Directed Electrocatalytic Nitrate Conversion via H-Bond Network Fortification

Abstract

Electrocatalytic reduction of nitrate (NO3–) is highly desired for the synthesis of value-added nitrogenous compounds, where precise selectivity control remains as a key challenge to be tackled. In addition to catalyst composition, electrolyte microenvironment offers another feasible handle for selectivity regulation, where the interfacial H-bond network could be effectively tuned for directed H-atom transfer for selectivity manipulation. Herein, two molecules with distinct molecular configurations, oxalic acid (OA) and acetic acid (HOAc), were introduced into the electrolyte microenvironment to investigate the in-depth structure-functional relationship between electrolyte structure and electrocatalytic NO3– selectivity, where vicinal H-bond acceptors (carboxylic groups) makes OA an ideal “molecular glue” to fortify the H-bond network for H atom transfer. As a result, OA significantly facilitates electrocatalytic NO3– hydrogenation, leading to efficient production of NH2OH (219 μmol·cm–2·h–1, 78.2%). Contrastingly, partially hydrogenated NO2– is characterized as the major product upon HOAc introduction (284.4 μmol·cm–2·h–1, 82.4%), which lacks vicinal carboxylic groups for H-bond network fortification. The NH2OH and NO2– products were effectively converted to formaldoxime and nitrophenol, which extended the directed electrocatalytic NO3– conversion toward synthetic applications.