Selective converting surface states of hematite photoelectrodes to catalytic active sites

Abstract

AbstractPhotoelectrochemical (PEC) water splitting is capable of converting solar energy to hydrogen and recombination loss at surface states inevitably compromises its efficiency. Selective conversion surface states to catalytic active sites would, therefore, have positive effect on photocurrent enhancement. We first adopted Zn(II) and Cr(III) to in situ passivate surface state of hydrothermally grown hematite electrodes. By plotting the photocurrent onset potential against the fraction of occupied adsorption site by Zn(II) and Cr(III), we found that surface state accounted for 0.1% of active sites of hematite electrodes. The fully passivated hematite possessed a reduced photocurrent onset potential by 0.12 V in comparison with that of raw hematite. Importantly, additional heat treatment of fully passivated hematite provided a great opportunity to selectively convert surface states to catalytic sites. For example, low temperature (120°C) treatment of Zn(II) passivated hematite was noted to exhibit almost doubled photocurrent at 1.1 VRHE in comparison with that of raw hematite. Our experimental results would be valuable for the insights into the electrode/electrolyte interface phenomenon and the strategies for PEC efficiency enhancement.