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Storing abundant solar energy in synthetic fuels is key to ensure a sustainable energy future by replacing fossil fuels and reducing global warming emissions. Practical implementation of the solar-to-fuel technology is predicated on finding new materials with higher efficiency and lower operation temperature than state-of-the-art materials. We use criteria aimed for designing such efficient solar-to-fuel conversion materials in the perovskite system. Based on thermodynamic considerations, the first perovskite solute–solution series, La0.6Sr0.4Cr1−xCoxO3−δ, is investigated to gain fundamental understanding on the role of B-site cationic doping in water and CO2 splitting to produce synthetic fuel. Notably, all of the novel material compositions operate in a strongly lowered temperature regime of 800–1200 °C compared to state-of-the-art binary oxides in the field. We found an optimum in doping for fuel production performance, namely La0.6Sr0.4Cr0.8Co0.2O3−δ, which viably splits both CO2 and H2O. Based on thermogravimetric analysis, we show that the highest performing perovskite splits 25 times more CO2 compared to the current state-of-the-art material, ceria, for two-step thermochemical cycling at 800–1200 °C. No adverse formation of carbonates in a CO2 atmosphere or cation segregation was observed in near and long range structural investigations, which highlight the durability and potential of these solid solutions. These new perovskite compositions enable lowering of the standard solar-to-fuel reactor temperature by 300 °C. The lowered operating temperature has tremendous implications for solar-synthesized fuels in a reactor in terms of lowered heat loss, increased efficiency, and reactor materials. [ABSTRACT FROM AUTHOR]

Sr-doped lanthanum manganite (LSM) is a widely used cathode material in solid oxide fuel cells (SOFC). Despite being a poor ion conductor, LSM electrodes can reduce oxygen via two pathways: a "3PB surface path" which includes surface diffusion of oxygen species and oxide ion incorporation at the three phase boundary (3PB), and a "bulk path" based on oxygen diffusion in LSM. In this work, the kinetics of both paths and their dependence on temperature and electrode geometry is investigated by impedance spectroscopy on micropatterned LSM thin film electrodes. Differently shaped and sized macroscopic and microscopic LSM electrodes as well as LSM electrodes with oxygen blocking Pt capping layers are employed to identify two parallel reaction pathways of oxygen reduction. On circular microelectrodes the 3PB surface path carries most of the current in the lower temperature region (below ca. 700°C), while at high temperatures (above ca. 700°C) the bulk path is dominating. The significance of each reduction path also depends on the microstructure of the columnar LSM films which can be changed by varying pulsed laser deposition (PLD) parameters or by annealing. Moreover, relevance of a pseudo-3PB path across edges of the LSM electrodes is discussed. [ABSTRACT FROM AUTHOR]

La[sub 0.6]Sr[sub 0.4]CoO[sub 3_δ]thin films of varying thicknesses (20-170 nm) were prepared by pulsed laser deposition on yttria-stabilized zirconia (100) substrates, and their electrochemical electrode performance was correlated with the chemical surface composition and microstructure (e.g. porosity, surface area). The surface cation composition was analyzed by an atomic etching procedure with on-line inductively coupled plasma optical emission spectrometry detection. The surface sensitivity of the method was increased by dynamically switching the etching reagent during the on-line analysis and quantitative results for even the top atomic layer were obtained. A water-soluble Sr-rich surface species could be quantified on top of the LSC films and in combination with electrochemical analysis of the films by impedance spectroscopy an improved understanding of the surface exchange resistance could be obtained. Microstructural features such as the effective porosity of the films became accessible by a combination of these methods. [ABSTRACT FROM AUTHOR]

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