Abstract: The photoelectrochemical behavior of the passive film on iron in pH=8.4 borate buffer solution was investigated. The mechanism considered for the generation of the photocurrent in the passive film, and the principle of the measurement of photocurrent were discussed. The band model of noncrytalline semiconductor was used to demonstrate the depedence of photocurrent on electrode potential and light wavelength. Results indicate that the passive film formed on iron in pH=8.4 borate solution is a noncrystalline semiconductor, its flatband potential (φ_(fb)) is -0.30 V(SCE), band gap energy (E_g) is affected by measuring potential (φ_m), When +0.30 V<φ_m<+0.80 V (SCE), E_g is 1.9 eV.

Key words: Passive film on iron, Semiconductor, Photoelectrochemical behavior, Photocurrent, Flatband potential