Nathan S. Lewis

Bio: Nathan S. Lewis is an academic researcher from California Institute of Technology. The author has contributed to research in topics: Semiconductor & Silicon. The author has an hindex of 112, co-authored 720 publications receiving 64808 citations. Previous affiliations of Nathan S. Lewis include Lawrence Berkeley National Laboratory & Massachusetts Institute of Technology.

Numerical Simulation and Modeling of Hydrogen Gas Evolution on Planar and Microwire Array Electrodes

Abstract: The impact of gas evolution on the electrochemical characteristics of planar electrodes and microwire array electrodes has been analyzed using modeling and simulation. The impacts can mainly be broken into three phenomena, a shift in the local reversible hydrogen electrode potential, hyperpolarization and an increase in the solution resistance of the electrolyte. The local reversible hydrogen electrode potential shift was found to play the most important role, constituting >40% of the total potential drop between the cathode and reference electrode, following correction for cell resistance. Compared to planar electrodes, a microwire array structure reduces the impact of bubbles on the solution conductance, but the shift in the local reversible hydrogen electrode potential varies with distance from the actual electrode surface.

Synthesis, Characterization, and Properties of Metal Phosphide Catalysts for the Hydrogen‐Evolution Reaction

Abstract: Hydrogen gas obtained by the electrolysis of water has long been proposed as a clean and sustainable alternative to fossil fuels. Noble metals such as Pt are capable of splitting water at low overpotentials, but the implementation of inexpensive solar-driven water-splitting systems and electrolyzers could benefit from the development of robust, efficient, and abundant alternatives to noble metal catalysts. Transition metal phosphides (MxPy) have recently been identified as a promising family of Earth abundant electrocatalysts for the hydrogen-evolution reaction (HER) and are capable of operating with low overpotentials at operationally relevant current densities while exhibiting stability under strongly acidic conditions. In this review, we highlight the progress that has been made in this field and provide insights into the synthesis, characterization, and electrochemical behavior of transition metal phosphides as HER electrocatalysts. We also discuss strategies for the incorporation of metal phosphides ...

Correlation of the photoelectrochemistry of the amorphous hydrogenated silicon/methanol interface with bulk semiconductor properties

Abstract: Semiconductor/liquid junctions derived from 0.5 /sigma phi/m thick films of amorphous hydrogenated silicon, a-Si:H, have been investigated in CH/sub 3/OH solvent. The a-Si:H films consist of a weakly doped n-type layer ove a 200A n/sup +/-a-Si:H layer on a stainless-steel substrate. The low series resistance and high ratio of minority carrier collection length to film thickness in this arrangement allows a study of the properties of semiconductor/liquid interfaces with minimal interference from bulk resistance losses. We find that a-Si:H anodes in 0.02M ferrocene, FeCp/sub 2//0.5 mM FeCp/sub 2//sup +//1.5M LiClO/sub 4//CH/sub 3/OH solutions exhibit poor short-circuit quantum yields and low fill factors with 632.8 nm irradiation, but that these junctions display internal quantum yields of close to unity and high fill factors with short wavelength (lambda < 450 nm) irradiation. Photons absorbed within a distance comparable to the minority carrier collection length are efficiently collected, and the fill factors and quantum yields under such conditions are insensitive to increases in photocurrent density over a range of 0.1-2 mA/cm/sup 2/. Solar-simulated irradiation (88 mW/cm/sup 2/) from a ELH-type tungsten-halogen lamp in the a-Si:H/0.02M FeCp/sub 2//0.5 mM FeCp/sub 2//sup +//1.5M LiClO/sub 4//CH/sub 3/OH system yields open-circuit photovoltages of 0.75-0.85V, shortcircuit photocurrents ofmore » 6-7 mA/cm/sup 2/, and photoelectrode efficiencies for conversion of light to electricity of 2.7%-3.3%. Photovoltages with the acetylferrocene /sup +/0/ redox system are among the highest reported for any a-Si:H surface barrier system, and can exceed 0.85V under AM1 illumination conditions. Variation in the redox potential of the solution leads to changes in open-circuit photovoltage in accord with theory, and does not yield evidence for pinning of the a-Si:H Fermi level by interface states or by surface oxides over the potential range investigated.« less

Hexathiapentacene Nanowires as Chemical Vapor Sensors

Abstract: Semiconducting hexathiapentacene (HTP) single–crystal nanowires were synthesized using a simple solution-phase route. Quartz Crystal Microbalance and complex resistance measurements were employed to investigate the sensing properties of an HTP nanowire to analytes including acid, amine, and hydrocarbon vapors. Cole-Cole plots (0.01Hz-4 MHz) of measured impedance spectra, modeled using equivalent circuits, were used to resolve the effects of adsorption and charge migration.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films

Abstract: THE large-scale use of photovoltaic devices for electricity generation is prohibitively expensive at present: generation from existing commercial devices costs about ten times more than conventional methods1. Here we describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency. The device is based on a 10-µm-thick, optically transparent film of titanium dioxide particles a few nanometres in size, coated with a monolayer of a charge-transfer dye to sensitize the film for light harvesting. Because of the high surface area of the semiconductor film and the ideal spectral characteristics of the dye, the device harvests a high proportion of the incident solar energy flux (46%) and shows exceptionally high efficiencies for the conversion of incident photons to electrical current (more than 80%). The overall light-to-electric energy conversion yield is 7.1-7.9% in simulated solar light and 12% in diffuse daylight. The large current densities (greater than 12 mA cm-2) and exceptional stability (sustaining at least five million turnovers without decomposition), as well as the low cost, make practical applications feasible.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Heterogeneous photocatalyst materials for water splitting

Abstract: This critical review shows the basis of photocatalytic water splitting and experimental points, and surveys heterogeneous photocatalyst materials for water splitting into H2 and O2, and H2 or O2 evolution from an aqueous solution containing a sacrificial reagent Many oxides consisting of metal cations with d0 and d10 configurations, metal (oxy)sulfide and metal (oxy)nitride photocatalysts have been reported, especially during the latest decade The fruitful photocatalyst library gives important information on factors affecting photocatalytic performances and design of new materials Photocatalytic water splitting and H2 evolution using abundant compounds as electron donors are expected to contribute to construction of a clean and simple system for solar hydrogen production, and a solution of global energy and environmental issues in the future (361 references)