Interfacial polarization in metal-organic framework reconstructed Cu/Pd/CuOx multi-phase heterostructures for electrocatalytic nitrate reduction to ammonia

Electrochemical reduction of nitrate wastewater to high value-added ammonia is of significance to promote the restoration of ecosystem nitrogen cycle imbalances, which requires highly active and selective catalysts. In this work, we develop a kind of Pd-incorporated Cu-based metal-organic framework (CuPd-MOF) as precatalysts for nitrate electroreduction to ammonia. It is demonstrated that the CuPd-MOF precatalyst is in-situ reconstituted to Cu/Pd/CuOx multi-phase heterostructures as the actual catalytic active material under electrocatalysis operating conditions. Multi-phase heterogeneous interface between Cu, Pd and CuOx can trigger uneven spatial charge distribution for enhancing interface polarization and result in electron transfer from Pd to Cu, which promoting NO3- adsorption on electron-deficient Pd sites and further reduction on electron-rich Cu sites, delivering a high ammonia yield of 1510.3 µg h−1 mg−1cat. and a maximum Faradaic efficiency of 84.04 %. The present study opens new avenues for the design of multi-phase heterostructured catalysts for electrosynthesis ammonia from nitrate.