Enhanced visible-light activities of porous BiFeO3 by coupling with nanocrystalline TiO2 and mechanism

In this work, different mole ratio percentage of nanocrystalline anatase TiO2/porous nanosized BiFeO3 (T/P-BFO) nanocomposites with effective contacts have been fabricated by putting the as-prepared P-BFO into the TiO2 sol, followed by drying at 80°C and then calcining at 450°C for 2h. The photoactivities of the obtained products for pollutant degradation and H2 evolution were measured. It is clearly demonstrated by means of the steady-state surface photo-voltage spectra, the transient-state surface photovoltage responses, and the photoluminescence spectra that the photogenerated charge carriers in the T/P-BFO nanocomposites with a proper mole ratio percentage of TiO2 (9%) display much long lifetime and high separation in comparison to the resulting P-BFO alone. This is well responsible for the enhanced activities for degrading gas-phase acetyldehyde, the liquid-phase phenol, and for producing H2 under visible-light irradiation. Based on the measurements of formed hydroxyl radical amount and photoelectrochemical behavior, it is suggested that the improved separation of photogenerated charges in the fabricated T/P-BFO nanocomposite is mainly attributed to the spatial transfer of visible-light-excited (λ≤500nm) high-energy electrons of P-BFO to TiO2. This work will provide a feasible route to enhance the photoactivities of visible-light responsive oxide composites as photocatalysts for efficient solar energy utilization.