Selective hydrogenation reactions over oxide catalysts are crucial in a variety of energy and catalytic conversion processes, in which surface hydrogen species are vital while controllable H2 activation and hydrogenation are still challenging over the complex oxide catalysts. Here, combining multiscale theoretical simulations and surface science studies, we find a series of single-site Zn (Zn1) species that are well orderly dispersed onto spinel ZnCr2O4 surfaces under syngas conversion conditions. A pair of coordinatively unsaturated Zn1 sites with specific spatial proximity (termed geminal-Zn1+1) facilitates H2 homolysis into hydrides, which even occurs below 123 K. Intriguingly, the geminal-Zn1+1 confined on ZnCr2O4(110) can stabilize both hydride species (as high as 673 K) and related formaldehyde intermediates, which enables controllable CO hydrogenation to ketene via a synergistic H- and CO-assisted CO activation mechanism instead of deep hydrogenation to methanol. Such coordinatively unsaturated geminal-atom (M1+1) confined by the oxide surface is expected to be generalized to more application scenarios of oxide-catalyzed H2 homolysis and selective hydrogenation catalysis.
Lin et al. (2026) studied this question.