Catalytic oxidation mechanism of ethyl acetate on O-ligand-single-atom-Ni/2-dimensional reduced graphene oxide: the essential role of the O ligand

Ligands play an important role in the dispersion of metal and catalytic activity in single-atom transition metal-doped catalysts (SATMCs). In this work, a series of oxygen-ligand (O-ligand)-single-atom-Ni/2-dimensional reduced graphene oxide (RGO) materials (SANiX-O-2DRGO (X = 0.5–5)) were fabricated by a simple one-step co-reduction method. The single Ni atom on SANi5-O-2DRGO is embedded into the RGO and ligated by four O-ligand atoms. A systematic study confirms that the O-ligand is conducive to the dispersion of Ni and the formation of SATMCs with high metal loading. Density functional theory (DFT) calculation results demonstrate that the d-band center value of O-ligand-single-atom-Ni is closer to the Fermi level than that of the conventional N coordination, which is beneficial for electronic transition and enhances catalytic activity, i.e., the O-ligand accelerates the electron transfer between the carrier and the single metal atom, thus improving the catalytic oxidation capacity of volatile organic compounds (VOCs) on SANi5-O-2DRGO. As a demonstration, SANi5-O-2DRGO exhibits excellent reusability, water resistance, and stability for ethyl acetate oxidation. The degradation of ethyl acetate remained at 100% over 150 hours of continuous onstream operation. The catalytic oxidation mechanism of ethyl acetate on SANi5-O-2DRGO was also investigated. The O-ligand atoms provide the key electron transfer in the activation of adsorbed oxygen and catalytic oxidation process of reaction intermediates.