Coordination environments of platinum single atom catalysts from NMR fingerprints

Single atom catalysts (SACs) have revolutionized the field of catalysis achieving an unprecedented level of control and metal utilization for solid materials, approaching what is expected with molecular catalysts.1-3 Establishing structure-activity relationships for their wide-ranging applications requires precise elucidation of the metal coordination environment, which remains a grand challenge.1,2 While electron microscopy reveals atomic dispersion, only average coordination environments can be deduced from state-of-the-art spectroscopic methods used in heterogeneous catalysis. Here, we establish 195Pt solid-state nuclear magnetic resonance (NMR) spectroscopy as a powerful methodology to acquire NMR signatures across a series of Pt-SACs dispersed on carbon based supports. Monte-Carlo simulations allow the conversion of NMR signatures into SAC fingerprints that describe local coordination environments with molecular precision and enable to quantitatively assess Pt-site distribution and homogeneity. This methodology can track the influence of synthetic parameters, e.g., specific protocols, synthetic steps and type of supports, on Pt-SAC structures, to guide the reproducible development of SACs with targeted structures; it also enables to monitor the change of coordination environment of SACs upon reaction. Such development provides a blueprint for the quantitative assessment of larger SAC families containing other NMR-active isotopes.