Selective spin injection of g-SiC6 monolayer for dioxygen activation

Abstract

Activation of molecular O2 is an important but difficulty step in many catalytic processes owing to the fact that a spin-flip based activation is normally required to transfer O2 from the triplet ground state to singlet state. Here, we report a new O2 activation mechanism, in which the catalyst can inject electrons with selective spins into O2 to directly result in a highly activated spin state. Our results show that the nonmagnetic g-SiC6 monolayer possesses a strong O2 binding, and the Si of g-SiC6 varies from sp2 to sp3 hybridization with the O2 incoming and injects electrons with antiparallel spins into the O2 with a super low energy barrier. The resulted high-activated spin state directly triggers the dissociation of bridge-on adsorbed O2 to ∗O with a very low activation energy of 0.09 eV. Further studies demonstrate that a CO molecule can be adsorbed by the activated O2 and the derived ∗O, and then be oxidized to CO2 subsequently. The weak adsorption of CO and CO2 prevents the poisoning of g-SiC6 by CO and promotes the catalyst regeneration. Our findings enriches the mechanistic understanding of oxygen reduction reaction and shed new light on the design of nonmagnetic metal-free catalysts for O2-activation.