst loading will be presented, and the activity will be compared to noble metal cocatalysts such as platinum. Additionally, electronic interactions between absorber and cocatalyst have been explored. [1] J. Yang, D. Wang, H. Han, C. Li, Acc. Chem. Res. 2013, 46, 1900–1909. [2] X. T. Xu, L. Pan, X. Zhang, L. Wang, J. J. Zou, Adv. Sci. 2019, 6, DOI 10.1002/advs.201801505. [3] D. Li, J. Shi, C. Li, Small 2018, 14, 1–22. [4] D. C. Rees, Annu. Rev. Biochem. 2002, 71, 221–246. [5] F. A. L. Laskowski, M. R. Nellist, J. Qiu, S. W. Boettcher, J. Am. Chem. Soc. 2019, 141, 1394–1405. [6] L. Wang, F. Dionigi, N. T. Nguyen, R. Kirchgeorg, M. Gliech, S. Grigorescu, P. Strasser, P. Schmuki, Chem. Mater. 2015, 27, 2360–2366. [7] C. Simon, J. Timm, D. Tetzlaff, J. Jungmann, U. P. Apfel, R. Marschall, ChemElectroChem 2021, 8, 227–239. [8] C. Simon, J. Zander, T. Kottakkat, M. Weiss, J. Timm, C. Roth, R. Marschall, ACS Appl. Energy Mater. 2021, acsaem.1c01341.

The use of earth-abundant transition metals as a noble metal replacement in catalysis is especially interesting if different catalytic reactivity is observed. We report, here, on the selective manganese-catalyzed base-switchable synthesis of N-alkylated amines or imines. In both reactions, borrowing hydrogen/hydrogen autotransfer (N-alkyl amine formation) or dehydrogenative condensation (imine formation), we start from the same amines and alcohols and use the same Mn precatalyst. The key is the presence of a potassium base to prefer N-alkylation and a sodium base to permit imine formation. Both bases react with the manganese hydride via deprotonation. The potassium manganate hydride reacts about 40 times faster with an imine to give the corresponding amine than the sodium manganate hydride. The selectivity seems unique for manganese complexes. We observe a broad scope with a complete product overlap, all amine alcohol combinations can be converted into an N-alkyl amine or an imine, and a good functional g...

Haplotype-specific extraction (HSE) is a new field of application for the separation of mitochondrial DNA (mtDNA) mixtures and is developed to identify the mtDNA haplotypes of the contributors subsequently by sequencing. Here we show the validation of HSE with an exemplary mitochondrial DNA mixture into its individual haplotypes according to our laboratory standards. These specify several critical areas of assay performance to be tested, such as sensitivity, robustness and mixture studies comprising varying proportions of their components,degraded samples and samples of different qualities and material. Wereport the successful and unambiguous analysis of the exemplary separated mitochondrial DNA mixture under various conditions as well as simulated casework samples, which manifest as mixed nucleotide calls at single base positions previously. Here we demonstrate that the HSE assay is high sensitive, stable against degradation and applicable in a wide range of sample qualities. Based on our findings from the validation study, we believe that this assay has great potential power and may be useful for distinguishing among the mtDNA of individuals and their geographical origin in mixed DNA samples.

A particularly challenging aspect of forensic casework is the accurate interpretation of samples that contain DNA from more than one contributor, since DNA analysis of specific identification markers often results in ambiguous mixed profiles. Physically separating the various haploid components of a diploid or polyploid DNA sample or of a specimen containing DNA from multiple individuals can resolve this problem. We adapted and combined previously developed methods of haplotype-specific extraction (HSE) to separate and analyze mitochondrial DNA (mtDNA) in samples containing DNA from two individuals. After optimizing conditions and probes, we performed HSE to separate mitochondrial DNA mixtures, which manifest as mixed nucleotide calls at single base positions. We were able to subsequently identify the DNA of the two individuals by sequencing. Based on our findings from this proof-of-concept experiment, this novel assay will be useful for distinguishing among the mtDNA of individuals in mixed DNA samples.

Aim A collaborative exercise with several institutes was organized by the Forensic DNA Service (FDNAS) and the Institute of the Legal Medicine, 2nd Faculty of Medicine, Charles University in Prague, Czech Republic, with the aim to test performance of different laboratories carrying out DNA analysis of relatively old bone samples. Methods Eighteen laboratories participating in the collaborative exercise were asked to perform DNA typing of two samples of bone powder. Two bone samples provided by the National Museum and the Institute of Archaelogy in Prague, Czech Republic, came from archeological excavations and were estimated to be approximately 150 and 400 years old. The methods of genetic characterization including autosomal, gonosomal, and mitochondrial markers was selected solely at the discretion of the participating laboratory. Results Although the participating laboratories used different extraction and amplification strategies, concordant results were obtained from the relatively intact 150 years old bone sample. Typing was more problematic with the analysis of the 400 years old bone sample due to poorer quality. Conclusion The laboratories performing identification DNA analysis of bone and teeth samples should regularly test their ability to correctly perform DNA-based identification on bone samples containing degraded DNA and potential inhibitors and demonstrate that risk of contamination is minimized.

Berlin originated from the two twin cities Berlin and Colln, which both were founded at the beginning of the 13th century. However the real date of their foundation as well as the origin of the first settlers is still unknown. On the Berlin site the historic city center is still visible in the Nikolaiviertel, but the medieval origin of Colln disappeared almost completely. In 2007 a large scale excavation, which comprised an area of about 1700m 2 of the historical center of the St. Peters church, recovers the remains of Colln's first citizens and span a period of 500 years of medieval population. Here we present the first genetic analysis of a fivefold children's burial from excavations in Berlin. The genetic data unveiled next to ancestry and eye color data also the kinship and the gender of the five individuals. Together with the archeological context the new gained information help to shed more light on the possible reasons for this burial.