Visible light induced generation of hydrogen from H₂S in mixed semiconductor dispersions; improved efficiency through inter-particle electron transfer

Abstract

Electron transfer from the conduction band of CdS to that of Ti02 particles occurs in alkaline suspensions containing SHions and is exploited to improve the performance of a system that decomposes H2S with visible light.

Effects of the preparation method of the ternary CdS/TiO2/Pt hybrid photocatalysts on visible light-induced hydrogen production

“…For example, Reber and Rusek reported that platinized CdS (Pt-CdS) obtained by the photodeposition showed an enhanced hydrogen production rate of 300 mL/h at 1.5 wt% loading of Pt, 10 whereas Serpone et al observed that the enhancement of hydrogen production by platinization was almost negligible. 23 Although photoplatinization is expected to make a better contact at the Pt/CdS interface than physical mixing, the former was reportedly much less effective than the latter for the photocatalytic degradation of lactic acid. 32 The surface chemistry of CdS usually interferes with the photochemical reduction of Pt ion (Pt 4+ ) as follows:…”

“…It enhanced hydrogen production compared to plain CdS, 25 but sometimes lowered the efficiency by 8 times. 23 We report a comparative study on the hybridization of CdS, TiO 2 , and Pt in terms of hydrogen production and photocurrent generation under visible light (l > 420 nm). It was found that changing the order of hybridization in the preparation step significantly altered the efficiency for both hydrogen production and photocurrent generation.…”

“…Therefore, the CdS-based photocatalytic system can be applied to producing hydrogen from water containing electron donors (e.g., wastewaters). The photocatalytic efficiency of CdS is substantially influenced by various factors such as crystallinity, 9 surface area, 10 surface etching, 11,14,15 pH and related properties (e.g., flat band potential, surface charge), [16][17][18][19][20] ED and solvent (e.g., alcohols, sulfide, sulfite), 10,18,21,22 cocatalyst (e.g., Pt, Ni), 10,14,15,[20][21][22][23][24][25][26][27] support materials (e.g., Al 2 O 3 , TiO 2 , ZnO, ZnS, zeolite, KNbO 3 ), 22,[28][29][30][31] etc. For hydrogen production, CdS particles are usually platinized either by physical mixing with Pt particles (e.g., Pt black, Pt sol) or by photoplatinization.…”

Photosensitization of TiO2 P25 with CdS Nanoparticles for Photocatalytic Applications

“…Differences in the electronic structure of nanocomposites based on metal oxides/sulphides have a profound influence on photocatalytic properties. The mixture of semiconductors based on TiO 2 /CdS has attracted attention because of their potential applications in the photodegradation of organic pollutants [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16], the photoelectrolysis of water for hydrogen production [17][18][19][20], and the sensitization of solar cells [21,22]. Due to its wide band gap (3.0 for rutile and 3.2 eV for anatase), TiO 2 is able to absorb light in the UV range, which constitutes 3-5% of solar irradiation, while semiconductors with a narrower band gap, such as CdS, are effective under visible light.…”

Growth of TiO2 nanotube arrays with simultaneous Au nanoparticles impregnation: photocatalysts for hydrogen production

“…Since UV light only accounts for about 5% of the solar radiation that reaches Earth's surface, the inability to utilize visible light limits the efficiency of solar photocatalytic hydrogen generation. Thus, different strategies have been adopted in order to improve this efficiency, including: i) varying the sizes of the nanoparticles, 10 ii) doping with metal/non-metal ions, 11 iii) coupling the titanium dioxide with low band gap semiconductors, 12 and iv) supporting metallic/metal oxide nanoparticles on the oxide surface to promote electron and hole transfer reactions at the TiO 2 /substrate interface. 13,14 In addition, it is desirable to produce TiO 2 structures composed mainly of the anatase phase, because it has higher catalytic activity than the rutile phase.…”