Effects of inorganic electron donors in photocatalytic hydrogen production over Ru/(CuAg)0.15In0.3Zn1.4S2 under visible light irradiation

Abstract

Selection of appropriate electron donors is important for charge transfer and photocatalytic hydrogen (H 2 ) production from water. The influence of different inorganic electron donors (i.e., I À , S 2À /SO 3 2À , S 2À , SO 3 2À , Fe 2þ , and Ce 3þ ) on H 2 production was investigated on the (CuAg) 0.15 In 0.3 Zn 1.4 S 2 photocatalyst under visible light. The highest photocatalytic H 2 production rates were 1750, 1317, 820, 360, 260, 10 lmol g À1 h À1 with electron donors of 0.2M KI, 0.25M Na 2 S in combination with 0.35M Na 2 SO 3 , 0.25M Na 2 S, 0.35M Na 2 SO 3 , 0.2M FeCl 2 , and 0.2M Ce 2 (SO 4 ) 3 , respectively. I À was determined as the most effective electron donor for (CuAg) 0.15 In 0.3 Zn 1.4 S 2 photocatalyst, probably because (1) the redox potential of I 3 À /I À is relatively more suitable than those of other redox pairs for the charge transfer to valence band and (2) the positive surface charge of the (CuAg) 0.15 In 0.3 Zn 1.4 S 2 photocatalyst at the solution pH of 2 facilitates the absorption of I À and subsequent reaction with the valence band holes. The effect of the initial I À concentrations on the H 2 production and the potential reaction routes of I À on the photocatalyst were both analyzed to shed light on the reaction mechanisms. This study compared the efficacy of different inorganic electron donors in improving photocatalytic H 2 production and provided fundamental insight into the search of appropriate electron donors and the efficient photocatalytic system design. V C 2014 AIP Publishing LLC. [http://dx.

Effect of different hole scavengers on the photoelectrochemical properties and photocatalytic hydrogen evolution performance of pristine and Pt-decorated TiO2 nanotubes

“…In the presence of Na2SO3, however, only 6 µL of H2 was produced, which is 2.15 times less than in the hole scavenger free 0.1 M Na2SO4 electrolyte (12.9 µL). It should be mentioned that certain hole scavengers are known to produce H2 in the absence of any photocatalysts, for example by light-induced decomposition [15,42]. In our example, the contribution of this reaction to the overall H2 evolution is significant only under irradiation at wavelengths below 300 nm [42], and therefore such short wavelengths were not considered in this work.…”

“…In the EDTA case, strong surface adsorption leads to species forming inner-sphere complexes on the surface of TiO2 (such as oxalic and formic acid) that can be directly oxidized by valence band holes, while in case of weaker interaction with TiO2 via hydrogen bonds, hole scavengers are less effective due to outer sphere reactions, the latter reaction being less effective and resulting in slower H2 evolution rates [46]. On the other hand, excessive adsorption of hole scavengers may lead to the occupation of active sites at the surface of a photocatalyst leaving no available sites for H2 evolution [15], and the decreased H2 evolution rates by Ce-doped TiO2 nanoparticles at high sulfite ion concentrations were also observed in [24]. This may explain the detrimental effect of Na2SO3 on the H2 evolution observed in the present study.…”

“…A wide range of compounds have been investigated for TiO2 nanopowders and particles, including various organics (alcohols [7][8][9][10][11][12], organic acids [8,[10][11][12][13] etc.) and inorganics (S 2-, SO3 2- [7,11,[14][15][16], H2S [14], I -/IO3 - [11,15], Ce 3+ [15,17], Fe 2+ [15] etc.). These species have a suitable energetics for a direct hole capture from TiO2 or for the reaction with intermediate •OH radicals.…”

Effects of RhCrOx Cocatalyst Loaded on Different Metal Doped LaFeO3 Perovskites with Photocatalytic Hydrogen Performance under Visible Light Irradiation

“…The results indicate that at 20% TEOA, the high hole capture capability could effectively accelerate the separation of photo-generated electron-hole pairs upon light irradiation, leading to the highest photocatalytic hydrogen evolution performance. However, when the photocatalysts were tested at 30% TEOA, it is likely that the excessive adsorption of hole scavengers occupied the active sites at the surface of the photocatalyst, leaving no available sites for H 2 evolution [40] and generating a corresponding decrease in H 2 evolution rates.…”

The inhibitory effect of graphene oxide on photocatalytic hydrogenation from organic fatty acids

“…Photocatalytic H 2 production was conducted in the same apparatus as described in our previous works . Figure shows that C‐TiO 2 produced more H 2 than C‐TiO 2 /rGO in the presence of acetic and propionic acids.…”