Solid-Liquid-Gas Management for Low-Cost Hydrogen Gas Batteries.

Aqueous nickel-hydrogen gas (Ni-H 2 ) batteries with excellent durability (>10,000 cycles) are important candidates for grid-scale energy storage but are hampered by the high-cost Pt electrode with limited performance. Herein, we report a low-cost nickel-molybdenum (NiMo) alloy as an efficient bifunctional hydrogen evolution and oxidation reaction (HER/HOR) catalyst for Ni-H 2 batteries in alkaline electrolytes. The NiMo alloy demonstrates a high HOR mass-specific kinetic current of 28.8 mA mg -1 at 50 mV as well as a low HER overpotential of 45 mV at a current density of 10 mA cm -2 , which is better than most nonprecious metal catalysts. Furthermore, we apply a solid-liquid-gas management strategy to constitute a conductive, hydrophobic network of NiMo using multiwalled carbon nanotubes (NiMo-hydrophobic MWCNT) in the electrode to accelerate HER/HOR activities for much improved Ni-H 2 battery performance. As a result, Ni-H 2 cells based on the NiMo-hydrophobic MWCNT electrode show a high energy density of 118 Wh kg -1 and a low cost of only 67.5 $ kWh -1 . With the low cost, high energy density, excellent durability, and improved energy efficiency, the Ni-H 2 cells show great potential for practical grid-scale energy storage.