RNA as a Precursor to N-doped Activated Carbon

Activated carbons (ACs) have applications in gas separation and power storage, and N-doped ACs in particular can be promising supercapacitors. In this context, we studied ACs produced from yeast-derived ribonucleic acid (RNA), which contains aza-aromatic bases and phosphate-linked ribose units, and is surprisingly inexpensive. The RNA was hydrothermally carbonized to produce hydrochars that were subsequently activated with CO2, KOH, or KHCO3 to give ACs. The ACs adsorbed up to ~7 mmol/g at 0 °C and 1 bar, and had capacitances as high as ~300 F/g in a three-electrode cell and a 6-M KOH(aq) electrolyte. The material that displayed the best capacitance was tested in a two-electrode cell, which displayed a specific capacitance of 181 F/g even at a current density of 10 A/g. The ACs with the highest uptake of CO2 and the highest capacitance were those activated with KOH and KHCO3; however, CO2 activation is arguably less expensive and more suitable for industrialization.