Exploring the semiconductor characteristics of a polyoxometalate-based organic-inorganic hybrid dimer and its photocatalytic applications

Polyoxometalate-based organic-inorganic hybrid compounds have been widely used in the field of photocatalysis, photoelectrocatalysis, interfacial materials of semiconductor device. However, their intrinsic semiconductor characteristics such as carrier diffusion lengths and carrier mobility are still unclear. Herein, we first unravel the carriers diffusion length and carrier mobility of the novel POM-based dimeric compound, {(HBW 12 O 40 )[Cu(2,2 ' -bipy) 2 ] 2 [CuO(2,2 ' -bipy)(H 2 O)]} 2 & sdot; 2H 2 O ( 1 ), which is successfully synthesized through coassembly of binuclear Cu(II)-complex and BW 12 in hydrothermal reaction. Space charge-limited currents (SCLC) method shows that the holes carriers mobility ( mu h ) of this compound reached 0.84 cm 2 V -1 s - 1 , which is more 30 times than that of raw BW 12 (2.6 x 10 -2 cm 2 V -1 s -1 ). The calculated carrier diffusion lengths of compound 1 is 82 nm, which is almost 3 time higher than that of BW 12 (25 nm), indicating that photogenerated carriers are more easily separated and diffused in compound 1 . Furthermore, the semiconductor properties of compound 1 have been demonstrated by the measurements of photocurrent response, VB-XPS spectrum and band gap (E g ) values. In addition, its applications of photocatalysis indicate the excellent activities of compound 1 with 71 % degradation rate for photodegradation of methylene blue (MB) and 67 % degradation rate for photocatalytic reduction of Cr(VI).