Unique amorphous/crystalline heterophase coupling for an efficient oxygen evolution reaction.

Designing amorphous/crystalline heterophase catalysts is still in the initial stage, and the study of amorphous/crystalline heterophase and carbon-free catalysts has not yet been realized. Herein, we report a unique amorphous/crystalline heterophase catalyst consisting of NiFe alloy nanoparticles (NPs) supported on Ti 4 O 7 (NiFe/Ti 4 O 7 ) for the first time, which is achieved by a heterophase supporting strategy of dual heat treatment. Surprisingly, the amorphous/crystalline heterophase is flexibly composed of amorphous and crystalline phases of alloy NPs and Ti 4 O 7 . The heterophase coupling endows the catalyst with a low overpotential (256 mV at 10 mA cm -2 ), a small Tafel slope (47 mV dec -1 ) and excellent endurance stability (over 100 h) in 1 M KOH electrolyte, which already outperforms commercial RuO 2 (338 mV and 113 mV dec -1 ) and exceeds most reported representative carbon-based and titanium-based non-precious metal catalysts. The density functional theory (DFT) calculations and experimental results reveal that the unique amorphous/crystalline heterophase coupling in NiFe/Ti 4 O 7 results in electron transfer between the alloy NPs and Ti 4 O 7 , allowing more catalytically active sites and faster interfacial electron transfer dynamics. This work provides insights into the synthesis of amorphous/crystalline heterophase catalysts and can be generalized to the heterophase coupling of other transition metal-based electrocatalysts.