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Authors thank the University of St Andrews for the PhD scholarship of FS. We acknowledge funding from MINECO/FEDER (Projects MAT2017-87579-R and MAT2016-81118-P) and from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 823717 –ESTEEM3. Ordered mesoporous cerias were synthesised by employing metal- and halogen- free ordered mesoporous carbons (OMCs) as the hard templates in a ‘nanocasting’ procedure. TEM, small angle (SA) and wide angle (WA) XRD, and N2 physisorption analyses were used to characterise the templates, intermediates and ceria products and electron tomography (STEM-HAADF) was used to explore the 3D morphology of the ceria nanostructures grown within the carbon templates. This allowed the relationships between the structures of the OMC templates and the products to be considered in detail as two parameters were varied. These were: the method of impregnation of the ceria precursor; and the temperature of calcination of the OMC template. Of the four impregnation methods tested, the solid-liquid method was found to be the most successful. This gave a high quality product with the highest yield of uniform mesopores, and crystalline nanorods of ceria arrayed in clear long-range order, as viewed by TEM and determined in SA and WAXRD. The specific surface area and pore volume exhibited by this sample were 111 m2/g and 0.39 cm3/g, respectively. 3D electron tomography reconstructions revealed the presence of a network of ordered, nanoscale, rod-like structures interlinked in a complex fashion. The effect of calcination temperature of the template on uptake of the ceria precursor during impregnation was studied by calcining OMCs at temperatures from 350 to 800 °C and using these as hard templates for the nanocasting of ceria. Of these, the carbon template calcined at 400 °C gave the highest quality product. Publisher PDF

In this work, nanostructured Ce0.9Gd0.1O2-δ (GDC) and Ce0.9Pr0.1O2-δ (PrDC) spheres previously obtained by microwave assisted hydrothermal homogeneous co-precipitation were impregnated with 1 wt% Pd by the incipient wetness impregnation by an aqueous Pd2+ solution. Their properties were characterized by synchrotron radiation X-ray diffraction (SR-XRD), X-ray absorption near-edge spectroscopy (XANES) and scanning and high resolution electron microscopy with X-ray spectroscopy. Spherical particles with average diameters around 200 nm were found to consist of crystallites of average size, 10 nm, with small particles of PdO finely dispersed over the sphere surface. In situ XRD and XANES experiments were carried out under reducing and oxidizing conditions in order to investigate the redox behaviour of these materials and to evaluate the effect of Pd loading on the oxidation state of Ce. All of the lanthanide-doped ceria (LnDC) supports were found to have a cubic crystal structure (Fm3m space group). An increase in lattice parameters was observed under reducing conditions which was attributed to the reduction of Ce4+ ions to the larger Ce3+ ions, and to the associated increase in oxygen vacancy (VO) concentration. Addition of Pd to the LnDC spheres increased their Ce3+ content. Finally, catalytic tests for CH4 combustion were performed on the LnDC and Pd/LnDC nanocatalysts. The best performance was observed in samples with 1 wt% Pd loading, which exhibited T50 values (temperature at which 50% of CH4 conversion was reached) close to 310 °C. These values are 220 °C and 260 °C lower than those obtained for nanostructured PrDC and GDC spheres alone, respectively. Fil: Fuentes, Rodolfo Oscar. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Acuña, Leandro Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina Fil: Leyva, A. Gabriela. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina Fil: Baker, Richard T.. University of St. Andrews; Reino Unido Fil: Pan, Huiyan. Universidad de Cádiz; España Fil: Chen, Xiaowei. Universidad de Cádiz; España Fil: Delgado Jaén, Juan J.. Universidad de Cádiz; España

This work is supported through the EPSRC (UK) critical mass research grant EP/J0118O58/1 awarded to PLG and EDB. PLG and EDB thank the EPSRC and Johnson Matthey Plc for the award of studentships to MRW and MW. KY thanks the Japan Society for the Promotion of Science (JSPS) for a visiting Fellowship at the Nanocentre of University of York during the early part of the work and the Japan Fine Ceramic Center for the AC-Titan facility. The water gas shift (WGS) reaction, CO+H2O = CO2 + H2, is the basis of heterogeneous catalysis important in the generation of clean hydrogen energy for fuel cells, transportation fuels and in ammonia manufacture. Ceria supported gold and related nanoparticles are potentially viable catalysts for the low temperature WGS reaction. The WGS catalytic reaction is a dynamic process and takes place on the solid catalyst surface at the atomic level. The current understanding of the reaction is inferred from studies of static catalysts and from indirect chemical studies without single atom sensitivity. Therefore the nature of dynamic atomic processes in the WGS reaction has remained inaccessible. Since the catalyst reaction site and atomic processes by which it activates and deactivates, change both in magnitude and mechanism with the reaction environment it is of fundamental importance to visualise the dynamic catalyst at the atomic level in WGS (CO + water mixture) environments, in real time. Novel environmental (scanning) transmission electron microscope with singe atom resolution is used herein to directly visualise and characterise, in real time, evolving atomic structures and processes in practical gold/ceria catalysts in controlled WGS environments. The in-situ observations in WGS have revealed the formation of clusters of only a few gold atoms resulting from single atom dynamics and the catalytic effect of low coordination surface sites. The new insights have important implications for applications of nanoparticles in chemical process technologies including for transportation fuels and emission control. Postprint

Soft actuators based on Ionic Polymer-Metal Composites (IPMCs) are of considerable interest for applications in biomedical devices and robotics. In this work, thin commercial and thick laboratory-prepared Nafion membranes were made into model IPMC actuator devices by incorporation of Pt electrode layers. In extensive electromechanical tests the maximum average tip displacement and maximum force generated were recorded. The effect of amplitude and frequency of the applied voltage on both displacement and force was examined as were the effects of the origin of the Nafion membrane, the Pt loading, the structure of the electrode and the presence or absence of an Au overlayer. The cast samples generated much smaller displacements but much larger forces than the commercial Nafion samples. For all samples, displacement and force increased with increasing applied voltage, with increased number of Pt plating cycles and when an Au overlayer was present but decreased with increasing applied voltage frequency. Waveform analysis of applied voltage, current and force was performed by considering the capacitive nature of the IPMC actuators.

By deploying a functioning electrochemical cell inside a Magnetic Resonance Imaging (MRI) instrument, images of the electrically-induced diffusion of water through a Li+ ion-exchanged Nafion ionic polymer film in the form of two-dimensional maps of proton density and transverse relaxation time, T2, were generated and changes in these images over time and with respect to changes made to the applied potential were followed.

Aqueous low temperature pathways are attractive for synthesizing colloidal iron–platinum nanoparticles, which are promising candidates for applications ranging from data storage to biomedicine. Identifying the inhomogeneous composition of the products as the major hurdle of such syntheses, we present and discuss data including synthesis time, iron precursors and reducing agent aiming at quantifying and understanding the effect of the ionic precursor and the reducing agent on the composition of alloyed nanomaterials. We demonstrate that the nanoparticle composition could be modulated by using faster reducing agents as well as iron(II) salts which are less susceptible to base hydrolysis than iron(III) salts. The strategy we highlight here should be applicable to other alloy nPs fabricated by low temperature co-reduction in aqueous solution.

Solid Oxide Fuel Cells (SOFCs) represent an attractive technology for the conversion of chemical to electrical energy because of their high efficiencies and low environmental impact, and because of the useful, high grade heat also generated. Direct utilisation of hydrocarbons in SOFCs would contribute to the more sparing utilisation of remaining fossil fuel reserves. In the longer term, this technology could be extended to work with more sustainable biofuel and waste-derived feedstocks. In this work, nanoparticulate Ceria–Zirconia mixed oxides, Ce1−xZrxO2 (x = 0.1, 0.25, 0.5, 0.75 and 0.9), were studied with a view to their application as anode materials in intermediate temperature (IT) SOFCs using hydrocarbon fuels. Impedance spectra were recorded in symmetrical cells under reducing conditions using gadolinium-doped ceria (GDC) as the electrolyte material. The spectra were analysed in terms of a double fractal finite length Gerischer impedance model. The model parameters were found to have monotonic dependences on temperature and more complex relationships with respect to Zr content. Diffusion-related processes and the electrochemical reaction were fastest for intermediate Zr contents while the chemical exchange reaction rate increased with decreasing Zr content. As a result, anode catalysts with 10 and 25 mol% Zr showed the lowest polarisation resistances of only 0.17 and 4.52 Ω cm2 at 700 °C in humidified 5% H2 and humidified 5% CH4, respectively. These values represented an approximately two-fold improvement on the pure ceria electrode. This performance compares very favourably with the currently most promising candidate anode materials applied in SOFCs for use with hydrocarbon fuels.

In this work, nanostructured gadolinia-doped ceria tubes (GdxCe1−xO2−x/2 with x = 0.1 and 0.2) were synthesised following a very simple, high yield procedure and their properties were characterised by XRD and by electron microscopy (SEM and HRTEM). Tubes of both oxide compositions were comprised of nanocrystals that exhibited the cubic phase (Fmm space group). In SEM, the tubes were found to have lengths of around 2 µm, diameters of around 700 nm and wall thicknesses of about 10 nm. The SEM and TEM results showed that individual tubes were composed of a thin sheet of nanoparticles curved round to form the tubular structure. The size of these primary nanoparticles was calculated from the peak-broadening seen in the XRD results. Average crystallite sizes of 7.8 and 9.4 nm were found for Gd0.1Ce0.9O1.95 and Gd0.2Ce0.8O1.9, respectively. Electron microscopy observations confirmed the size range of these nanoparticles by direct observation. The nanostructured Gd0.1Ce0.9O1.95 tubes exhibited a higher value of specific surface area, at 97 m2 g−1, than the other composition (61 m2 g−1).

SBA-15 was employed as the hard template in the preparation of ordered mesoporous ZrO2 by the replica method. The resultant ZrO2-SR product was characterized by XRD, TEM, EDX, SEM and nitrogen physisorption. The starting material, intermediate and product were studied by FT-IR. The formation of Zr–O–Si crosslinks made it impossible to obtain a pure ZrO2 product, although the material did have a similar ordered mesoporous structure to the SBA-15 template. The results showed that the replica method itself could be successfully used to prepare ordered mesoporous ZrO2, but that the use of mesoporous silica as the hard template meant that the silicon could not be completely removed from the product. The product was seen to contain both the normally stable monoclinic form of zirconia as well as the metastable tetragonal phase. The presence of the latter was considered to be related to the constriction of particle size by the SBA-15 template and by the Si-containing surface layer. These could both hinder sintering of the zirconia particles and prevent crystallite growth to sizes above the critical size, where the tetragonal phase would not be expected. The mesoporous zirconia product had a specific surface area of 220 m2 g−1 and a pore volume of 0.57 cm3 g−1, making it of great interest for applications as a support in catalysis and electrocatalysis.

The physical structure and the actuation mechanism of a Nafion-based soft actuator – a Pt-containing ionic polymer–metal composite (IPMC) – were investigated using in situ magnetic resonance imaging (MRI) during application of four different electrical regimes. Importantly, the raw MRI data were used to generate spatial maps of both proton density (PD) and proton spin–spin relaxation time (T2) across the sample. These were successfully employed to study changes in the distribution and chemical environment of water molecules absorbed within the operating actuator device. The IPMC sample was mapped in this way during the application of a small d.c. potential across its thickness. Three main phenomena were observed in the results: initial rapid increase in T2 at both electrodes, without an observed change in PD; slower formation of a region of high T2 and high PD at the IPMC cathode; and contraction of the polymer along the anode and its expansion along the cathode, giving rise to bending actuation. Reversing the polarity of the applied potential resulted in the reversal of the direction of the bending deformation of the IPMC sample and of the distribution of PD and T2 within it. These phenomena were explained in terms of the unusual structure of Nafion and its interaction with host ions and the electric field. Up to 20% of the total water content of the IPMC was found to be involved in long-range electro-diffusion.