Synthesis of carbon from carbon dioxide and its application as a catalyst for oxygen reduction reaction and electrode for energy storage material

Abstract

The needs for reducing carbon dioxide ($CO_2$) have been increasing because of global warming effect. One of the ways to reduce $CO_2$ include conversion of $CO_2$ into various carbon materials. In this thesis, converting $CO_2$ to heteroatom-doped carbon material using reducing agent of ammonia borane ($NH_3BH_3$) and sodium borohydride ($NaBH_4$) was studied. The synthesized carbon material was utilized as a catalyst for oxygen reduction reaction (ORR), electrode materials for supercapacitor and lithium ion battery anode materials after some surface modifications. The thermal treatment, incorporation of iron oxide species were used to enhance electrocatalytic activity for ORR and the KOH treatment was used to increase capacity in supercapacitor applications. For lithium ion battery applications, two-dimensional metal carbide of $Mo_2C$ MXene was used and it was oxidized by using $CO_2$ as a mild oxidant, resulting molybdenum oxide and amorphous carbon composite. The procedure of $CO_2$ conversion by using $NaBH_4$ as a reducing agent can be also applied flue gas conversion. The porous carbon can be made through flue gas conversion with further KOH treatment to be tested for supercapacitor electrode. The B, N-incorporated flue gas derived carbon shows 210 F/g at 1 A/g and this value which is comparable to activated carbon (150 - 200 F/g). The iron-atom incorporated carbon derived from flue gas shows comparable ORR activity to commercially available platinum-based catalyst. The iron-atom incorporated porous carbon from $CO_2$ shows the current density of $4.7 \times 10^{-3} A/cm^2$ at -0.8 V vs. Ag/AgCl and onset potential of -0.07 V vs. Ag/AgCl and this value is comparable to platinum-based catalysts showing current density of $4.4 \times 10^{-3} A/cm^2$ at the same potential and onset potential of -0.06 V vs. Ag/AgCl. The $CO_2$ -derived molybdenum oxide and carbon composite shows 323 mAh/g at 50 mA/g in lithium-based electrolyte with good cycle stability of 85 % after 280 cycles.