2D Ag-Doped Cu–Zn–Sn–S Nanosheets for the Electrocatalytic Nitrate Reduction Reaction

The electrocatalytic nitrate reduction reaction (NO 3 RR) has been receiving increasing attention for ammonia (NH 3 ) production, but it still faces great difficulty in real applications due to low NH 3 selectivity and high nitrite (NO 2 – ) residue, necessitating an intermediate pathway and microenvironment modulation beyond active sites. Here, we report a quasi-homogeneous nanoreactor via in situ NO 3 – -mediated reconstruction in 2D Ag-doped Cu–Zn–Sn–S nanosheets for efficient NO 3 RR with ultralow NO 2 – release. Both Ag doping and NO 3 – were found to be critical during the reconstruction process, resulting in increased bidentate NO 3 – as a key intermediate. The catalyst achieves a high NH 3 yield of 0.33 mmol h –1 cm –2 and Faradaic efficiency (FE) of 91.04% with an extremely low yield of NO 2 – (2.57 ppm). In situ spectroscopies further evidence the quasi-homogeneous phase with greatly enhanced adsorption of both NO 3 – and H 2 O, favoring restricted and directional conversion to *NO 2 and ultimately strong *NH 3 with negligible NO 2 – release. Moreover, the catalyst in a flow cell delivers an increased NH 3 yield and maintains low NO 2 – release (<15 ppm) under widely varied concentrations and potentials simulating industrial conditions. This study provides a substrate-mediated reconstruction strategy toward a quasi-homogeneous active phase for high-selectivity NO 3 RR, which is also inspiring for other complex reactions.