Improving charge transfer kinetics of Ti-doped hematite photoanodes via surface modification with metal phytate complexes as cocatalysts for photoelectrochemical water oxidation

Abstract

Oxygen evolution catalysts (OECs) coating on metal-based oxide photoelectrodes has been considered as a very effective approach to boost photoelectrochemical (PEC) activity. In the study, the metal (Fe-, Co-, Ni- and Mn-) based phytate complexes as OECs were employed on Ti-doped hematite (Ti-Fe₂O₃) photoanode to promote charge migration and enhance PEC water oxidation performance. As a result, the OECs modified-Fe₂O₃ photoelectrodes yielded improved PEC photocurrent compared with that of Ti-Fe₂O₃ photoanode and the Ni-based phytate complex (Ni-PA) decorated on Ti-Fe₂O₃ (TFO) achieved the best photocurrent registered at 0.87 mA·cm^-2 at 1.23 V vs RHE, which is about 1.5- and 21.8-fold stronger than the performance of Ti-Fe₂O₃ (0.57 mA·cm^-2) and pristine Fe₂O₃ (0.04 mA·cm^-2) photoelectrodes, respectively. Besides, the constructed TFO-NiPA photoanode presented a prominent improvement in the long-term PEC stability, the incident photon-to-current efficiency (IPCE) and surface charge separation efficiency in contrast to the TFO photoelectrode. The effect of Ni-PA layer on charge dynamics and PEC efficiency of Ti-Fe₂O₃ photoanode were further explored and the results implied the Ni-PA cocatalyst made significant contributions in increasing charge carrier density, accelerating charge transfer kinetics and improving charge transfer efficiency, which determined the enhanced charge separation and superior PEC performance. The work guides the rational design of hematite-based photoelectrode to boost solar water oxidation performance by decorating metal phytate cocatalyst.