Capability of Activated Carbon and Multiwalled Carbon Nanotubes in Hydrogen Adsorption

Abstract

The overexploitation of fossil fuels in producing energy caused significant impact to nature. The accumulation of greenhouse gases from the burning of fossil fuels threatened the ozone layer and enhanced the impact of global warming. Furthermore, fossil fuel was predicted to be depleted soon. Due to those reasons, many researchers have been looking for environmental-friendly energy sources. There have been various renewable energy sources such as solar energy, wind energy, and hydropower energy discovered. However, it was difficult to find a highly efficient and economical energy source [1-12]. Among those energy sources, hydrogen has arisen as a potential candidate. Hydrogen has an energy density three times higher than that of gasoline and diesel, and its combusted byproduct is water vapor. The main hindrance of utilizing this energy is difficulty in finding an economical and effective method of storing hydrogen. Hydrogen was often stored in liquid form at high pressure and extremely low temperature conditions. This method costs much energy and requires advanced utility systems. Another method which is also applied in storing hydrogen gas is known as physisorption. In this method, the hydrogen gas will be stored in the materials at atmospheric pressure and room temperature. In this study, we investigated the capability of two carbon materials, activated carbon and multiwalled carbon nanotubes, in adsorbing hydrogen. The hydrogen adsorption process and surface area of each material was examined by Micromeritics ASAP 2020. Each material was characterized by Powdered X-ray diffraction (P-XRD), Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Even though activated carbons (AC) had surface area (~ 870 m2/g) much higher than that of multiwalled carbon nanotubes (MWCNT) (~ 119 m2/g), the percentage of uptake hydrogen per gram of activated carbon (2%) was lower than that of carbon nanotubes (7%). The pore size of AC was smaller than that of MWCNT. This study provided some insights about the effects of physical and chemical properties of carbon materials on their hydrogen adsorption ability.