Facile Tri‐Metallic Catalyst Fabrication Using the Dynamic Hydrogen Bubble Template method

Abstract Electrocatalysts play a fundamental role in enabling and enhancing the efficiency of a variety of energy‐transition‐relevant reactions (e.g. water electrolysis, fuel cells, and CO ₂ conversion to value‐added products). Multi‐elemental electrocatalysts are particularly attractive because they often outperform their mono‐ or bi‐metallic counterparts. However, the design and fabrication of such catalysts with high surface area remains challenging due to limitations in synthetic control and compositional complexity. Here, the Dynamic Hydrogen Bubble Template (DHBT) method is used—a facile approach to fabricate freestanding, binder‐free metallic foams with hierarchical porosity—to synthesize Ni‐based mono‐, bi‐, and tri‐metallic electrocatalysts. The materials are subsequently annealed and evaluated for two model reactions: oxygen evolution and glucose oxidation. Annealing enhances both crystallinity and electrochemically active surface area (ECSA), likely due to Mn surface segregation and nanocrystallization at grain boundaries. Among the compositions, NiMn exhibits the highest post‐anneali mass‐normalized ECSA (36 m ² ), although this does not translate into improved catalytic activity. In contrast, NiMn and NiMnFe achieve the highest mass‐specific activities, followed by NiFeMo. Anion Exchange Membrane Water Electrolysis tests (AEMWE) showed that NiMnFe achieved over 3.4 A cm ⁻² at 2.0 V in alkaline conditions. This study demonstrates that DHBT is a viable and versatile method for fabricating multimetallic electrocatalysts with tunable porosity and composition, enabling the controlled synthesis of porous multi‐metallic structures and offering a promising route toward high‐entropy alloy formation through electrolyte composition tuning and annealing procedures.