Synergistic Effect of Ni2+ and Fe3+ of Bimetallic Oxyhydroxide NiFeOOH as OER Cocatalyst for Fe2O3 Photoanode with Enhanced Photoelectrochemical Water Splitting

Hydrogen production via photoelectrochemical water splitting represents one of the sustainable development approaches for future energy. Herein, we demonstrate the fabrication optimization of alpha-Fe2O3 nanoparticles modified by bimetallic oxyhydroxide NiFeOOH layers. The optimized alpha-Fe2O3/NiFeOOH photoanode is successfully applied for the photoelectrochemical hydrogen production process. The electrodeposition and annealing process of the alpha-Fe2O3 nanoparticles are optimized for better photoelectrochemical performance. NiFeOOH layers are subsequently deposited on the surface of the optimized alpha-Fe2O3 photoanode by the impregnation process. The physical and chemical characterization results show that bimetallic oxyhydroxide NiFeOOH layers are modified on the surface of the alpha-Fe2O3 nanoparticles with an amorphous form. After optimization, a highly enhanced photocurrent density is achieved in the optimized alpha-Fe2O3 photoanode with a value of 0.96 mA/cm(2), which is 50-fold higher than that of the bare alpha-Fe2O3 photoanode (0.019 mA/cm(2)). After NiFeOOH layers were deposited, the photocurrent density of the alpha-Fe2O3/NiFeOOH photoanode is enhanced to 1.35 mA/cm(2) (measured at 1.23 V versus RHE), 1.53-fold and 80-fold higher than those of the optimized alpha-Fe2O3 and bare alpha-Fe2O3 photoanodes, respectively. In addition, the alpha-Fe2O3/NiFeOOH photoanode yields an improved applied bias photon-to-current efficiency of 0.13% (measured at 1.05 V versus RHE), 1.65 times higher than that of the optimized alpha-Fe2O3 photoanode. Photoelectrochemical and electrochemical characterization confirms that the synergistic effect of Ni2+ and Fe3+ of the NiFeOOH cocatalyst on accelerating the consumption of holes and promoting the surface OER dynamics could improve the efficiency of electron/hole separation and injection in the alpha-Fe2O3/NiFeOOH photoanode. Therefore, the PEC properties of the alpha-Fe2O3 photoanode are significantly improved.