Activating La-O-Ni Bridge in Ordered Macroporous Interface for Electrochemical Urea Wastewater Purification.

Electrochemical treatment of urea wastewater purification significantly aids in environmental protection, but it remains a considerable challenge in designing high performance anode urea oxidation electrocatalysts. Herein, we report a La-induced three-dimensional ordered macroporous (3DOM) NiO heterostructure to improve Ni sites electron density for urea electrooxidation by activating the La-O-Ni bridge. This material demonstrated exceptional performance in a membrane electrode assembly (MEA) device, characterized by a low cell voltage (1.49 V @ 80 °C) and 280 h stability test at 1 A cm-2 current density (25 °C) and displayed promising efficiency in urea wastewater purification. Permeation experiments revealed the crucial role of 3DOM morphological in facilitating mass transfer processes. A high valence nickel mechanism (HNM) on the La-O-Ni bridge during catalysis was proposed, based on various in situ characterizations and theoretical calculations. Experimentally, in situ Raman and UV-vis spectra demonstrated that Ni active species Niδ+ (δ ≥ 3) promote urea oxidation kinetics, while in situ ATR-IR proved strong adsorption of C=O with Ni sites and the enhancement of urea N-H bonds cleavage, supporting the HNM. This work enables us to underscore the critical importance of La-O-Ni electron bridge with 3DOM architectures and promising contributions to urea wastewater purification.