Cascade Design and Facile Fabrication of Cu/Cu2O/CuAl-Layered Double Hydroxides as Efficient Nitrate Reduction Electrocatalysts

Abstract

Nitrate (NO₃¯) reduction reaction (NITRR) presents a promising pathway for the production of renewable NH₃ while concurrently decontaminating NO₃¯ wastewater. However, the multi-electron transfer sequence and complex reaction network involved in NO₃¯ conversion pose significant challenges to achieving high Faradaic efficiency (FE). Herein, this work presents ternary Cu/Cu₂O/CuAl-layered double hydroxides (LDHs) catalysts designed through a cascade approach and synthesized via a straightforward one-step electrodeposition method. The resulting catalysts demonstrate peak activity at -0.4 V versus RHE, achieving an impressive $F{E}_{N{H}_3}$ of 92.0%, which significantly surpasses most reported binary and ternary catalysts. Density functional theory calculations and atomic force microscopy reveal that the Cu/Cu₂O/CuAl-LDHs exploit cascade design by integrating three distinct functions essential for efficient NO₃¯ reduction: CuAl-LDH initiates NO₃¯ adsorption, Cu(111) and Cu₂O(111) cooperatively facilitate NO₃¯ activation, and Cu(111) promotes NH₃ desorption. Durability tests further confirm that both NH₃ yield and $F{E}_{N{H}_3}$ remain stable after 10 cycles, indicating the excellent stability of the Cu/Cu₂O/CuAl-LDHs catalysts. These findings underscore the critical role of cascade design strategies in enhancing the performance of electrocatalysts for NO₃¯ reduction to NH₃, providing a transformative approach for sustainable ammonia synthesis.

Keywords: cascade design; density functional theory calculations; facile fabrication; nitrate reduction; ternary system.