Enhancing Charge Separation in Photocatalysts with Internal Polar Electric Fields

ChemPhotoChem ◽  
2017 ◽  
Vol 1 (5) ◽  
pp. 136-147 ◽  
Author(s):  
Zaizhu Lou ◽  
Peng Wang ◽  
Baibiao Huang ◽  
Ying Dai ◽  
Xiaoyan Qin ◽  
...  
Keyword(s):  
Electric Fields ◽  
Charge Separation

Spatial distribution of active sites on a ferroelectric PbTiO3 photocatalyst for photocatalytic hydrogen production

2017 ◽  
Vol 198 ◽  
pp. 463-472 ◽  
Author(s):  
Rengui Li ◽  
Yue Zhao ◽  
Can Li
Keyword(s):  
Spatial Distribution ◽  
Hydrogen Production ◽  
Solar Energy ◽  
Energy Conversion ◽  
Electric Fields ◽  
Charge Separation ◽  
Active Sites ◽  
Solar Energy Conversion ◽  
Photogenerated Electrons ◽  
The Right

The separation of photogenerated charge carries is a challenging issue in artificial photocatalyst systems for solar energy conversion. It has been reported that spatial charge separation can take place between different facets of semiconductor-based crystals with regular morphology and facets, which could be used to rationally deposit cocatalysts on the right facets. However, the spatial separation of photogenerated electrons and holes is still a big challenge for a particulate photocatalyst without regular morphology and specific facets. In this work, we demonstrated that photogenerated electrons and holes can be regularly separated on ferroelectric PbTiO3 photocatalyst even without regular morphology and facets. The reduction cocatalyst and oxidation cocatalyst could be selectively formed on different sites via an in situ photochemical deposition method. It is found that the photoactivity and hydrogen production for PbTiO3 with spatially separated dual-cocatalysts is remarkably enhanced to more than 100 times greater compared to native PbTiO3, which is much higher than that the case of dual-cocatalysts with a random distribution. The intrinsic electric fields and spontaneous electric polarization in the bulk of PbTiO3 are proposed to play important roles in the spatial distribution of active sites on irregular PbTiO3 particles. Our work emphasizes the essential roles of two important factors, efficient charge separation strategy and the location of dual-cocatalysts on the right sites, to construct integrated artificial photocatalyst systems for solar energy conversion.

scholarly journals Outlook for the Future

2020 ◽  
pp. 797-825
Author(s):  
C. Joshi ◽  
A. Caldwell ◽  
P. Muggli ◽  
S. D. Holmes ◽  
V. D. Shiltsev
Keyword(s):  
Electric Fields ◽  
Charge Separation ◽  
Short Distance ◽  
Density Wave ◽  
Charged Particles ◽  
Electron Plasma ◽  
Longitudinal Component ◽  
Relativistic Wave ◽  
Electrons And Ions ◽  
Total Separation

AbstractThe charge separation between electrons and ions that exists within an electron plasma density wave can create large electric fields. In 1979 Tajima and Dawson first recognized that the longitudinal component of the field of a so-called “relativistic” wave (one propagating with a phase velocity close to c), could be used to accelerate charged particles to high energies in a short distance [1]. The accelerating gradient of such a plasma wave, Eo, can be approximated—assuming a total separation of electrons and ions in such a wave with wavelength λp = 2πc/ωp—as

scholarly journals Ionospheric control of space weather

2021 ◽  
Vol 39 (3) ◽  
pp. 455-460
Author(s):  
Osuke Saka
Keyword(s):  
Phase Space ◽  
Electric Fields ◽  
Charge Separation ◽  
Substorm Onset ◽  
Auroral Ionosphere ◽  
Polar Ionosphere ◽  
Electrons And Ions ◽  
Cold Electrons ◽  
Local Accumulation ◽  
Characteristic Process

Abstract. As proposed by Saka (2019), plasma injections arising out of the auroral ionosphere (ionospheric injection) are a characteristic process of the polar ionosphere at substorm onset. The ionospheric injection is triggered by westward electric fields transmitted from the convection surge in the magnetosphere at field line dipolarization. Localized westward electric fields result in local accumulation of ionospheric electrons and ions, which produce local electrostatic potentials in the auroral ionosphere. Field-aligned electric fields are developed to extract excess charges from the ionosphere. This process is essential to the equipotential equilibrium of the auroral ionosphere. Cold electrons and ions that evaporate from the auroral ionosphere by ionospheric injection tend to generate electrostatic parallel potential below an altitude of 10 000 km. This is a result of charge separation along the mirror fields introduced by the evaporated electrons and ions moving earthward in phase space.

Charge-Separation Electric Fields in Laser Plasmas

1975 ◽  
Vol 34 (14) ◽  
pp. 859-862 ◽  
Author(s):  
C. W. Mendel ◽  
J. N. Olsen
Keyword(s):  
Electric Fields ◽  
Charge Separation ◽  
Laser Plasmas

Unravelling charge separation via surface built-in electric fields within single particulate photocatalysts

2017 ◽  
Vol 198 ◽  
pp. 473-479 ◽  
Author(s):  
Ruotian Chen ◽  
Jian Zhu ◽  
Hongyu An ◽  
Fengtao Fan ◽  
Can Li
Keyword(s):  
Electric Fields ◽  
Charge Separation ◽  
Energy Conversion Efficiency ◽  
Single Particles ◽  
Kelvin Probe ◽  
Force Microscopy ◽  
Transfer Processes ◽  
Spatially Resolved ◽  
P Type

Kelvin Probe Force Microscopy (KPFM) and spatially resolved surface photovoltage (SRSPV) techniques were employed to reveal built-in electric fields and surface photogenerated charge distribution on single particulate photocatalysts. The photogenerated holes and electrons spread over the whole surface of the particulate photocatalyst are imaged on n-type BiVO4 and p-type Cu2O single particles, respectively. It is demonstrated that the built-in electric field in the surface Space Charge Region (SCR) dictates the charge separation/transfer processes and allows the drift of one kind of the photogenerated carriers to the surface, while holding another kind of the carriers in the bulk. The results emphasize the role of the SCR played in the unidirectional charge transport between the bulk and surface in the particulate photocatalyst, which may be the crucial reason for low solar energy conversion efficiency.

scholarly journals Observed Enhancement of Reflectivity and the Electric Field in Long-Lived Florida Anvils

2007 ◽  
Vol 135 (10) ◽  
pp. 3362-3380 ◽  
Author(s):  
James E. Dye ◽  
John C. Willett
Keyword(s):  
Electric Fields ◽  
Charge Separation ◽  
Particle Interactions ◽  
Particle Collisions ◽  
Ice Particles ◽  
Particle Spectra ◽  
Strong Electric Fields ◽  
The Many ◽  
Convective Cells ◽  
Inductive Mechanism

Abstract A study of two long-lived Florida anvils showed that reflectivity >20 dBZ increased in area, thickness, and sometimes magnitude at the midlevel well downstream of the convective cores. In these same regions electric fields maintained strengths >10 kV m−1 for many tens of minutes and became quite uniform over tens of kilometers. Millimetric aggregates persisted at 9–10 km for extended times and distances. Aggregation of ice particles enhanced by the strong electric fields might have contributed to reflectivity growth in the early anvil, but is unlikely to explain observations farther out in the anvil. The enhanced reflectivity and existence of small, medium, and large ice particles far out into the anvil suggest that an updraft was acting, perhaps in weak convective cells formed by instability generated from the evaporation and melting of falling ice particles. It is concluded that charge separation must have occurred in these anvils, perhaps at the melting level but also at higher altitudes, in order to maintain fields >10 kV m−1 at 9–10 km for extended periods of time over large distances. The authors speculate that charge separation occurred as a result of ice–ice particle collisions (without supercooled water being present) via either a noninductive or perhaps even an inductive mechanism, given the observed broad ice particle spectra, the strong preexisting electric fields, and the many tens of minutes available for particle interactions. The observations, particularly in the early anvil, show that the charge structure in these anvils was quite complex.

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