Single-atom catalysts (SACs) exhibit excellent performance in a range of hydrogenation reactions. However, the mechanistic understanding of hydrogen intermediates formed following H2 dissociation, particularly their reactivity on SAC surfaces, remains limited. In this study, we show that single-atom palladium alloyed with cobalt (Pd1Co SACs) efficiently catalyzes the hydrogenation of anthraquinone, exhibiting high stability and recyclability. In contrast, a cobalt oxide-supported Pd single-atom catalyst (Pd1–Co3O4) displays only limited activity. Experimental results indicate hydrogen dissociation as the rate-determining step in the anthraquinone hydrogenation process. Density functional theory calculations reveal that Pd1Co SACs enable homolytic H2 dissociation with a low activation energy and facilitate electron transfer from the support to the hydrogen intermediates, resulting in the formation of highly reactive hydride-like species. The combination of high atomic efficiency and low energy barrier enables Pd1Co SACs to achieve a remarkable H2O2 production rate of up to 210 mol gPd–1 h–1, which is 240 times greater than that of commercial Pd/Al2O3.
Chen et al. (Mon,) studied this question.