Hydrogen is a promising renewable and environmentally friendly fuel to meet future global energy needs. Also, it serves as an important chemical feedstock for fertilizer production. The water-gas shift (WGS) reaction is an important reaction in the production of hydrogen and has grown significantly in usage over time. In this work, we explore a new strategy that can create single-atom catalysts (SACs) from metal-ligand single-sites on high surface area oxide supports for catalyzing WGS reaction. The metal-ligand approach results in high metal loading and exhibits an ultimate dispersion of metal species, maximizes atom efficiency, and significantly reduces the use of precious metals. 1,10-phenanthroline-5,6-dione (PDO), was chosen as the ligand for its oxidative potential for stabilizing metal cations in two bidentate sites. The single-atom nature of the Pt is characterized by EXAFS, XPS, XRD, DRIFTS, and TEM. The catalytic activity is evaluated for the WGS reaction, and it is discovered that Pt-ligand SAC supported on defective TiO<sub>2</sub> shows higher inherent catalytic activity than Pt NPs with significantly lower activation energy which is generally desirable for the redox mechanism. Density functional theory (DFT) calculations reveal that metal-ligand SACs allow CO interaction with support oxygen, so the metal is in close contact with the support, and the ligands are not blocking that interaction and that the redox mechanism of WGS reaction has a lower effective activation barrier than the associative mechanism for Pt-ligand SAC.

Ligand coordinated Pt single-atom catalyst allows adsorbed CO to extract oxygen from the support during water-gas shift reaction

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