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Two novel ternary air-stable transition-metal carbodiimides, MnHf(NCN)3and FeHf(NCN)3, were synthesized via solid-state metathesis using either ZnNCN or Na2NCN as the carbodiimide source and the corresponding binary metal chlorides. These two phases are the first examples of transition-metal carbodiimides with an AB(NCN)3composition, akin to ubiquitous ABO3perovskite oxides. The crystal structure of MnHf(NCN)3was determined and refined from powder X-ray diffraction (XRD) data in the non-centrosymmetric space group P6322 allowing for chirality, the assignment of which is supported by second-harmonic generation (SHG) measurements. FeHf(NCN)3was found to crystallize isotypically, and the presence of iron(II) in a high spin state was confirmed by 57Fe Mößbauer spectroscopy. The structures are revealed to be NiAs-derived and can be described as a hexagonal stack of NCN2–anions with metal cations occupying 2/3 of the octahedral voids. Both IR spectroscopic measurements and DFT calculations agree that the NCN2–unit is a bent carbodiimide with C2vsymmetry, necessary to account for the size difference present in such a vacancy-ordered structure. Magnetic studies reveal predominantly strong antiferromagnetic interactions but no long-range order between the paramagnetic Mn2+centers, likely due to the dilution of Mn2+over the octahedral sites or perhaps even due to some degree of magnetic frustration. The optical and electrochemical properties of MnHf(NCN)3were then studied, revealing a wide band gap of 3.04 eV and p-type behavior.

Although the formation of thallium hydrogen fluorides TlHxFx+1(x= 1, 1.5, 2, 3, 5, 6.5, and 7) from TlF and HF was reported in the 1970s, little is known about the corresponding crystal structures. To shed light on the crystal chemistry of the thallium fluorides, we reinvestigated the structure of α-TlHF2, which was obtained by crystallization of TlF from 50% HF at room temperature. We disclose that β-TlHF2is isostructural with α-MHF2(M = K, Rb, and Cs), γ-TlHF2is isostructural with β-MHF2(M = K and Rb), whereas α-TlHF2crystallizes in an unusual structure type. During the reaction of TlHF2with the glass of the microscope slide, crystals of the previously unknown compound Tl2[SiF6]·2TlF were formed. We disclose that the related Tl2[GeF6]·2TlF can be obtained by the crystallization of stoichiometric amounts of Tl2[GeF6] with TlF from water at room temperature. The crystal structures of α-TlHF2, Tl2[SiF6]·2TlF, Tl2[SiF6]·TlCl, Tl2[GeF6]·2TlF, Tl2[GeF6]·TlCl, and Tl2[GeF6] were determined by single-crystal X-ray diffraction analysis. The crystal structures of α-TlF and Tl2[SiF6]·xTlF (x= 0, 1) were redetermined at low temperatures.

The high degree of interest in scientific topics (science and research) has been observed especially since the pandemic. This includes the ongoing transition of the chemical industry toward sustainability because the accompanied changes have to be coordinated in dialogue with society. Parallelly, there is increasing interest in science communication in general, as well as the increasing need for its proper understanding. How we communicate is probably today as important as what we communicate. The purpose of this study is to explore how society perceives science, research, scientific results, and their role in the modern world. The method used in the study was a diagnostic survey, and the data was collected using an online questionnaire. This study used a quantitative method. The results showed that science communication needs to be developed much more with special attention paid to the economic, social, and political context. The results analysed and integrated in this article could provide substantive suggestions and help develop science communication.

This mini-review focuses on up-to-date advances of hybrid materials consisting of organic and inorganic components and their applications in different chemical processes. The purpose of forming such hybrids is mainly to functionalize and stabilize inorganic supports by attaching an organic linker to enhance their performance towards a target application. The interface chemistry is present with the emphasis on the sustainability of their components, chemical changes in substrates during synthesis, improvements of their physical and chemical properties, and, finally, their implementation. The latter is the main sectioning feature of this review, while we present the most prosperous applications ranging from catalysis, through water purification and energy storage. Emphasis was given to materials that can be classified as greento the best in our consideration. As the summary, the current situation on developing hybrid materials as well as directions towards sustainable future using organic-inorganic hybrids are presented.

The electrocatalytic conversion of gluconic acid, an aldonic acid, as a model component of spent sulfite liquor (SSL) represents a green approach for side stream valorization. The biotechnological valorization of SSL to more valuable products is inhibited by aldonic acids. Here, we discovered silver as an electrocatalyst for the reduction of gluconic acid to glucose as a sustainable strategy to convert aldonic acids into fermentable carbohydrates. A potential screening in a two-electrode compartment cell was performed and showed the best conversion at −1.56 V vs.reversible hydrogen electrode (RHE) with 0.296 mmol L−1. The conversion rate decreased with higher and lower potentials than −1.56 V vs.RHE. SEM, EDS, and XPS analyses revealed no clear influence of the reaction on the electrocatalyst. LEIS measurements indicated only ion adsorption from the electrolyte and a slight surface oxidation. The electrocatalytic behavior of silver reveals a similar trend to that of electrocatalytic CO2reduction reaction and nitrogen reduction reaction, where a maximum conversion is reached at one cathodic potential before the hydrogen reduction reaction becomes dominant. This highlights a key challenge in merging electrocatalysis and the biorefinery concept to create a bioelectrorefinery for side stream valorization, a crucial element of a bio-circular-green economy.

Quaternary transition metal cyanamides Na2MSn2(NCN)6with M = Mn, Fe, Co, and Ni were prepared via solid-state metathesis reactions between Na2Sn(NCN)3and binary transition metal fluorides MF2in a 2:1 molar ratio. All phases crystallize isotypically in [NiAs]-derived structures (P3̅1m) with inter- and intra-layer cation ordering over the octahedral sites. This leads to a highly asymmetric coordination of the NCN2–anion, resulting in a strong degree of cyanamide character, which is confirmed via IR measurements. Intriguingly, the optical properties of Na2MSn2(NCN)6phases change markedly as the nature of the divalent transition metal is varied, and UV–vis measurements evidence a band gap reduction from Mn (3.43 eV) via Fe (1.90 eV) to Co (1.75 eV), which broadly mirrors the DFT+Ucalculated energetic interval from the Fermi level to the unoccupied 3d states. Mott–Schottky analysis then goes on to characterize Na2FeSn2(NCN)6and Na2CoSn2(NCN)6as n-type semiconductors with flat-band potentials of 0.46 and −0.24 eV, respectively, vs RHE. This study demonstrates the utility of transition metal substitutions, within a flexible cyanamide framework, to electronically tune this growing family of pseudo-oxides.

The development of smart and sustainable photocatalysts is in high priority for the synthesis of H2O2because the global demand for H2O2is sharply rising. Currently, the global market share for H2O2is around 4 billion US$ and is expected to grow by about 5.2 billion US$ by 2026. Traditional synthesis of H2O2via the anthraquinone method is associated with the generation of substantial chemical waste as well as the requirement of a high energy input. In this respect, the oxidative transformation of pure water is a sustainable solution to meet the global demand. In fact, several photocatalysts have been developed to achieve this chemistry. However, 97% of the water on our planet is seawater, and it contains 3.0–5.0% of salts. The presence of salts in water deactivates the existing photocatalysts, and therefore, the existing photocatalysts have rarely shown reactivity toward seawater. Considering this, a sustainable heterogeneous photocatalyst, derived from hydrolysis lignin, has been developed, showing an excellent reactivity toward generating H2O2directly from seawater under air. In fact, in the presence of this catalyst, we have been able to achieve 4085 μM of H2O2. Expediently, the catalyst has shown longer durability and can be recycled more than five times to generate H2O2from seawater. Finally, full characterizations of this smart photocatalyst and a detailed mechanism have been proposed on the basis of the experimental evidence and multiscale/level calculations.

Electrochemical reduction of nitrate into ammonia is one potential strategy to valorize pollutants needed to close the nitrogen cycle. The understanding of carbonaceous materials as metal-free representatives of electrocatalysts is of high importance to ensure sufficient activity and target selectivity. We report on the role of defects in cellulose-derived nitrogen-doped carbon (NDC) materials, produced by ammonolysis at different temperatures, to obtain efficient electrocatalysts for the nitrate reduction reaction (NO3RR). Carbon catalyst ammonolysis at 800 °C (NDC-800) yields the highest electrochemical performance, exhibiting 73.1% NH4+selectivity and nearly 100% NO3−reduction efficiency with a prolonged NO3RR time (48 h) at −1.5 V vs.Ag/AgCl in a 0.1 M Na2SO4electrolyte. We provide support to our findings by undertaking complementary structural analyses with scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, low-temperature N2adsorption, and theoretical studies based on multi-scale/level calculations. Atomistic molecular dynamics simulations based on a reactive force field combined with quantum chemistry (QC) calculations on representative model systems suggest possible realistic scenarios of the material structure and reaction mechanisms of the NO3−reduction routes.

We report the first magic-angle spinning (MAS) nuclear magnetic resonance (NMR) study on Sn(NCN). In this compound the spatially elongated (NCN)2−ion is assumed to develop two distinct forms: either cyanamide (N≡C–N2−) or carbodiimide (−N=C=N−). Our 14N MAS NMR results reveal that in Sn(NCN) the (NCN)2−groups exist exclusively in the form of symmetric carbodiimide ions with two equivalent nitrogen sites, which is in agreement with the X-ray diffraction data. The 14N quadrupolar coupling constant |CQ|$\vert {C}_{\text{Q}}\vert $ ≈ 1.1 MHz for the −N=C=N−ion in Sn(NCN) is low when compared to those observed in molecular compounds that comprise cyano-type N≡C– moieties (|CQ|$\vert {C}_{\text{Q}}\vert $ > 3.5 MHz). This together with the information from 14N and 13C chemical shifts indicates that solid-state NMR is a powerful tool for providing atomic-level insights into anion species present in these compounds. The experimental NMR results are corroborated by high-level calculations with quantum chemistry methods.

14N magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of diamagnetic LaTiO2N perovskite oxynitride and its paramagnetic counterpart CeTiO2N are presented. The latter, to the best of our knowledge, constitutes the first high-resolution 14N MAS NMR spectrum collected from a paramagnetic solid material. The unpaired 4f-electrons in CeTiO2N do not induce a paramagnetic 14N NMR shift. This is remarkable given the direct Ce−N contacts in the structure for which ab initiocalculations predict substantial Ce→14N contact shift interaction. The same effect is revealed with 14N MAS NMR for SrWO2N (unpaired 5d-electrons).

The growing interest in gene therapy is coupled with the strong need for the development of safe and efficient gene transfection vectors. A composite based on chitosan and fumed silica has been found to be a prospective gene delivery carrier. This study presents an investigation of the nature of the bonds between a series of nucleotides with a chitosan layer deposited on a fumed silica surface. Experimentally measured surface complex formation constants (logK) of the nucleotides were found to be in the range of 2.69–4.02, which is higher than that for the orthophosphate (2.39). Theoretically calculated nucleotide complexation energies for chitosan deposited on the surface range from 11.5 to 23.0 kcal·mol–1, in agreement with experimental data. The adsorption of nucleotides was interpreted using their calculated speciation in an aqueous solution. Based on the structures of all optimized complexes determined from quantum-chemical PM6 calculations, electrostatic interactions between the surface-located NH3+groups and −PO3H––/–PO32–fragments of the nucleotides were identified to play the decisive role in the adsorption mechanism. The saccharide fragment of monophosphates also plays an important role in the binding of the nucleotides to chitosan through the creation of hydrogen bonds.

Mixed-anion inorganic compounds offer diverse functionalities as a function of the different physicochemical characteristics of the secondary anion. The quaternary metal oxynitrides, which originate from substituting oxygen anions (O2–) in a parent oxide by nitrogen (N3–), are encouraging candidates for photoelectrochemical (PEC) water splitting because of their suitable and adjustable narrow band gap and relative negative conduction band (CB) edge. Given the known photochemical activity of LaTiO2N, we investigated the paramagnetic counterpart NdTiO2+xN1–x. The electronic structure was explored both experimentally and theoretically at the density functional theory (DFT) level. A band gap (Eg) of 2.17 eV was determined by means of ultraviolet–visible (UV–vis) spectroscopy, and a relative negative flat band potential of −0.33 V vs reversible hydrogen electrode (RHE) was proposed via Mott–Schottky measurements. 14N solid state nuclear magnetic resonance (NMR) signals from NdTiO2+xN1–xcould not be detected, which indicates that NdTiO2+xN1–xis berthollide, in contrast to other structurally related metal oxynitrides. Although the bare particle-based photoanode did not exhibit a noticeable photocurrent, Nb2O5and CoOxoverlayers were deposited to extract holes and activate NdTiO2+xN1–x. Multiple electrochemical methods were employed to understand the key features required for this metal oxynitride to fabricate photoanodes.

The simultaneous removal of organic and inorganic pollutants from wastewater is a complex challenge and requires usually several sequential processes. Here, we demonstrate the fabrication of a hybrid material that can fulfill both tasks: (i) the adsorption of metal ions due to the negative surface charge, and (ii) photocatalytic decomposition of organic compounds. The bioinorganic hybrid membrane consists of cellulose fibers to ensure mechanical stability and of Bi4O5Br2/BiOBr nanosheets. The composite is synthesized at low temperature of 115 °C directly on the cellulose membrane (CM) in order to maintain the carboxylic and hydroxyl groups on the surface that are responsible for the adsorption of metal ions. The composite can adsorb both Co(II) and Ni(II) ions and the kinetic study confirmed a good agreement of experimental data with the pseudo-second-order equation kinetic model. CM/Bi4O5Br2/BiOBr showed higher affinity to Co(II) ions than to Ni(II) ions from diluted aqueous solutions. The bioinorganic composite demonstrates a synergistic effect in the photocatalytic degradation of rhodamine B (RhB) by exceeding the removal efficiency of single components. The fabrication of the biologic-inorganic interface was confirmed by various analytical techniques including scanning electron microscopy (SEM), scanning transmission electron microscopy with energy dispersive X-ray spectroscopy (STEM EDX) mapping, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The presented approach for controlled formation of the bioinorganic interface between natural material (cellulose) and nanoscopic inorganic materials of tailored morphology (Bi–O–Br system) enables the significant enhancement of materials functionality.

Bismuth(III) oxide-carbodiimide (Bi2O2NCN) has been recently discovered as a novel mixed-anion semiconductor, which is structurally related to bismuth oxides and oxysulfides. Given the structural versatility of these layered structures, we investigated the unexplored photochemical properties of the target compound for photoelectrochemical (PEC) water oxidation. Although Bi2O2NCN does not generate a noticeable photocurrent as a single photoabsorber, the fabrication of heterojunctions with the WO3thin film electrode shows an upsurge of current density from 0.9 to 1.1 mA cm–2at 1.23 V vs reversible hydrogen electrode (RHE) under 1 sun (AM 1.5G) illumination in phosphate electrolyte (pH 7.0). Mechanistic analysis and structural analysis using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and scanning transmission electron microscopy energy-dispersive X-ray spectroscopy (STEM EDX) indicate that Bi2O2NCN transforms during operating conditions in situto a core–shell structure Bi2O2NCN/BiPO4. When compared to WO3/BiPO4, the in situelectrolyte-activated WO3/Bi2O2NCN photoanode shows a higher photocurrent density due to superior charge separation across the oxide/oxide-carbodiimide interface layer. Changing the electrolyte from phosphate to sulfate results in a lower photocurrent and shows that the electrolyte determines the surface chemistry and mediates the PEC activity of the metal oxide-carbodiimide. A similar trend could be observed for CuWO4thin film photoanodes. These results show the potential of metal oxide-carbodiimides as relatively novel representatives of mixed-anion compounds and shed light on the importance of the control over the surface chemistry to enable the in situactivation.

Spherical mesoporous carbon (with a particle size in the range of 40–75 μm) was synthesized by nanoreplication of a hard silica template using sucrose as the carbon precursor. The mesoporous carbon with BET surface areas higher than 1200 m2/g was doped with N by a treatment in an aqueous solution of nitric acid and/or in a flow of gaseous ammonia. The highest N content (3.2 wt % of N in bulk) was obtained when both modification methods were combined. Complementary physicochemical characterization techniques, including scanning electron microscopy (SEM), low-temperature N2adsorption, powder X-ray diffraction (XRD), and Raman spectroscopy revealed the morphology, structure, and textural properties of the synthesized N-loaded carbon materials. For the identification of the detailed chemical structure on the surface of the carbons, 1H, 13C, and 15N solid-state nuclear magnetic resonance (NMR) measurements were performed, and the data were supported by chemical shift calculations with accurate quantum chemistry methods and X-ray photoelectron spectroscopic (XPS) analyses. All NMR experiments were performed at natural isotope abundance. The verified experimental data clearly showed that after the introduction of the N-containing moieties by the combined methods of treatment, a high concentration of pyridinic N at the edge, and pyrrolic N being external to the edge, was achieved for the mesoporous carbon. The distributed N surface species promoted the catalytic activity in the oxidative dehydrogenation of ethylbenzene to styrene but did not significantly influence the efficiency of the carbon materials in the electrochemical reduction of nitrate ions.

Chitosan was deposited on fumed silica without the addition of cross-linkers or activating agents. The chitosan surface layer has a high affinity toward organic molecules, e.g., Acid Orange 8 (AO8) dye, robust to a broad range of simulated conditions (variance with respect to temperature, time, and concentration of solute). Experimental equilibrium data were analyzed by the generalized Langmuir equation taking into consideration the energetic heterogeneity of the adsorption system. The effect of temperature on dye uptake and adsorption rate was studied. According to the calculated thermodynamic functions ΔG°, ΔH°, and ΔS° from the equilibrium data at different temperatures, the adsorption of AO8 onto chitosan–fumed silica composite is exothermic and spontaneous. The studies of temperature effect on adsorption equilibrium show that the maximum adsorption capacity (determined from the Langmuir–Freundlich equation) of synthesized composite toward AO8 is about one-third higher in the case of an isotherm measured at 5 °C than this value obtained for the isotherm measured at 45 °C. The quantitative binding of dye molecules to chitosan coating on the surface of silica was proved by 1H MAS NMR. The deep kinetics study through the application of various theoretical models—the first-order equation, pseudo-first-order equation, second-order equation, pseudo-second-order equation, mixed first, second-order equation, and multiexponential equation—was applied for getting inside the mechanism of AO8 binding to the chitosan coating. Structural characteristics of chitosan-coated silica were obtained from the low-temperature adsorption/desorption isotherms of nitrogen and imaging by scanning electron microscopy. The effects of a synthetic route for polymer coating on thermal stability and the ability to degrade were studied by differential scanning calorimetry.

Conjugated polymers are emerging as alternatives to inorganic semiconductors for the photoelectrochemical water splitting. Herein, semi-transparent poly(4-alkylthiazole) layers with different trialkylsilyloxymethyl (R3SiOCH2−) side chains (PTzTNB, R = n-butyl; PTzTHX, R = n-hexyl) are applied to functionalize NiO thin films to build hybrid photocathodes. The hybrid interface allows for the effective spatial separation of the photoexcited carriers. Specifically, the PTzTHX-deposited composite photocathode increases the photocurrent density 6- and 2-fold at 0 V versus the reversible hydrogen electrode in comparison to the pristine NiO and PTzTHX photocathodes, respectively. This is also reflected in the substantial anodic shift of onset potential under simulated Air Mass 1.5 Global illumination, owing to the prolonged lifetime, augmented density, and alleviated recombination of photogenerated electrons. Additionally, coupling the inorganic and organic components also enhances the photoabsorption and amends the stability of the photocathode-driven system. This work demonstrates the feasibility of poly(4-alkylthiazole)s as an effective alternative to known inorganic semiconductor materials. We highlight the interface alignment for polymer-based photoelectrodes.

The two-dimensional p-type semiconductor WSe2is a promising candidate for photo-electrochemical (PEC) H2generation. Despite its high absorption coefficient, the PEC hydrogen evolution reaction (HER) efficiency is low and necessitates a catalyst to achieve higher photocurrents. Here, we investigate the monodisperse spherical alloy FePt and pure Pt nanocrystals (NCs) as catalysts for the PEC HER on p-WSe2single-crystal photocathodes. After deposition of Pt or FePt, photocurrents of −0.27 and −4.0 mA cm–2at 0 V versus the reversible hydrogen electrode were achieved for the HER, which were 7.4 and 15 times higher compared to pristine WSe2single crystals, respectively. Calculations at the density functional theory level show that the water adsorption and thus enhanced H2O dissociation are preferential on FePt in comparison to Pt. The edge sites of both Pt and FePt have a more negative adsorption energy than the (111) and (100) facets, indicating that the edges are the preferential sites for hydrogen production. The computational results show that the size of the Pt NC, within the range of Pt55(1.1 nm) and Pt147(1.6 nm), does not significantly influence the mechanism for the HER on the NCs.

Quaternary tantalum-based oxynitrides ATa(O,N)3, with electronic band gaps between 1.8 and 2.4 eV, are promising materials for photochemical water-splitting. The tailoring of their surface properties is a critical aspect to obtain efficient hole extraction. We report on the origin of improved photoelectrochemical (PEC) water oxidation by means of acidic treatment for this class of compounds on the example of cubic CaTaO2N particles. We address the effect of acidic treatment by using complementary physical characterization techniques, such as X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, 1H and 14N solid-state nuclear magnetic resonance (NMR) spectroscopy, electron microscopy, and electronic band structure calculations at the density functional theory level. In combination with PEC measurements, solid-state NMR indicates that the restructured surface displays a meaningfully higher concentration of terminating OH groups. Subsequent deposition of a nickel borate (NiBi) catalyst on the acid-treated surface yields a higher percentual upsurge of photocurrent in comparison to pristine CaTaO2N. Our results highlight the application of solid-state NMR spectroscopy for understanding the semiconductor–catalyst interface in photochemical devices.

The unusually high oxidation state + IV of cobalt is stabilized by ligands based on [B11H11]4–in dark blue colored Cs4[Co(B11H10.11(OH)0.75)2]·4.56H2O, K4[Co(B11H9.19(OH)1.81)2]·2H2O, Cs8[Co{(B11H6)2(O)(O2BOH)4}]2·4H2O and K4[Co{(B11H6)2(O2BOH)5}]·7H2O. These compounds were obtained by reacting Co2+salts with [B11H14]−under alkaline conditions. In the absence of oxygen, Co(+III) compounds such as the light brownish K4[Co(B11H11)(CN)3]·KCl·2.5H2O are formed. The title compounds were characterized by X-ray crystallography. Cs8[Co{(B11H6)2(O)(O2BOH)4}]2·4H2O and K4[Co(B11H11)(CN)3]·KCl·2.5H2O were also characterized using IR-, UV–vis and cyclovoltammetry. Magnetic measurements of Cs4[Co(B11H10.11(OH)0.75)2]·4.56H2O and ESR measurements of Cs8[Co{(B11H6)2(O)(O2BOH)4}]2·4H2O show that in these Co(+IV) low-spin d5complexes the unpaired electron is on the dx2–y2, dxy(E2g) orbitals.

Mössbauerite, a trivalent iron-only layered oxyhydroxide, has been recently identified as an electrocatalyst for water oxidation. We investigated the material as potential cocatalyst for photoelectrochemical water oxidation on semiconductor photoanodes. The band edge positions of mössbauerite were determined for the first time with a combination of Mott–Schottky analysis and UV–vis diffuse reflectance spectroscopy. The positive value of the Mott–Schottky slope and the flatband potential of 0.34 V vs reversible hydrogen electrode (RHE) identifies the material as an n-type semiconductor, but bare mössbauerite does not produce noticeable photocurrent during water oxidation. Type-II heterojunction formation by facile drop-casting with WO3thin films yielded photoanodes with amended charge carrier separation and photocurrents up to 1.22 mA cm–2at 1.23 V vs RHE. Mössbauerite is capable of increasing the charge carrier separation at lower potential and improving the photocurrent during photoelectrochemical water oxidation. The rise in photocurrent of the mössbauerite-functionalized WO3photoanode thus originates from improved charge carrier separation and augmented hole collection efficiency. Our results highlight the potential of mössbauerite as a second-phase catalyst for semiconductor electrodes.

A nanowire photoanode SrTaO2N, a semiconductor suitable for overall water-splitting with a band gap of 2.3 eV, was coated with functional overlayers to yield a core–shell structure while maintaining its one-dimensional morphology. The nanowires were grown hydrothermally on tantalum, and the perovskite-related oxynitride structure was obtained by nitridation. Three functional overlayers have been deposited on the nanowires to enhance the efficiency of photoelectrochemical (PEC) water oxidation. The deposition of TiOxprotects the oxynitride from photocorrosion and suppresses charge-carrier recombination at the surface. Ni(OH)xacts a hole-storage layer and decreases the dark-current contribution. This leads to a significantly improved extraction of photogenerated holes to the electrode–electrolyte surface. The photocurrents can be increased by the deposition of a cobalt phosphate (CoPi) layer as a cocatalyst. The heterojunction nanowire photoanode generates a current density of 0.27 mA cm–2at 1.23 V vs the reversible hydrogen electrode (RHE) under simulated sunlight (AM 1.5G). Simultaneously, the dark-current contribution, a common problem for oxynitride photoanodes grown on metallic substrates, is almost completely minimized. This is the first report of a quaternary oxynitride nanowire photoanode in core–shell geometry containing functional overlayers for synergetic hole extraction and an electrocatalyst.

Layered bismuth oxides exhibit a broad range of tunable physical properties as a result of their excellent structural versatility which facilitates compositional substitutions at both cationic and anionic positions. Here we expand this family in a new direction through the preparation of the first example of a bismuth-containing oxide carbodiimide, Bi2O2NCN, which assumes an extended variant of the anti-ThCr2Si2structure-type adopted by Bi2O2Ch(Ch= Se or Te) oxide chalcogenides. Electronic structure calculations reveal the title compound to be an indirect band gap semiconductor with a band gap of approximately 1.4 eV, in good agreement with the measured value of 1.8 eV, and intermediate between that of structurally related Bi2O2S (1.12 eV) and β-Bi2O3(2.48 eV). Mott–Schottky experiments demonstrate Bi2O2NCN to be an n-type semiconductor with a conduction band edge position of −0.37 V vs reversible hydrogen electrode. This study highlights the pseudochalcogenide nature of the –N═C═N–carbodiimide anion, which may be substituted in place of oxide or chalcogenide anions in this and potentially other structural classes as an effective means of electronic tuning.

CuWO4is a potential photoanode candidate with a band gap of 2.2–2.4 eV for photoelectrochemical (PEC) water oxidation in neutral electrolytes. We present a facile method to improve the PEC efficiency of CuWO4thin-film photoanodes by postannealing in a nitrogen atmosphere at 623 K for 3.5 h. The photocurrent increases from 30 to 80 μA cm–2at 1.23 V versus reversible hydrogen electrode under AM 1.5G illumination in a phosphate buffer electrolyte at pH 7 after the nitrogen treatment. We investigate the origin of the amended photocurrents by means of ultraviolet–visible spectroscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy. Annealing of CuWO4thin films in a nitrogen atmosphere at 623 K does not yield a bathochromic effect, that is, nitrogen is not being incorporated into the crystal structure. The better PEC performance is due to the greater concentration of oxygen vacancies, improved charge carrier separation, and reduction of charge-transfer resistance.

We investigated CuWO4as a promising photoanode and its surface functionalization with Ag2NCN. The composite photoanode displays a synergetic effect between its constituents during photoelectrochemical (PEC) water oxidation. After placing Ag2NCN particles on the CuWO4thin film, the photocurrent density increases from 15 to 45 μA cm–2at 1.23 V vs reversible hydrogen electrode (RHE) in phosphate buffer electrolyte at pH 7 under simulated AM1.5 G illumination. The different positions of the band edges of CuWO4and Ag2NCN favor charge carrier separation at their interface. Upon illumination, photogenerated electrons of both semiconductors are transferred to the conduction band and can migrate to the counterelectrode. The higher position of the conduction band edge of Ag2NCN allows its electrons to be injected into the conduction band of CuWO4. Simultaneously, holes from the cyanamide are blocked, because the valence band edge position of CuWO4is positioned lower than for Ag2NCN. This results in more efficient charge separation and hole collection efficiencies. Herein, we emphasize the potential of carbodiimides and cyanamides in the design of photoelectrodes beyond oxide and nitride semiconductors.

Quaternary Li/Sr/Eu/Ge compounds display a rich variety of structural modifications and magnetic phases. In LiSr2Ge3, the Sr atoms can be substituted with Eu and this leads to only one of the three structure types of the parent compound. Previous evidence indicates that in the solid solution, LiSr2–xEuxGe3, Sr and Eu atoms are not evenly distributed over the two inequivalent crystallographic sites. Here we present a model that accounts quantitatively for this site-preference, combining electronic structure calculations and statistical mechanics. Alongside we report on a new exemplar, LiSr1.5Eu0.5Ge3, which becomes the eighth obtained within the LiSr2–xEuxGe3system. We also measured the magnetic susceptibility of LiSr1.5Eu0.5Ge3, which shows evidence of mixed ferromagnetic and antiferromagnetic interactions. Ab initio calculations reveal that the electronic structure of LiSr2–xEuxGe3exhibits, beneath the intermetallic appearance, traces of a Zintl anion.

A general difficulty in the comparison of catalysts regarding their electrochemical activities is the significant dependency on the electrode preparation method. In addition to single-crystal, thin-film, and polycrystalline electrodes, most electrocatalysts contain a physical mixture of catalytically active nanocrystals (NCs), conductive carbon support, and binding agent. This type of preparation makes the agglomeration of NCs to larger entities inevitable and simultaneously decreases the catalytically active surface area. In this work, electocatalysts based on two-dimensional arrays of self-assembled monodisperse Au NCs with a particle size of 8 nm have been fabricated. Their electrocatalytic performance in the electrochemical oxidation reaction of methanol and ethanol was investigated for different pH values. The self-assembly of Au NCs into two-dimensional arrays enables to fabricate electrocatalysts with a high mass activity in alkaline electrolytes for alcohol oxidation reactions.

Semi transparent three-dimensional macroporous (3DM) photoanodes based on quaternary oxynitrides have the potential to simultaneously realize superior light harvesting and efficient charge transfer in a tandem photoelectrochemical (PEC) cell. A 3DM CaTaO2N photoanode was prepared for the first time on a GaN/Al2O3substrate viaa chemical route, and it exhibits a high transmittance of >60% in the wide solar spectrum and a photoresponse onset at −0.3 V versusthe reversible hydrogen electrode (VRHE) under simulated solar illumination. In particular, a plateau photocurrent density of 0.21 mA cm–2was achieved at a low potential of 0.4 VRHE, which was 1.6-fold and more than 50-fold higher than a two-dimensional macroporous (2DM) CaTaO2N/GaN/Al2O3photoanode and a conventional particle-based CaTaO2N/GaN/Al2O3photoanode, respectively. The bicontinuous, interconnected pore structure within this 3DM film can improve charge carrier separation and collection by reducing the average diffusion distance for minority carriers toward the electrolyte. Optical measurements and simulations verified the enhanced sunlight harvesting in the 3DM photoanode, which was ascribed to the concentrated distribution of the electric field and multiple scattering. This study provides guidance for future synthesis of highly efficient semitransparent 3DM quaternary oxynitride-based photoanodes for a tandem PEC device.

The ability of mimicking the extracellular matrix architecture has gained electrospun scaffolds a prominent space into the tissue engineering field. The high surface-to-volume aspect ratio of nanofibers increases their bioactivity while enhancing the bonding strength with the host tissue. Over the years, numerous polyesters, such as poly(lactic acid) (PLA), have been consolidated as excellent matrices for biomedical applications. However, this class of polymers usually has a high hydrophobic character, which limits cell attachment and proliferation, and therefore decreases biological interactions. In this way, functionalization of polyester-based materials is often performed in order to modify their interfacial free energy and achieve more hydrophilic surfaces. Herein, we report the preparation, characterization, and in vitroassessment of electrospun PLA fibers with low contents (0.1 wt %) of different curcuminoids featuring π-conjugated systems, and a central β-diketone unit, including curcumin itself. We evaluated the potential of these materials for photochemical and biomedical purposes. For this, we investigated their optical properties, water contact angle, and surface features while assessing their in vitrobehavior using SH-SY5Y cells. Our results demonstrate the successful generation of homogeneous and defect-free fluorescent fibers, which are noncytotoxic, exhibit enhanced hydrophilicity, and as such greater cell adhesion and proliferation toward neuroblastoma cells. The unexpected tailoring of the scaffolds’ interfacial free energy has been associated with the strong interactions between the PLA hydrophobic sites and the nonpolar groups from curcuminoids, which indicate its role for releasing hydrophilic sites from both parts. This investigation reveals a straightforward approach to produce photoluminescent 3D-scaffolds with enhanced biological properties by using a polymer that is essentially hydrophobic combined with the low contents of photoactive and multifunctional curcuminoids

Scheelite-related monoclinic BiVO4is one of the most promising metal oxide photoanode materials. It is therefore highly desirable to explore its new nanostructured morphologies in order to achieve higher performance. We present a new method for the fabrication of porous BiVO4nanotubes. Powder XRD experiments show that the electrodeposited BiVO4nanotubes crystallize in the scheelite-related monoclinic phase. The produced BiVO4nanotubes are highly hierarchically ordered and aligned perpendicular to the electrically conductive substrate. The nanostructures were produced by template-assisted electrochemical deposition inside porous anodized alumina oxide. Our method may be extended to other semiconductor materials used in photoelectrochemical systems, such as Bi2WO6and γ-Bi2MoO6.