• Energy Research

AbstractNi‐Zn and Ni‐Zn‐P alloys supported on Vulcan XC‐72 are effective materials for the spontaneous deposition of palladium through redox transmetalation with PdIV salts. The materials obtained, Pd‐(Ni‐Zn)/C and Pd‐(Ni‐Zn‐P)/C, have been characterized by a variety of techniques. The analytical and spectroscopic data show that the surface of Pd‐(Ni‐Zn)/C and Pd‐(Ni‐Zn‐P)/C contain very small, highly dispersed, and highly crystalline palladium clusters as well as single palladium sites, likely stabilized by interaction with oxygen atoms from NiO moieties. As a reference material, a nanostructured Pd/C material was prepared by reduction of an aqueous solution of PdCl2/HCl with ethylene glycol in the presence of Vulcan XC‐72. In Pd/C, the Pd particles are larger, less dispersed, and much less crystalline. Glassy carbon electrodes coated with the Pd‐(Ni‐Zn)/C and Pd‐(Ni‐Zn‐P)/C materials, containing very low Pd loadings (22–25 μg cm−2), were studied for the oxidation of ethanol in alkaline media in half cells and provided excellent results in terms of both specific current (as high as 3600 A g(Pd)−1 at room temperature) and onset potential (as low as −0.6 V vs Ag/AgCl/KClsat).

We report the energy performance of a new platinum-free alkaline direct formate fuel cell, equipped with a commercial anion exchange membrane, a nanostructured Pd/C anode and a Fe-Co/C cathode. The cell was investigated both at room temperature and at 60 degrees C for the determination of the following parameters: (i) maximum power density, (ii) delivered energy, (iii) faradic (fuel conversion) and energy efficiency. These parameters show a dramatic dependence on fuel composition. The highest energy efficiency is obtained using high energy density fuel (4 M KCOOH and 4 M KOH) and with a maximum operating temperature of 60 degrees C. This represents a key step in the progress of alkaline platinum-free DFFC technology, demonstrating their potential as power sources for portable electronic devices and remote power generation systems. For example, a fuel load of 750 ml in a DFFC device operating at 60 degrees C would be able to produce 90 W h of energy, that required to fully charge the battery of a laptop computer. (C) 2016 Elsevier Ltd. All rights reserved.

Hydrogen storage and distribution will be two very important aspects of any renewable energy infrastructure that uses hydrogen as energy vector. The chemical storage of hydrogen in compounds like sodium borohydride (NaBH4) could play an important role in overcoming current difficulties associated with these aspects. Sodium borohydride is a very attractive material due to its high hydrogen content. In this paper, we describe a reactor where a stable cobalt based catalyst supported on a commercial Cordierite Honeycomb Monolith (CHM) is employed for the hydrolysis of alkaline stabilized NaBH4 (SBH) aqueous solutions. The apparatus is able to operate at up to 5 bar and 130 °C, providing a hydrogen generation rate of up to 32 L min-1.

Quaternary semiconducting sulphides are promising and sustainable candidates to replace the silicon-based semiconducting materials currently leading the market of the photovoltaic energy production. Recent efforts were paid to CZTS (Copper Zinc Tin Sulphides) semiconductors, due to their suitable electronic properties, the abundance in nature of their constituents, and the low toxicity. In this study, we synthetized Cu3-xZnxSnS4 samples by two different solvothermal approaches, with the aim of developing a sustainable synthetic route in the cradle-to-grave full life cycle assessment. These two routes are characterized by either a single step, or a two-steps procedure and allow operating in mild conditions limiting the use of additional chemicals. A multi-technique characterization protocol has been adopted to evaluate chemical, structural and functional properties of the final products. The selected analyses demonstrated that, in both cases, members of the kesterite-kuramite solid solution series were obtained. Still, only in the case of the two steps approach pure Cu2ZnSnS4 samples can be synthesized, whereas the single step synthesis yields Zn-poor samples. The optical characterization of the optimized CZTS material obtained with the two-steps approach revealed a band gap value (1.6 eV), in line with literature's values, confirming the suitability of this synthesis for the development of materials for photovoltaic applications.

Lowering the platinum group metal content of oxygen reduction reaction catalysts is among the most prevalent research focuses in the field. This target is herein approached through supported Pd(II) complexes. Starting from a commercial macrocycle, a new ligand is synthesized, its solution behavior and binding properties briefly explored (potentiometry, UV-Vis) and then used to prepare a new catalyst. A supramolecular approach is used in order to obtain homogeneous decoration of carbon nanotubes surfaces, fostering novel possibilities to access single-ion active sites. The novel catalyst is characterized through X-ray photoelectron spectroscopy and scanning transmission electron microscopy and its promising oxygen reduction reaction performance is evaluated via rotating ring-disk electrode and rotating disk electrode in half-cell studies.

In this article is proposed a new preparation method for composite ultra-thin films for photovoltaic application. Compounds such as Kesterites (CZTS, ternary and quaternary copper and zinc sulfides) could be used in virtue of their semiconductor behavior in conjunction with electrodeposition from aqueous media methodologies; in particular E-ALD (Electrochemical Atomic Layer Deposition) method seems a legitimate alternative to the high pressure and temperature methods used since today. We studied the feasibility of the electrodeposition process of two layers of semiconductors (Cux Zny S, with p electronic proprieties, and CdS with n electronic proprieties), one above the other, by means of E-ALD. Preliminary electrochemical studies revealed the complex nature of the composite film, impairing the anodic stripping of Cd. In order to confirm that the Cd electrodeposition is surface limited, two sets of samples were compared using different conventional and charge controlled potentiostatic electrodeposition methodologies. SEM and XPS characterization was then performed to characterize morphologically and quantitatively the samples. Consequently, the conditions for the surface limited deposition of Cd over Cux Zny S have been reckoned through the electrochemical and spectroscopical analysis. The layered (p-n) structure of the thin film has been confirmed.

The catalytic activation of polycrystalline platinum toward ethanol electro-oxidation in alkaline environment has been obtained by a square wave potential treatment.A detailed analysis that explores the effect of the period of the square wave on the evolution of the catalytic properties of the Pt surface is reported. The catalytic behavior of the treated and untreated surfaces has been interpreted both in terms of real surface area and surface structure evolution.The most active surface has been produced with a treating period time of 120. min. Interestingly the maximum stability has been obtained with the sample produced with square wave potential with a period of 360. min with slightly lower initial performance.We have also found that the treated samples limit C. C cleavage, as compared to bare Pt, offering an effective strategy to minimize the formation of CO. Via in situ FTIR we have demonstrated that the major oxidation product is acetate. These findings are especially important in view of the application of Pt as a catalyst in alkaline direct ethanol fuel cells.