Rational design of hierarchical defect-rich NiSe2/Se-NiCuOx heterostructures: Modulating electronic structure for exceptional ammonia oxidation performance

Direct ammonia oxidation reaction (AOR) is a promising route for efficiently removing ammonia-nitrogen from wastewater. However, the sluggish kinetics and poor N 2 selectivity present significant challenges for AOR catalysts. Herein, a novel cost-effective hierarchical catalyst was constructed by selenizing NiCuO x nanorods on nickel foam support (NiSe 2 /Se-NiCuO x /NF) via the hydrothermal-calcination selenization method. The selenizing procedure radically manipulates the surface structure of NiSe 2 /Se-NiCuO x /NF, enriching it with oxygen vacancy defects and heterostructures to achieve high efficiency towards AOR. Consequently, the optimal NiSe 2 /Se-NiCuO x /NF only requires 1.50 V to achieve a current density of 65 mA cm - 2 . Furthermore, the N 2 selectivity was up to 98.18% after 5 h of electrolysis. Density functional theory (DFT) calculation elucidates that the defects and heterostructures effectively facilitates electron transfer between NiSe 2 and Cu 2 O, significantly reduces the energy barrier of the rate-determining step (RDS) of O-S mechanism. This work demonstrates the feasibility of metallic selenides as efficient electrocatalysts for AOR.