In-situ growth of Co/Zn bimetallic MOF on GO surface to prepare GO supporting Co@C single-atom catalyst for Hg0 oxidation

• GO support sigle-atom Co catalysts were successfully synthesized. • MOF on GO has highly dispersion degree giving a large BET surface area. • The Co in MOF mainly stay in single-atom status which is the main active site. • The Hg 0 oxidation activity of Co 2.5 -SAs@NC/GO-1 is above 95 % at 120–180 °C. Oxidation of Hg 0 to Hg 2+ is an efficient way to remove Hg 0 from flue gas. Chemisorbed oxygen as the main active site plays an important role in Hg 0 oxidation process. Single-atom catalyst has an excellent ability of transforming gaseous oxygen into chemisorbed oxygen. In the present work, graphene oxide (GO) was used as support to in-situ grow Co/Zn bimetallic MOF on GO surface. After pyrolysis, a GO supported Co@C single-atom catalyst was obtained. SEM and TEM results show that GO supporting gives a high dispersion for calcined MOF particles. HAADF-STEM results prove that most of the Co atoms in calcined MOF particles stay as single-atom status. EXAFS indicated that the Co atoms in the catalyst was coordinated with N, and the coordination was dominated by CoN 2 . CoN 2 can capture and activate gaseous oxygen forming more chemisorbed oxygen. Thanks to the high dispersion of calcined MOF and higher chemisorbed oxygen concentration, the Hg 0 oxidation efficiency of the obtained catalyst (Co 2.5 -SAs@NC/GO-1) can reach above 90 % in the temperature range of 120–180 °C with 0.075 g loading amount at the GHSV of 180, 000 h −1 . The probable reaction pathway was analyzed by an adsorption–desorption experiment and XPS over the used and regenerated Co 2.5 -SAs@NC/GO-1.