Decoration of Co-MOF on α-Fe2O3 for boosting photoelectrochemical water oxidation in alkaline and neutral electrolyte

Hematite (α-Fe2O3) shows great promise for photoelectrochemical (PEC) water splitting due to the advantages of broad light absorption, abundant reserves and environmental friendliness, however faces challenges of unsatisfactory charge separation and charge transfer. In this work, series surface modification was adopted to facilitate charge separation and charge transfer between Fe2O3 semiconductor / electrolyte interface. At first, polyethylene pyrrolidone (PVP) molecules was employed as intermedia to treat Fe2O3 electrode surface, then an ultrathin Co based metal-organic framework (Co-MOF) shell was controllably grown on PVP-Fe2O3. As a result, the as-fabricated Co-MOF/PVP-Fe2O3 photoelectrode displays photocurrents of 1.9 times and 5.3 times as pristine Fe2O3 towards water oxidation at 1.23 V vs. RHE in alkaline and neutral solution, respectively. Photoluminescence (PL) spectroscopy, Mott-Schottky and electrochemical impedance spectroscopy (EIS) measurements reveal that the superior performance of Co-MOF/PVP-Fe2O3 attributes to the lower carrier recombination, higher electron density and faster interfacial charge transfer brought by the decoration of Co-MOF. This study offers a valuable insight into the architectural design of MOFs/semiconductor hybrid photoelectrodes for PEC reactions.