Chemical grafting of CoS onto C for hydrogen spillover and storage.

Metal modified C is considered to be a potential hydrogen storage medium due to its high theoretical capacity. Research interest is growing in various hybrid inorganic compounds-C. While the design and synthesis of a novel hybrid inorganic compound-C is difficult to attain, it has been theorized that the atomic hydrogen could transfer from the inorganic compound to the adjacent C surfaces via spillover and surface diffusion. Here, as a proof of concept experiment, we graft CoS onto Cvia a facile high energy ball milling process. The Raman, XPS, XRD, TEM, HTEM and EELS measurements have been conducted to evaluate the composition and structure of the pizza-like hybrid material. In addition, the electrochemical measurements and calculated results demonstrate that the chemical "bridges" (C-S bonds) between these two materials enhance the binding strength and, hence, facilitate the hydriding reaction of C during the hydrogen storage process. As a result, an increased hydrogen storage capacity of 4.03 wt% is achieved, along with a favorable cycling stability of ∼80% after 50 cycles. Excluding the direct hydrogen storage contribution from CoS in the hybrid paper, the hydrogen storage ability of C was enhanced by 5.9× through the hydriding reaction caused by the CoS modifier. Based on these experimental measurements and theoretical calculations, the unique chemical structure reported here could potentially inspire other C-based advanced hybrids.