Optimization of hydrogen storage at ambient temperature via central composite design using hybrid nanocomposites of zeolitic imidazolate frameworks-8 incorporated rice husk graphene-like as adsorbent

Surface area and porosity are the main factors that affect hydrogen storage at room temperature. However, there are several external factors such as pressure of gas, reaction time and the amount of sample used during the process that might affect the performance of the hybrid nanocomposites towards hydrogen storage. In this study, central composite design (CCD) for response surface methodology (RSM) was used in determining the optimum conditions namely mass of sample (A), pressure of hydrogen gas (B) and reaction time (C) towards the hydrogen storage at room temperature. Rice husk derived graphene-like material (GRHC) was added into zeolitic imidazolate frameworks-8 (ZIF-8) to form a hybrid nanocomposite of ZIF-8/GRHC (ZGK) via in-situ synthesis. Due to synergistic effect, the surface area of ZGK (1065.51 m²/g) shows a great enhancement as 0.04 g GRHC was introduced as compared to pristine ZIF-8 (687.32 m²/g). On the other hand, the thermal stability of ZGK improved significantly as it can withstand up to 1000 ºC as compared to pristine GRHC and ZIF-8 respectively. Due to superior physicochemical properties of ZGK, it was chosen to undergo optimization of hydrogen storage at room temperature. From the confirmatory test which was run for three times, the optimum hydrogen storage at room temperature in ZGK was 1.95 wt.% when 0.50 g of ZGK was used; 15 bar of hydrogen gas was applied and the reaction time was 60 min as per suggested from the CCD.

Graphical abstract