Progress in material selection for solid oxide fuel cell technology: A review

Applications of rechargeable batteries are diverse and range from storing energy from renewable resources such as wind generators and solar arrays , powering electric vehicles and portable electronic devices. Significant R&D efforts have focused on achieving high energy density, long cycling life, low cost, and safety.1 Among all known rechargeable battery systems, lithium-sulfur (Li-S) batteries have attracted considerable attention.2, 3 Elemental sulfur is abundant, and is a very attractive cathode material for lithium batteries because of its high theoretical capacity (1672 mAh g-1) and specific energy (2600 Wh kg-1), assuming complete reaction of lithium with sulfur to form Li2S.

A Soft Approach to Encapsulate Sulfur: Polyaniline Nanotubes for Lithium‐Sulfur Batteries with Long Cycle Life

Low-temperature selective catalytic reduction of NOx with NH3 over metal oxide and zeolite catalysts—A review

The increasing world population and the need to improve quality of life for a large percentage of human beings are the driving forces for the search for sustainable energy production systems, alternative to fossil fuel combustion. Among the various types of alternative energy production technologies, solid oxide fuel cells (SOFCs) operating at intermediate temperatures (400–700 °C) show the advantage of possible use both for stationary and mobile energy production. To reach the goal of reducing the SOFC operating temperature, proton-conducting oxides are gaining wide interest as electrolyte materials. This critical review provides a broad overview of the most recent progresses obtained tailoring the properties of proton-conducting oxides for fuel cell applications, analyzing and comparing the different strategies proposed to match high-proton conductivity with good chemical stability (170 references).

Materials challenges toward proton-conducting oxide fuel cells: a critical review

The development of high-temperature PEM fuel cells (working at 150–200 °C) is pursued worldwide in order to solve some of the problems of current cells based on Nafion® (CO tolerance, improved kinetics, water management, etc.). Polybenzimidazole membranes nanoimpregnated with phosphoric acid have been studied as electrolytes in PEMFCs for more than a decade. Commercially available polybenzimidazole (PBI) has been the most extensively studied and used for this application in membranes doped with all sorts of strong inorganic acids. In addition to this well-known polymer we also review here studies on ABPBI and other polybenzimidazole type membranes. More recently, several copolymers and related derivatives have attracted many researchers' attention, adding variety to the field. Furthermore, besides phosphoric acid, many other strong inorganic acids, as well as alkaline electrolytes have been used to impregnate benzimidazole membranes and are analyzed here. Finally, we also review different hybrid materials based on polybenzimidazoles and several inorganic proton conductors such as heteropoly acids, as well as sulfonated derivatives of the polymers, all of which contribute to a quickly-developing field with many blooming results and useful potential which are the subject of this critical review (317 references).

Proton-conducting membranes based on benzimidazole polymers for high-temperature PEM fuel cells. A chemical quest

The interaction of H2S with the surface of either α-Fe2O3 or amorphous ferric hydroxide at low temperatures has been characterized using FTIR and quantified using volumetric methods. The mechanism of the interaction of H2S with either reagent is ionic and involves heterolytic dissociation of H2S and exchange of S2- and SH- anions for O2- or OH-. Subsequently water is eliminated and, in coupled redox reactions, sulfide is oxidized to elemental sulfur and Fe3+ cations are reduced to Fe2+. Initially, almost all the surface sites can interact readily with H2S, to form a layer of iron sulfides. Over longer reaction times reaction occurs with deeper sites, to form bulk sulfides. Regeneration of ferric (hydr)oxide by oxidation with oxygen converts Fe2+ to Fe3+, and S2- anions are replaced by O2- with formation of elemental sulfur. The surface species involved in each reaction have been characterized using FTIR and, for the first time, direct evidence has been obtained for the presence of SH- anions as very react...

Mechanism of H2S Oxidation by Ferric Oxide and Hydroxide Surfaces

ZnO-doped BaZr0.85Y0.15O3−δ proton-conducting electrolytes: Characterization and fabrication of thin films

Chemical stability of Y-doped Ba(Ce,Zr)O3 perovskites in H2S-containing H2

BaZr0.8Y0.2O3-δ electrolyte with and without ZnO sintering aid: Preparation and characterization

Anode catalysts comprising MoS 2 and composite metal sulfides have been investigated for electrochemical oxidation of hydrogen sulfide in solid oxide fuel cells (SOFCs) at temperatures up to 850°C. All catalysts exhibited good electrical conductivity and catalytic activity at all temperatures. MoS 2 and composite catalysts were found to be more active than Pt, an established catalyst for high-temperature H 2 S-air fuel cells at 650-830°C. However, MoS 2 itself sublimes above 450°C. In contrast, composite catalysts (M-Mo-S) derived from a mixture of sulfides of Mo and other transition metals (Fe, Co, Ni) have been shown to be stable and effective for electrochemical conversion of H 2 S in SOFCs up to 850°C. Electrical contact is poor between platinum current collecting layers and metal sulfide anode catalysts. This problem has been overcome by mechanically mixing conductive Ag powder into the anode layer, instead of applying a thin layer of platinum to the anode.

Alan R. Sanger

Papers

Mechanism of H2S Oxidation by Ferric Oxide and Hydroxide Surfaces

ZnO-doped BaZr0.85Y0.15O3−δ proton-conducting electrolytes: Characterization and fabrication of thin films

Chemical stability of Y-doped Ba(Ce,Zr)O3 perovskites in H2S-containing H2

BaZr0.8Y0.2O3-δ electrolyte with and without ZnO sintering aid: Preparation and characterization

Use of Metal Sulfides as Anode Catalysts in H 2 S -Air SOFCs