Where E nO * is the total energy of the oxidized nanoparticle, E * is the energy of the clean nanoparticle, and G H 2 O , G H 2 are the Gibbs free energies of gaseous water and dihydrogen respectively. For the latter two, zero point energy and entropy contributions, taken from thermodynamic tables are added. Equation 1 is obtained by considering a CHE compliant oxidation reaction given by Equation 2