Highly Stable Bifunctional Heterostructured Electrocatalyst Integrated with LDPE‐Derived Spherical Carbon for Longevous Alkaline Seawater Splitting

Abstract The development of innovative electrocatalysts for seawater splitting shows great potential for large‐scale green energy. Specifically, interface engineering plays a vital role in improving surface properties and charge transfer. However, seawater electrolysis encounters considerable challenges like chloride‐induced corrosion, impurities, and microorganisms that hinder efficiency. Herein, we design a highly durable electrocatalyst based on selenium‐enriched NiMn‐S _x supported on low‐density polyethylene‐derived spherical carbon‐Ni foam (Se‐NiMnS _x @SC/NF) using combination of pyrolysis and hydrothermal processes. The resulting Se‐NiMnS _x @SC/NF bifunctional catalyst with hollow cycas cone structure exhibited exceptional electrochemical performance and corrosion resistance in alkaline seawater with an ultralow overpotential of 146 and 262 mV for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) to achieve a large current density of 500 mA cm⁻ ² . In a simulated alkaline seawater splitting setup, the Se‐NiMnS _x @SC/NF catalyst maintained a cell voltage of 2.07 V at 500 mA cm⁻ ² , demonstrating outstanding durability for over 100 h with ≈100% Faradaic efficiency. Se and S doping in the heterostructured electrocatalyst refines the electronic structure and boosts reaction kinetics, while the hollow cycas cone design increases the exposure of active sites. Additionally, the carbon layer provided strong resistance to seawater corrosion, making Se‐NiMnS _x @SC/NF an excellent bifunctional catalyst for alkaline seawater electrolysis.