Nanoscale Ni-NiO-ZnO Heterojunctions for Switchable Dehydrogenation and Hydrogenation through Modulation of Active Sites

Catalystsconsisting of metal-metal hydroxide/oxideinterfacesare highly in demand for advanced catalytic applications as theirmulticomponent active sites will enable different reactions to occurin close proximity through synergistic cooperation when a single componentfails to promote it. To address this, herein we disclosed a simple,scalable, and affordable method for synthesizing catalysts consistingof nanoscale nickel-nickel oxide-zinc oxide (Ni-NiO-ZnO)heterojunctions by a combination of complexation and pyrolytic reduction.The modulation of active sites of catalysts was achieved by varyingthe reaction conditions of pyrolysis, controlling the growth, andinhibiting the interlayer interaction and Ostwald ripening throughthe efficient use of coordinated acetate and amide moieties of Zn-Nimaterials (ZN-O), produced by the reaction betweenhydrazine hydrate and Zn-Ni-acetate complexes. We foundthat the coordinated organic moieties are crucial for forming heterojunctionsand their superior catalytic activity. We analyzed two antagonisticreactions to evaluate the performance of the catalysts and found thatwhile the heterostructure of Ni-NiO-ZnO and their cooperativesynergy were crucial for managing the effectiveness and selectivityof the catalyst for dehydrogenation of aryl alkanes/alkenes, theyfailed to enhance the hydrogenation of nitro arenes. The hydrogenationreaction was influenced by the shape, surface properties, and interactionof the hydroxide and oxide of both zinc and nickel, particularly accessibleNi(0). The catalysts showed functional group tolerance, multiple reusabilities,broad substrate applicability, and good activity for both reactions.

Automated summary

By controlling the reaction conditions and utilizing coordinated acetate and amide moieties, we successfully synthesized catalysts consisting of nanoscale nickel-nickel oxide-zinc oxide heterojunctions, which exhibited superior catalytic activity. These catalysts showed tolerance to various functional groups, can be reused multiple times, and demonstrated good activity for both dehydrogenation and hydrogenation reactions.