Co-doped Carbon Layer to Lower the Onset Potential of Hematite for Solar Water Oxidation

Abstract Hematite is a promising photocatalyst for water oxidation while the practical performance of hematite has been hindered by poor conductivity and strong charge recombination. Here we report a Co-doped carbon layer on hematite to significantly enhance the solar water oxidation performance, which shows a large cathodic onset potential shift of 300 mV representing one of the largest values ever reported for hematite photoanodes. The final photocurrent at 1.23 V vs. RHE can also achieve a high value of 2.24 mA/cm 2 . Based on synchrotron radiation X-ray absorption spectroscopy, the thin Co-doped carbon layer consists of both sp 2 carbon structure with good conductivity and embedded CoCO 3 (or CoO) with good OER kinetics. A thin layer itself can also block the surface defects to suppress the recombination. Thus the Co-doped carbon layer can act as a triple functional material to simultaneously improve the surface conductivity, block the surface defects, and accelerate the OER process, which can finally result in a large onset potential shift. The facile method to decorate hematite with an effective carbon layer may help for the rational design of hematite with high efficiency.