The ultrafast reconfigurability and ultrahigh durability of an NiFe phosphide electrocatalyst with an Fe-rich surface induced by in situ acid corrosion for water oxidations

Abstract

NiFe-based catalysts are expected to replace commercially available noble metal-based electrocatalysts for the oxygen evolution reaction (OER) owing to their reconfigurability into high-performance NiFe oxyhydroxides from their phosphides. However, how to rapidly reconstruct NiFe phosphides into oxyhydroxides for efficient water oxidation remains a challenge in this field. In this work, we proposed an in situ acid corroding-phosphating strategy to build a Fe-rich layer-coated NiFe phosphide electrocatalyst on NiFe foam (o-NiFeP/NFF). Our uniquely synthesized o-NiFeP/NFF delivers an extremely low overpotential of 224 mV to achieve 100 mA cm⁻² and holds ∼320 mA cm⁻² at an overpotential of 427 mV for 468 h without degeneration, demonstrating excellent activity and stability in the OER. Acid corrosion not only facilitates the immediate conversion of phosphides to oxyhydroxides in alkaline electrolytes, but also increases the surface Fe/Ni atomic ratio, thereby significantly enhancing water oxidation activity. Moreover, the monolithic nature between a electrocatalyst and a conductive substrate substantially enhances the stability of the catalyst, which was achieved by obtaining the metal ions in the electrocatalyst through acid etching of the conductive substrate. This work not only constructs a highly reconfigurable electrocatalyst, but also proposes a straightforward and universal strategy to fabricate durable OER electrocatalysts.