Copper Inhibits the Over-Oxidation of Rh during Methane Oxidation Catalyzed by Bimetallic Cation CuRh ⁺

Partial oxidation of methane with molecular oxygen to produce hydrogen is a promising strategy for hydrogen generation. However, maintaining catalyst stability remains challenging, as the catalyst is prone to overoxidation by the strong oxidant O 2 during the reaction. Herein, benefiting from state-of-the-art mass spectrometry, we demonstrate that heteronuclear metal cation CuRh + catalyzes the reaction of methane with O 2 at room temperature to yield 2H 2 and CO 2 . Comparative studies show that even though the homonuclear Rh 2 + system can construct an analogous catalytic cycle, it is more susceptible to overoxidation by O 2, leading to the formation of the undesirable intermediate Rh 2 O 3 + . Cu-doping markedly enhances the antioveroxidation capability of CuRh + to result in the generation of stable and desirable intermediate CuRhO + under an oxygen atmosphere. Density functional theory shows that Cu plays a suppressive role during two steps of the overoxidation reaction. By reducing the electron supply from the metal site to O 2, Cu hampers the initial adsorption step and compels the O–O bond dissociation to rely on orbital reorganization across a large energy gap. This finding not only provides new insights into the unique role of copper in heterogeneous catalysis but also offers a valuable guidance for the rational design of low-cost and stable catalysts for CH 4 -to-H 2 under mild conditions.