Upcycling simulated food wastes into superactivated hydrochar for remarkable hydrogen storage

In an effort of developing hydrogen storage material, the goal of this study was to explore the potential of the abounding food waste biomass as a precursor for the development of porous carbon materials for remarkable hydrogen storage. Therefore, in this study, simulated food waste, a mixture of six commonly disposed food items (apple, bread, green bean, cabbage, cheese, and canned chicken), was hydrothermally carbonized at 220 °C followed by chemical activation at 800 °C using various activating agent (KOH) to food waste hydrochar ratio (i.e., 2:1, 3:1 and 4:1). The solid products, hereafter called superactivated hydrochars, were characterized by proximate and ultimate analyses as well as X-ray diffractometer (XRD) and through nitrogen adsorption isotherms at 77 K to analyze the changes in the material including its surface porosity parameters (surface area, pore volume, and pore size distribution) as the food waste underwent chemical and morphological modifications. The gravimetric (wt%) hydrogen storage capacity of the superactivated hydrochars were then conducted under 77 K and various pressure of 0–23 bar. Results showed that the surface area and total pore volume in the superactivated hydrochars were in the range of, as high as, 2070 to 2885 m²/g and 0.98 to 1.93 cm³/g, respectively. The remarkable hydrogen storage capacity was observed of as high as 6.15 wt% at 23 bar and 77 K for the superactivated hydrochar produced with a KOH to food waste hydrochar ratio of 4:1. This distinctly highlights the pertinent upcycling technique of food waste to be effective in developing efficient hydrogen storage material.