A Zr/Sm co-doped Fe2O3:NiCo-MOF heterojunction photoanode for augmented photoelectrochemical water splitting

It is of utmost importance to enhance the photoelectrochemical water splitting effectiveness of Fe2O3 photoanodes by addressing photoanode/electrolyte interface defects, as well as bulk and surface charge carrier recombination. Herein, Zr/Sm co-doped Fe2O3 in conjunction with a bimetallic NiCo-metal–organic framework (MOF) cocatalyst to construct an n–p heterojunction is reported. The bulk conductivity was significantly improved by Zr/Sm co-doping, which was accomplished by increasing donor density. The NiCo-MOF cocatalyst passivated surface-trapping states/recombination surface states via alleviating the Fermi level pinning effect, hastened hole transfer to the electrolyte by suppressing surface charge recombination and recombination within the space-charge layer and extended hole lifetime at the intermediate surface states. In addition, the formed p–n heterojunction between NiCo-MOF and Zr/Sm–Fe2O3 facilitated bulk conductivity by utilizing an internal built-in electric field at the interface of the heterostructure. As a result, at 1.23 VRHE, the Zr/Sm–Fe2O3:NiCo-MOF exhibited a photocurrent density of 2.36 mA cm−2 with surface charge separation and surface charge transfer efficiencies of 95.3 and 91.6%, respectively. This present investigation offers valuable insights into the rational design of co-doped semiconductors with MOF-based heterojunctions for the intent of photoelectrochemical water splitting.