Ultrahigh-Density Double-Atom Catalyst with Spin Moment as an Activity Descriptor for the Oxygen-Reduction Reaction

One of the great challenges facing atomically dispersed catalysts, including single-atom catalysts (SACs) and double-atom (DACs), is their ultralow metal loading (typically less than 5 wt %), which limits practical catalytic applications, such as in oxygen-reduction reaction (ORR), crucial for hydrogen fuel cells metal-air batteries. Although some important progress has been achieved ultrahigh-density (UHD) SACs, reports on UHD DACs with stable uniform dispersion are still lacking. Herein, based experimentally synthesized ${M}_{2}{\mathrm{N}}_{6}$ motif ($M\phantom{\rule{0.25em}{0ex}}=\phantom{\rule{0.25em}{0ex}}\mathrm{Sc}$-$\mathrm{Zn}$), we theoretically demonstrate existence DACs, a >40 %, confirmed by systematic analyses dynamic, thermal, mechanical, thermodynamic, electrochemical stabilities. Furthermore, ORR activities comparable to or even better those low-density counterparts, ${\mathrm{Fe}}_{2}{\mathrm{N}}_{6}$ ${\mathrm{Co}}_{2}{\mathrm{N}}_{6}$ located at peak activity volcano overpotentials 0.31 0.33 V, respectively. Finally, spin magnetic moment active center found be descriptor DACs. Our work can stimulate experimental exploration provides an insight into relationship between states.