Interfacially engineered Co-MOF@P-SnCoFe layered double hydroxides electrocatalyst for chloride-resistant bifunctional water electrolysis in saline wastewater

The oxygen evolution reaction (OER) remains a major bottleneck in water electrolysis due to its sluggish kinetics, which fundamentally limits the overall efficiency of hydrogen production. In contrast, the urea oxidation reaction (UOR) offers a promising alternative with significantly lower overpotential, thereby reducing energy consumption. However, the development of stable and multifunctional electrocatalysts for simultaneous efficient hydrogen production and wastewater treatment poses a considerable challenge. In this study, a hierarchical amorphous Co-MOF-modified P-SnCoFe-layered double hydroxides (LDHs) heterostructure (denoted as Co-MOF@P-SnCoFe-LDHs) electrocatalyst was developed through a “MOF interfacial anchoring-dual doping electronic reconstruction” strategy, which integrates ZIF-67 Co-MOF with P/Sn co-doped CoFe-LDHs. The optimized catalyst exhibits exceptional bifunctional activity, achieving outstanding UOR performance with potentials of 1.34 and 1.53 V (vs. RHE) to achieve current densities of 10 and 50 mA cm −2 , respectively. For the OER, it requires low overpotentials of 213 mV (1 mol L −1 KOH) and 237 mV (oilfield wastewater) at 10 mA cm −2 . Mechanistic studies reveal that the spatial confinement effect of amorphous Co-MOF enhances chloride corrosion resistance, leading to a 27% improvement in operational stability. Concurrently, π–d conjugation between the imidazole ligands and the Sn–P network facilitates charge transfer, reducing the charge-transfer resistance by 31% ( R ct  = 1.98 Ω). Furthermore, the constructed multi-phase interfaces promote the generation of active intermediates at lower applied potentials (1.0–1.1 V vs. RHE). This work provides a rational catalyst design strategy for energy-efficient hydrogen production and wastewater treatment under harsh saline conditions. Graphical abstract Co-MOF@P-SnCoFe-LDH/NF was successfully prepared via a simple electrodeposition-immersion method. The π–d conjugation between imidazole ligands and the Sn-P network facilitates charge transfer, while the constructed heterogeneous interface promotes the generation of active intermediates at a low applied potential (1.0–1.1 V vs. RHE), enabling efficient hydrogen evolution and wastewater treatment under high-salt conditions.