(545ap) Feasibility of H2O2 Production at Graphite Cathode Using Quantum Chemical Calculations

Hydrogen peroxide (H₂O₂) with redox potential of 1.8 eVis used as a strong oxidant in Fenton oxidation. Commercially, H₂O₂ is produced by catalytic oxidation of anthrahydroquinone which is energy-intensive. This incurs economic glitches aside the intense need of exploring a sustainable solution for H₂O₂ production. In this regard, Microbial fuel cell (MFC) is a sustainable technology which uses graphite as cathode for H₂O₂ production. One of the limitations of using graphite cathode is the slow kinetics of oxygen reduction reaction (ORR). Nitrogen doping has demonstrated to be an efficient approach to regulate the electronic as well as surface characteristics of graphite cathode. Therefore, quantum chemical approaches are essential to comprehend the molecular nature of this process. Thus, DFT/B3LYP/6-31G* method was employed and bond dissociation energy (BDE) analysis was performed to determine the feasibility of H₂O₂ production at graphite and nitrogen doped graphite (Graphite-N) cathode. According to the suggested mechanism, oxygen adsorption is the first step of ORR. Calculated values showed that with energy value of 23.50 kcal/mol oxygen adsorption at Graphite-N cathode is energetically more favourable than graphite cathode (E_ad= 65.08 kcal/mol). Considering the ORR mechanism, second-electron oxygen reduction is identified as a key step for both H₂O and H₂O₂ production. Therefore, BDEs were compared at the second-electron oxygen reduction step. Negative values obtained for H₂O₂ production suggests the feasibility of H₂O₂ production. On the average, -320.92 and -286.04 kcal/mol of BDEs for graphite and Graphite-N cathode showed the feasibility of H₂O₂ production at Graphite-N cathode. The negative values obtained for BDEs show that H₂O₂ production is spontaneous one and energy provided in the initial step is sufficient to carry out two electrons ORR. The results are in agreement with the literature. Thus it is concluded that nitrogen doping of graphite cathode increases the feasibility of H₂O₂ production.

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