Enhanced photoelectrochemical water splitting efficiency of hematite electrodes with aqueous metal ions as in situ homogenous surface passivation agents.

Passivation of surface states is known to reduce the onset photocurrent potential by removing the Fermi level pinning effect at the Helmholtz layer and enhance the photocurrent plateau by suppressing recombination loss in the space charge region. We report for the first time that metal ions can effectively passivate surface states in situ that improves the photoelectrochemical (PEC) performance of hematite electrodes. Among metal ions studied, Cr(iii), Mn(ii), Fe(ii), Co(ii), Cu(ii) and Zn(ii) were found to enhance the photocurrent by 30-300%; whereas photocurrent density significantly dropped by 90% in Ni(ii) solution after 90 min of illumination.