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The N≡N bond (225 kcal mol−1) in dinitrogen is one of the strongest bonds in chemistry therefore artificial synthesis of ammonia under mild conditions is a significant challenge. Based on current knowledge, only bacteria and some plants can synthesise ammonia from air and water at ambient temperature and pressure. Here, for the first time, we report artificial ammonia synthesis bypassing N2 separation and H2 production stages. A maximum ammonia production rate of 1.14 × 10−5 mol m−2 s−1 has been achieved when a voltage of 1.6 V was applied. Potentially this can provide an alternative route for the mass production of the basic chemical ammonia under mild conditions. Considering climate change and the depletion of fossil fuels used for synthesis of ammonia by conventional methods, this is a renewable and sustainable chemical synthesis process for future.

Perovskite-related materials, (La 0.75 Sr 0.25 ) 1Ϫx Cr 0.5 Mn 0.5 O 3Ϫ␦ (0 р x р 0.1) ͑LSCM͒, have been synthesised and examined as potential anode materials for solid oxide fuel cells ͑SOFCs͒. La 0.75 Sr 0.25 Cr 0.5 Mn 0.5 O 3 exhibits a rhombohedral structure. It appears to be chemically compatible with yttria-stabilized zirconia ͑YSZ͒ to at least 1300°C. At 900°C, its electrical conductivity is about 38 S/cm in air and 1.5 S/cm in 5% H 2 (p O 2 Ϸ 10 Ϫ21 atm͒. Good performance was achieved using LSCM as anode with a polarization resistance 0.9 and 0.47 ⍀ cm 2 in wet 5% H 2 /Ar and wet H 2 , respectively. The anode polarization was further reduced to 0.6 and 0.25 ⍀ cm 2 in wet 5% H 2 /Ar and wet H 2 when a thin layer of Ce 0.8 Gd 0.2 O 2Ϫ␦ ͑CGO͒ layer was coated between YSZ and LSCM anode. Stable performance was sustained for at least for 4 h operating in wet methane. By improving the electrode microstructure, the electrode polarization resistance approaches 0.2 ⍀ cm 2 at 900°C in 97% H 2 /3% H 2 O for LSCM containing a small amount of YSZ to improve adherence but without CGO. Very good performance is achieved for methane without using excess steam. Using ambient humidification ͑i.e., 3% H 2 O), the same performance is achieved with methane at 950°C as for hydrogen at 850°C. The anode is stable in both fuel and air conditions and shows stable electrode performance in methane. Thus, both redox stability and operation in low-steam hydrocarbons have been demonstrated, overcoming two of the major limitations of the current generation of nickel zirconia cermet SOFC anodes. LSCM and other complex perovskites are promising anode materials for SOFCs.

There is now considerable interest in proton-conducting oxide electrolytes for intermediate-temperature fuel cells. [1][2][3][4][5][6][7] The most technologically promising moderate-temperature proton conductors are those perovskites based upon the cerates or zirconates of barium doped with yttria or lanthanide oxides. Such materials offer high protonic conductivity without too severe a contribution from oxide ionic or electronic mechanisms over a useful range of temperature and oxygen partial pressures. [3,6,7] Barium cerates, e.g., BaCe 0.generally exhibit the highest proton conductivities; however, these materials are unstable at high temperature in the presence of CO 2 and steam. [8,9] The zirconates are much more resistant to degradation, and the conductivity of BaZr 1-x Y x O 3-d with x = 0.1 and 0.2 has been investigated by several research groups. [10][11][12][13][14] However, very significant differences exist in reported conductivities, which seem to be related to synthetic history. The zirconates do not sinter easily, and the highest conductivities are only obtained when sintering occurs at or approaching 1700°C. [10,11] The very poor grain-boundary conductivity of these materials is a major problem; even after sintering at very high temperatures, these do not deliver performance appropriate for practical application. Although the crystal component is difficult to resolve in polycrystalline samples, it does seem that this is only optimized when fired at very high temperatures, above 1600°C. This seems to imply that achievement of the highest conductivities is influenced by some form of phase transformation or segregation or, as suggested by Snijkers et al., [15] by a slow kinetic process of water absorption. The stability of doped BaCeO 3 is improved by the introduction of Zr at the B site, [16,17] but the typical sintering temperature of Zr-replaced BaCeO 3 is still above 1550°C. These high sintering temperatures are a major issue for the required low-cost thin-film fabrication methods, and densification is not expected below 1450°C even for the zirconia-free barium cerates. Here we present a novel doping mechanism that greatly improves sinterability at temperatures suitable for device manufacture. Zinc may seem an unlikely B-site dopant for such protonconducting perovskites due to its low charge and small size, and indeed it has been previously shown to reduce the ionic conductivity of strontium calcium zirconate phases; [18] however, in this study it is found to be extremely beneficial in terms of increasing stability and improving sintering without impairing conductivity, if used at low levels. [11] On Zn substitution tetragonality increases from 0.16 to 0.36 % and volume decreases by about 0.4 % per primitive cell, consistent with the smaller ionic radius of Zn. This significant reduction in cell size is clear confirmation of solid-solution formation.Zn-doped samples showed enhanced sintering and so were further investigated using dilatometry. Initially BaZr 0.8 -Y 0.2 O 3-d was prepared by a soli...

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The fi eld of research into solid oxide fuel cell (SOFC) anode materials has been rapidly moving forward. In the four years since the last in-depth review signifi cant advancements have been made in the reduction of the operating temperature and improvement of the performance of SOFCs. This progress report examines the developments in the fi eld and looks to draw conclusions and inspiration from this research. A brief introduction is given to the fi eld, followed by an overview of the principal previous materials. A detailed analysis of the developments of the last 4 years is given using a selection of the available literature, concentrating on metal-fl uorite cermets and perovskitebased materials. This is followed by a consideration of alternate fuels for use in SOFCs and their associated problems and a short discussion on the effect of synthesis method on anode performance. The concluding remarks compile the signifi cant developments in the fi eld along with a consideration of the promise of future research. The recent progress in the development of anode materials for SOFCs based on oxygen ion conducting electrolytes is reviewed.