Over 7500 Cycles Achieved in Platinum-Group-Metal-Free Ni-H2 Battery Through Reversible Hydrogen Spillover.

Abstract

Traditional Ni-H2 batteries employing platinum-group metal (PGM) catalysts exhibit ultralong lifetimes (> 10 000 cycles), yet comparable durability has not been achieved in recently developed PGM-free systems, mainly due to sluggish hydrogen evolution and oxidation reactions (HER/HOR) in alkaline media. Herein, we employ reaction-dependent hydrogen spillover across a metal-support interface to decouple the physical and electrochemical hydrogen steps onto distinct active sites, thereby accelerating HER/HOR kinetics and markedly extending battery lifetime. As a proof of concept, we develop a low-cost catalyst consisting of Ni nanoclusters supported on oxygen-deficient TiO2-x. Owing to the difference in *H adsorption strength, hydrogen species migrate from Ni to TiO2-x during HOR and in the reverse direction during HER, enabling physical hydrogen processes on Ni and electrochemical steps on TiO2-x. The resulting electrode exhibits polarization performance surpassing that of Pt/C and outstanding durability for both HER and HOR, sustaining 3000 h operation at 15 mA cm-2. Moreover, the assembled Ni-H2 battery delivers excellent wide-temperature performance (-20°C to 55°C) and achieves over 7500 cycles at a practical capacity of 15 mAh cm-2. This work demonstrates that hydrogen spillover-enabled decoupling of HER/HOR steps provides an effective route toward ultralong-life PGM-free Ni-H2 batteries.