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This work addresses the solar-driven thermochemical production of CO and O 2 from two-step CO 2-splitting cycles, using both ceria granules prepared from cork templates (CG) and ceria foams from polyurethane templates (CF). These materials were cycled in a high-temperature indirectly-irradiated solar tubular reactor using a temperature-swing process. Samples were typically reduced at 1400°C using concentrated solar power as a heating source and subsequently oxidised with CO 2 between 1000-1200°C. On average, CO production yields for CG were two times higher than for CF, indicating that the morphology of this three-dimensionally ordered macroporous (3-DOM) CeO 2 improves the reaction kinetics. Their performance stability was demonstrated by conducting 11 cycles under solar irradiation conditions. Slightly increasing the reduction temperature strongly enhanced the reduction extent, and thus the CO production yield (reaching about 0.2 mmol g −1 after reduction at 1450°C in inert gas), while decreasing the oxidation temperature mainly improved the CO production rate (up to 1.43 μmol s −1 g −1 at 1000°C). Characterisation of the 3-DOM structure, by means of XRD and SEM, provided insights into the reactivity behaviour of the developed materials. The pre-sintered ceria granules retained their structure after cycling. The fact that the mean cell size of CG is smaller (at least one order of magnitude) than that of CF suggests that its exposed surfaces enhanced reaction rates by a factor of two. Moreover, the maximum fuel production rate of CG was roughly three times greater than that reported previously for a ceria reticulated porous foam with dual-scale porosity.

Forsyth and co-workers reported studies on combination of rare earth metallic element with a multifunctional organic component to achieve synergistic corrosion protection of AA2024. 24,25 Recently, Kallip and co-workers reported the synergistic inhibition of galvanically coupled Ze + Fe metals, when 1,2,3-benzotriazole and Ce(NO 3 ) 3 were combined. 26One topic that has not yet been covered in detail is the co-intercalation of different corrosion inhibitors within the same carrier. The incorporation of MBT in cerium molybdate hollow nanospheres were found to render corrosion protection to galvanized steel substrates when combined in coatings with LDH-MBT. 12 In this case, authors suggested that the inhibiting effect could be associated with MBT, as well as to dissolution of cerium and molybdate ions from the nanospheres under acidic conditions. Very recently, Ferrer and co-workers reported the preparation of NaY zeolites with cerium and diethyldithiocarbamate corrosion inhibitors, investigating the effect of this double-doped zeolite for corrosion protection of AA2024 alloy.27 Positive results were obtained with the zeolites in solution and when added to sol-gel coatings. Apart from these works, not much has been done in the co-intercalation of corrosion inhibitors.In this paper we go beyond mono-, towards multiintercalation and release of corrosion inhibitors in a controlled manner (Scheme 1). The strategy followed consists of using a system well known for its intrinsic controlled release mechanism (LDHs), modifying its surface with polyelectrolytes by the Layer-by-Layer (LbL) technique. The use of polyelectrolytes allows the intercalation of additional corrosion inhibitors between layers, which can be released due to pHdependent permeability of polyelectrolytes. 28,29The objective of this work is to investigate Zn-Al LDHs as containers for two corrosion inhibitors simultaneously. 2-mercaptobenthiazole (MBT), a well-known corrosion inhibitor for AA2024, 30 was intercalated in interlayer of the LDH structure by anion-exchange according to a procedure described in the literature, 31 while Ce 3+ , also known as an effective corrosion inhibitor for AA2024, 32 was adsorbed between polyelectrolyte layers on the surface of LDH-MBT platelets. The modied LDH particles (LDH-Mod) were characterized by X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). Furthermore, the inuence of LDH surface modication in the release of MBT was investigated by UV-visible spectrophotometry and correlated with electrochemical studies by DC polarization and electrochemical impedance spectroscopy (EIS), in solution and as additives to a hybrid sol-gel coating. Experimental MaterialsAll the chemicals were obtained from Aldrich, Fluka, and Riedel-de Haen, with $98% of ground substance, and used as received. AA2024-T3 with the following composition was used: Cu 3.8-4.9%, Mg 1.2-1.8%, Mn 0.3-0.9%, Fe 0.5%, Si 0.5%, Zn 0.25%, Ti 0.15%, Cr 0.1%, other 0.15%, balance Al. All the alloy pane...

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This review explores the advances in the synthesis of ceria materials with specific morphologies or porous macro- and microstructures for the solar-driven production of carbon monoxide (CO) from carbon dioxide (CO2). As the demand for renewable energy and fuels continues to grow, there is a great deal of interest in solar thermochemical fuel production (STFP), with the use of concentrated solar light to power the splitting of carbon dioxide. This can be achieved in a two-step cycle, involving the reduction of CeO2 at high temperatures, followed by oxidation at lower temperatures with CO2, splitting it to produce CO, driven by concentrated solar radiation obtained with concentrating solar technologies (CST) to provide the high reaction temperatures of typically up to 1,500°C. Since cerium oxide was first explored as a solar-driven redox material in 2006, and to specifically split CO2 in 2010, there has been an increasing interest in this material. The solar-to-fuel conversion efficiency is influenced by the material composition itself, but also by the material morphology that mostly determines the available surface area for solid/gas reactions (the material oxidation mechanism is mainly governed by surface reaction). The diffusion length and specific surface area affect, respectively, the reduction and oxidation steps. They both depend on the reactive material morphology that also substantially affects the reaction kinetics and heat and mass transport in the material. Accordingly, the main relevant options for materials shaping are summarized. We explore the effects of microstructure and porosity, and the exploitation of designed structures such as fibers, 3-DOM (three-dimensionally ordered macroporous) materials, reticulated and replicated foams, and the new area of biomimetic/biomorphous porous ceria redox materials produced from natural and sustainable templates such as wood or cork, also known as ecoceramics.

For the first time the feasibility of using an alkaline wastewater coming from the pulp and paper industry as an activator, partially (50 vol.%) replacing commercial sodium hydroxide, in the production of cork-based activated carbons was evaluated. The activated carbons showed the highest value of specific surface area ever reported for cork-based activated carbons (1670 m 2 /g), surpassing several other commercial and waste-based ones. These eco-friendly cork and paper waste-based activated carbons were then evaluated as methylene blue adsorbent materials. The influence of contact time, methylene blue initial concentration and adsorbent amount on the methylene blue removal efficiency by the activated carbons was studied. Extremely fast (>99.9 % removal in 5 min) and efficient methylene blue adsorption (uptake of 350 mg/g) by the cork and paper waste-based adsorbents was achieved, which demonstrates the huge potential of these innovative adsorbents. These activated carbons were produced using two unexplored industrial by-products (alkaline wastewater and cork) and, therefore, may be an inexpensive source of activated carbons, which can be used for the effective removal of dyes from wastewaters. Furthermore, despite the very large surface area and high removal efficiency this is not a nano material (being around 30-50 µm in size), its capabilities being due to its unique cork-derived microstructure, and hence it can be handled and removed/filtered much more easily than nanocarbons, and without any associated health or environmental risks.

Synthesis of cork-derived ceria ecoceramic, an emerging porous catalyst, for enhancing solar thermochemical water splitting.

Ordinary Portland Cement is the most widely used binder in the construction sector; however, a very high carbon footprint is associated with its production process. Consequently, more sustainable alternative construction materials are being investigated, namely, one-part alkali activated materials (AAMs). In this work, waste-based one-part AAMs binders were developed using only a blast furnace slag, as the solid precursor, and sodium metasilicate, as the solid activator. For the first time, mortars in which the commercial sand was replaced by two exhausted sands from biomass boilers (CA and CT) were developed. Firstly, the characterization of the slag and sands (aggregates) was performed. After, the AAMs fresh and hardened state properties were evaluated, being the characterization complemented by FTIR and microstructural analysis. The binder and the mortars prepared with commercial sand presented high compressive strength values after 28 days of curing-56 MPa and 79 MPa, respectively. The mortars developed with exhausted sands exhibit outstanding compressive strength values, 86 and 70 MPa for CT and CA, respectively, and the other material’s properties were not affected. Consequently, this work proved that high compressive strength waste-based one-part AAMs mortars can be produced and that it is feasible to use another waste as aggregate in the mortar’s formulations: the exhausted sands from biomass boilers.