Chloride ligand stablizes single-atom on nanoporous metal oxides in a pyrolysis process

Pyrolysis-induced single-atom (SA) immobilization is a facile approach for the large-scale synthesis of single-atom materials, which holds promising potential in catalysis. The transition behavior from metal precursor to SA is not yet fully understood. Here, we report that coordinating chloride ligands play a pivotal role in stabilizing Pt/Ir/Ru SA when pyrolyzing their precursors on nanoporous metal oxide (Co3O4, NiO, and Fe2O3). The electrochemical and spectroscopic analysis combined with theoretical calculations suggests a thermal-driven progressive decomposition of metal precursors. Pyrolysis at a critical temperature of 250 ℃ drives the formation of the Ir-O3 motif between the Ir-based precursor and the supporting Co3O4, whereas three residual chloride ligands remain coordinated on the top and prohibit them from reacting with free Ir-containing species. Ir-SA/Co3O4 with an Ir loading of up to 3 at.% is produced. For electrocatalytic oxygen evolution reaction, it delivers a current density of 10 mA/cm² at an overpotential of only 220 mV, corresponding to 11-fold higher mass activity over their corresponding nanoclusers/Co3O4. Our work highlights the essential role of ligands in the formation of SA, offering new insights into the thermal stability of SA, as well as a new avenue to increasing the loading of SAs.