The theoretical route for the transformation of bicarbonate ( \([\hbox {HCO}_{3}]^-\) ) into \({\hbox {H}_2\hbox {C}_2\hbox {O}_4}\) was explored with density functional theory (DFT). Chromatography analysis evidences the formation of \({\hbox {H}_2\hbox {C}_2\hbox {O}_4}\) . Calculations show that \([HCO_3]^{\bullet }\) can be present on the surface as the radical \(^{\bullet }\hbox {OCOOH}\) or as the anion ( \([\hbox {HCO}_{3}]^-\) ). This indicates that oxalic acid can be obtained from bicarbonate. The identified theoretical energy barrier was 1.65 eV, corresponding to the activation of the \(^{\bullet }\hbox {OCOOH}\) by an electron.
