In situ growth of ultrathin Co-MOF nanosheets on α-Fe2O3 hematite nanorods for efficient photoelectrochemical water oxidation

Abstract Efficient charge transport is an important factor in photoelectrochemical (PEC) water splitting. The charge transfer at the semiconductor/electrolyte interface is of great importance, especially for the complex water oxidation reaction. In this study, we explored the feasibility of improving charge transfer efficiency at the interface of semiconductor/electrolyte by in situ growth of Co based Metal-Organic Frame work (Co-MOF) through a facile ion-exchanging method. Under optimized conditions, the Co-MOF nanosheet-modified hematite gave a photocurrent density of 2.0 mA cm −2 (200% improvement) at 1.23 V RHE with a cathodic shift of 180 mV in the photocurrent onset potential, in comparison to bare α-Fe 2 O 3 (0.71 mA cm −2 @1.23 V RHE ). To elucidate the role of Co-MOF, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy and Mott-Schottky measurements were carried out. It was found that the atomically distributed Co 2+ in Co-MOF possessed excellent hole storage capability and charge transfer efficiency, as evidenced by the high surface capacitance and extremely low surface charge transfer resistance.