Au-Assisted CHO Formation Promotes O ₂ Activation for HCHO Oxidation over Au/Co ₃ O ₄

In this study, we systematically investigate HCHO oxidation on Au/Co 3 O 4 single-atom catalysts (SACs) using density functional theory (DFT) combined with ab initio thermodynamics. The most stable configuration under realistic conditions is identified as Au substituting a tetrahedral Co atom on the pristine surface. The reaction pathway involves HCHO adsorption, C–H cleavage to form CHO*, followed by O 2 activation, and the decomposition of COOH* to CO 2 . Importantly, Au plays a dual promotional role: it not only significantly lowers the energy barrier of C–H dissociation, but also, through the generated CHO*, indirectly facilitates the subsequent O 2 adsorption and activation on the Co site. Electronic structure analysis reveals that Au enhances charge transfer and facilitates hydrogen migration, while CHO* groups change the electronic state of Co, promoting O 2 activation. This work provides a new perspective on O 2 activation by uncovering the crucial yet previously overlooked role of the intermediate, and offers a strategic guide for the design of high-performance single-atoms catalysts.