Novel proton conductors in the layered oxide material LixlAl0. 5Co0. 5O2

It is demonstrated that good proton conductors can be obtained in transition-element-rich layered intercalation materials such as LixAl0.5Co0.5O2. A power density of 173 mW cm−2 is achieved at 525 °C with a thick electrolyte (0.79 mm thick). The ionic conductivity of nominal LiAl0.5Co0.5O2 is 0.1 S cm−1 at 500 °C. This is the highest among known polycrystalline proton-conducting materials

Synthesis of ammonia directly from wet nitrogen using a redox stable La 0.75 Sr 0.25 Cr 0.5 Fe 0.5 O 3− δ–Ce 0.8 Gd 0.18 Ca 0.02 O 2− δ composite cathode

Ammonia was directly synthesised from wet nitrogen at an intermediate temperature (375–425 °C) based on the oxygen-ion conduction of the Ce0.8Gd0.18Ca0.02O2−δ–((Li/Na/K)2CO3) composite electrolyte. A redox stable perovskite-based catalyst, La0.75Sr0.25Cr0.5Fe0.5O3−δ (LSCrF), was synthesised via a combined EDTA–citrate complexing sol–gel process to be used as a component of the La0.75Sr0.25Cr0.5Fe0.5O3−δ–Ce0.8Gd0.18Ca0.02O2−δ composite cathode for ammonia synthesis. Ammonia formation was studied at 375, 400 and 425 °C and a maximum ammonia formation rate of 4.0 × 10−10 mol s−1 cm−2 with corresponding Faradaic efficiency of 3.87% was observed at 375 °C when the applied voltage was 1.4 V. This is much higher than 7.0 × 10−11 mol s−1 cm−2 at 1.4 V and 400 °C when Cr-free Sr-doped LaFeO3−δ, La0.6Sr0.4FeO3−δ was used as the catalyst for the electrochemical synthesis of ammonia, indicating LSCrF is potentially a better catalyst. Ammonia was successfully synthesised using a redox stable cathode with higher formation rates at reduced temperature. Introduction of Cr3+ ions at the B-site of doped LaFeO3 improves both the chemical stability and catalytic activity for ammonia synthesis

Investigation of Perovskite Oxide SrCo _0.8Cu _0.1Nb _0.1O _3–δ as a Cathode Material for Room Temperature Direct Ammonia Fuel Cells

Single‐phase perovskite oxide SrCo0.8Cu0.1Nb0.1O3–δ was synthesized using a Pechini method. X‐ray diffraction (XRD) analysis indicated a cubic structure with a=3.8806(7) Å. The oxide material was combined with active carbon, forming a composite electrode to be used as the cathode in a room temperature ammonia fuel cell based on an anion membrane electrolyte and NiCu/C anode. An open circuit voltage (OCV) of 0.19 V was observed with dilute 0.02 m (340 ppm) ammonia solution as the fuel. The power density and OCV were improved upon the addition of 1 m NaOH to the fuel, suggesting that the addition of NaOH, which could be achieved through the introduction of alkaline waste to the fuel stream, could improve performance when wastewater is used as the fuel. It was found that the SrCo0.8Cu0.1Nb0.1O3−δ cathode was converted from irregular shape into shuttle‐shape during the fuel cell measurements. As the key catalysts for electrode materials for this fuel cell are all inexpensive, after further development, this could be a promising technology for removal of ammonia from wastewater

Promotion effect of proton-conducting oxide BaZr0. 1Ce0. 7Y0. 2O3− δ on the catalytic activity of Ni towards ammonia synthesis from hydrogen and nitrogen

In this report, for the first time, it has been observed that proton-conducting oxide BaZr0.1Ce0.7Y0.2O3−δ (BZCY) has significant promotion effect on the catalytic activity of Ni towards ammonia synthesis from hydrogen and nitrogen. Renewable hydrogen can be used for ammonia synthesis to save CO2 emission. By investigating the operating parameters of the reaction the optimal conditions for this catalyst were identified. It was found that at 620 °C with a total flow rate of 200 mL min−1 and a H2/N2 mol ratio of 3, an activity of approximately 250 μmol g−1 h−1 can be achieved. This is ten times larger than that for the unpromoted Ni catalyst under the same conditions although the stability of both catalysts in the presence of steam was not good. The specific activity of Ni supported on proton-conducting oxide BZCY is approximately 72 times higher than that of Ni supported on non-proton conductor MgOCeO2. These promotion effects were suspected to be due to the proton conducting nature of the support. Therefore it is proposed that the use of proton conducting support materials with highly active ammonia synthesis catalysts such as Ru and Fe will provide improved activity of at lower temperatures

Synthesis of ammonia directly from air and water at ambient temperature and pressure

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

A direct urea fuel cell - power from fertiliser and waste

For the first time, a working direct urea and direct urine fuel cell has been developed to generate electricity directly from urea or urine

A perovskite oxide with high conductivities in both air and reducing atmosphere for use as electrode for solid oxide fuel cells

Electrode materials which exhibit high conductivities in both oxidising and reducing atmospheres are in high demand for solid oxide fuel cells (SOFCs) and solid oxide electrolytic cells (SOECs). In this paper, we investigated Cu-doped SrFe0.9Nb0.1O3−δ finding that the primitive perovskite oxide SrFe0.8Cu0.1Nb0.1O3−δ (SFCN) exhibits a conductivity of 63 Scm−1and 60 Scm−1 at 415 °C in air and 5%H2/Ar respectively. It is believed that the high conductivity in 5%H2/Ar is related to the exsolved Fe (or FeCu alloy) on exposure to a reducing atmosphere. To the best of our knowledge, the conductivity of SrFe0.8Cu0.1Nb0.1O3−δ in a reducing atmosphere is the highest of all reported oxides which also exhibit a high conductivity in air. Fuel cell performance using SrFe0.8Cu0.1Nb0.1O3−δ as the anode, (Y2O3)0.08(ZrO2)0.92 as the electrolyte and La0.8Sr0.2FeO3−δ as the cathode achieved a power density of 423 mWcm−2 at 700 °C indicating that SFCN is a promising anode for SOFCs

Investigation of perovskite oxide SrFe0.8Cu0.1Nb0.1O3-δ as cathode for a room temperature direct ammonia fuel cell

Through Pechini method, a single phase shuttle-shaped perovskite oxide was successfully synthesised at 1000 °C. It was combined with active carbon, forming a composite electrode to be used as cathode in a room temperature ammonia fuel cell based on an alkaline membrane electrolyte and Pt/C anode. Reasonable OCV and power density were observed for an ammonia fuel cell using /C composite cathode. Although the power density is not high enough for conventional portable or transport applications, it has the potential for stationary application in removal of ammonia from wastewater because the requirements on power density is relatively low. When a dilute 0.02 M ammonia solution (340 ppm) was used as the fuel, the fuel cell using this perovskite oxide can obtain an open circuit voltage of 0.35 V and a power density of 0.03 mW/cm2. In order to obtain higher OCV, NaOH is necessary to be added in the fuel, especially when the fuel contains a low concentration of ammonia. This study indicates that perovskite oxides are potential good cathode for low temperature direct ammonia or alkaline membrane fuel cells

Achieving both high selectivity and current density for CO2 reduction to formate on nanoporous tin foam electrocatalysts

Currently, low catalytic activity, selectivity and stability are the biggest challenges which restrict the large scale applications of CO2 electrochemical reduction. Formic acid, one of the highest value-added products from electrochemical reduction of CO2, has gathered much interest. Here, we develop nanoporous tin foam catalysts which exhibit significantly high selectivity and faster production rate to formate. In a 0.1 M NaHCO3 solution, the maximum Faradaic efficiency for formate production reaches above 90% with a current density over 23 mA cm-2 , which are among the highest reported value to date under ambient conditions. The improved production rate can be attributed to the high surface area and porous structure. Moreover, the electrocatalysts are quite stable, namely, the Faradaic efficiency remains unchanged during 16 hour electrolysis. This is a promising technology to convert CO2 into useful hydrocarbons