Self-sacrificial FeOOH-triggered Co(OH)2 heterointerface enables Co3+ enrichment and boosted high-current oxygen evolution

Hierarchical Co(OH) 2 /FeOOH is constructed via a facile one-step heterogeneous nucleation strategy. • Self-sacrificial FeOOH nanoneedles protects Co-based active phases under high current. • Efficient Co 2+ →Co 3+ conversion enriches high-valence active sites for accelerated OER kinetics. • The catalyst delivers an low overpotential of 275 mV at 200 mA cm −2 . • The catalyst achieves remarkable operational stability for over 450 h at 1 A cm −2 for OER. Cobalt hydroxide-based catalysts are promising candidates for electrochemical water splitting, yet their practical application in industrial electrolysis is hindered by insufficient activity under high-current conditions. Herein, we rationally construct a hierarchical Co(OH) 2 /FeOOH composite via a one-step heterogeneous nucleation strategy, where FeOOH nanoneedles are uniformly anchored on Co(OH) 2 nanosheets frameworks. The composite achieves an ultra-low overpotential of 275 mV at 200 mA cm −2 for oxygen evolution reaction (OER), with a lower Tafel slope. More notably, it maintains stability with negligible potential fluctuation over 450 h under an industrially relevant current density of 1 A cm −2 . The FeOOH promotes efficient Co 2+ →Co 3+ valence transition, while the hierarchical interfacial interactions enhance charge transfer efficiency and stabilize high-valence Co active species. A unique self-sacrificial mechanism is unveiled that preferential tip dissolution of FeOOH nanoneedles effectively protects the underlying Co-based active sites from over-oxidation and structural collapse, thereby ensuring long-term catalytic stability. Mechanistic studies further suggest that Co(OH) 2 /FeOOH exhibits enhanced lattice-oxygen-participated character relative to CoFe-LDH, which tends to follow the adsorbate evolution mechanism. This work develops a self-sacrificial interface engineering strategy to boost the activity and stability of Co(OH) 2 , and provides a feasible structural design paradigm for developing durable OER electrocatalysts toward industrial-relevant high-current conditions. A unique self-sacrificial interface engineering strategy to boost the activity and stability of Co(OH) 2 for oxygen evolution reaction. Download: Download high-res image (157KB) Download: Download full-size image