Enhanced Mass Transport in the Electrical Double Layer for Hydrogen Electrocatalysis toward Long-Life Ni–H₂ Batteries

The Ni–H2 battery has emerged as a promising candidate for grid-scale energy storage owing to its ultralong calendar-life over 30 years. However, its development is constrained by lacking an effective catalyst for alkaline hydrogen electrocatalysis at the anode. Herein, different from the traditional concept of charge transfer-determining activities, we suggest the importance of optimizing interfacial hydrogen-bond networks to enhance the mass transfer of water molecules, protons, and hydroxyls across an electrical double layer (EDL), given the severely damaged interfacial water networks in strong alkaline electrolytes used for the Ni–H2 battery. We provide a low-cost model catalyst of defect-rich N–Ni3C/Ni that possesses abundant OH-grafting sites. The EDL structures are reconstructed through an OH-induced hydrogen-bond connectivity with interfacial water. The resultant electrode shows performance that can compete with a commercial Pt/C electrode. Notably, this electrode exhibits excellent duration over 7137 h and discharge capacity over 214,110 mAh cm–2, with overpotential <65 mV at an oxidative current of 30 mA cm–2. Moreover, the Ni–H2 cell achieves an unprecedented cyclability with negligible decay over 3000 cycles under a high capacity of 30 mAh cm–2. A practical 8-Ah Ni–H2 battery with lifetime over 2400 cycles further validates scalability. This work demonstrates the importance of mass transfer in EDL via interfacial hydrogen-bond networks toward a long-life Ni–H2 battery.