Dependence of the Band Bending of the Oxide Semiconductors on pH

The dependence of the band bending of the oxide semiconductors on p H have been studied by measuring the flatband potential photopotential, and rest dark potential in the solution without redox species. The rest dark potentials were almost constant with p H, while the flatband potential showed the 60 mV/ p H dependence. This indicates that only the band in the space charge layer bends by p H with the 60 mV/ p H dependence under the rest dark potential state. The flatband states were held at for , , , and , respectively, under the rest dark potentials The above phenomenon is based on the reaction of the oxide surface state with H + and/or OH − in the solution. This mechanism is described in detail. The enhancement of the water photolysis on catalyst by the alkaline treatment is well explained by the large band bending in alkaline solution under the rest dark potential state.