Abstract:

Developing robust bifunctional catalysts for water splitting is challenging. High-entropy phosphides (HEPs) have attracted significant interest owing to their tunable electronic structure and stability, yet their synthesis is hindered by incompatibility among multiple metallic and nonmetallic elements. Herein, to the best of our knowledge, we report the first successful synthesis of (CoFeNiCuY)_XP HEP via a continuous-wave (CW) CO₂ laser–assisted phosphidation technique. This rapid and energy-efficient strategy facilitates the direct formation of compositionally homogeneous HEP at ambient conditions, obviating conventional high-temperature and chemically aggressive phosphidation protocols. The synthesized (CoFeNiCuY)_XP catalyst demonstrates outstanding bifunctional catalytic performance, requiring low overpotentials of 234 mV for the oxygen evolution reaction and 206 mV for the hydrogen evolution reaction at a current density of 10 mA cm⁻². Consequently, the assembled electrolyzer requires a low cell voltage to drive overall water splitting (OWS) and exhibits excellent catalytic stability. In-depth analysis of OWS kinetics using in situ Raman reveals information on reaction intermediates, while ex situ X-ray diffraction confirmed excellent electrochemical stability of (CoFeNiCuY)_XP. This study establishes a facile and scalable synthesis route based on CW CO₂ laser phosphidation for high-entropy compounds, harnessing their transformative potential for energy conversion and electrocatalysis via precise entropy engineering.