Understanding the Influence of Lattice Composition on the Photocatalytic Activity of Defect‐Pyrochlore‐Structured Semiconductor Mixed Oxides

Abstract

The defect‐pyrochlore‐structured photocatalyst CsTaWO6 is an ideal starting material for anion doping from the gas phase, and is known to be highly active for solar hydrogen generation under simulated sunlight without co‐catalysts. To investigate the active site of CsTaWO6 for hydrogen generation and to understand the effects of the two d0 elements in the compound, systematic and successive element substitution of tantalum and tungsten on the crystallographic 16c sites of the starting material has been performed. Substituting lattice tantalum with niobium hardly changes the band gap of the resulting compounds CsTa(1 −x)Nb x WO6, but the photocatalytic activity for hydrogen generation and oxidation reactions is strongly influenced. By investigating the surface reactivity toward adsorption, surface effects altering the activity are identified. In contrast, substituting lattice tungsten with molybdenum reduces the band gap of CsTaWO6 into the visible‐light range. Materials containing Mo are however not able to generate hydrogen anymore, due to the altered conduction band positions proven by density functional theory calculations. CsTaMoO6 exhibits a band gap of 2.9 eV and evolves oxygen efficiently under UV light irradiation after CoPi co‐catalyst deposition, and even under visible light small amounts of oxygen.

Fabrication of the heterostructured CsTaWO6/Au/g-C3N4 hybrid photocatalyst with enhanced performance of photocatalytic hydrogen production from water

“…4b, which is close to the previously reported [50,51]. But the band gap of CsTaWO 6 was calculated to be 3.30 eV, smaller than previous reports (3.8 eV [14] The photocatalytic generation of hydrogen from water was carried out on the different photocatalysts, and the photocatalytic activities were shown in Figure 6.…”

“…The corresponding Tauc plot was graphed by (αhv) 2 versus photon energy (hv). However, the CsTaWO 6 has been classified as an indirect optical transition type so that the Tauc plot was graphed by (αhv) 1/2 versus hv [14]. The band gap of g-C 3 N 4 was estimated to be 2.74 eV from the Tauc plots in Fig.…”

“…One capable example is CsTaWO 6 , which was reported to be photocatalytically active under UV light (Eg = 3.8 eV and 3.6 eV) [11][12][13][14][15]. This semiconductor photocatalyst with a defect-pyrochlore structure can generate hydrogen from aqueous alcohol without any cocatalyst under solar irradiation [8].…”

The Influence of Tin(II) Incorporation on Visible Light Absorption and Photocatalytic Activity in Defect‐Pyrochlores

“…[32] After ion exchange the elemental composition of the samples was Sn 0.09 K 0. 49 ). The large Sn surplus in the water exchanged sample results most likely from the parallel decompositiono ft in(II) acetate.…”

“…[49] K 2 CO 3 ,W O 3 (ChemPur, 9 9,9 %) and Ta 2 O 5 (H. C. Starck) have been mixed in as toichiometric 0.5:1:0.5 ratio in an agate mortar and subsequently calcined at 810 8Cf or 18 hi na ir atmosphere. [49] K 2 CO 3 ,W O 3 (ChemPur, 9 9,9 %) and Ta 2 O 5 (H. C. Starck) have been mixed in as toichiometric 0.5:1:0.5 ratio in an agate mortar and subsequently calcined at 810 8Cf or 18 hi na ir atmosphere.…”