Unraveling the controversy over a catalytic reaction mechanism using a new theoretical methodology: One probe and non-equilibrium surface Green's function

We propose a new methodology called one probe and non-equilibrium surface Green's function (OPNS) to elucidate the longstanding controversial issue of a catalytic reaction mechanism, especially iodine reduction reaction (IRR) mechanisms. With aid of OPNS overcoming the limitations of conventional approach based on the free energy diagram and theoretical slab model, we clearly elucidate that the IRR follows a consecutive mechanism where the configurational preference of approaching I-2 molecules depending on the external electric field governs the IRR mechanism. Under reductive potential, I-2 molecules prefer a vertical configuration (I2V) rather than a parallel configuration (I2P), which leads to the consecutive mechanism where I atoms are sequentially reduced due to asymmetric charge accumulation on a single I atom that is subsequently desorbed. In addition, we provide new convincing descriptors for catalytic activity evaluation, the slope of the linear relation between the reductive process and the electric field strength representing the ability of the partial reduction and the threshold electric field of minimum required potential for the complete reduction.