Mastering Electrocatalytic Microenvironment Achieves Aqueous Hydrogen Batteries Exceeding 200 Wh kg-1

High-safety, low-cost, and long-life aqueous hydrogen gas batteries (AHGBs) driven by hydrogen electrocatalysts are considered one of the most reliable systems in advanced aqueous batteries for large-scale energy storage. However, the rational design of low-loading and high-activity electrocatalysts remains a challenge for bifunctional hydrogen oxidation and evolution reaction (HOR/HER) catalysis to unleash the potential for higher-performance AHGBs. In this study, we propose an atomic engineering approach that precisely tailors the reactive microenvironments for the catalytic interface in AHGBs. A coupling Ru-based catalyst with high activity is developed as a demonstration. Theoretical calculations and in situ spectroscopy reveal that the synergy between Ru and Ni sites effectively accelerates the microenvironmental water dissociation process, while the interfacial hydrogen bond network is significantly optimized, collectively accelerating reaction kinetics and facilitating mass transfer. The assembled nickel-hydrogen (Ni-H2) battery with a low loading of 40.5 μgRu cm-2 exhibits stability over 3000 cycles at a high current density of 30 mA cm-2, more than 4 times that of the battery with Pt/C catalyst. Importantly, a 5 Ah-scale Ni-H2 battery achieves the highest energy density of 204.4 Wh kg-1 among previously reported AHGBs, which even exceeds most state-of-the-art aqueous batteries and conventional LiFePO4 batteries. This work highlights atomic-level design for mastering reactive microenvironments, offering a strategy to develop efficient, low-cost electrocatalysts toward high-energy-density AHGBs in practical energy storage applications.