Journals

Laser Photochemistry Laboratory

#252. High-Entropy Interphase Switching with 3d Transition Metal Crossover for Zinc–Nitrite Battery and Ammonia Supply
Author
Jayaraman Theerthagiri† , Juhyeon Park† , M.L. Aruna Kumari, Anuj Kumar, Yewon Oh, Mohd Ubaidullah, Myong Yong Choi *
Journal
submitted(2024)

Abstract: The electrochemical nitrite reduction (eNO 2 R) reaction advances a green strategy to ammonia (NH 3 ) production, while zinc–nitrite solution batteries enable a “three-in-one” strategy for electricity, NH 3 generation, and NO 2

− removal. However, developing low-cost,

selective, and durable electrocatalysts remains a challenge. Herein, a high-entropy Prussian blue analog (HEPBA) was synthesized via coprecipitation of divalent 3d transition metal crossover (Co, Ni, Cu, and Zn) with trivalent Fe species. This then underwent high-entropy interphase switching into a single-phase spinel high-entropy oxide (FeCoNiCuZn-high-entropy oxide [HEO]) via calcination, followed by pulsed laser irradiation in liquids to form a highentropy alloy (FeCoNiCuZn-high-entropy alloy [HEA]). The HEA electrocatalyst reaches a Faradaic efficiency of 88.9% for NH 4

+ production during eNO 2 R, with a utmost yield rate of

894.3 μg h −1 cm −2 at −1.0 V versus Ag/AgCl, while maintaining stability over multiple cycles.

The superior eNO 2 R performance of FeCoNiCuZn-HEA, compared to HEPBA and HEO, stems from its stable atomic arrangement, along with the combined effects of lattice defects and high-entropy stabilization. In situ and ex situ spectroscopy, validated via density functional theory, confirm the eNO 2 R pathway on the uniformly distributed active sites on the HEAsurface, involving NO 2-adsorption, deoxygenation, protonation, and NH 4

+ formation through *NO and *NOH 2 intermediates. Finally, an aqueous Zn–NO 2 battery using the HEA cathode exposes a high open circuit voltage of 1.4 V versus Zn/Zn 2+ and a power density of 2.14 mWcm −2 , along with an impressive NH4+ production.