Constructing a Graphene-Encapsulated Amorphous/Crystalline Heterophase NiFe Alloy by Microwave Thermal Shock for Boosting the Oxygen Evolution Reaction

Abstract

Rationally designing efficient and robust catalysts for the oxygen evolution reaction (OER) is increasingly vital for energy conversion technologies. Herein, we develop a core–shell electrocatalyst consisting of an amorphous/crystalline heterophase NiFe alloy encapsulated by ultrathin graphene layers (a/c-NiFe-G) via a rapid microwave thermal shock strategy. The amorphous/crystalline heterostructure generates enriched active sites with high intrinsic activity, while the graphene coatings serve as electron transport pathways and protective layers, resulting in dramatically enhanced OER performance in 1 M KOH with an overpotential (η10) of 250 mV at 10 mA cm–2, a Tafel slope of 36.5 mV dec–1, a high turnover frequency (TOF) of 0.87 s–1 that is 24 times as high as that of the crystalline counterpart when evaluated on a glassy carbon electrode. Further, when supported on porous Ni foam, the catalyst exhibited an η10 as low as 217 mV, along with excellent durability (136 h). Various characterization methods, including X-ray absorption fine structure analysis and density functional theory calculations, reveal that unsaturated coordination configurations and abundant amorphous/crystalline boundaries in a/c-NiFe-G are responsible for its superior OER performance. This work offers insights for constructing metastable amorphous/crystalline heterophase catalysts toward highly efficient electrocatalysis.