Porous carbon composites as clean energy materials with extraordinary methane storage capacity

Abstract

The main hurdle that is holding back the use of natural gas as a fuel for vehicles and in other forms of transportation is the lack of materials that can store sufficient amounts under accessible operating conditions to make it both viable and competitive. In this regard, the main challenge is finding materials that have the right balance of porosity and packing density, and that can store and deliver methane to the set volumetric targets. Here we report a new approach to achieving such materials by presenting the concept of carbon composites that simultaneously have high porosity (up to ca. 2800 m² g⁻¹ and 1.5 cm³ g⁻¹) and high packing density (up to ca. 1.0 g cm⁻³). Using plastic waste as starting material, we have prepared carbon composites that are modelled on activated carbons but with an added inorganic component, and that achieve (at 25 °C) methane storage of 285 cm³ (STP) cm⁻³ at 35 bar, 374 cm³ (STP) cm⁻³ at 65 bar and 447 cm³ (STP) cm⁻³ at 100 bar. The carbon composites can also deliver methane of up to 256 cm³ (STP) cm⁻³ for a pressure swing of 35 to 1 bar, 280 cm³ (STP) cm⁻³ for a 65 to 5 bar pressure swing, and 358 cm³ (STP) cm⁻³ for a 100 to 5 bar pressure swing. This methane storage performance is greater, by some margin, than any previously reported and meets set volumetric uptake targets even at a low pressure of 35 to 65 bar. Our findings offer a new concept and insights in the much wider area of the development of porous materials for the storage of energy-related gas (CH₄, H₂, CO₂, etc), and could offer a step change in the achievable level of volumetric storage of methane as a fuel especially for vehicular transport use.