Nonprecious Core–Shell Catalysts for Durable High-Performance Water Electrolysis

Electrocatalysts, suitable for at-scale applications, must integrate high activity, long-term durability, and cost-effectiveness, with the latter presenting a major challenge for platinum-group-metal (PGM) electrocatalysts. Alkaline systems enable the use of cost-effective transition metals. However, developing non-PGM electrocatalysts that can catalyze the high-potential oxygen evolution reaction (OER) with high stability remains challenging. Here, we report on metallic Ni catalysts with a Co- and Fe-rich shell (Ni@FeCo), which, during OER operation, transforms into an active oxide shell. Anion exchange membrane water electrolyzers (AEMWEs) employing Ni@FeCo catalysts exhibited excellent performance, reaching 10 A cm–2 at 2.18 V. Operando X-ray characterizations revealed the oxidation of Co and Fe, while Ni remained mostly metallic across all AEMWE operating potentials. Structural characterization, by scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS), revealed that the active Ni@FeCo catalysts feature a metallic Ni core and a Ni–Fe–Co spinel oxide shell. This metal-core/oxide-shell heterostructure provides efficient electron transport and OER activity while remaining stable under AEMWE operating potentials. The Ni@FeCo catalysts operated stably for over 1700 h in an AEMWE, highlighting their potential for practical applications and demonstrating a viable strategy for designing nonprecious metal-based electrocatalysts.