Self-Tandem Electrocatalytic NO Reduction to NH3 on a W Single-Atom Catalyst

We design single-atom W confined in MoO3-x amorphous nanosheets (W1/MoO3-x) comprising W1-O5 motifs as a highly active and durable NORR catalyst. Theoretical and operando spectroscopic investigations reveal the dual functions of W1-O5 motifs to (1) facilitate the activation and protonation of NO molecules and (2) promote H2O dissociation while suppressing *H dimerization to increase the proton supply, eventually resulting in a self-tandem NORR mechanism of W1/MoO3-x to greatly accelerate the protonation energetics of the NO-to-NH3 pathway. As a result, W1/MoO3-x exhibits the highest NH3-Faradaic efficiency of 91.2% and NH3 yield rate of 308.6 μmol h-1 cm-2, surpassing that of most previously reported NORR catalysts.