Effect of Ni Content on the Microstructure and Catalytic Performance of NiFeCoCrMn Alloy

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Ammonia borane (AB) has drawn extensive attention in hydrogen production research due to its excellent hydrogen-storage properties. To address the challenges of agglomeration and difficult recovery associated with nanocatalysts, a series of macroscopic five-component, non-noble metal catalysts were fabricated via rapid solidification. With increasing Ni content, the catalyst transforms from a biphase structure with Mn solid-solution distributed on the face-centered cubic (FCC) matrix to a single-phase FCC structure. The distribution of the Mn element undergoes the following changes: solid-solution phase → grain-boundary segregation → uniform distribution. The catalytic activity shows a parabolic trend with the microstructural evolution of the catalyst. Among them, the Ni13.5 alloy exhibits the highest catalytic activity and excellent cycling stability, achieving a catalytic rate of 1292 mL –1 ·min –1 ·m –2 under standard conditions. Also, the activation energy is 15.13 kJ mol –1, which is lower than many nickel-based catalysts. The excellent catalytic performance of Ni13.5 can be attributed to two aspects. First, Mn segregation at grain boundaries accelerates etching, exposing numerous catalytically active Ni elements on the surface. Second, the electron enrichment around Ni enhances the catalytic activity. This study provides valuable insights for the design and development of macroscopic scale catalysts in hydrogen-related catalysis.