Outstanding inhibition of H2O2 generation in doubly doped graphene: The synergy of two heteroatoms opens a new chemical path.

Abstract

Dual sulfur-nitrogen (SN) doped graphene surfaces have been revealed as a powerful active material in fuel cell applications. The experimental results presented in this work show a clear preference of the material doped with SN towards a 4-electron mechanism, almost completely inhibiting the formation of H2O2. However, materials doped only with nitrogen (N) or sulfur (S) favor the 2-electron mechanism, and therefore, the production of H2O2. A reasonable theoretical explanation is proposed to justify the inhibition of the H2O2 reaction with the use of SN doped graphenes in accordance with the experimental results. The interactions and charge transfer between N and S are the origin of an alternative dissociative step that inhibits the generation of H2O2, which is energetically favored, according to Density Functional Theory (DFT) calculations. These two dopant atoms generate a frustrated Lewis pair (FLP), resulting in an enhancement of the catalytic activity of the graphene. Atomic Dipole Corrected Hirshfeld charges (ADCH model) and Non-Covalent Interactions (NCI) are employed to identify the most active sites and support the explanation of the dissociative pathway which inhibits H2O2 formation.