Asymmetric Coordination of Iridium Single-atom IrN3O Boosting Formic Acid Oxidation Catalysis

Rational design of the proximal coordination of an active site to achieve its optimum catalytic activity is the ultimate goal in single-atom catalysis, but still challenging. Here, we report theoretical prediction and experimental realization of an asymmetrically coordinated iridium single-atom catalyst (IrN3O) for the formic acid oxidation reaction (FAOR). Theoretical calculations reveal that the substitution of one or two nitrogen with more electronegative oxygen in the symmetric IrN4 motif splits and downshifts the Ir 5d orbitals with respect to the Fermi level, moderating the binding strength of key intermediates on IrN4-xOx (x=1, 2) sites, especially that the IrN3O motif shows ideal activity for FAOR with a near-zero overpotential. The as-designed asymmetric Ir motifs were realized by pyrolyzing Ir precursor with oxygen-rich glucose and nitrogen-rich melamine, exhibiting a mass activity of 25 and 87 times greater than those of state-of-the-art Pd/C and Pt/C, respectively.

Automated summary

This study presents the theoretical prediction and experimental realization of an asymmetrically coordinated iridium single-atom catalyst for the formic acid oxidation reaction. Theoretical calculations show that the substitution of nitrogen with oxygen in the symmetric IrN4 motif can moderate the binding strength of key intermediates and achieve near-zero overpotential. The as-designed catalyst exhibits significantly higher mass activity compared to state-of-the-art Pd/C and Pt/C catalysts.