Effect of direct and indirect in-situ sonochemical synthesis methods of MWCNTs–CoNiFerrite on the hydrogen storage

This work includes the synthesis of MWCNTs–CoNiFerrite composites in two methods, direct method and indirect method; however, in both cases, ultrasound was used as an environmentally friendly method. These composites were characterized using XRD, SEM, and TEM to verify the compositional effects of both methods, which would have effects on hydrogen storage capacity. The XRD measurements showed that, in both cases, cobalt–nickel ferrite was formed on the carbon nanotubes. Furthermore, the SEM and TEM measurements proved that the composition of the resulting materials was different in shape and size. The prepared composites were used as new materials for hydrogen storage in the solid state, using two different temperatures, 298 and 77 K, at a pressure ranging from 0 to 900 mmHg. The results showed that the H 2 storage results reached 1.65 and 1.12 wt% at 77 K for both direct and indirect synthesized MWCNTs–CoNiFe 2 O 4 , respectively, which indicates the importance of the preparation method in the ability to store gases. Graphical Abstract Highlights MWCNTs–CoNiFerrite composites were produced by direct and indirect ultrasonic methods. The composites were used for hydrogen storage at 298 and 77 K, and at a pressure ranging from 0 to 900 mmHg. The results showed that at 77 K, the storage results reached 1.65 and 1.12 wt% for both MWCNTs–CoNiFe 2 O 4 by the direct and indirect methods, respectively.