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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Low temperature open-air plasma deposition of amorphous tin oxide for perovskite solar cells
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Integrating computation and experiment to investigate photoelectrodes for solar water splitting at the microscopic scale.
CONSPECTUS: Photoelectrochemical water-splitting is a promising and sustainable way to store the energy of the sun in chemical bonds and use it to produce hydrogen gas, a clean fuel. The key components in photoelectrochemical cells (PECs) are photoelectrodes, including a photocathode that reduces water to hydrogen gas and a photoanode that oxidizes water to oxygen gas. Materials used in photoelectrodes for PECs must effectively absorb sunlight, yield photogenerated carriers, and exhibit electronic properties that enable the efficient shuttling of carriers to the surface to participate in relevant water-splitting reactions. Discovering and understanding the key characteristics of optimal photoelectrode materials is paramount to the realization of PEC technologies. Oxide-based photoelectrodes can satisfy many of these materials requirements, including stability in aqueous environments, band edges with reasonable alignment with the redox potentials for water splitting, and ease of synthesis. However, oxide photoelectrodes generally suffer from poor charge transport properties and considerable bulk electron-hole separation, and they have relatively large band gaps. Numerous strategies have been proposed to improve these aspects and understand how these improvements are reflected in the photoelectrochemical performance. Unfortunately, the structural and compositional complexity of multinary oxides accompanied by the inherent complexity of photoelectrochemical processes makes it challenging to understand the individual effects of composition, structure, and defects in the bulk and on the surface on a material's photoelectrochemical properties. The integration of experiment and theory has great potential to increase our atomic-level understanding of structure-composition-property relationships in oxide photoelectrodes. In this Account, we describe how integrating experiment and theory is beneficial for achieving scientific insights at the microscopic scale. We highlight studies focused on understanding the role of (i) bulk composition via solid-state solutions, intercalation, and comparison with isoelectronic compounds, (ii) dopants for both the anion and cation and their interactions with oxygen vacancies, and (iii) surface/interface structure in the photocurrent generation and photoelectrochemical performance in oxide photoelectrodes. In each instance, we outline strategies and considerations for integrating experiment and theory and describe how this integration led to valuable insights and new directions in uncovering structure-composition-property relationships. Our aim is to demonstrate the unique value of combining experiment and theory in studying photoelectrodes and to encourage the continued effort to bring experiment and theory in closer step with each other.
Modulating Hole Transport in Multilayered Photocathodes with Derivatized p-Type Nickel Oxide and Molecular Assemblies for Solar-Driven Water Splitting
We report here a new photocathode composed of a bi-layered doped NiO film topped by a macro-mesoporous ITO (ioITO) layer with molecular assemblies attached to the ioITO surface. The NiO film containing a 2% K+ doped NiO inner layer and a 2% Cu2+ doped NiO outer layer provides sufficient driving force for hole transport after injection to NiO by the molecular assembly. The tri-layered oxide, NiK0.02O | NiCu0.02O | ioITO, sensitized by a ruthenium polypyridyl dye and functionalized with a nickel-based hydrogen evolution catalyst, outperforms its counterpart, NiO | NiO | ioITO, in photocatalytic hydrogen evolution from water over a period of several hours with a Faradaic yield of ~90%.
Solar energy conversion, storage, and release using an integrated solar-driven redox flow battery
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Alkyl chain engineering of chlorinated acceptors for elevated solar conversion
Abstract not provided
An asymmetrical A-DAD-A-type acceptor simultaneously enhances voltage and current for efficient organic solar cells
Abstract not provided
Evaluation of sputtered nickel oxide, cobalt oxide and nickel–cobalt oxide on n-type silicon photoanodes for solar-driven O 2 (g) evolution from water
Thin films of nickel oxide (NiO x ), cobalt oxide (CoO x ) and nickel–cobalt oxide (NiCoO x ) produced integrated, protected Si (111) photoanodes integrated, protected Si photoanodes that did not require deposition of a separate heterogeneous electrocatalyst for water oxidation.
Solar-driven electrochemical synthesis of ammonia using nitrate with 11% solar-to-fuel efficiency at
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Pressure Separation and Gas Flows in a Prototype Vacuum Pumped Solar Thermochemical Reactor.
Abstract not provided.
Hard x-ray bursts observed in association with Rayleigh-Taylor instigated current disruption in a solar-relevant lab experiment
Here, measurements by multiple X-ray detectors show transient emission of a 1 μs pulse of non-mono-energetic ~6 keV X-rays by a cold, dense MHD-driven plasma jet. Because the collision mean free path is much smaller than the jet dimensions, the acceleration of particles to high energy was not expected. The X-ray pulse occurs when the jet undergoes a kink instability which accelerates the jet laterally so that a fast-growing secondary Rayleigh-Taylor instability is triggered which then breaks the jet. The jet breaking is correlated in time with several other fast changing phenomena. It is proposed that despite the short collision mean free path, an inductive electric field associated with this breaking accelerates a certain subgroup of electrons to keV energies without any of these electrons undergoing collisions. Moreover, it is proposed that after being accelerated to high energy, these fast electrons are suddenly decelerated via collisions and radiate X-rays.
Theory of solar cell light trapping through a nonequilibrium Green's function formulation of Maxwell's equations
Not Available
A Three-Stage Enhanced Reactive Power and Voltage Optimization Method for High Penetration of Solar
This paper presents a three-stage enhanced volt/var optimization method to stabilize voltage fluctuations in transmission networks by optimizing the usage of reactive power control devices. In contrast with existing volt/var optimization algorithms, the proposed method optimizes the voltage profiles of the system, while keeping the voltage and real power output of the generators as close to the original scheduling values as possible. This allows the method to accommodate realistic power system operation and market scenarios, in which the original generation dispatch schedule will not be affected. The proposed method was tested and validated on a modified IEEE 118-bus system with photovoltaic data.
Comparison of Solar and Wind Power Generation Impact on Net Load across a Utility Balancing Area.
Abstract not provided.