Two-dimensional peak-valley alternating self-supporting electrode accelerating nitrate electrocatalytic reduction: Ammonia synthesis and wastewater treatment

Electrochemical nitrate reduction synthesis of ammonia can use clean energy to convert low-value nitrate pollutants into high value-added ammonia yield. The development of eNitRR catalyst with high activity, high selectivity and stability is the key to achieve distributed small-scale production of nitrate. In this study, a self-supported catalyst (Cu/PTS) with high catalytic activity (for eNitRR) was constructed by anodic oxidation combined with hydrothermal/pyrolysis strategy to realize the embedding of Cu species on the substrate of porous titanium sheet. The ammonia production rate of Cu/PTS catalyzed eNitRR is as high as 7292.43 μg h−1 cm−2 (−1.0 V vs. RHE), the Faradaic efficiency is close to 100 %, reaching 97.34 %, and isotope labeling and Operando ATR-FTIRAS verified and revealed the fact that NO3− to NH3, respectively. Density functional theory calculations well reveal the roles of various components in Cu/PTS and reveal the factors for the enhancement of eNitRR performance. Thanks to the self-supporting characteristics of porous titanium sheet and the surface embedding of copper species, Cu/PTS not only have good electrochemical stability when catalyzing eNitRR, but also can drive eNitRR to operate efficiently in complex water environment. While realizing the purification of nitrate wastewater and the synthesis of ammonia, Cu/PTS can be used as a positive electrode to construct a nitrate–zinc battery to realize the dual functions of self-driven ammonia production and external power supply.