Generalised predictability in the synthesis of biocarbons as clean energy materials: targeted high performance CO2 and CH4 storage

Abstract

This work shows how knowledge of any biomass and choice of carbonisation process can offer a generalised route to predictability in the preparation of activated biocarbons. We demonstrate that based on O/C ratio of carbonaceous matter, it is possible to predictably generate biocarbons with suitable porosity, surface area density, volumetric surface area and packing density targeted towards record levels of CO₂ and CH₄ storage capacity. Highly porous carbons with controlled levels of microporosity of up to 97% of the surface area and 92% of the pore volume are generated. The level of synthetic control is such that it enables, on the one hand, exceptional CO₂ storage at 25 °C and low pressure (1.5 and 5.4 mmol g⁻¹ at 0.15 and 1 bar, respectively) or moderate pressure (23.7 mmol g⁻¹ at 20 bar), indicating superior uptake under both post-combustion and pre-combustion CO₂ capture conditions. The carbons may also be directed towards storing record levels of methane; at 25 °C and 100 bar, volumetric methane uptake of between 309 and 334 cm³ (STP) cm⁻³ was obtained, which values are considerably higher than all current benchmark materials and, moreover, surpass the United States Department of Energy (US DOE) target of 263 cm³ (STP) cm⁻³. Crucially, the carbons also have very attractive working capacity (deliverable methane for 100–5 bar) of 262 cm³ (STP) cm⁻³, 234 cm³ (STP) cm⁻³ (80–5 bar), and 210 cm³ (STP) cm⁻³ (65–5 bar).