A hierarchically engineered FeCoP/Cu ₂ S flake-like clustered heterostructure with benchmark-level trifunctional electrocatalytic activity and long-term durability in challenging alkaline systems

Rational design of trifunctional electrocatalysts that can efficiently drive the HER, OER, and ORR on a single, efficient and robust electrode remains a key challenge for integrated energy conversion systems. Here, we construct a hierarchical FeCoP/Cu₂S core-shell architecture by growing a Cu₂S nanorod array directly on copper foam followed by electrodeposition of ultrathin FeCoP nanoflakes. The Cu₂S nanorods provide a highly conductive, corrosion-resistant, and binder-free 3D scaffold with abundant accessible sites, while the amorphous FeCoP shell supplies catalytically active multi-metal phosphide domains; the intimate FeCoP-Cu₂S interface promotes fast charge transfer and strong interfacial synergy. As a result, the FeCoP/Cu₂S catalyst achieves outstanding activity for all three key reactions: low overpotentials of 69 mV for HER and 147 mV for OER at 10 mA cm^-2 and an ORR half-wave potential of 0.81 V (limiting current 4.8 mA cm^-2) in alkaline media. When assembled in a two-electrode alkaline water electrolyzer, FeCoP/Cu₂S requires only 1.505 V to achieve 10 mA cm^-2 in 1.0 M KOH and 1.544 V in alkaline seawater, while maintaining excellent structural and electrochemical stability over 21 h of continuous operation. Moreover, the oxygen bi-functionality gap (Δ<i>E</i> = 0.67 V between the OER and ORR) compares favourably with state-of-the-art non-precious catalysts. This work demonstrates that combining a 1D Cu₂S current collector with an amorphous FeCoP shell is an effective strategy to engineer low-cost, self-supported, trifunctional electrocatalysts for overall water splitting and rechargeable metal-air batteries.