Methanol synthesis from amine-captured CO2 involves a key mechanistic step in which formate is converted into formamide, a process previously reported to be accelerated by a heterogeneous ZnO promoter. In this study we investigate how ZnO stability under Ru-MACHO catalysed reaction conditions influences catalytic performance. Under nearly all reaction conditions studied, and irrespective of whether dimethylethylenediamine (DMEDA) or pentaethylenehexamine (PEHA) was used, ZnO was found to dissolve completely in the polar ammonium-carbonate/formate product layer. When using PEHA, electrospray ionisation mass spectrometry identified cationic [Zn-PEHA]2+ complexes (base peak at m/z 148.0830 with a distinctive isotopic pattern indicative of Zn) which strongly bound formate reaction intermediates. As a result, methanol TON decreased from 607 Ru-1 to 118 Ru-1, 101 Ru-1 and 89 Ru-1 on the addition of 20, 40 and 60 mg ZnO respectively, equating in the case of 20 mg ZnO to an 80% decrease in TON. A similar 61% decrease in TON was observed when DMEDA was used. Only when mixing between the ammonium-carbonate layer and ZnO was minimised through reduction in reaction volume or stirring rate could a solid Zn phase be recovered and catalytic activity modestly promoted (at 48 h the methanol TON of 780 Ru-1 was observed with ZnO vs. 531 Ru-1 without). However, even under these conditions ZnO stability was found to be limited with post reaction analysis revealing partial conversion of ZnO into Zn4CO3(OH)6 & centerdot;4H2O formed from solvated Zn2+ ions reacting with the CO32- in solution. The results demonstrate that while heterogeneous ZnO may increase catalytic turnover (i.e. through promoter behaviour), its solubilisation leads to a catalytic performance that decreases beyond the baseline activity without ZnO (i.e. a poison). The findings underscore the potential and challenges of combining homogeneous and heterogeneous catalysis to influence the complex mechanistic pathways involved in a combined amine-CO2 capture and hydrogenation process.

This study explores the green and sustainable catalytic properties of pulcherrimin, a naturally occurring iron chelate, for the base-free oxidation of 5-hydroxymethylfurfural (5-HMF) to high-value products such as 2,5-furandicarboxylic acid (FDCA), a vital precursor for renewable bioplastics. Pulcherrimin, derived from Metschnikowia pulcherrima, selectively oxidised 5-HMF to 5,5-diformylfuran (DFF) at 100 °C, while at 120 °C, the oxidation proceeded efficiently to FDCA with a conversion of 73.3 ± 1.1%, and FDCA selectivity of 89.0 ± 1.9% under mild, base-free conditions. Adding a mild base enhanced overall conversion but diverted the reaction pathway towards 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), reducing the FDCA yield. The reusability of the pulcherrimin catalyst was tested over five reaction cycles, retaining a conversion activity of 59.1% and FDCA selectivity of 39.8%. These findings establish pulcherrimin as a promising, water-tolerant biocatalyst with potential environmental advantages, such as base-free operation and simplified product recovery, contributing to greener catalytic processes. Eliminating a homogenous base co-catalyst makes the process greener by avoiding the need for subsequent neutralisation steps while reducing environmental and economic costs.

Bioethanol upgrading, via the Guebert reaction, to produce n-butanol can be catalysed by homogeneous catalysts under mild conditions, while under equivalent conditions heterogeneous catalysts commonly have significantly poorer performance. Here we use a heterogeneous catalyst comprised of an atomically dispersed Ru(bipy) complex incorporated into a polyphenylene polymer support, which attempts to combine the distinct nuclearity of a homogenous catalyst and the recyclability of a heterogeneous catalyst. Catalytic performance exceeded that of contemporary homogeneous and heterogeneous catalysts under mild, solventless liquid phase reaction conditions, with an initial TOF of 970 h-1, a TON of 3565 Ru-1 and 82% selectivity to n-butanol. Catalyst deactivation was observed after 16h in a time-on-line study, which can be attributed to inhibition by the water byproduct and structural transformation of the catalyst. The catalyst could be partially reactivated through removal of water from the reaction, via recharging the reactor with fresh ethanol, or by the co-addition of molecular sieve 3Å to remove water in situ. Interestingly, the Ru polyphenylene catalyst showed greater stability in the presence of molecular sieve compared to the homogeneous catalyst, presenting a viable strategy to achieve high butanol yields. Detailed characterisation by TEM, XAFS and XPS shows structural transformation of the single atom Ru(bipy) into small nanoparticles of Ru(0), which grow during the reaction, from 1.6 ± 0.4 nm at 2h time-on-line to a stabilised 2.6 ± 0.9 nm at 16h. While the used 16 h catalyst had moderate recyclability (TON of 1000 Ru-1) the highly active species seen in the fresh catalyst are not stable. It remains unclear if the highly active species are the initial single atom Ru(bipy) species or <1.6 nm Ru(0) clusters formed during the initial reaction period.

Prussian Blue is widely utilized as a cathode material in batteries, due to its ability to intercalate alkaline metal ions, including potassium. However, the exact location of potassium or other cations within the complex structure, and how it changes as a function of cycling, is unclear. Herein, we report direct insight into the nature of potassium speciation within Prussian Blue during cyclic voltammetry, via oper-ando potassium K-edge X-ray Absorption Near Edge Structure (XANES) analysis. Clear and identifiable spectra are experimentally differen-tiated for the fully intercalated (fully reduced Fe2+FeII Prussian White), partially intercalated (Prussian Blue; Fe3+FeII), and free KNO3(aq) elec-trolyte. Comparison of the experiment with simulated XANES of theoretical structures indicates that potassium lies within the channels of the Prussian blue structure, but is displaced towards the periphery of the channels by occluded water and/or structural water present resulting from [Fe(CN)6]4- vacancies. The structural composition from the charge carrier perspective was monitored for two samples of differing crystallinity and electrochemical stability. Reproducible potassium XANES spectral sequences were observed for crystalline Prus-sian blue, in agreement with retention of capacity; in contrast, the capacity of the poorly crystalline sample declined as the potassium became trapped within the partially intercalated poorly-crystalline Prussian blue. The cause of degradation could be attributed to a signif-icant loss of [Fe(CN)6]-[Fe(NC)6] ordering and the formation of a potassium-free non-conducting ferrihydrite phase. These findings demonstrate the potential of XANES to directly study the nature and evolution of potassium species during an electrochemical process.

Nickel hydroxide materials described as having stacking fault and phase interstratification disorder were synthesised and shown by spectroscopic methods to contain multiple layered hydroxide and hydroxysalt structures.

The zeolitic imidazolate framework, ZIF-8, has been shown by experimental methods to have a maximum saturation adsorption capacity of 0.36 g g-1 for n-butanol from aqueous solution, equivalent to a loading of 14 butanol molecules per unit cell or 7 molecules per sodalite β-cage. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) shows the presence of hydrogen bonding between adsorbed butanol molecules within the cage; the presence of three different O-H stretching modes indicates the formation of butanol clusters of varying size. Ab initio molecular dynamics simulations show the formation of intermolecular hydrogen bonding between the butanol molecules, with an average hydrogen-bond coordination number of 0.9 after 15 ps simulation time. The simulations also uniquely demonstrate the presence of weaker interactions between the alcohol O-H group and the π-orbital of the imidazole ring on the internal surface of the cage during early stages of adsorption. The calculated adsorption energy per butanol molecule is -33.7 kJ mol-1, confirming that the butanol is only weakly bound, driven primarily by the hydrogen bonding. Solid-state MAS NMR spectra suggest that the adsorbed butanol molecules possess a reasonable degree of mobility in their adsorbed state, rather than being rigidly held in specific sites. 2D 13C-1H heteronuclear correlation (HETCOR) experiments show interactions between the butanol aliphatic chain and the ZIF-8 framework experimentally, suggesting that O-H interactions with the π-orbital are only short lived. The insight gained from these results will allow the design of more efficient ways of recovering and isolating n-butanol, an important biofuel, from low-concentration solutions.

Experiments to investigate the catalytic pyrolysis of methane using an iron ore-based catalyst were carried out to optimize catalytic activity and examine the purity of the car-bon produced from the process for the first time. Ball milling of the iron ore at 300 rpm for varying times -from 30 to 330 min -was studied to determine the effect of milling time on methane conversion. Optimal milling for 270 min led to a five-fold increase in methane conversion from ca. 1%-5%. Further grinding resulted in a decline of methane conversion to 4% shown by SEM to correspond to an increase in particle size caused by agglomeration. Data from Raman and Moeurossbauer spectroscopy and H2 temperature programmed reduc-tion indicated a change in phase from magnetite to maghemite and hematite (at the par-ticle surface) as the grinding time increased. Analysis of the carbon produced as a byproduct of the reaction indicated a highly pure material with the potential to be used as an additive for steel production.& COPY; 2023 The Authors. Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC. This is an open access article under the CC BY license (http://creativecommons.org/ licenses/by/4.0/).

This article reports a safe, low-cost, and industrially applicable magnetite supported on activated carbon catalyst that can be magnetically retrieved from the solid and reused multiple times without the need of a regeneration step. The FeOx/C catalyst improved the bio-oil yield by 19.7 +/- 0.96 % when compared to the uncatalysed reaction at 320 degrees C for the HTL of draff (brewer's spent grains). The use of homogeneous Na2CO3 base as a catalyst and co-catalyst, improved carbon extraction into the aqueous phase. The exceptional catalytic activity can be attributed to the Fe3O4 phase which can produce in-situ H-2 that improves the biomass decomposition and oil property with an energy recovery of similar to 84 %. The FeOx/C catalyst was separated using magnetic retrieval and maintained its catalytic activity even up to 5 reaction cycles showing potential as a cheap catalyst for HTL reactions and can be scaled-up for industrial applications.

To bridge the materials gap of single crystal work on the Fischer-Tropsch chain-growth mechanism, ethylene adsorption on a model skeletal cobalt catalyst was studied. Speciation and mobility of surface species were characterised using inelastic (INS) and quasi-elastic (QENS) neutron scattering. INS spectra demonstrated that highly reactive sites facilitated ethylene dehydrogenation at lower temperature than in single crystal studies. Adsorbed hydrogen was assigned to Co3H and potentially a Kubas species. After adsorption at 30 °C, methyl groups were identified. CO co-adsorption was shown to modify the dynamics of the adsorbed species. Further analysis demonstrated the sensitivity of skeletal cobalt to surface hydroxylation.

The formation of different nickel and cobalt layered hydroxide phases by a variety of solution and solid-state synthesis methods has been investigated. Initially, preparative methods were refined to generate single-phase products from metal(II) nitrate hexahydrate starting materials which were then characterised by powder X-ray diffraction, vibrational spectroscopy and thermogravimetric analysis. As well as the brucite type β-M(OH)2 and the hydrotalcite-like [M(OH)2-x(H2O)x]x+ alpha-phases (where M = Ni, Co), two different hydroxynitrate phases were isolated with the generic formula M(OH)2-x(NO3)x with x = 0.67 and 1.0 (where M = Ni, Co). The reduction of symmetry of the nitrate anion from D3h to C2v allows the alpha-phases to be distinguished from the two different layered hydroxynitrate phases by both infrared and Raman spectroscopy through the loss of symmetry and concomitant splitting of the degenerate bands. The symmetric N-O stretch enables the two hydroxynitrate phases to be distinguished from one another through the sharp absorption bands at ca. 1000 cm-1 (x = 0.67) and ca. 1050 cm-1 (x = 1.0). The thermogravimetric analysis data of the phases showed key differences between the layered hydroxides, with anhydrous phases having singular weight losses over short temperature ranges and hydrated phases having multiple losses over more extended temperature ranges.

Porous organic molecular materials represent an emergent field of research in Chemistry and Materials Science due to their unique combination of properties. To enhance their performance and expand the number of applications, the incorporation of hierarchical porosity is required, as exclusive microporosity entails several limitations. However, the integration of macropores in porous organic molecular materials is still an outstanding challenge. Herein, we report the first example of a hydrogen-bonded organic framework (MM-TPY) with hierarchical skeletal morphology, containing stable micro- and macroporosity. The crystal size, from micro to centimetre scale, can be controlled in a single step without using additives or templates. The mechanism of assembly during the crystal formation is compatible with a skeletal crystal growth. As proof of concept, we employed the hierarchical porosity as a platform for the dual, sequential and selective co-recognition of molecular species and microparticles.

Surface-modified zeolite Y has been synthesised and studied for potential application as an adsorbent for the removal of metal cations from aqueous solutions. Zeolite Y was synthesised under hydrothermal conditions at 100 °C in an autoclave and characterised by elemental analysis and thermogravimetric analysis to determine the chemical formula of the host material as Na54.91Al56Si136O384.246.5H2O.3-Aminopropyltriethoxysilane (APTES) grafted zeolite Y was prepared by first preparing proton-exchanged zeolite Y using an 0.1 M ammonium nitrate solution followed by calcination at 350 o C. The APTES ligand was then grafted onto the protonated zeolite using three different solvent media. CHN analysis, FTIR spectroscopy, SSNMR and TG analysis indicated that the ligand was bonded covalently to zeolite Y attaching onto the inorganic surface through the available silanol groups. CHN analysis showed that hexane was the most effective solvent for carrying out ligand grafting, as indicated by the highest proportion of carbon present in the product after removal of free solvent (5.08%). APTES grafted zeolite Y was exposed to aqueous solutions containing different concentrations of divalent nickel cations (0.01 M to 0.1 M). An increase to 73.8% Ni (II) removal compared to 18.1% uptake by the parent zeolite Y without any graft was observed when the concentration of nickel was 0.01 M. The selectivity study using a solution containing five different transition metal cations; Ni (II), V (IV), Cu (II), Zn (II), and Fe (II) to mimic the species most often observed in hydrotreatment extract from crude oil, showed proportional removals of 83.7%, 91.3%, 82.8%, 70.6% and 85.7% respectively. This study indicates that APTES modified zeolite Y could be a useful material for the removal of catalytic poisons in hydroprocessing solutions during the processing of heavier crude oils.

Following nuclear releases to the environment, Cs-137 (half-life 30 years) is a long-term contaminant of many ecosystems, including forests. We recently sampled soils under pine forests in temperate and tropical climates to test the hypothesis that migration of Cs-137, 50 years after nuclear weapons fallout, is coupled with organic matter (OM) accumulation in these soils. Depth profiles of Cs-137, naturally-occurring Pb-210 and weapons-derived Am-241 were measured. After 50 years, migration of Cs-137 into the temperate and tropical soils is limited to half-depths of 7-8 cm and 2-3 cm, respectively. At both locations, most Cs-137 is associated with OM that accumulated from the early to mid-1960s. Illite, which immobilises radiocaesium, was undetectable by X-ray diffraction in the layer of peak Cs-137 accumulation in the temperate forest soil, but apparent in the zone of peak concentration in the tropical soil. Data indicate that long-term(50 year) fate of Cs-137 in organic-rich, temperate forest soil is coupled with OM accumulation; fixation of Cs-137 by illite is more important in the tropical forest soil where OM is rapidly decomposed. Models of long-term radiocaesium migration in forest soils should explicitly account for the role of OM, especially when considering forests under contrasting climatic regimes. (C) 2019 Elsevier B.V. All rights reserved.

Mineral phases which can be thought of as members of a metatorbernite–metazeunerite solid solution (Cu(UO2)2(PO4)2−x(AsO4)x.8H2O have been identified in radioactive samples from spoil heaps at the uranium mine site in South Terras, Cornwall (grid referenceSW935523). A complete solid solution (0 < x < 2) was synthesized by precipitation from solution using uranium (VI) nitrate and copper (II) chloride and phosphoric acid/arsenic acid in the appropriate molar proportions. Refined unit cell parameters determined by Pawley fitting of powder X-ray diffraction data showed a linear variation in theaunit cell parameter according to Vegard's Law, allowing the composition of the natural mineral phases found at South Terras to be determined from measurement of their unit cell parameters. High-resolution variable-temperature synchrotron powder X-ray diffraction studies were carried out at the Diamond Light Source on three members of this solid solution (x = 0, 1, 2) and showed different structural behaviour as a function of composition and temperature. Metatorbenite (x = 0) retains its tetragonal symmetry at low temperatures and dehydrates to an amorphous phase at 473 K, whereas metazeunrite (x = 2) transforms to an orthorhombic phase at low temperatures, regains its tetragonal symmetry on heating to 323 K and undergoes a further transition to an, as yet, unidentified phase at 473 K.This article is part of the theme issue ‘Fifty years of synchrotron science: achievements and opportunities’.

Ferrosilicon 75, a 50:50 mixture of silicon and iron disilicide, has been activated toward hydrogen generation by processing using ball milling, allowing a much lower concentration of sodium hydroxide (2 wt %) to be used to generate hydrogen from the silicon in ferrosilicon with a shorter induction time than has been reported previously. An activation energy of 62 kJ/mol was determined for the reaction of ball-milled ferrosilicon powder with sodium hydroxide solution, which is around 30 kJ/mol lower than that previously reported for unmilled ferrosilicon. A series of composite powders were also prepared by ball milling ferrosilicon with various additives in order to improve the hydrogen generation properties from ferrosilicon 75 and attempt to activate the silicon in the passivating FeSi2 component. Three different classes of additives were employed: salts, polymers and sugars. The effects of these additives on hydrogen generation from the reaction of ferrosilicon with 2 wt% aqueous sodium hydroxide were investigated. It was found that composites formed of ferrosilicon and sodium chloride, potassium chloride, sodium polyacrylate, sodium polystyrene sulfonate-co-maleic acid or fructose showed reduced induction times for hydrogen generation compared to that observed for ferrosilicon alone, and all but fructose also led to an increase in the maximum hydrogen generation rate. In light of its low cost and toxicity and beneficial effects, sodium chloride is considered to be the most effective of these additives for activating the silicon in ferrosilicon toward hydrogen generation. Materials characterisation showed that neither ball milling on its own nor use of additives was successful in activating the FeSi2 component of ferrosilicon for hydrogen generation and the improvement in rate and shortening of the induction period was attributed to the silicon component of the mixture alone The gravimetric storage capacity for hydrogen in ferrosilicon 75 is therefore maintained at only 3.5% rather than the 10.5% ideally expected for a material containing 75% silicon. In light of these results, ferrosilicon 75 does not appear a good candidate for hydrogen production in portable applications. (C) 2018 The Authors. Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.

• NOTICE: this is the author's version of a work that was accepted for publication in Solid State Sciences. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published at: http://dx.doi.org/10.1016/j.solidstatesciences.2013.08.006

We report on this paper on the Mössbauer characterisation of the family of synthetic helvite analogues, Fe4M4[BeSiO4]6X2 (M = Fe, Mn, Zn; X = S, Se). The data show iron to be present as high spin Fe(II) in tetrahedral coordination. The room temperature Mössbauer spectra are composed either by singlets or doublets with small quadrupole splitting values suggesting a small valence contribution at that temperature. From the dependence of the quadrupole splitting with temperature the separation Δ between the two \(e_{g}\) orbitals has been estimated. The values of \({\Delta } \) range from 46.3 cm− 1 for the material Fe8[BeSiO4]6S2 to 58.2 cm1 for the material Fe4Zn4[BeSiO4]6S2. The lack of long-range magnetic order observed in the Mössbauer spectra was confirmed by neutron diffraction data which suggests that the M4X units are largely magnetically isolated within their cages leading to a frustrated magnet with no long range interaction for the sulfide species.

For the first time, the process of hydrogen evolution from ferrosilicon 75 using sodium hydroxide solution has been investigated as a function of temperature using a combination of X-ray photoelectron spectroscopy, X-ray diffraction and physical measurements. Ferrosilicon 75, a mixture of silicon (50wt.%) and iron disilicide (50wt.%), has been shown to produce hydrogen by the action of sodium hydroxide solution on the silicon only, with the iron disilicide acting in the role of spectator/protector species for the silicon. Neither iron disilicide alone nor ferrosilicon 45, which does not contain a pure metallic silicon phase, was found to generate hydrogen under similar reaction conditions, further indicating that the presence of a pure metallic silicon phase is essential for hydrogen generation. As the iron disilicide acts as a diluent for the active silicon, it is hypothesized that this would result in a slower release of hydrogen than that which would be obtained from the reaction of silicon alone, which may be useful for applications which require a long-term, sustained release of hydrogen. A hydrogen yield of 462.5mL/g and a maximum hydrogen generation rate of 83mL/ming were obtained within 10min of reaction with 40wt.% NaOH at 348K. (c) 2017 The Authors. International Journal of Energy Research Published by John Wiley & Sons Ltd.