Tuning Y‐Mg Supports for Improved Ni‐Catalyzed NH ₃ Decomposition: Structural Modulation and Mechanistic Insights

ABSTRACT Catalytic NH 3 decomposition has garnered substantial attention for hydrogen transformation and storage. Ni‐based catalysts continue to suffer from limited thermal stability and suboptimal low‐temperature activity, largely attributed to an incomplete understanding of the structure‐activity relationships and reaction mechanisms governing their performance. In this study, we designed and constructed a novel Y‐Mg bimetallic oxide support system to synergistically modulate the properties of Ni‐based catalysts for NH 3 decomposition. Unlike conventional Ni/MgO or Ni/Y 2 O 3 , the precisely tuned Y/Mg ratio in the 20Ni/YMg 8 catalyst creates a unique interface that couples the structural and electronic advantages of both components. A series of Ni‐based catalysts with varying Y/Mg ratios was synthesized, and the 20Ni/YMg 8 catalyst with a 1:8 ratio of Y: Mg achieved a hydrogen production rate of 29.77 mmol g cat −1 min −1 at 600°C. Characterizations revealed that Mg incorporation primarily increased surface area and refined Ni dispersion, whereas Y enhanced reducibility and active metal distribution. More importantly, their synergy optimally tailors the electronic structure of Ni and the distribution of basic sites, which collectively promote *NH 2 formation and accelerate N 2 desorption—the rate‐determining step. Mechanistic studies confirmed that the optimized catalyst promoted *NH 2 formation and accelerated N 2 evolution, indicating enhanced NH 2 activation and dehydrogenation. This study presents a rational design approach of bimetallic supports to modulate structural and surface properties, offering valuable insights into the development of efficient and stable Ni‐based catalysts for ammonia decomposition.