The photocatalytical activities for water decomposition of K4R2M10O30 (R = Y, La, Ce, Nd, Sm; M = Ta, Nb) and their photophysical properties based on the first principle calculation

Series of photocatalysts K4R2M10O30 (R = Y, La, Ce, Nd, Sm; M = Ta, Nb) were presented as iso-structural compounds by solid-state reaction method. These photocatalysts showed water decomposition activities under λ > 300 nm irradiation with Na2SO3 and AgNO3 solution acting as hole and electron scavenges respectively. Among them, R = Ce demonstrated water decomposition activities under visible light irradiation (λ > 420 nm) and R = La showed overall water splitting activities under λ > 300 nm irradiation. The first principle calculation based on density functional theory with Plane-wave pseudo potential method and Generalized Gradient Approximation was conducted on M = Nb as representatives to investigate their electronic structure closely, so did on their precursor oxides. Combined with the electronic structures and absorption properties, the band structures of K4R2M10O30 (R = Y, La, Ce, Nd, Sm; M = Ta, Nb) were proposed and this model of band structure is in good agreement with their photocatalytical activities. Furthermore, the visible light responsive ability of R = Ce, as the only one among them, is regarded as the hybridization and overlap of partial occupied and unoccupied Ce 4f with O 2p and Nb 4d (Ta 5d), while in other cases, the band gap transition from O 2p to Nb 4d Ta (5d), which mainly consist their valence band and conduction band respectively, is dominant. Furthermore, there showed obvious inherent relationship between K4R2M10O30 (R = Y, La, Ce, Nd, Sm; M = Ta, Nb) and their precursor rare earth oxides in terms of electronic structure and photophysical properties.

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► Photocatalysts K4R2M10O30 (R = Y, La, Ce, Nd, Sm; M = Ta, Nb) were presented.
► These photocatalysts showed water decomposition activities under λ > 300 nm.
► Only R = Ce showed photocatalytical activities under λ > 420 nm.
► Their electronic structures were studied based on the first principle calculation.
► The band structures were proposed and showed good agreement with activities.