Surfactant-assisted controlled synthesis of a metal-organic framework on Fe2O3 nanorod for boosted photoelectrochemical water oxidation

As an ideal semiconductor material, hematite (alpha-Fe2O3) has been applied extensively in the realm of photoelectrochemical (PEC) water oxidation in recent years. However, there still exist several intrinsic shortcomings, such as low surface reaction kinetics and positive onset potential. Here, metal-organic framework (MOF) with active Co sites (Co-ZIF-67) as cocatalyst has been grown onto the alpha-Fe2O3 nanoarrays with a facile surfactant-assisted controlled synthetic method, which can not only provide the seeds to the nucleation of MOF overlayer but also control the amount of MOF loading. Indeed, the photocurrent densities of the composites achieve an almost 2-fold value at 1.23 V vs. RHE and the onset potential is also significantly reduced by 180 mV relative to alpha-Fe2O3. The charge injection efficiency of Fe2O3@ZIF-67 composite is around 85% at 1.23 V vs. RHE, which is 1.6-times of alpha-Fe2O3 Electrochemical impedance spectroscopy and Bode analysis reveal that ZIF-67 overlayer can efficiently utilize the surface-reaching holes for PEC water oxidation and reduce surface charge recombination, thus facilitating water oxidation kinetics. Moreover, intensity modulated photocurrent spectroscopy further confirms the above conclusion. Consequently, the controlled synthetic method provides a pathway to induce the moderate growth of MOF overlayer on the semiconductor towards improving PEC performance.