Reshaping hydrogen bond network in aqueous-aprotic hybrid electrolyte to achieve highly selective ambient ammonia synthesis.

Aqueous electrolytes are extensively applied in electrochemical nitrogen reduction reaction, while the overwhelming H 2 O always produce much protons, favoring the electron-stealing hydrogen evolution reaction (HER) and thus leaving the current ammonia synthesis much to be desired. Here, we propose an aqueous-aprotic hybrid electrolyte system by introducing trimethyl phosphate (TMP) as a cosolvent to achieve highly selective ammonia synthesis. TMP features higher Gutmann donors than that of H 2 O, preferring to serve as hydrogen bond (HB) acceptor and reshaping the HB network in the electrolyte. Molecular dynamics simulations suggest that, compared with H 2 O-H 2 O HB, the H 2 O-TMP HB exhibits longer lifetime and better stability. The intensified interaction between H 2 O and TMP weakens the interaction between H 2 O and H 2 O, which strengthens the O-H bond of H 2 O and makes it more difficult to be broken, thus greatly inhibiting the dissociation of H 2 O and leading to a suppressed HER activity. Correspondingly, a significantly improved NRR performance with a superior NH 3 yield rate of 82.1 ± 2.7 μg h–1 mg–1 and an optimum Faradaic efficiency of 73.3 ± 2.7% is achieved in the H 2 O-TMP hybrid electrolyte, indicative of order of magnitude enhancement compared with that delivered in the conventional aqueous electrolyte. [Display omitted] • An aqueous-aprotic hybrid electrolyte system is proposed. • TMP featuring higher Gutmann donors serves as hydrogen bond acceptor. • The intensified interaction between H 2 O and TMP inhibits the dissociation of H 2 O. • A significantly improved NRR performance is achieved. [ABSTRACT FROM AUTHOR]