Enhanced chemical looping hydrogen production via lattice engineering of NiFe2O4 with small-radius cations

This study investigates the enhancement of chemical looping hydrogen production (CLHP) performance in NiFe 2 O 4 oxygen carriers via B-site doping with small-radius metals (Al, Cr, Co, Ga). Experimental and density functional theory (DFT) results demonstrate that doping induces lattice contraction and increases FeO 6 octahedral distortion, thereby improving lattice oxygen mobility and reduction extent. Specifically, NiFe 1.8 Al 0.2 O 4 exhibited a 63.7% increase in H 2 yield compared to undoped NiFe 2 O 4 . Dopants with smaller ionic radii also raised oxygen vacancy formation energy, suppressing Ni reduction kinetics and promoting FeNi alloy formation, which enhanced cyclic stability. Optimal doping concentration was identified at x = 0.2. These findings provide valuable clues for designing high-performance oxygen carriers for efficient hydrogen.