FeCo-LDH@Ni <sub>3</sub> S <sub>2</sub> heterostructure with engineered d-band center for efficient oxygen evolution in alkaline electrolysis of freshwater and seawater
Wenjing LI, Xiaohong Cheng, Xiaoman Xiong, Qi Wu
Abstract
Abstract The search for efficient oxygen evolution reaction (OER) electrocatalysts capable of high-current-density water electrolysis is critical for scalable hydrogen production. Herein, we present a rationally designed FeCo-LDH@Ni3S2 heterostructure on nickel foam (NF), synthesized through a controlled approach. This electrode delivers ultralow overpotentials of 220, 235, and 245 mV at 10 mA·cm−2 in alkaline freshwater, simulated seawater, and natural seawater, respectively, alongside remarkable 100 h stability at industrial-level conditions (100 mA·cm−2 in seawater). Furthermore, a symmetric electrolyzer utilizing FeCo-LDH@Ni3S2 as both cathode and anode achieves low voltages of 1.60, 1.64, and 1.69 V at 10 mA·cm−2 in the corresponding electrolytes and exhibits over 100 h stability at 50 mA·cm−2. Density-functional theory (DFT) analysis confirms that the FeCo-LDH@Ni3S2 heterointerface enables charge redistribution, optimizes the d-band center, and reduces the energy barrier for OER rate-determining steps. This study demonstrates an effective interface engineering strategy for d-band center reduction via heterostructure design, offering a durable electrocatalyst for marine hydrogen production.