Utilizing coal to supply energy leads to the release of pollutants such as NOx, SOx, CO2, and trace elements, such as mercury, into the environment. Currently, of the three main locations (China, United States, and India) with recoverable coal reserves, the US is leading the effort to decrease harmful emissions into the environment, through regulations such as the EPA's Clean Air Interstate Rule (CAIR), which places caps on NOx and SOx emissions from the Eastern states, and the Clean Air Mercury Rule, which places a cap on mercury emissions from coal-fired power plants (US EPA, 2007).

Gold nanoclusters could potentially be useful for adsorbing mercury (Hg) from coal-fired power plants, since gold and mercury are commonly found together in nature. Gold nanoclusters typically have oxide supports, which are classified as reducible oxide supports (TiO2, TiO3, NiO, Fe2O3, etc.) or irreducible oxide supports (Al2O3, MgAlO4). In particular, reducible oxides such as TiO2 have shown promise in the adsorption of Hg and other trace species since the oxide support acts as an insulator and pushes the electron density outward, in turn increasing the activity of the gold nanocluster.

Gold nanoclusters on various support materials have been investigated using both Vienna Ab Initio and Gaussian03 software packages. Additionally, their effectiveness for the adsorption of various components from coal-fired combustion flue gas (Hg, HgS, CO2, and SO3) has been determined. Overall, this study indicates that gold nanoclusters on certain reducible oxide supports may serve as effective multi-pollutant sorbents for high-temperature capture applications.