Among these reactions, the hydrogen

Among these reactions, the hydrogen oxidation (2), reverse water–gas shift (RWGS) (3), and CO/CO2 hydrogenation (4, 5) reactions are undesired. A variety of catalysts basedon supported noble metals (Pt, Rh, Ru, Ir, and Au) and metal (Ag, Mn, Fe, Co, Ni, and Cu) oxides have been investigated for the CO-PROX reaction [3–7]. Although the platinum group metals supported on reducible metal oxides exhibit good performance [7], the requirement for high temperatures and insufficient control over the unwanted conversion of H2 have been the main drawbacks associated with the platinum group metal catalysts. On theother hand, supported gold catalysts exhibit very high performance for low-temperature CO oxidation [8–12].The limited capacity of gold to chemisorb hydrogen relative to the platinum group metals is related to the lower catalytic activity of gold for reactions involving the dissociation of hydrogen [13]. This is a particular advantage for the CO-PROX, in which the oxidation of H2 into water must be minimized as much as possible. Hence, gold-based catalysts have gained focus for utilization in CO-PROX.