An unprecedented FeB-based co-catalyst for Fe2O3 nanorod photoanodes is explored for the first time by a simple room-temperature dipping method. The FeB overlayer formed in situ, which inherently possesses good interfacial contact, can remarkably suppress charge carrier recombination in Fe2O3 photoanodes and dramatically decrease electrode/electrolyte interface resistance. These beneficial features promote a twofold increment in photocurrent density and significantly reduce the onset potential of Fe2O3 photoanodes. Furthermore, their photoelectrochemical (PEC) performance can be further improved by co-loading of Co-Pi. The photocurrent density of 1.9 mA/cm(2) at 1.23 V vs. RHE and the particularly low onset potential of 0.61 V, which is dominantly smaller than those reported so far, can be realized controllably. Hence, our work suggests a new and promising co-catalyst for Fe2O3 photoanode. It also offers a facile strategy for fabricating low-cost and efficient PEC solar energy conversion devices. (C) 2017 Elsevier Inc. All rights reserved.