As one of the components of dye-sensitized solar cells (DSSCs),the counter electrode (CE) catalyst plays a role in promoting the catalytic reduction of I3-to I-in the electrolyte and collecting electrons from external circuits.Pt is recognized as an optimal CE;however,its limited reserves and high price have restricted industrial production of Pt-based DSSCs.Therefore,developing a Pt-free catalyst is critical to application of DSSCs.Taking into account special layered structure of nickel-iron layered double hydroxide (Ni-Fe LDH),Ni-Fe LDH was used as a precursor and pyrolyzed to controllably synthesize flake-like Ni-Fe bimetallic oxide of NiFe2O4 in this work.The special flake-like structure of NiFe2O4 can expose more effective catalytic active sites,thereby accelerating the process of triiodide reduction reaction.The assembled DSSC with NiFe2O4 CE achieves an outstanding photoelectric conversion efficiency of 6.15%,which is close to that ofPt CE (7.32%) and higher than that ofNi-Fe LDH CE (1.05%).Further,the catalytic mechanism of NiFe2O4 promoting triiodide reduction reaction is deeply explored by density functional theory.The present work highlights a simple and controllable method by pyrolysising LDH to create high-performance electrocatalysts for triiodide reduction reaction and other important electrochemical reactions.