Coordinatively Unsaturated IrC₃ Single-Atom Catalysts for Efficient Methanol Oxidation Reaction.

Abstract

Methanol oxidation reaction (MOR) plays a crucial role in renewable energy conversion and storage, where the key steps involve dehydrogenation and subsequent ^*CO electrooxidation. However, ^*CO oxidation remains challenging due to its strong adsorption and insufficient ^*OH species at active sites, severely limiting reaction kinetics. Here, the single Ir atom catalyst with abundant coordinatively unsaturated IrC₃ sites is developed to electrocatalysis MOR under elevated temperature, the IrC₃ sites with stronger CH₃OH adsorption and weaker ^*CO adsorption, which break the scaling relationship between methanol and ^*CO adsorption energy. Moreover, the IrC₃ could accelerate the electrochemical water dissociation with assistance of protophilic IrC₄ to form adsorbed ^*OH. The balanced adsorption energy and the appearance of ample ^*OH would efficiently decrease the reaction energy barriers, and further accelerate the methanol dehydrogenation and ^*CO oxidation. By assemble the high temperature polymer electrolyte membrane electrolyzer (HT-PEME) with IrC₃ sites at 180°C, it shows an excellent MOR efficiency with onset potential about 0.05 V and H₂ generation rate with 8694 mol_H2 mol_Ir ^-1 h^-1 at cathode, which is much higher than that of Ir-C SACs parent catalyst and Pt/C catalysts. This finding provides an avenue to conquer the formidably sluggish kinetics of MOR for hydrogen utilization.