Versatile and Robust Nickel Single Atom Catalysts

A vast number of industrial catalytic processes rely on noble metals, also called platinum group metals (PGMs), which are scarce and expensive. Replacing these expensive noble metals with earth abundant metals (EAMs) represents a major challenge. Although nickel is known to be an excellent catalyst for certain reactions, like hydrogenation, it is unselective in metallic form and is inactive when oxidized during CO oxidation or methane oxidation reactions. Here we show that many of the reactions catalyzed by PGMs, such as oxidation or hydrogenation, can also be carried out effectively by a base metal such as nickel, when it is stabilized in the form of isolated single atoms in the fluorite lattice of CeO2. Incorporating Ni into the CeO2 lattice (formally Ce0.9Ni0.1O1.8(OH)0.2) creates a versatile and robust Ni single atom catalyst. Protons help to balance the charge imbalance created by the Ni(II). We propose the resultant Ce(IV) participate actively in catalysis. The working catalyst contains atomically dispersed Ni(II) sites that are stable under reaction conditions. Unlike metallic Ni, this single atom catalyst is not pyrophoric, can be handled in air and easily activated for hydrogenation reactions. The synthesis described here is scalable and yields a high loading of Ni (~3 wt%) within the fluorite CeO2 lattice while also allowing facile substitution of Ce with co-dopants, such as Zr, to further tune the environment of the active sites.