Photocatalytic Hydrogen Evolution over Exfoliated Rh-Doped Titanate Nanosheets

摘要

Various amounts of Rh-doped titanate nanosheets (Ti_(3)NS:Rh(x ), where x is doped amount) were prepared to develop a new nanostructured photocatalyst based on metal oxide compounds that can split water to produce H_(2) under sunlight. Ti_(3)NS:Rh(x ) was obtained by acid exchange, intercalation, and exfoliation of Rh-doped layered sodium titanate compound (Na_(2)Ti_(3–x )Rh_(x )O_(7)). A new energy gap was found in the diffuse reflection spectrum of the Ti_(3)NS:Rh(x ) colloidal suspension solution; this new energy gap corresponds to electrons in the 4d level of Rh~(3+) or Rh~(4+), which are doped in the Ti~(4+) site. A photocatalyst activity of Ti_(3)NS:Rh(x ) for H_(2) evolution in water with triethylamine (TEA) as an electron donor was investigated. The appropriate amount of Rh doping can improve the photocatalytic activity of Ti_(3)NS for H_(2) evolution from water using triethylamine (TEA) as a sacrifice agent. The reason was related to the rich state of Rh~(3+) or Rh~(4+) doped in the Ti~(4+) site of Ti_(3)NS. Doping Rh 1 mol % of Ti, Ti_(3)NS:Rh(0.03) shows the H_(2) evolution rates up to 1040 nmol/h, which is about 25 times larger than that of nondoped Ti_(3)NS under UV irradiation (>220 nm) and 302 nmol/h under near-UV irradiation (>340 nm). These results show that the development of new nanostructured photocatalyst based on Rh-doped titanate compounds that can produce H_(2) under near-UV irradiation present in sunlight was a success.