Dinu Iuga

Capture of greenhouse gases, especially CO ₂ , can reduce the effects of global warming and generate valuable minerals as feedstock for industry. Herein, the mineral products formed by capture of atmospheric CO ₂ by potassium hydroxide (KOH) in aqueous, aqueous‐ethanol, and aqueous‐acetone solutions, and aqueous‐acetone enriched using solid CO ₂ are studied. A multimodal analysis combining single‐crystal X‐ray diffraction (SCXRD), powder X‐ray diffraction (PXRD), with Pawley and Rietveld refinements, and 850 MHz, 1 GHz, and 1.2 GHz ¹ H, as well as ¹³ C, and ³⁹ K nuclear magnetic resonance (NMR), is used to analyze the composition of the mineral products. SCXRD identifies KHCO ₃ in space group P 2 ₁ / n (transformable to P 2 ₁ / a ) as a product from all reactions. PXRD and NMR data show the presence of both crystalline and amorphous phases in products, predominantly as mixtures of KHCO ₃ and K ₂ CO ₃ and its hydrates, with KOH as a minor component, except for aqueous‐ethanol which gives KHCO ₃ in high purity. Analysis of complex ¹ H NMR data is aided by 2D nuclear Overhauser effect spectroscopy (1 GHz), which characterizes COH···OC interactions. Revealing K ₂ CO ₃ hydration is aided by deconvolution of ultrahigh‐field 28.2 T (56 MHz) ³⁹ K spectra. This multimodal approach provides new insights into the speciation of potassium minerals from CO ₂ capture.

A ¹⁷O solid‐state NMR method for salt/co‐crystal discrimination in binary compounds of carboxylic acids is presented. The method incorporates a quick and relatively inexpensive labelling protocol for mechanochemical ¹⁷O enrichment of the carboxyl oxygen positions, as previously described by Metro et al. Angew. Chem. 2017, 56, 6803, followed by a visual interpretation of the recorded ¹⁷O solid‐state magic‐angle spinning (MAS) NMR spectra in terms of the nature of the enriched oxygen sites in the prepared binary compound. Care must be taken where variable‐temperature changes in the ¹⁷O MAS spectra are observed. Nevertheless, we observe that, at low temperatures, the averaging effect of chemical exchange of the carboxyl/carboxylate moieties can be avoided and two well separated ¹⁷O lines are obtained for a carboxylic acid, whereas the almost equivalent carboxylate oxygen sites give rise to a single NMR signal. The method is illustrated in two cases, one in which salts can be identified also from their ¹H solid‐state NMR spectra by the absence of high ppm resonances due to hydrogen bonding, and another one, the more general case of organic crystals with multiple hydrogen bonding, where only ¹⁷O solid‐state NMR spectra can be employed for salt/co‐crystal discrimination. A quantitative analysis of ¹⁷O solid‐state NMR spectral parameters can provide useful information in structural studies by NMR crystallography approaches.

The drawbacks of high temperature solid oxide fuel cells (HT‐SOFCs) prompt efforts to lower operating temperatures to near ambient temperatures (NAT). Here the high mixed OH⁻/H⁺ ionic conductivity in doped SrCeO₃ below 100 °C is reported. The SrCe_0.8Y_0.2O_3−δ (SCYO20) electrolyte demonstrates a high ionic conductivity of 12 mS cm⁻¹ in water and 9 mS cm⁻¹ in wet air at 60 °C and an excellent long‐term stability over 100 h. Solid state nuclear magnetic resonance confirms the presence of protons and hydroxide ions in the hydrated oxides and their correlation with Y dopant. Demonstration of direct ammonia fuel cells using the SCYO20 electrolyte indicates the practical application value of this material. The OH⁻ conduction of SrCe_0.7Sn_0.2Y_0.1O_3−δ (SCSY721) is demonstrated by electrolysis of D₂O. The introduction of KOH significantly increases the availability of OH⁻ feed ions, leading to a remarkable improvement of ionic conductivity of SCSY721 electrolyte which is increased by 27 times, 56.34 mS cm⁻¹ in 6 m KOH at 90 °C. The increased ionic conductivity due to the presence of high concentration of extrinsic conducting ions, here are OH⁻ ions, is called as ‘feeding effect’. This study offers new electrolyte materials for cost‐effective, and durable electrochemical devices such as NAT‐SOFCs.

Using multicomponent gels based on Phe and amino- l -phenylalanine (NH ₂ -Phe), we explore the trends of assembly and disassembly of the gels depending on their compositions and patterns of intermolecular interactions in the gel fibres and at the fibre/solution interfaces.

Low temperature ionic conducting materials such as OH⁻ and H⁺ ionic conductors are important electrolytes for electrochemical devices. Here we show the discovery of mixed OH⁻/H⁺ conduction in ceramic materials. SrZr_0.8Y_0.2O_3-δ exhibits a high ionic conductivity of approximately 0.01 S cm⁻¹ at 90 °C in both water and wet air, which has been demonstrated by direct ammonia fuel cells. Neutron diffraction confirms the presence of OD bonds in the lattice of deuterated SrZr_0.8Y_0.2O_3-δ. The OH⁻ ionic conduction of CaZr_0.8Y_0.2O_3-δ in water was demonstrated by electrolysis of both H₂¹⁸O and D₂O. The ionic conductivity of CaZr_0.8Y_0.2O_3-δ in 6 M KOH solution is around 0.1 S cm⁻¹ at 90 °C, 100 times higher than that in pure water, indicating increased OH⁻ ionic conductivity with a higher concentration of feed OH⁻ ions. Density functional theory calculations suggest the diffusion of OH⁻ ions relies on oxygen vacancies and temporarily formed hydrogen bonds. This opens a window to discovering new ceramic ionic conducting materials for near ambient temperature fuel cells, electrolysers and other electrochemical devices.

Plant biomass plays an increasingly important role in the circular bioeconomy, replacing non-renewable fossil resources. Genetic engineering of this lignocellulosic biomass could benefit biorefinery transformation chains by lowering economic and technological barriers to industrial processing. However, previous efforts have mostly targeted the major constituents of woody biomass: cellulose, hemicellulose and lignin. Here we report the engineering of wood structure through the introduction of callose, a polysaccharide novel to most secondary cell walls. Our multiscale analysis of genetically engineered poplar trees shows that callose deposition modulates cell wall porosity, water and lignin contents and increases the lignin–cellulose distance, ultimately resulting in substantially decreased biomass recalcitrance. We provide a model of the wood cell wall nano-architecture engineered to accommodate the hydrated callose inclusions. Ectopic polymer introduction into biomass manifests in new physico-chemical properties and offers new avenues when considering lignocellulose engineering.

OH^- and H⁺ ionic conductors are important electrolyte materials for electrochemical devices such as fuel cells. The high cost of the best low temperature H⁺ ionic conductor, Nafion membrane, and the poor chemical compatibility with CO₂ in air of alkaline membrane based on quaternary ammonium groups have seriously affected the large-scale application of low temperature fuel cells. Here we show the discovery of a fast ceramic mixed OH^-/H⁺ conductor, perovskite oxide SrZr_0.8Y_0.2O_3-δ, which exhibits a high ionic conductivity of approximately 0.01 S cm^-1 at 90°C when measured in water and wet air, sufficient to be used as electrolyte for low temperature fuel cells. The ionic conductivity is stable in wet air during the measured 130 hours. The ionic conduction was also demonstrated by near ambient temperature solid oxide fuel cells (NAT-SOFCs). This opens a window on discovering new ionic conducting materials for low temperature fuel cells.

Photocatalytic reduction of CO2 to carbon fuels is an important target but highly challenging to achieve. Here, we report the efficient photoconversion of CO2 into formic acid over a Ga(III)-based ... Description

Solid titanium phosphate, TiP, materials hold great promise for wastewater treatment for removal of metal ions and complexes. A series of TiP materials, synthesised at mild conditions and short reaction times, have been structurally characterised using solid-state X-ray absorption spectroscopy, phosphorus and titanium K edge XANES and EXAFS, and ³¹P and ^47/49Ti NMR spectroscopy. The titanium K edge EXAFS data of α-Ti(HPO₄)₂·H₂O (α-TiP) revealed octahedral coordination of oxygens around titanium. Repeated washing of primary β-/γ-TiP with hydrochloric acid results in formation of a weakly ordered solid, TiO(OH)(H₂PO₄)·H₂O, TiP1-H. The structure of TiP1-H is shown by Ti EXAFS to be a titanyl compound, containing a short TiO bond. The analogous data for linked titanium phosphate compounds (LTP) disclosed that inter-linkage occurs between α-TiP and titanyl phosphate units, supported by ³¹P–³¹P NOESY NMR data. ^47/49Ti NMR and Ti pre-edge XANES show evidence of two different titanium environments in LTP, one very similar to that observed in TiP1-H and a second more symmetric octahedral environment. Data are discussed in terms of induced acidic hydrolyses of titanium(IV) and phosphate counterpart during washings with hydrochloric acid and water. A straightforward relation between synthesis parameters/post synthetic treatment and structural re-arrangement in the materials is established.