A Powder That Whips Itself into Shape express
Iron powder heated to 650–800 degrees absorbs hydrogen like a dry sponge soaks up water. But after a few cycles, the particles fuse into a dense lump, and the sponge stops working. Adding tungsten changes the picture: with each heating, the powder foams itself, staying loose and porous.
In a reactor with a kilogram of such powder, researchers managed to store 42 grams of hydrogen and use 96% of its capacity over 30 cycles. Even after 90 incomplete cycles, the powder didn't lose its ability to absorb gas. Tungsten evaporates when heated and travels through the pores, preventing particles from sticking together.
This storage method is safer than pressurized tanks and cheaper than cryogenic containers. Iron powder with tungsten is a compact and reliable "sponge" for hydrogen, which can be used at fueling stations or in energy storage facilities.
Original abstract
as written by the authors arXiv:2602.22807
H2-H2O redox cycling of iron powder beds at 650-800 {\deg}C offers a compact, safe, economical hydrogen storage method, but sintering-induced capacity loss has stalled its scalability for decades. Here, we show that adding redox-active tungsten to Fe powders solves this problem in static powder beds: Fe-25W (at%) alloyed powder self-foams during redox cycling via W gas-phase transport, increasing porosity and preserving capacity. In a custom automated reactor, a kilogram-scale powder bed reversibly stores 42g H2 and sustains 96+/-3% capacity utilization over 30 redox cycles. Temperature-resolved in-situ X-ray diffraction reveals a chemical-vapor-transport-mediated self-foaming mechanism that redistributes W to refine the microstructure, complemented by a contact-barrier stabilization mechanism during high-temperature holds. Partial-capacity cycling up to 90 cycles further confirms sintering resistance under incomplete redox conditions. These results establish Fe-W powder beds as a robust, scalable, and compact platform for safe, stationary hydrogen storage.
Tungsten is one of the most refractory metals: it melts at 3422°C, but in this process it evaporates already at 650°C and travels through the powder like steam through a teapot.