Dimensionality junctional Janus nanocrystals with heterogeneous stacking fault-lined interface achieve tandem...

Electrocatalytic nitrate reduction reaction (NO₃RR) holds substantial potential to close nitrogen cycle, while the selectivity toward ammonia in NO₃RR is still too low to meet practical applications. Here, we report precise synthesis of a class of Ag-Cu dimensionality junctional Janus nanocrystals (DJJNs) with heterogeneous stacking fault-lined interface for tandem electrocatalytic reduction of nitrate to ammonia. Site-selective growth of Cu with a three-dimensional structure on one edge of two-dimensional Ag triangular nanoplates can be realized via controlling reduction kinetics of the Cu precursor. Quantitative analysis of correlations between the composition and the interface length of Ag-Cu DJJNs and their NO₃RR selectivity toward NH₃ reveals that the optimal composition of Ag/Cu nanocatalysts as well as the dimensionality junctional interface plays a key role in selectivity achievement. Density functional theory calculations reveal that the Ag/Cu(111) interface can work in a tandem manner to catalyze NO₃RR to form NH₃ over Ag-Cu DJJNs. This study offers a synthetic design strategy for advancing tandem catalysts toward NO₃RR.