Abstract
Surface states passivation is known capable of reducing onset photocurrent potential through reducing Fermi level pinning effect occurring at Helmholtz layer and enhancing photocurrent plateau via suppressing recombination loss at space charge region. In this preliminary study, we noted that solution metal ions could function as in situ homogeneous surface passivation reagents and thus improve photoelectrochemical performance of hematite electrodes. Among examined metal ions, Cr(III), Fe(II), Co(II), Cu(II) and Zn(II) were found to enhance the photocurrent by 30 - 300 % while Ni(II) significantly reduces the PEC performance and Mn(II) has no significant influence. We further hypothesized that these surface states might be high affinity adsorption sites on hematite surfaces. Once they are occupied with solution metal ions, surface states are passivated along with the induced Schottky barrier effect at the hematite/solution interface created by adsorbed metal ions and therefore PEC performance is greatly enhanced.