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Engineering a Stable High Entropy Infused Spinel Oxide for Electrocatalytic Conversion of Nitrate to Ammonia #MMPMID41319324
Raj G; Midya S; Nandan R; Bisen OY; Chakraborty A; Kumari M; Yadav AK; Singh AK; Nanda KK
Small 2025[Nov]; ? (?): e07803 PMID41319324show ga
A sustainable strategy to mitigate nitrate (NO(3) (-)) contamination in water involves its electrochemical reduction to ammonia (NH(3)), a valuable green fuel. However, nitrate reduction reaction (NO(3)RR) is hindered by sluggish kinetics and poor selectivity due to the competing hydrogen evolution reaction (HER). Herein a strategic synthesis of a spinel high-entropy oxide (HEAO) heterostructure is reported as an efficient electrocatalyst for NO(3)RR. The HEAO exhibits a Tafel slope of 275 mV dec(-1), a Faradaic efficiency of 84%, and an impressive NH(3) production rate of 314 micromol h(-1) cm(-2) at -0.6 V versus RHE. Mott-Schottky analysis reveals a high donor density and a low flat-band potential, which contribute to the enhanced reaction kinetics. Hydrophobicity studies demonstrate that the water-repellent nature of the HEAO suppresses the HER, favoring NO(3)RR selectivity. Finally, an energy conversion device based on this catalytic system is proposed, which delivers a promising open-circuit potential of 0.61 V and a peak power density of 2.3 mW cm(-2) at 27 mA cm(-2). A comprehensive density functional theory (DFT) analysis reveals that the Fe-Mn bridge site in HEAO possesses optimal adsorption energy for NO(3) (-) ions and its capability to selectively reduce NO(3) (-) toward NH(3).
Small 2025 ; ? (?): e07803
