Abstract
Visible-light-active Fe-POMs was fabricated
via
precipitating Fe
3+
with Keggin type polyoxometalates (H
3
PW
12
O
40
, H
4
SiW
12
O
40
or H
3
PMo
12
O
40
) under solvothermal condition. The as-prepared Fe-POMs were denoted as FePW, FeSiW and FePMo, respectively. Among the three kinds of Fe-POMs, FePMo displayed the highest visible light absorption, the largest specific surface area, the most sensitive photocurrent response and the smallest charge transfer resistance, which were all beneficial for heterogeneous photocatalysis. The efficiency for Cr(VI) reduction was
ca.
88% by FePMo after 50 min visible light irradiation. The estimated rate constant(0.042 min
−1
) was
ca.
2.5 and 1.8 times that by FePW and FeSiW, respectively. FTIR spectra indicated that the Keggin structure of PMo
12
O
40
3−
was maintained in FePMo. Mechanism study indicated that the photogenerated electrons in LUMO and the holes in HOMO were thermodynamically feasible for Cr(VI) reduction and H
2
O oxidation, respectively. Using FePMo as an optimized photocatalyst, good stability was also observed after 5 cyclic runs in both photocatalytic performance and XRD structure.