Solar Water Splitting Using Powdered Photocatalysts Driven by Z-Schematic Interparticle Electron Transfer without an Electron Mediator

Abstract

Ru/SrTiO 3 :Rh photocatalyst powder for H 2 evolution and varied photocatalyst powders for O 2 evolution such as BiVO 4 and WO 3 were suspended in acidified aqueous solutions, resulting in showing activities for water splitting into H 2 and O 2 in a stoichiometric ratio without an electron mediator under visible light irradiation. The photocatalytic activities were dependent on pH. The highest activity was obtained at pH 3.5. An optical microscope observation of the aqueous suspension containing Ru/SrTiO 3 :Rh and BiVO 4 powders at pH 3.5 revealed that these powders aggregated with suitable contact. The condition of Rh doped in SrTiO 3 also affected strongly the photocatalytic activity and quenching of the photoluminescence of BiVO 4 . The high photocatalytic activity was obtained and the luminescence was remarkably quenched, when SrTiO 3 :Rh containing Rh species with reversible redox properties was used and mixed. These results indicated that the photocatalytic water splitting and quenching of the photoluminescence occurred through interparticle electron transfer from the conduction band of BiVO 4 to impurity level consisting of the reversible Rh species doped in SrTiO 3 . Thus, we succeeded in constructing unique and simple Z-scheme photocatalysis systems driven by interparticle electron transfer under visible light irradiation. In addition, the (Ru/SrTiO 3 :Rh)-(BiVO 4 ) system split water under simulated sunlight (AM-1.5).

Modeling, Simulation, and Implementation of Solar‐Driven Water‐Splitting Devices

“…[5c, 59] Two types of particle-based PEC systems, termed a Type 1 reactor for a single-vessel reactor (Figure 4 c1) and a Type 2 reactor for a dual-vessel reactor (Figure 4 c2), have been proposed conceptually and demonstrated experimentally at different levels of device integration. For the Type 1 reactor, single particle systems, including In 1Àx Ni x TaO 4 , [60] (Zn 1+x Ge)(N 2 O x ) solid solution, [61] (Ga 1Àx Zn x )(N 1Àx O x ) solid solution, [62] CoO [63] and C 3 N 4 /C-dots, [64] as well as tandem-particle systems, including SrTiO 3 :Rh//BiVO 4 [65] and nitrogen-doped graphene oxide (NGO) [66] that are electrically connected with a solidstate electron mediator have been investigated. The STH conversion efficiency in the demonstrated and stable Type 1 reactor systems is often low (< 2 %).…”

Functioning devices for solar to fuel conversion

“…Solar panels for heating and production of electricity as such do not store energy, although batteries and chemical flow batteries are available and being improved. Two other major routes suggest themselves, for storing the collected photonic energy in the form of chemicals: -H 2 production by water splitting [11][12][13][14][15][16] -CO 2 reduction, combined with water oxidation (to O 2 ), yielding liquids such as alcohols or even hydrocarbons. This process is commonly referred to as artificial photosynthesis [17][18][19][20][21][22][23].…”

“…Factors that determine the applicability of other catalysts than TiO 2 in photocatalytic water splitting are inertness and chemical stability (the catalyst should not change state in the process), the price, and the toxicity. An interesting design route to create a visible light sensitive water decomposition system is based on the so-called Z-scheme [14,49]. This is schematically illustrated in Fig.…”

“…The photo-excited electron of this second catalyst induces hydrogen generation. In particular, Kudo and co-workers [14,49] (Fig. 8) developed various visible-light-responsive catalyst systems for OWS based on a Z-scheme and an electron transfer by a Fe 2+ /Fe 3+ redox couple.…”

Photocatalytic Splitting of Water

“…Hence a useful system without any disadvantages has yet to be developed (Sayama et al 2001;Kato et al 2004;Abe et al 2005;Higashi et al 2008;Sasaki et al 2009;Abe et al 2009;Maeda et al 2010;Tabata et al 2010). (Sayama et al 2001;Sayama et al 2002;Abe et al 2001 (Erbs et al 1984;Kato et al 2004).…”