The Photochemical Oxidation of Zinc and Cadmium Sulfide

Markham, M. Glare; Barry, J. C.; Iava, Marion; Haddad, Janet

doi:10.1021/j150558a025

Cited by 5 publications

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“…They 122 also noted that H 2 was liberated via the reaction Zn(0) + 2 H + → H 2 + Zn 2+ . In addition, enhanced photochemical activities have been reported after photoreduction of metal sulfides. ,, …”

Section: Discussionmentioning

confidence: 99%

“…In addition, enhanced photochemical activities have been reported after photoreduction of metal sulfides. 110,111,123 Gutierrez and Henglein 124 reported that highly reactive elemental Cd deposits were formed during the illumination of colloidal CdS in the presence of SO 3 2or S 2 O 4 2-. They reported quantum yields for the formation of Cd(0) of φ ) 0.005 in the absence of excess Cd 2+ and φ ) 0.053.…”

Section: Discussionmentioning

confidence: 99%

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Photocatalytic Production of H₂ on Nanocomposite Catalysts

Ryu

Choi

Balcerski

et al. 2007

Ind. Eng. Chem. Res.

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The photocatalytic production of H2 in water with visible light using nanocomposite catalysts, which include quantum-sized (Q-sized) CdS, CdS nanoparticles embedded in zeolite cavities (CdS/zeolite), and CdS quantum dots (Q-CdS) deposited on KNbO3 (CdS/KNbO3 and Ni/NiO/KNbO3/CdS), is investigated. The rate of H2 production in alcohol/water mixtures and other electron donors at λ ≥ 400 nm is the highest with the hybrid catalyst, Ni/NiO/KNbO3/CdS with a measured quantum yield, φ, of 8.8%. The relative order of reactivity as a function of catalyst is Ni(0)/NiO/KNbO3/CdS > Ni(0)/KNbO3/CdS > KNbO3/CdS > CdS/NaY-zeolite > CdS/TiY-zeolite > CdS, while the reactivity order with respect to the array of electron donors is 2-propanol > ethanol > methanol > sulfite > sulfide. In addition, the rates of H2 production from water and water−alcohol mixtures are correlated with fluorescent emission spectra and fluorescence lifetimes. Irradiation of Ni/NiO/KNbO3/CdS proceeds via the partial reduction of Cd(II) to Cd(0) on the surface of CdS. The coupling of Ni(0)/NiO and Cd(0) on the surface of KNbO3 appears to have some of the chemical principles of a Ni/Cd battery at high overvoltages. Evidence for the formation of nickel hydride as an important intermediate has been obtained.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Photocatalytic Production of H₂ on Nanocomposite Catalysts

Ryu

Choi

Balcerski

et al. 2007

Ind. Eng. Chem. Res.

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The effects of pH and adsorbed hydrolysed metal ions on the photodissolution of colloidal cadmium sulphide

Hayes

Freeman

Mulvaney

et al. 1987

Ber Bunsenges Phys Chem

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Colloides J PhotochemistryThe quantum yields for the photodissolution of colloidal CdS in Ludox stabilized aerated solutions, have been measured as a function of pH. It has been found that the quantum yield decreases with increasing pH. Electrophoresis measurements indicate that this decrease is due to the formation of Cd2+ hydrolysis products on the surface of the colloid as the pH is increased. Support for this conclusion is obtained from experiments in which hydrolysed Co", Nil' and Zn" species were deliberately deposited onto CdS colloids. The reactions involved in the photocorrosion of CdS are discussed in light of the present results and with respect to mechanims proposed in the literature. IntroductionThe thermal-and photo-oxidation of metal sulphides have received considerable attention over many years because of their relevance to mineral flotation [l]. The products of oxidation are various: elemental sulphur, metal hydroxides, thiosulphates (SzOi-), polythionates (S,O;-, x = 2 -6), sulphate (SO: -) and volatile SO2. The amount and type of oxidation product depends on the conditions such as pH, oxygen pressure, temperature, presence of catalytic agents and duration of the oxidation reaction.In more recent years the photo-oxidation of metal sulphides has come under quite intense study because of the possibility of utilizing some colloidal metal sulphides as photocatalysts for the production of H2 from water [2]. CdS in particular has been extensively investigated because its catalytic activity can be initiated using visible light, an important advantage for the photochemical conversion of solar energy [3].Although a good deal of understanding of the photooxidation of CdS has been attained, there remain some aspects that are unclear. The purpose of the present study was to provide additional information on the photo-degradation of CdS as a function of pH and in the presence of hydrolysable metal ions in order to explain some of the observed photocatalytic behaviour of CdS colloids. To this end we have investigated CdS particles in 3 systems (i) CdS/Ludox solutions, (ii) CdS in water (iii) systems (i) and (ii) with added hydrolysable metal ions. The two metal ions Ni" and Co" were investigated in order to test their potential as scavengers for photoproduced holes in CdS. Both ions have been shown to catalyse H2Oz/OZ formation from H 2 0 [4,5].

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