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- Water photolysis at 12.3% efficiency via perovskite photovoltaics and Earth-abundant catalysts. [Journal Article, Research Support, Non-U.S. Gov't]
- Science 2014 Sep 26; 345(6204):1593-6.
Although sunlight-driven water splitting is a promising route to sustainable hydrogen fuel production, widespread implementation is hampered by the expense of the necessary photovoltaic and photoelectrochemical apparatus. Here, we describe a highly efficient and low-cost water-splitting cell combining a state-of-the-art solution-processed perovskite tandem solar cell and a bifunctional Earth-abundant catalyst. The catalyst electrode, a NiFe layered double hydroxide, exhibits high activity toward both the oxygen and hydrogen evolution reactions in alkaline electrolyte. The combination of the two yields a water-splitting photocurrent density of around 10 milliamperes per square centimeter, corresponding to a solar-to-hydrogen efficiency of 12.3%. Currently, the perovskite instability limits the cell lifetime.
- The ancient heritage of water ice in the solar system. [Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.]
- Science 2014 Sep 26; 345(6204):1590-3.
Identifying the source of Earth's water is central to understanding the origins of life-fostering environments and to assessing the prevalence of such environments in space. Water throughout the solar system exhibits deuterium-to-hydrogen enrichments, a fossil relic of low-temperature, ion-derived chemistry within either (i) the parent molecular cloud or (ii) the solar nebula protoplanetary disk. Using a comprehensive treatment of disk ionization, we find that ion-driven deuterium pathways are inefficient, which curtails the disk's deuterated water formation and its viability as the sole source for the solar system's water. This finding implies that, if the solar system's formation was typical, abundant interstellar ices are available to all nascent planetary systems.
- Detection of a branched alkyl molecule in the interstellar medium: iso-propyl cyanide. [Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.]
- Science 2014 Sep 26; 345(6204):1584-7.
The largest noncyclic molecules detected in the interstellar medium (ISM) are organic with a straight-chain carbon backbone. We report an interstellar detection of a branched alkyl molecule, iso-propyl cyanide (i-C3H7CN), with an abundance 0.4 times that of its straight-chain structural isomer. This detection suggests that branched carbon-chain molecules may be generally abundant in the ISM. Our astrochemical model indicates that both isomers are produced within or upon dust grain ice mantles through the addition of molecular radicals, albeit via differing reaction pathways. The production of iso-propyl cyanide appears to require the addition of a functional group to a nonterminal carbon in the chain. Its detection therefore bodes well for the presence in the ISM of amino acids, for which such side-chain structure is a key characteristic.
- Evidence for global electron transportation into the jovian inner magnetosphere. [Journal Article]
- Science 2014 Sep 26; 345(6204):1581-4.
Jupiter's magnetosphere is a strong particle accelerator that contains ultrarelativistic electrons in its inner part. They are thought to be accelerated by whistler-mode waves excited by anisotropic hot electrons (>10 kiloelectron volts) injected from the outer magnetosphere. However, electron transportation in the inner magnetosphere is not well understood. By analyzing the extreme ultraviolet line emission from the inner magnetosphere, we show evidence for global inward transport of flux tubes containing hot plasma. High-spectral-resolution scanning observations of the Io plasma torus in the inner magnetosphere enable us to generate radial profiles of the hot electron fraction. It gradually decreases with decreasing radial distance, despite the short collisional time scale that should thermalize them rapidly. This indicates a fast and continuous resupply of hot electrons responsible for exciting the whistler-mode waves.
- Parenting: roots of the sweet tooth. [Comment, Letter]
- Science 2014 Sep 26; 345(6204):1571-2.
- Parenting: section deserves a scolding. [Comment, Letter]
- Science 2014 Sep 26; 345(6204):1571.
- Brazil's new laws bug collectors. [Letter]
- Science 2014 Sep 26; 345(6204):1571.
- Nitrogenase Mechanism. A dynamic tool for nitrogen reduction. [Comment, Journal Article, Research Support, Non-U.S. Gov't]
- Science 2014 Sep 26; 345(6204):1568.
- Chemistry. Perovskites take lead in solar hydrogen race. [Comment, Journal Article]
- Science 2014 Sep 26; 345(6204):1566-7.
- Developmental Biology. Managing patterns and proportions over time. [Comment, Journal Article]
- Science 2014 Sep 26; 345(6204):1565-6.