Prussian-Blue-Analogue-Derived Ultrathin Co<sub>2</sub>P-Fe<sub>2</sub>P Nanosheets for Universal-pH Overall Water Splitting.

Zhang, Ju-Zhen; Zhang, Zichu; Zhang, Hong-Bo; Mei, Yi; Zhang, Feng; Hou, Peng-Xiang; Liu, Chang; Cheng, Hui-Ming et al. · Nano Lett · 2023

basic_science · Level V

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Abstract

The great interest in large-scale electrochemical water splitting toward clean hydrogen has spurred large numbers of studies on developing cost-efficient and high-performance bifunctional electrocatalysts. Here, a Prussian-blue-analogue-derived method is proposed to prepare honeycomb-like ultrathin and heterogeneous Co<sub>2</sub>P-Fe<sub>2</sub>P nanosheets on nickel foam, showing low overpotentials of 0.080, 0.088, and 0.109 V for the hydrogen evolution reaction (HER) at 10 mA cm<sup>-2</sup> as well as 0.290, 0.370, and 0.730 V for the oxygen evolution reaction (OER) at 50 mA cm<sup>-2</sup> in alkaline, acidic, and neutral electrolytes, respectively. When directly applied for universal-pH water electrolysis, excellent performances are achieved especially at ultralow voltages of 1.45 V at 10 mA cm<sup>-2</sup>, 1.66 V at 100 mA cm<sup>-2</sup>, and 1.79 V at 500 mA cm<sup>-2</sup> under alkaline conditions. <i>In situ</i> Raman spectroscopy measurements demonstrate that the excellent HER performance can be attributed to heterogeneous Co<sub>2</sub>P-Fe<sub>2</sub>P while the ultrahigh alkaline OER performance originates from reconstruction-induced oxyhydroxides.