Phase Diagram and Theoretical Calculation Guided Rational Design of Cu _6.26 Sn ₅ /Sn Heterostructured Aerogel for Hydroxylamine Electrosynthesis

ABSTRACT

Electrosynthesizing hydroxylamine (NH ₂ OH) from nitrite (NO ₂ ⁻ ) promises a green alternative to the hazardous Raschig process, yet catalyst development is trapped in a persistent selectivity–activity dilemma. Excessively strong adsorption of intermediates on the catalyst drives the over‑reduction of ^* NH ₂ OH to ammonia, whereas overly weak adsorption depletes the interfacial reactant supply and yields to the competing hydrogen evolution reaction. Herein, guided by binary phase diagrams and density functional theory calculations, we report a one‐step co‐reduction strategy for the general synthesis of 3D intermetallic/metal heterostructured aerogels with freely tunable components—bypassing the sacrificial templates required by conventional methods. The resultant aerogel comprises a porous Sn scaffold decorated with Cu _6.26 Sn ₅ intermetallic nanoparticles that form stable heterointerfaces. With cyclohexanone trapping in 0.5 

Na ₂ SO ₄ , the Cu ₁₀ Sn ₉₀ heterostructured aerogel achieves a remarkable Faradaic efficiency of 79.7% and yield rate of 0.731 mmol h ⁻¹  cm ⁻² toward cyclohexanone oxime. Molecular dynamics simulations reveal that the Cu _6.26 Sn ₅ phase accelerates interfacial NO ₂ ⁻ accumulation and mass transport, whereas the Sn scaffold serves as the dominant active center to undergo the reduction of NO ₂ ⁻ and boost ^* NH ₂ OH desorption. This study delivers a novel material design strategy for heterostructured aerogels toward highly selective electroreduction of NO ₂ ⁻ to NH ₂ OH.