Micro‐ and Macrostructure Effects on Hydrogen Release Using 3D‐Printed Reactor‐Catalysts

We report the design, fabrication, and testing of 3D‐printed Al–stainless steel reactor‐catalyst monoliths for potassium borohydride hydrolysis. Three scaffold geometries—Gyroid, Schwarz P, and Schwarz P4534—were produced via selective laser melting. The monoliths were subjected to tailored acid and base leaching, increasing internal porosity and exposing and activating the catalytic sites. Structural and compositional analyses, including SEM‐EDX, XPS, and x‐ray diffraction (XRD), confirmed the homogeneous distribution of Al, Fe, Ni, and Cr, as well as the formation of an FeAl crystalline phase. Hydrogen release experiments at industrially relevant conditions showed that the Schwarz P and P4534 geometries gave the fastest hydrogen evolution, whereas the Gyroid structure was the slowest. This study highlights how 3D‐printed macrostructure design and surface activation can be combined to optimize metallic catalysts for a variety of applications.