Photoelectrochemical Study of the Delafossite AgNiO2 Nanostructure: Application to Hydrogen Production

2020 ◽  
Vol 17 (3) ◽  
Author(s):  
R. Bagtache ◽  
R. Brahimi ◽  
O. Mahroua ◽  
L. Boudjellal ◽  
K. Abdmeziem ◽  
...  
Keyword(s):  
Bulk Material ◽  
Surface Oxidation ◽  
Nyquist Plot ◽  
Flat Band ◽  
Bandgap Energy ◽  
Relaxation Processes ◽  
Hydrothermal Route ◽  
Metallic Behavior ◽  
Oxygen Insertion ◽  
P Type

Abstract AgNiO2 is a semiconductor crystallizing in the delafossite structure; it is prepared by the hydrothermal route, and the photoelectrochemical properties are studied for the first time. The TG/DSC analyses show a low stability not exceeding 290 °C before its reduction into Ag and NiO. The direct bandgap energy of the bulk material is 0.87 eV, due to the d–d transition of Ag+ linearly coordinated. AgNiO2 is chemically stable in the pH region (4–14); a flat band potential of −0.022 VRHE with p-type behavior, inferred to oxygen insertion is reported in KOH solution (10−2 M). The holes density (1.92 × 1022 cm−3) agrees with a semi-metallic behavior. Positive potentials give rise to surface oxidation of AgNiO2 in the diffusion plateau before oxygen evolution. The electrochemical oxygen insertion, investigated by chrono-amperometry, is found to be slow with a diffusion coefficient of ∼8 × 10−16 cm2 s−1. The Nyquist plot exhibits a semicircle centered below the abscissa axis, whose diameter 4200 Ω cm2 decreases down to 760 Ω cm2 under visible illumination. Such results indicate dipolar and multi-relaxation processes and confirm the existence of the optical gap. The conduction band (−0.88 VRHE) derived from Ag+: 4d orbital is more cathodic than the potential of H2O/H2 (∼−0.64 VRHE) level and hydrogen is evolved under visible irradiation. An evolution rate of 1.43 mL g−1 min−1 at pH ∼ 12.8 is obtained with a light-to-chemical energy efficiency of 2.40%.

scholarly journals Photo-electrochemical Characterization of New Lead-free Ferroelectric Ba0.975Ho0.017(Zr0.2Ti0.75)Sn0.05O3) Ceramic. Application to Bezacryl Oxidation Under Solar Light

2021 ◽  
Author(s):  
S. Smail ◽  
Gharib Rekhila ◽  
K. Taïbi ◽  
A. Lahmar ◽  
M. Trari
Keyword(s):  
Electrochemical Impedance ◽  
Bulk Material ◽  
Rietveld Method ◽  
Solar Light ◽  
Flat Band ◽  
Oh Radicals ◽  
Dielectric Study ◽  
Relaxor Behavior ◽  
Order Kinetic ◽  
Electronic Density

Abstract Ba0.975Ho0.017(Zr0.20Ti0.75)Sn0.05O3 (abbreviated BHZ20TS) was elaborated by solid-state reaction at high temperature. The X-ray diffraction pattern, refined by the Rietveld method, indicated that the ceramic has a perovskite structure with a cubic symmetry. The Scanning electron microscopy revealed a high density and low porosity with reduced particle sizes upon substitution ofBa2+ by the rare earth ion Ho3+. The dielectric study as a function of temperature (-150 – 200 °C) and frequency (102 - 106 Hz) showed relaxor ferroelectric behavior. The modified Curie-Weiss law allowed us to evaluate the diffuse phase transition parameters. BHZ20TS obeys the empirical Vogel–Fulcher relation which confirms the relaxor behavior of this composition. With an optical band gap of 2.56 eV, BHZ20TS is attractive for photocatalytic applications. The capacitance-potential (C-2 - E) characteristic plotted in Na2SO4 (0.1 M) indicates n type behavior with a flat band potential (Efb) of -0.60 VSCE and electronic density (NA) of 2.2×1016cm-3. The semicircle in the Electrochemical Impedance Spectroscopy (EIS) measured in the range (10-3 – 105 Hz) is ascribed to the bulk material BHZ20TS (80 kW cm2) with a constant phase element (CPE) and a depletion angle of -5°. As application, the oxide was tested with success for the photooxidation under solar light of Bezacryl (BEZ), a hazardous dye. The energy band diagram shows an electron transfer from the conduction band of BHZ20TS to dissolved oxygen, generating O2· and OH·- radicals, responsible of the BEZ mineralization whose disappearance was followed by UV-Vis spectrophotometry. An abatement of 60% is obtained in BEZ solution (10 mg L-1) within 100 min under a solar irradiance of 97 mWcm-2; the mineralization obeys a first order kinetic model with a half photocatalytic life of 57 min.

scholarly journals Electrochemical Study of Copper Ferrite as a Catalyst for CO2 Photoelectrochemical Reduction

2018 ◽  
Vol 13 (2) ◽  
pp. 236 ◽  
Author(s):  
Kaykobad Md. Rezaul Karim ◽  
Huei Ruey Ong ◽  
Hamidah Abdullah ◽  
Abu Yousuf ◽  
Chin Kui Cheng ◽  
...  
Keyword(s):  
Sol Gel ◽  
Co2 Reduction ◽  
Linear Sweep Voltammetry ◽  
Band Gap Energy ◽  
Reduction Reaction ◽  
Electrochemical Study ◽  
Flat Band ◽  
Copper Ferrite ◽  
Onset Potential ◽  
P Type

In this work, p-type CuFe2O4 was synthesized by sol gel method. The prepared CuFe2O4 was used as photocathode catalyst for photoelectrochemical (PEC) CO2 reduction. The XRD, UV-Visible Spectroscopy (UV-Vis), and Mott-Schottky (MS) experiments were done to characterize the catalyst. Linear sweep voltammetry (LSV) was employed to evaluate the visible light (λ>400 nm) effect of this catalyst for CO2 reduction.  The band gap energy of the catalyst was calculated from the UV-Vis and was found 1.30 eV. Flat band potential of the prepared CuFe2O4 was also calculated and found 0.27 V versus Ag/AgCl. Under light irradiation in the CO2-saturated NaHCO3 solution, a remarkable current development associated with CO2 reduction was found during LSV for the prepared electrode from onset potential -0.89 V with a peak current emerged at -1.01 V (vs Ag/AgCl) representing the occurrence of CO2 reduction reaction. In addition, the mechanism of PEC was proposed for the photocathode where the necessity of a bias potential in the range of 0.27 to ~ -1.0 V vs Ag/AgCl was identified which could effectively inhibit the electron-hole (e-/h+) recombination process leading to an enhancement of CO2 reduction reactions. Copyright © 2018 BCREC Group. All rights reservedReceived: 4th July 2017; Revised: 5th November 2017; Accepted: 15th November 2017; Available online: 11st June 2018; Published regularly: 1st August 2018How to Cite: Karim, K.M.R., Ong, H.R., Abdullah, H., Yousuf, A., Cheng, C.K., Khan, M.K.R. (2018). Electrochemical Study of Copper Ferrite as a Catalyst for CO2 Photoelectrochemical Reduction. Bulletin of Chemical Reaction Engineering & Catalysis, 13 (2): 236-244 (doi:10.9767/bcrec.13.2.1317.236-244) 

Built-in Potential and Open Circuit Voltage of Heterojunction CuIn1-xGaxSe2 Solar Cells

2005 ◽  
Vol 865 ◽  
Author(s):  
Akimasa Yamada ◽  
Koji Matsubara ◽  
Keiichiro Sakurai ◽  
Shogo Ishizuka ◽  
Hitoshi Tampo Hajime ◽  
...  
Keyword(s):  
Solar Cells ◽  
Conduction Band ◽  
Fermi Energy ◽  
Open Circuit Voltage ◽  
Material Selection ◽  
Open Circuit ◽  
Flat Band ◽  
Band Energy ◽  
Low X ◽  
P Type

AbstractThe reasons why the open circuit voltage (Voc) of high-x CuIn1-xGaxSe2 (CIGS)/ZnO solar cells remain low are discussed. Here it is shown that the Voc ceiling can be interpreted simply on the basis of a model that the valence-band energy (Ev) of CIGS is almost immovable irrespective of x. When the conduction-band energy (Ec) of ZnO is lower than that of high-x CIGS (DEc<0), the built-in potential (Vbi) of a CIGS/ZnO junction is equivalent to the flat-band potential (Vbi) that arises from the separation between the Fermi energies of the two materials. If the Ev (and therefore the Fermi energy) of p-type CIGS is constant with increasing x, the Vbi and Voc that follows the Vbi remain unchanged since the Fermi energy of ZnO is constant. This unchangeable Voc reduces the conversion efficiency of high-x CIGS cells in cooperation with reduced photocurrents due to a larger bandgap. A positive offset, ΔEc>o gives rise to a photoelectrons barrier in the conduction-band that partially cancels Voc, thus the Voc of a low-x CIGS cell is governed by the Ec of CIGS. Based upon this concept, a material selection guideline is given for the windows and transparent electrodes appropriate for high-x CIGS absorbers-based solar cells.

Defects Introduced by Plasma Processing of Silicon

1992 ◽  
Vol 262 ◽  
Author(s):  
J. L. Benton
Keyword(s):  
Bulk Material ◽  
Surface Region ◽  
Surface Damage ◽  
Near Surface ◽  
Enhanced Diffusion ◽  
Interstitial Defect ◽  
Comprehensive Picture ◽  
Reaction Region ◽  
Defect Reactions ◽  
P Type

ABSTRACTThe electrical and optical properties of defects introduced by Reactive Ion Etching (RIE) in the near surface region of Si after dry etching with various gases and plasma conditions is studied with spreading Resistance (SR), photoluminescence (PL), and capacitance-voltage profiling (C-V). Plasma etching in chlorine and fluorine based gases produce donors at the surface in both n-type and p-type, Czochralski and float-zone silicon. Isochronal annealing reveals the presence of two distinct regions of dopant compensation. The surface damage region is confined to 1000 Å and survives heat treatment at 400°C, while the defect reaction region extends ≥ 1 μm in depth and recovers by 250°C. A comprehensive picture of the interstitial defect reactions in RIE silicon is completed. The interstitial defects, Ci and Bi, created in the ion damaged near surface region, undergo recombination enhanced diffusion caused by the presence of ultraviolet light in the plasma, resulting in the long range diffusion into the Si bulk. Subsequently, the interstitial atoms are trapped by the background impurities forming the defect pairs, CiOi, CSCi, or BiOi, which are observed experimentally. The depth of the diffusion-limited trapping and the probability of forming specific pairs depends on the relative concentrations of the reactants, oxygen, carbon or boron, present in the bulk material.

Highly improved electrical and photoelectrical properties of electro-deposited p-type cuprous oxide

2020 ◽  
Vol 13 (08) ◽  
pp. 2051049
Author(s):  
G. Wu ◽  
Y. Zhang ◽  
W. Zhang ◽  
D. Jin ◽  
L. Wang
Keyword(s):  
Cuprous Oxide ◽  
Surface Defect ◽  
Annealing Temperature ◽  
Defect Density ◽  
Lower Surface ◽  
Flat Band ◽  
Electrical And Optical Properties ◽  
Text Type ◽  
Photoelectrical Properties ◽  
P Type

In this work, the effect of annealing on the electrical and optical properties of electro-deposited [Formula: see text]-type cuprous oxide was studied in detail. It is found that the flat band potential linearly increased with annealing temperature and the carrier concentration was improved from 6.56 × 10[Formula: see text] cm[Formula: see text] to 23.3 × 10[Formula: see text] cm[Formula: see text]. The photocurrent intensity of cuprous oxide was improved from 12.1 [Formula: see text]A to 106.6 [Formula: see text]A after annealing. The dramatically improved electrical and photoelectrical properties might be ascribed to the highly improved crystallinity and the lower surface defect density caused by annealing.

Single Crystalline 4H-SiC MEMS Devices with N-P-N Epitaxial Structure

2014 ◽  
Vol 1693 ◽  
Author(s):  
Feng Zhao ◽  
Allen Lim ◽  
Zhibang Chen ◽  
Chih-Fang Huang
Keyword(s):  
Single Crystal ◽  
Electronic Devices ◽  
Device Fabrication ◽  
Flat Band ◽  
Harsh Environment ◽  
Mems Devices ◽  
Etching Technique ◽  
Epitaxial Structure ◽  
Single Crystal Sic ◽  
P Type

ABSTRACTIn this paper, single crystal 4H-SiC MEMS devices with n-p-n epitaxial structure was fabricated. A dopant-selective photoelectrochemical etching technique was applied to etch the sacrificial p-type SiC layer to release n-type SiC suspended structures on n-type SiC substrate. The selective etching was achieved by applying a bias which employs the different flat-band potentials of n-SiC and p-SiC in KOH solution. Such MEMS devices have the potential to fully exploit the superior properties of single crystal SiC for harsh environment operation, as well as mature epitaxial growth and device fabrication of 4H-SiC. The n-p-n structure, together with the previously reported p-n structure, extends the capability of monolithic integration between MEMS with electronic devices and circuits on SiC platform.

Flat-band Voltage Study Of Atomic-layer-Deposited Aluminum-oxide Subjected To Spike Thermal Annealing

2003 ◽  
Vol 765 ◽  
Author(s):  
V. R. Mehta ◽  
A. T. Fiory ◽  
N. M. Ravindra ◽  
M. Y. Ho ◽  
G. D. Wilk ◽  
...  
Keyword(s):  
Atomic Layer ◽  
Oxide Thickness ◽  
Atomic Diffusion ◽  
Flat Band ◽  
Gate Electrodes ◽  
Layer Deposition ◽  
Thermal Oxide ◽  
P Type ◽  
Low Thermal Budget ◽  
Spike Annealing

AbstractHigh-κ dielectrics based the oxide of Al were prepared by atomic layer deposition (ALD) on 200-mm p-type Si wafers. Films were deposited directly on clean Si or on 0.5-nm underlayers of rapid thermal oxide or oxynitrides grown in O2 and/or NO ambients. The purpose of the underlayer films is to provide a barrier for atomic diffusion from the crystal Si to the high-κ dielectric film. Deposited Al-oxide films varied in thickness from 2 to 6 nm. Post deposition anneals were used to stabilize the ALD oxides. Equivalent SiO2-oxide thickness varied from 1.0 to 3.5 nm. In situ P-doped amorphous-Si 160 nm films were deposited over the oxides to prepare heavily doped n-type gate electrodes in MOS structures. Samples were rapid thermal annealed in N2 ambient at 800°C for 30 s, or spike annealed at 950, 1000, and 1050°C (nominally zero time at peak temperature). Flat band voltages, VFB were determined from C-V measurements on dot patterns. The 800°C anneals were used as a baseline, at which the poly-Si electrodes are crystallized and acquire electrical activation while subjecting the high-κ dielectrics to a low thermal budget. Positive shifts in VFB were observed, relative to a pure SiO2 control, ranging from 0.2 to 0.8 V. Spike annealing reduces the VFB shift for ALD films deposited over underlayer films. The VFB shift and the changes with annealing temperature show systematic dependence on the nitridation of the underlayer.

Modified ITAT Model for Data Retention in Nanocrystals Based Flash Memory Gate Stack

2017 ◽  
Vol 45 ◽  
pp. 1-11
Author(s):  
Rasika Dhavse ◽  
Kumar Prashant ◽  
Chetan Dabhi ◽  
Anand Darji ◽  
R.M. Patrikar
Keyword(s):  
Flash Memory ◽  
Low Voltage ◽  
Flat Band ◽  
Data Retention ◽  
Gate Stack ◽  
Tunneling Model ◽  
Idle Mode ◽  
Direct Tunneling ◽  
Device Lifetime ◽  
P Type

This work applies combination of Direct Tunneling model and BSIM4 based ITAT model to explain the leakage of electrons from charged nanocrystals to p-type silicon substrate in data retention condition, for an ultra-thin tunnel oxide, low voltage programmable silicon nanocrystal based flash gate stack. Basic expressions of these models are modified to incorporate the nanocrystals related charge leakage in idle mode. The concept is supported by simulating these models and comparing them with the experimental data. Transition of electrons is considered as a result of Direct Tunneling and their trapping de-trapping via water related hydrogen traps. However, it is found that modified ITAT mechanism is the dominant one. Flat-band voltage shift profile fits accurately with the model with an extrapolated 10 years device lifetime without memory closure. 3 nm thick tunnel oxide and 100 nm sized nanocrystal fabrication with Electron Beam Lithography are main features of the devices.

Annealing Effect on the Thermoelectric Properties of Undoped CoSb3

2006 ◽  
Vol 118 ◽  
pp. 565-570 ◽  
Author(s):  
Il Ho Kim ◽  
Jung Il Lee ◽  
Soon Chul Ur ◽  
Kyung Wook Jang ◽  
Good Sun Choi ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Phase Transitions ◽  
Thermoelectric Properties ◽  
Hot Pressing ◽  
Annealing Effect ◽  
Metallic Behavior ◽  
Arc Melting ◽  
P Type ◽  
Type Conduction

Binary skutterudite CoSb3 compounds were prepared by the arc melting and hot pressing processes and their thermoelectric properties were investigated at 300K-600K. Annealing effect was examined and it was correlated to phase transformation and homogenization. Thermoelectric properties of the arc-melted and hot-pressed CoSb3 were discussed and compared. Undoped CoSb3 prepared by the arc melting showed p-type conduction and metallic behavior at all temperatures examined. However, hot pressed specimens showed n-type conduction, possibly due to Sb evaporation. Thermoelectric properties were remarkably improved by annealing in vacuum and they were closely related to phase transitions.

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