Hydrogen sorption capacity of diatomaceous earth for geological hydrogen storage

The increasing importance of hydrogen energy has driven the demand for large-scale hydrogen storage facilities. Cavern storage in underground hydrogen reservoirs has received the most widespread attention, but many places in China lack suitable salt formations for this storage option. Here, we evaluate the hydrogen storage capacity of Jilin diatomaceous earth as a potential alternative material for large-scale hydrogen storage. The basic features of samples collected from Linjiang (Jilin, China) were characterized through scanning electron microscopy, X-ray diffraction, X-ray fluorescence spectroscopy, and nitrogen adsorption-desorption analyses. The diatomaceous earth samples showed well-preserved diatom frustules, primarily of the Coscinodiscus Ehrenberg type, resembling circular sieves with evenly distributed mesopores and macropores. The nitrogen adsorption-desorption curves exhibited type IV isotherms (IUPAC classification) with an H3 hysteresis loop, indicating well-developed pores with diameters mainly in the 20-100 nm range. The samples demonstrated strong hydrogen sorption capacity, with a sorption of 1.5 cm3/g at 25 degrees C and 4 MPa. The sorption capacity was proportional to the specific surface area and total pore volume. The confirmed reserve of Jilin diatomaceous earth in Jilin Province (3.8 x 108 t) can potentially sorb 5.7 x 108 m3 of hydrogen, indicating a large hydrogen storage capacity. Our study provides a new perspective for exploring materials with large-scale hydrogen storage capability.