Oxide pyrochlores — A review

Kinetic of crystallization from the melt and chain folding in polyethylene fractions revisited: theory and experiment

Harnessing solar energy for the production of clean hydrogen fuels by a photoelectrochemical (PEC) cell represents a very attractive but challenging alternative This review focuses on recent developments of some promising photoelectrode materials, such as BiVO4, a-Fe2O3, TaON, and Ta3N5 for solar hydrogen production Some strategies have been developed to improve PEC performances of the photoelectrode materials, including: (i) doping for enhancing visible light absorption in the wide bandgap semiconductor or promoting charge transport in the narrow bandgap semiconductor, respectively; (ii) surface treatment for removing segregation phase or surface states; (iii) electrocatalysts for decreasing the overpotentials; (iv) morphology control for enhancing the light absorption and shortening transfer distance of minority carriers; (v) other methods, such as sensitization, passivating layer, and band structure engineering using heterojunction structures, and so on Photochemical durability of the photoelectrodes is also discussed, since any potential PEC technology must balance efficiency against cost and photochemical durability Photochemical durability may be amended by optimizing the photoelectrode, electrocatalyst, and electrolyte at the same time In addition, solar seawater splitting is briefly introduced because it has received attention recently Finally, trends in research in PEC cells for solar hydrogen production are detailed

Photoelectrochemical cells for solar hydrogen production: current state of promising photoelectrodes, methods to improve their properties, and outlook

The science describing semiconductor−liquid interfaces is highly interdisciplinary, broad in scope, interesting, and of importance to various emerging technologies. We present a review of the basic physicochemical principles of semiconductor−liquid interfaces, including their historical development, and describe the major technological applications that are based on these scientific principles.

Physical Chemistry of Semiconductor−Liquid Interfaces

Through decades of sustained effort, researchers have made substantial progress on developing technologies for solar-driven water splitting. Nevertheless, more basic research is needed before prototype devices with a chance for commercial success can be demonstrated. In this Perspective, we summarize the major design constraints that motivate continued research in the field of solar-driven water splitting. Additionally, we discuss key device components that are now available for use in demonstration systems and prototypes. Finally, we highlight research areas where breakthroughs will be critical for continued progress toward commercial viability for solar-driven water-splitting devices.

http://pubs.acs.org/doi/pdf/10.1021/cm4021518

Will Solar-Driven Water-Splitting Devices See the Light of Day?

The photoelectrochemical cell [$p$-type InP(Ru)]/HCl-KCl/Pt(Rh) converts 12% of the incident solar energy into two useful chemicals, hydrogen and chlorine, by photoassisted electrolysis of aqueous hydrochloric acid. At the threshold for electrolysis, the voltage required is reduced from 1.3 to 0.65 V. Hydrogen evolution takes place at microscopic islands of catalysts such as Rh, Ru, and Pt. The high efficiency of the cell derives from a thin surface oxide on InP, preventing carrier recombination, and from efficient transport of electrons to the catalyst.

Efficient Solar to Chemical Conversion: 12% Efficient Photoassisted Electrolysis in the [ p -type InP(Ru)]/HCl-KCl/Pt(Rh) Cell

Intercrystalline links in polyethylene have been revealed by crystallizing from the melt mixtures of fractionated polymer and the linear hydrocarbon n-C32H66, the latter constituent being removed later by washing at room temperature in an organic solvent. These fibrous links measure up to 15,000 A. in length and are 30–300 A. in thickness. Molecular chains are oriented parallel to the lengths of the links, and apparently nucleate on tie molecules formed by the simultaneous crystallization of different parts of the same molecule on the surfaces of different, and often widely separated, crystals. The maximum length of the links found in a given polymer varies as the square root of molecular weight, and there are indications that molecules in the melt are much more extended than is predicted by conventional configurational statistics. The links are under tension and presumably exert a significant influence on physical properties.

Intercrystalline links in polyethylene crystallized from the melt

Previous electron microscopic studies have demonstrated the presence of intercrystalline links between thin lateral edges of chain‐folded lamellar crystals in spherulitic polymers. We now present evidence that links also connect broad faces of superimposed neighboring lamellae. The latter links have been observed by electron microscopy of polyethylene lamellae standing normal to the surface of uniaxially drawn Mylar on which they had been crystallized epitaxially. Links of this kind are similar to those observed in the first instance and are evidently produced by the same mechanism. We consider also, in a critical way, the formation of intercrystalline links and tie molecules, and their important influence on mechanical properties, in bulk polymers crystallized either from quiescent or flowing melts. We show that links and tie molecules are formed mostly during primary crystallization, and few additional ones are produced during later stages. We examine, finally, a variety of ways in which links and tie molecules strengthen adhesion between crystals to promote ductile, rather than brittle, response to applied stress.

Intercrystalline Links: Critical Evaluation

A previous study of intercrystalline links in polyethylene, carried out using fractionated polymer only, has now been extended to mixtures of fractions and to whole polymer. There is little difference between links grown from concentrated (50%) solutions of polyethylene in n‐C32H66, regardless of the molecular weight distribution of the polymer. These links exhibit surfaces that are more or less featureless and the evidence indicates that they are composed of molecules crystallized, for the most part, with extended conformations. However, when these links are used as substrates upon which polyethylene is deposited epitaxially from dilute (1% or less) solution in later, quite separate, crystallization experiments, lamellar overgrowths are formed which demonstrate unambiguously the crystallization of molecules in folded conformations.The marked difference between these cases is attributed to entanglements which, as crystallizing molecules are ``reeled in'' to growth fronts, cause neighboring molecules to be...

R. G. Vadimsky

Papers

Efficient Solar to Chemical Conversion: 12% Efficient Photoassisted Electrolysis in the [ p -type InP(Ru)]/HCl-KCl/Pt(Rh) Cell

Intercrystalline links in polyethylene crystallized from the melt

Intercrystalline Links: Critical Evaluation

Further Studies of Intercrystalline Links in Polyethylene

CuInS2 Liquid Junction Solar Cells