Interfacial Electronic Interactions in Hierarchical Heterostructure Electrocatalyst for Energy‐Saving Hydrogen Production at Industrial Current Densities

ABSTRACT Developing low‐energy‐input electrocatalytic systems for efficient hydrogen production is crucial for advancing sustainable energy technologies. The overall hydrazine splitting (OHzS) has emerged as a promising strategy to reduce the overall energy consumption by replacing the sluggish oxygen evolution reaction. Herein, a hierarchical heterostructure electrocatalyst is designed using a two‐step hydrothermal process, in which Pt nanoparticles are uniformly coupled with NiFe‐layered double hydroxide (LDH) nanosheets grown on vertically aligned cobalt fluoride nanorods (Co(OH)F NRAs), denoted as Pt/NF@CF. The Pt/NF@CF catalyst exhibits superhydrophilic and superaerophobic properties, enhancing mass and charge transfer, thereby promoting both the hydrogen evolution reaction (HER) and hydrazine oxidation reaction (HzOR). The structural analysis and theoretical simulations indicate significant interfacial electronic interactions between Pt nanoparticles and the NF@CF substrate. These interactions improve the adsorption of H 2 O and help maintain a balance between the adsorption and desorption of hydrogen intermediates, thereby facilitating the kinetics of the HER. Consequently, the Pt/NF@CF catalyst achieves overpotentials of 193 and 222 mV to drive 1000 mA cm −2 in alkaline freshwater and seawater, respectively, maintaining stable performance for over 200 h at 200 mA cm −2 . In an OHzS electrolyzer assembled with Pt/NF@CF serving as both electrodes, this system delivers 1000 mA cm −2 at only 1.05 V in alkaline freshwater and 0.99 V in seawater containing 0.5 M hydrazine, significantly outperforming conventional overall water splitting under the same conditions. This work presents a novel approach to developing bifunctional electrocatalysts that enable energy‐efficient hydrogen production at industrial‐level current densities.