Hollow nanocubic CoP-FeP/NC heterostructures for efficient electrocatalytic oxygen evolution reaction

Slow mass transport and charge transfer restrict the electrocatalytic oxygen evolution reaction (OER) activity of FeP. Herein, we synthesized Fe-based bimetallic Prussian blue analogues (CoFe, NiFe, and CuFe-PBAs), and further prepared nitrogen-doped carbon anchored FeP-based heterostructures namely CoP-FeP/NC, Ni2P-FeP/NC, and Cu3P-FeP/NC using template-assisted and phosphating annealing strategies. It is worth noting that CoP-FeP/NC shows a hollow nanocubic structure, shortening the ion transport pathway and facilitating surface atom exposure, thus improving reaction kinetics. Meanwhile, the similar atomic radius of Co and Fe promotes the formation of stable CoP-FeP heterointerfaces with the same crystal system components and low lattice mismatch, inducing the electron transfer from Co to Fe and generating more low-valent Fe cations, thereby enhancing activity. Besides, Co and Fe sites underwent surface reconstruction into CoOOH and FeOOH active species, therefore achieving efficient synergistic electrocatalytic OER. As a result, CoP-FeP/NC exhibits superior OER activity (254 mV@10 mA cm−2) than Ni2P-FeP/NC and Cu3P-FeP/NC in 1.0 M KOH solution, even exceeds commercial RuO2 (266 mV@10 mA cm−2), and presents no obvious performance decay (11.26 %) after continuous electrolysis at 100 mA cm−2 for 100 h, showing practical application prospects. Our work provides a general approach for preparing efficient and stable FeP-based heterostructures as OER electrocatalysts.