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Title: The Role of Water for Photodecomposition of Aqueous Hydrogen Sulfide Using Stratified Photocatalyst--Experimental Part

Abstract

Splitting of hydrogen sulfide using sunlight is a useful reaction to produce hydrogen. Alkaline sulfide solution, which is prepared by dissolving hydrogen sulfide into alkaline water, is selected as the reaction medium of photocatalytic hydrogen generation reaction. In this system, the photocatalytic reaction is assumed to occur as follows: 2H{sub 2}O + 2e{sup -} {yields} H{sub 2} + 2OH{sup -} (1) 2S{sup 2-} + 2h{sup +} {yields} S{sub 2}{sup 2-} (2) However, as the reaction progresses white solids precipitate in the reaction medium. Furthermore, the HPLC analysis suggested that the ratio between the consumption of sulfide ion and the amount of hydrogen generation was about 3:2, which is not stoichiometric. Thus, in this paper, we characterized the white solid precipitate and tried to optimize the solution condition to prevent the precipitation of the same. From our study, the white solid precipitate was confirmed as sulfur derived from the oxidation of the disulfide ion. It was confirmed that the addition of sulfite ions prevented the oxidation of disulfide ions, which causes the precipitation. In the absence of sulfite ions and for sufide ion concentration less than 0.1M, the precipitation of sulfur occurs in a very short reaction time. On the othermore » hand the hydrogen evolution rate retarded when the sulfide ion concentration is higher than 0.1M. This was due to the degradation of the stratified CdS particles. Thus, the optimal concentration of Na2S solution was determined to be around 0.1M.« less

Authors:
; ;  [1];  [2];  [3];  [4]
  1. Graduate School of Environmental Studies, Tohoku University, Aramaki Aza Aoba 20, Aoba-Ku, Sendai 980-8579 (Japan)
  2. Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1, Katahira, Aoba, Sendai 980-8577 (Japan)
  3. Deptertment of Geoscience and Technology, Tohoku University, Aramaki Aza Aoba 01, Aoba-Ku, Sendai 980-8579 (Japan)
  4. Grid Technology Research Center, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba 305-8568 (Japan)
Publication Date:
OSTI Identifier:
20798639
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 833; Journal Issue: 1; Conference: 3. international workshop on water dynamics, Sendai (Japan), 16-17 Nov 2005; Other Information: DOI: 10.1063/1.2207085; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CADMIUM SULFIDES; CATALYSTS; DISULFIDES; HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY; HYDROGEN; HYDROGEN SULFIDES; MOLECULAR IONS; OXIDATION; PHOTOCHEMISTRY; PRECIPITATION; SOLUTIONS; STOICHIOMETRY; SULFITES; SULFUR; WATER

Citation Formats

Arai, Takeo, Shinoda, Kozo, Tohji, Kazuyuki, Matsumoto, Takatoshi, Sakima, Shuhei, and Nagashima, Umpei. The Role of Water for Photodecomposition of Aqueous Hydrogen Sulfide Using Stratified Photocatalyst--Experimental Part. United States: N. p., 2006. Web. doi:10.1063/1.2207085.
Arai, Takeo, Shinoda, Kozo, Tohji, Kazuyuki, Matsumoto, Takatoshi, Sakima, Shuhei, & Nagashima, Umpei. The Role of Water for Photodecomposition of Aqueous Hydrogen Sulfide Using Stratified Photocatalyst--Experimental Part. United States. doi:10.1063/1.2207085.
Arai, Takeo, Shinoda, Kozo, Tohji, Kazuyuki, Matsumoto, Takatoshi, Sakima, Shuhei, and Nagashima, Umpei. Mon . "The Role of Water for Photodecomposition of Aqueous Hydrogen Sulfide Using Stratified Photocatalyst--Experimental Part". United States. doi:10.1063/1.2207085.
@article{osti_20798639,
title = {The Role of Water for Photodecomposition of Aqueous Hydrogen Sulfide Using Stratified Photocatalyst--Experimental Part},
author = {Arai, Takeo and Shinoda, Kozo and Tohji, Kazuyuki and Matsumoto, Takatoshi and Sakima, Shuhei and Nagashima, Umpei},
abstractNote = {Splitting of hydrogen sulfide using sunlight is a useful reaction to produce hydrogen. Alkaline sulfide solution, which is prepared by dissolving hydrogen sulfide into alkaline water, is selected as the reaction medium of photocatalytic hydrogen generation reaction. In this system, the photocatalytic reaction is assumed to occur as follows: 2H{sub 2}O + 2e{sup -} {yields} H{sub 2} + 2OH{sup -} (1) 2S{sup 2-} + 2h{sup +} {yields} S{sub 2}{sup 2-} (2) However, as the reaction progresses white solids precipitate in the reaction medium. Furthermore, the HPLC analysis suggested that the ratio between the consumption of sulfide ion and the amount of hydrogen generation was about 3:2, which is not stoichiometric. Thus, in this paper, we characterized the white solid precipitate and tried to optimize the solution condition to prevent the precipitation of the same. From our study, the white solid precipitate was confirmed as sulfur derived from the oxidation of the disulfide ion. It was confirmed that the addition of sulfite ions prevented the oxidation of disulfide ions, which causes the precipitation. In the absence of sulfite ions and for sufide ion concentration less than 0.1M, the precipitation of sulfur occurs in a very short reaction time. On the other hand the hydrogen evolution rate retarded when the sulfide ion concentration is higher than 0.1M. This was due to the degradation of the stratified CdS particles. Thus, the optimal concentration of Na2S solution was determined to be around 0.1M.},
doi = {10.1063/1.2207085},
journal = {AIP Conference Proceedings},
number = 1,
volume = 833,
place = {United States},
year = {Mon May 15 00:00:00 EDT 2006},
month = {Mon May 15 00:00:00 EDT 2006}
}
  • Stratified type photocatalyst with the extremely higher photocatalytic activities can be synthesized by using the chemical reaction between the Na{sub 2}S solution and Cd(OH){sub 2} precursors. This type of photocatalyst has the specific morphology which constructed by the nano-sized and capsule like formed structure, and the metal concentration was gradually changed in its wall. The 'charge gradient' was formed at the metal sulfide and oxide/hydroxide junction in the wall, which favored for the separation of the photo excited electron-hole pair. Consequently, stratified type photocatalyst shows the high catalytic activity than the usual nano CdS particles. By the addition of sulfurmore » compound into the bio reactor contained the sulfur reducing bacteria, the H{sub 2}S gas concentration can increased to about 1000 times enlarge than the usual condition. Therefore, we can conclude that the enhancement of the H{sub 2}S gas evolved from the bio reactor was successfully achievement, and we don't need to afraid the shortage risk of H{sub 2}S supply. These H{sub 2}S gas concentration can enlarged to 80% by using A type zeorite. Especially, Ca-A type zeorite is considered as the suitable material.« less
  • Among CdS, Rh/CdS, Rh{sub 2}S{sub 3}/CdS, and Rh{sub 2}S{sub 3}/Rh/CdS, the ternary material, viz., Rh{sub 2}S{sub 3}/Rh/CdS, is found to be the most active photocatalyst for the decomposition of aqueous sulfide. X-ray photoelectron spectroscopic studies show that Rh as it is photodeposited on CdS is in the zero oxidation state but is prone to aerial oxidation.
  • In this report, silver sulfide (Ag{sub 2}S) was selected as a new H{sub 2}S splitting photocatalyst material, and considered the synthesis method of Ag{sub 2}S photocatalyst particles with stratified structure. Previous stratified particles were synthesized by using metal oxide (hydroxide) as the precursor. Ag{sub 2}O particles as the precursor of Ag{sub 2}S were synthesized by mixing AgNO{sub 3} solution and NaOH, and their particle sizes could be controlled by the solutions' concentration. Then, Ag{sub 2}S particles were obtained by adding Na{sub 2}S solution into suspending solution of Ag{sub 2}O particles with optimum sizes. Particle sizes of Ag{sub 2}S were changedmore » by Na{sub 2}S concentration control, and remaining Ag{sub 2}O precursor could be dissolved by adding NH{sub 3} solution. The photocatalytic H{sub 2}S splitting could be realized by UV-light irradiation on the Ag{sub 2}S particles without co-catalyst like Pt.« less
  • In this paper the degradation of 2,4-dichlorophenol in the presence of cadmium sulfide suspensions by ultraviolet illumination is studied under various solution pH conditions, reaction times, and CdS loadings. The increase in the 2,4-dichlorophenol removal at alkaline condition by photocatalysis is possibly attributed to the distribution of protonated and deprotonated species at different solution pH conditions. The degradation and demineralization of 2,4-dichlorophenol by the photocatalytic process can be described fairly well by a simplified two step consecutive reaction scheme based on carbon balance.
  • Highlights: ► The nanostructured NiS/CdS photocatalyst was prepared by a facile two-step method. ► After aged for six days, the photocatalyst achieved a maximal rate of H{sub 2} evolution. ► The rate of H{sub 2} evolution on NiS(0.14)/CdS-6 is about 33 times that of CdS-6. - Abstract: The nanostructured NiS/CdS-t (t = aging period in day number) composite photocatalysts were prepared by a facile two-step synthesis method. The photocatalytic activity of H{sub 2} evolution over NiS/CdS could be greatly enhanced by changing the aging period of CdS. The NiS/CdS achieved a maximal rate of H{sub 2} evolution when CdS wasmore » aged for 6 days before hydrothermal treatment. It was demonstrated that the composite NiS(0.14)/CdS-6 could achieve a H{sub 2} evolution rate up to 1517 μmol h{sup −1} and show high photocatalytic stability for H{sub 2} evolution under long-term light irradiation. The rate of H{sub 2} evolution on NiS(0.14)/CdS-6 is about 7.5 times that of NiS(0.14)/CdS-3 and 33 times that of CdS-6. The notable improvement can be attributed to the fast electron transfer from CdS to NiS, which is proved by the surface photovoltage spectroscopy and photoluminescent measurements, as well as the increasing percentage of hexagonal-CdS in the mixture of cubic and hexagonal CdS.« less