Heterointerface-engineered iron and cerium based bimetallic nanosheets for energy-efficient hydrogen production via nucleophilic sulfide oxidation assisted alkaline seawater electrolysis.

Developing energy-efficient and corrosion-resistant electrocatalysts for alkaline seawater electrolysis remains a critical challenge for sustainable hydrogen production. In this work, we report a rationally designed FeO(OH)-CeO2 heterointerface nanosheets catalyst (FeCe-NS) directly grown on nickel foam for enhanced hydrogen evolution reaction (HER) and sulfide oxidation reaction (SOR). The strong electronic coupling between Fe 3d and Ce 4f orbitals induces interfacial charge redistribution, abundant oxygen vacancies (OV), and optimized hydrogen adsorption energetics. As a result, the FeCe-NS electrode performs a lower HER overpotential of 88 mV in 1 M KOH at 10 mA cm-2 and maintains excellent activity (98 mV) in seawater-containing electrolytes, demonstrating remarkable chloride tolerance. Electrochemical impedance spectroscopy (EIS) and double-layer capacitance (Cdl) measurements demonstrate enhanced charge-transfer kinetics and a greater number of active sites that are electrochemically accessible, attributable to the ultrathin nanosheet architecture. Importantly, replacing the kinetically hindered oxygen evolution reaction (OER) with the kinetically favorable SOR significantly reduces the overall cell voltage to 0.51 V at 10 mA cm-2 in a symmetric FeCe-NS electrolyzer, achieving ∼67.11% savings in energy consumption compared with conventional HER||OER overall water splitting. The SOR proceeds with ∼91% Faradaic efficiency at 0.5 V vs. RHE, corresponding to an elemental sulfur (S8) production rate of 54 mg h-1, while the HER delivers 95% Faradaic efficiency, confirming high selectivity and minimal parasitic losses at both electrodes. The system further maintains long-term operational stability, underscoring its practical viability. This work reveals interfacial orbital engineering as an effective strategy for low-energy, seawater-compatible hydrogen production coupled with value-added sulfur recovery.