Martin Lerch's research while affiliated with Technische Universität Berlin and other places
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Publications (286)
Fe 3 Mo 3 N was synthesized successfully via ammonolysis out of an oxidic precursor prepared by a modified Pechini route. Rietveld refinement using X‐ray powder data confirmed that the compound crystallizes in space group with a lattice parameter of a =11.0777 Å. Group theoretical methods were applied to elucidate the relation between the crystal s...
A protocol for the mechanochemical synthesis of copper(I)/N-heterocyclic carbene complexes using cheap and readily available K 3 PO 4 as base has been developed. This method employing a ball mill is amenable to typical simple copper(I)/NHC complexes but also to a sophisticated copper(I)/N-heterocyclic carbene complex bearing a guanidine moiety. In...
A metastable polymorph of Ti 3 Sn (called c-Ti 3 Sn) exhibiting the cubic Cr 3 Si-type structure was prepared by a mechanochemical route. At temperatures of about 450 °C, it transforms to the well-known hexagonal phase (Ni 3 Sn type, called h-Ti 3 Sn). 0.5% of iron was incorporated into the material originating from the steel beaker and the steel b...
Phase‐pure and highly crystalline Na2ZnSnS4 was prepared via a mechanochemical synthesis route. It crystallizes in the kesterite‐type structure. The unusual large Debye‐Waller factors of the sodium atoms were analyzed in detail, respecting also group‐theoretical aspects. The results point to the existence of static disorder, mainly to the presence...
BaTaO2N is appraised to be one of the few promising 600 nm-class photocatalysts for solar water splitting. However, the presence of structural defects and low charge separation limits its photocatalytic activity. Compared with mono substitution, dual substitution can be more effective in engineering the structural defects and improving the photocat...
The presence of defects, which act as the recombination hubs for photogenerated charge carriers, hinders the improvement of photocatalytic activity for oxygen evolution reaction of LaTiO2N under visible light irradiation via a four-electron-transfer reaction pathway. Here, we involve titanium nitride (TiN) in a varying content (0-17.8%) to improve...
We performed an in-depth investigation and analysis of the effect of temperature on the Raman-active A-modes of bulk kesterite-type Cu2ZnSnS4 within the 300–460 K temperature range. We acquired the individual contributions to each Raman mode, namely, the thermal expansion and anharmonic interactions terms responsible for the Raman shift and broaden...
A sophisticated bifunctional catalyst bearing a copper(I)/N-heterocyclic carbene and a guanidine organocatalyst has been prepared by a mechanochemical synthesis in a ball mill. This approach circumvents commonly employed silver(I) complexes which are associated with significant and undesired waste formation. Due to the bifunctional nature of the de...
A sophisticated bifunctional catalyst bearing a copper(I)/N-heterocyclic carbene and a guanidine organocatalyst has been prepared by a mechanochemical synthesis in a ball mill. This approach circumvents commonly employed silver(I) complexes which are associated with significant and undesired waste formation. Due to the bifunctional nature of the de...
Two new copper bismuth sulfide halides, CuBi 2 S 3 Cl and CuBi 2 S 3 Br, were synthesized by a two-step process of ball milling followed by annealing. Both compounds are obtained as dark grey powders and crystallize in the monoclinic space group C 2/ m with lattice parameters a = 12.9458(11) Å, b = 3.9845(3) Å, c = 9.1024(8) Å and β = 91.150(3)° fo...
Ag 2 FeGeS 4 was synthesized as a phase-pure and highly crystalline product by mechanochemical milling from the binary sulfides and iron metal, followed by annealing in H 2 S atmosphere. The structure evaluation was carried out using X-ray powder diffraction with subsequent Rietveld refinements. As Fe and Ge atoms are not distinguishable using conv...
![Unit cell of the kesterite (KS, SG I4¯\documentclass[12pt]{minimal}...](publication/353397318/figure/fig1/AS:11431281093081255@1667098786840/Unit-cell-of-the-kesterite-KS-SG-I4documentclass12ptminimal-usepackageamsmath_Q320.jpg)
We have investigated the high-pressure structural and vibrational behavior of the disordered kesterite-type Cu 2 ZnSnS 4 compound at ambient temperature. Our experimental and theoretical investigations have revealed a clear structural transition to a GeSb-type phase close to 15 GPa, a tetragonally distorted variant of the NaCl-type phase. The latte...
Ternary II-IV-N2 materials have been considered as a promising class of materials that combine photovoltaic performance with earth-abundance and low toxicity. When switching from binary III-V materials to ternary II-IV-N2 materials, further structural complexity is added to the system that may influence its optoelectronic properties. Herein, we pre...
Nanosized samples of the cubic thiospinel FeCr2S4 were synthesized by ball milling of FeS and Cr2S3 precursors followed by a distinct temperature treatment between 500 and 800 °C. Depending on the applied temperature, volume weighted mean (Lvol) particle sizes of 56 nm (500 °C), 86 nm (600 °C), and 123 nm (800 °C) were obtained. All samples show a...
Ru supported on mayenite electride, [Ca24Al28O64]4+(e−)4 a calcium aluminum oxide denoted as C12A7e−, are described in the literature as highly active catalysts for ammonia synthesis, especially under conditions of low absolute pressure. In this study, we investigated the application of recently reported plasma arc melting synthesized C12A7e− (alum...
A new member to the A2IBIICIVX4 compound family, Cu2ZnSbS4, was synthesized successfully using ball milling and postannealing in H2S-atmosphere. For comparative purposes, Cu3SbS4 was additionally prepared using the same synthetic approach. As is common for A2IBIICIVX4 compounds, Cu2ZnSbS4 crystallizes isostructural to Cu3SbS4 in the stannite-type s...
The oxygen ion conductivities of Sm doped ceria and Gd doped ceria are the highest for a rare-earth doped cerium oxide, which can be applied in solid oxide fuel cells (SOFC), high-temperature electrolysis with solid oxide electrolysis cells (SOEC), and high-temperature batteries. At the same time, zirconium oxide is a common impurity that has been...
The new sulfochloride FeBiS2Cl is obtained as a black powder following a mechanochemical synthesis procedure. The product crystallizes in the orthorhombic space group Cmcm (no. 63) with lattice parameters a = 3.82142(7), b = 12.2850(2) and c = 9.2911(2) Å. While the iron atom has an octahedral coordination environment, the bismuth atom is coordinat...
A new member of the A 2 I B II C IV X 4 compound family, Na 2 MgSnS 4 , has been synthesized by ball milling of the binary sulfides SnS, Na 2 S, and MgS with elemental sulfur in a high-energy planetary mill, followed by annealing in an atmosphere of H 2 S ( T = 600 °C/3 h). Na 2 MgSnS 4 adopts the NaCrS 2 -type structure (rhombohedral, space group...
The substitution of Cu/Ag by lithium in complex thiospinels with the general formula A I 2 B II C IV 3 X VI 8 was achieved by ball milling and a subsequent annealing step in an atmosphere of H 2 S. Four hitherto unknown compounds Li 2 M Sn 3 S 8 with M = Mg, Mn, Fe, Ni were obtained without side phases and have been structurally investigated. From...
Ag 2 CdSnS 4 was synthesized by a two step mechanochemical synthesis route. From a detailed analysis of the observed reflections in the X-ray powder diffraction pattern, the crystal structure proposed in the literature (space group Cmc 2 1 [E. Parthé, K. Yvon, R. H. Deitch, Acta Crystallogr.1969 , B25 , 1164–1174; O. V. Parasyuk, I. D. Olekseyuk, L...
Two new thiospinels of the type AI2BIICIV3SVI8 were successfully synthesized via a mechanochemical route using binary sulfides and sulfur. Cu2MgSn3S8 and Ag2MgSn3S8 are the first AI2BIICIV3SVI8 compounds with magnesium as divalent cation. The crystal structures of Cu2MgSn3S8 and Ag2MgSn3S8 were refined in the cubic space group Fd3m using X‐ray powd...
The reduction of Pt content in the cathode for proton exchange membrane fuel cells is highly desirable to lower their costs. However, lowering the Pt loading of the cathodic electrode leads to high voltage losses. These voltage losses are known to originate from the mass transport resistance of O2 through the platinum–ionomer interface, the locatio...
The oxygen evolution reaction (OER) through water oxidation is a key process for multiple energy storage technologies required for a sustainable energy economy such as the formation of the fuel hydrogen from water and electricity or metal‐air batteries. Herein, we investigate the suitability of Cu2FeSnS4 for the OER and demonstrate its superiority...
![Crystal structure of F:BiVO4 in polyhedral representation (Bi[O,F]8...](publication/337181391/figure/fig2/AS:11431281118127826@1675686990880/Crystal-structure-of-FBiVO4-in-polyhedral-representation-BiO-F8-polyhedra-in-blue_Q320.jpg)
![Plot of d[ln(A/λ)]/d(1/λ) vs. (1/λ) for F:BiVO4 (orange curve) and...](publication/337181391/figure/fig5/AS:11431281118135484@1675686991112/Plot-of-dlnA-l-d1-l-vs-1-l-for-FBiVO4-orange-curve-and-BiVO4-black-curve_Q320.jpg)
BiVO 4 is one of the most investigated and most promising metal oxide based photoanode materials for photoelectrochemical (PEC) water oxidation. Although it has several advantages (suitable band gap around 2.4 eV, suitable valence-band position for water oxidation, low toxicity, high abundance), it suffers from slow charge-carrier transport propert...
After momentary attention as potential battery materials during the 1980s, sodium titanium disulphides, like the whole Na–Ti–S system, have only been investigated in a slapdash fashion. While they pop up in current reviews on the very subject time and again, little is known about their actual crystal-structural features and sodium-ion diffusion wit...
One of the major drawbacks towards PEMFC (polymer exchange membrane fuel cell) commercialization is the high amount of platinum needed at the cathodic electrode, due to the inherent slow kinetics of the oxygen reduction reaction. It has been widely known that the reduction of the Pt loading at the cathodic electrode leads to significant voltage los...
Li7La3Zr2O12 (LLZO) garnet-type ceramics are considered as very promising candidates for solid electrolytes and have been extensively studied in the past few years. Several studies report on an increase in ionic conductivity by doping with ions, such as Al³⁺ and Ga³⁺, to stabilize the cubic modification of LLZO. Unfortunately, so far ion dynamics h...
Anion substitution is an emerging strategy to enhance the photoelectrochemical performance of metal oxide photoelectrodes. In the present work, we investigate the effect of fluorine incorporation on the photoelectrochemical water oxidation performance of BiVO4 and Mo:BiVO4 thin film photoanodes. The BiVO4 and Mo:BiVO4 thin film photoanodes were pre...
ZnGeN2 as exemplary compound for II‐IV‐N2 materials allows fascinating insights into this class of materials that can be thought of as earth‐abundant alternative to wurtzite‐type III–V semiconductors. A classical route to achieving ZnGeN2 is through the ammonolysis reaction of Zn2GeO4 at higher temperatures. Using a combination of X‐ray and neutron...
Supplementary Material for “Commensurate Nb2Zr5O15: Accessible Within the Field Nb2ZrxO2x+5 After All”
Doped niobium zirconium oxides are applied in field-effect transistors and as special-purpose coatings. Whereas their material properties are sufficiently known, their crystal structures remain widely uncharacterized. Herein, we report on the comparably mild sol-gel synthesis of Nb2Zr5O15 and the elucidation of its commensurately modulated structur...
The importance of the synthesis conditions on the structural and photocatalytic properties of tantalum oxide nitride was investigated by comparing two variants of phase-pure β -TaON obtained from application of two different synthesis routes, leading to one unstrained and one heavily anisotropically microstrained β -TaON as shown by XRD-based Rietv...
Additional figures and tables: diffraction pattern with fit of an α-PbO2-type model, ellipsoid plots, stereoview of crystal structure, bond lengths, de-Wolff sections, and Bärnighausen tree
Generic mixtures in the system (Zr,Hf)O2-(Nb,Ta)2O5 are employed as tunable gate materials for field-effect transistors. Whereas production processes and target compositions are well-defined, resulting crystal structures are vastly unexplored. In this study, we summarize the sparse reported findings and present the new phase Hf3Ta2O11 as synthesize...
Nitrogen-enriched porous carbons have been discussed as supports for Pt nanoparticle catalysts deployed at cathode layers of Polymer Electrolyte Membrane fuel cells (PEMFC). Here, we present an analysis of the chemical process of carbon surface modification using ammonolysis of pre-oxidized carbon blacks, and correlate their chemical structure with...
We have performed structural investigations of ordered kesterite-type Cu2ZnSnS4 up to 30 GPa. Our current X-ray diffraction results clearly excluded the presence of a kesterite → disordered kesterite transition reported previously between 7 and 9 GPa. Nevertheless, specific anomalies connected with the Cu-S bond length of the starting kesterite-typ...
A metastable bixbyite-type polymorph of vanadium sesquioxide, V 2 O 3 , is known since 2011. Beyond 550°C the novel material transforms to corundum-type V 2 O 3. Density-functional theory calculations including explicit electronic correlation corroborate the metastability of bixbyite-type V 2 O 3 and further predict that it is approximately 0.1 eV...
The first scalable synthesis of phase-pure crystalline and air-stable manganese nitride (Mn3N2) from a molecular precursor is reported; it acts as a superiorly active and durable electrocatalyst in the oxygen evolution reaction (OER) from water under alkaline conditions. While electrophoretically deposited Mn3N2 on fluorine tin oxide (FTO) requires...
The first scalable synthesis of phase-pure crystalline and air-stable manganese nitride (Mn3N2) from a molecular precursor is reported; it acts as a superiorly active and durable electrocatalyst in the oxygen evolution reaction (OER) from water under alkaline conditions. While electrophoretically deposited Mn3N2 on fluorine tin oxide (FTO) requires...
In a recent experimental study it has been shown, that fluorine-containing bismuth vanadate (F:BiVO4) reveals enhanced photoelectrochemical activity compared to pristine BiVO4. This work is a combined experimental and theoretical analysis of structural and electronic properties of F:BiVO4. A theoretical analysis of three different possible defect m...
The development of all-solid-state electrochemical energy storage systems, such as lithium-ion batteries with solid electrolytes, requires stable, electronically insulating compounds with exceptionally high ionic conductivities. Considering ceramic oxides, garnet-type Li7La3Zr2O12 and derivatives, see Zr-exchanged Li6La3ZrTaO12 (LLZTO), have attrac...
The n-type semiconductor bismuth vanadate (BiVO4) is one of the most promising ternary oxide materials for visible light-induced water oxidation, offering a theoretical solar-to-hydrogen efficiency of 9.1%. However, several factors strongly limit its actual efficiency and among these, poor charge transport has been identified as one major limitatio...
Blue-colored Mo2(O,N,□)5-type oxide nitrides with an average oxidation state of +5 for molybdenum were synthesized. They are structurally related to VNb9O24.9-type phases; the magnetic behavior is in agreement with compounds exhibiting MoVO6 units. The results demonstrate the possibility of a future synthesis of the binary oxide Mo2O5. On the basis...
Solid solutions of ceria and praseodymia are highly relevant for electrochemical applications as the incorporation of praseodymium into the ceria lattice shifts the range of mixed ionicelectronic conductivity to higher oxygen partial pressures. To better understand the influence of praseodymium substitution on the transport processes and oxygen sto...
Synthesis of phase-pure materials in the system Sc-Nb-O-N is challenging. In this contribution we report on the preparation of the first scandium niobium oxide nitrides via reaction of water-saturated gaseous ammonia or an ammonia-oxygen mixture with amorphous scandium niobium oxides. Two new phases were obtained: rutile-type ScNb4O7N3, which cryst...
In this work the Cu/Zn order-disorder transition in Cu2ZnSnS4 kesterites on Wyckoff positions 2c and 2d was investigated by a structural and electronic analysis in theory and experiment. For experimental investigations stoichiometric samples with different Cu/Zn order, annealed in the temperature range of 473–623 K and afterwards quenched, were use...
Some time ago, we reported the synthesis of bixbyite-type V2O3, a new metastable polymorph of vanadium sesquioxide. Since, a number of investigations followed, dealing with different aspects like electronic and magnetic properties of the material, the deviation from ideal stoichiometry or the preparation of nanocrystals as oxygen storage material....
Geometric information about ion migration (diffusion pathways) and knowledge about the associated energy landscape (migration activation barriers) are essential cornerstones for a comprehensive understanding of lithium transport in solids. Although many lithium-ion conductors are discussed, developed, and already used as energy-storage materials, f...
Phase-pure tantalum/zirconium oxide nitrides and nitrides were synthesized by the ammonolysis of amorphous oxide precursors. The nitrogen-rich oxide nitrides with variable anion composition and the nitride TaZrN3 crystallize in the cubic bixbyite-type structure (space group Ia3̅). The nitrogen content of these compounds has a significant influence...
Ti-based materials exhibit suitable properties for usage in secondary Li-and Na-ion batteries and were in the focus of several electrochemical and ion conductivity studies. A material of such interest is layer-structured, monoclinic Na2Ti3O7. Additionally, the sodium in Na2Ti3O7 can be replaced completely with lithium to achieve monoclinic Li2Ti3O7...
Pyrochlore-type Eu2Ta2(O,N)7+δ phases were prepared by reaction of ammonia with an amorphous europium tantalum oxide precursor. 151Eu Mössbauer and EPR spectroscopy as well as magnetic susceptibility measurements point to the presence of exclusively Eu3+. For phase-pure samples (X-ray powder diffraction), the nitrogen content varies between 1.0 and...
High-pressure molybdenum dioxide (HP-MoO2) was synthesized using a multianvil press at 18 GPa and 1073 K, as motivated by previous first-principles calculations. The crystal structure was determined by single-crystal X-ray diffraction. The new polymorph crystallizes isotypically to HP-WO2 in the orthorhombic crystal system in space group Pnma and w...
Fundamental research on lithium ion dynamics in solids is important to develop functional materials for, e.g. sensors or energy storage systems. In many cases a comprehensive understanding is only possible if experimental data are compared with predictions from diffusion models. Nuclear magnetic resonance (NMR), besides other techniques such as mas...
We have investigated the high-pressure structural and vibrational behavior of the ordered kesterite-type Cu2ZnSnS4 compound. Our investigations have revealed two structural transitions: a kesterite-to-disordered kesterite transition was observed between 7 and 9 GPa, which involves a Zn/Cu disorder within the respective cationic sublattice, whereas...
Solid-state nuclear magnetic resonance spectroscopy is an efficient technique to characterize dynamics and structure of materials. It has been widely used to elucidate ion dynamics in lithium ion conductors. Fast moving lithium ions are needed in energy storage devices, whereas slow ion motion is exploited in some materials used, for example, as bl...
Despite many actual and proposed uses for solid lithium-ion conductors (foremost in energy storage), transport phenomena within them are still poorly understood at a fundamental level. The crucial role of the latter in applications is the reason for our interest in γ-LiAlO2 , as it is a so-called “ultraslow” three-dimensional conductor. Neutron dif...
Single crystalline ceria samples with the composition Ce0.9Gd0.1O2-δ were pre-polarized with ±5 V for up to 300 s using a Pt coated AFM tip as working electrode. The direct contact zone had a diameter of <50 nm. Subsequently, the effect of the polarization on the surface potential of the samples was investigated by mapping the introduced defect gra...
Low yttria-doped cubic zirconium oxide nitride single crystals with high nitrogen contents show unexpected high oxygen ion conductivity in a temperature range between 100 °C and 300 °C. The observed values are about two orders of magnitude higher than the conductivities for conventionally used 9.5 YSZ. This can be related to an optimal anion vacanc...
Kesterite-type Cu2ZnSnS4 was synthesized from the corresponding binary sulfides by a mechanochemical route in a planetary ball mill. The reaction progress during this milling step was followed within a time range of 10–180 min by powder X-ray diffraction. In addition, the crystallization of the milled material was studied in situ by high-temperatur...
The solid-state kinetics of the reduction of VO2 to corundum-type V2O3 were investigated by temperature-programmed measurements. Experimental parameters were chosen to be similar to those used in conventional testing of heterogeneous catalysts. In situ X-ray diffraction experiments showed that the oxidation of V2O3 to corundum-type VO2 during prope...
In this work a series of B- and C-type off-stoichiometric CZTS samples was prepared by a mechanochemical synthesis route. For structural characterization X-ray diffraction measurements were performed. Furthermore, compositional analyses of the powder samples were carried out by means of wavelength-dispersive X-ray spectroscopy (WDS). For detailed c...
CrNb2O4F5, and Fe2Nb3O6F9 are prepared by adding stoichiometric amounts of Cr(NO3)3 or Fe(NO3)3 to a HF solution of Nb2O5 (15 h; drying at 80 °C, 2 d).
Phase-pure LiBi3S5 powder is prepared by solid state reaction of equimolar amounts of LiBiS2 and Bi2S3 in H2S (Al2O3 crucible, 600 °C, 4 h).
With respect to absorber materials in solar cells, single-phase Cu2ZnSnS4 (CZTS) is prepared by intermittent high-energy ball milling of CuS, ZnS, and SnS in the atomic ratio 2:1:1 (400 rpm, 3 h).
The local structure and oxygen ion dynamics in pure CeO2 and CeO2 doped with Ta and Gd is studied by 17O nuclear magnetic resonance (NMR) spectroscopy, Raman spectroscopy, and conductivity measurements. 17O magic-angle spinning nuclear magnetic resonance spectra of CeO2 doped with Ta show two oxygen environments. A major peak at 876 ppm represents...
Among chalcogenide semiconductors for thermoelectric applications, alkali-metal bismuth compounds occur in many complex compositions favorable for high performance. Although LiBi3S5 had been announced in 1977, the potential 1D lithium-ion conductor has hitherto eluded selective synthesis and structure determination. In this study, we present a soli...
Phase-pure Ba3TaV5O14N is prepared via a sol-gel based Pechini route by heating (200 °C) a 3:5 molar mixture of BaCl2 and TaCl5 in EtOH/citric acid/ethylene glycol prior to calcination at 400 °C.
