Electrocatalytic Reduction of Nitrate to Nitrous Oxide by a Copper-Modified Covalent Triazine Framework

It was found that copper-modified covalent triazine frameworks (Cu-CTF) efficiently catalyze the electrochemical reduction of nitrate and promote N–N bond formation of nitrous oxide (N2O), a key intermediate for N2 formation (denitrification). A Cu-CTF electrode exhibited an onset potential of −50 mV versus RHE for the electrochemical nitrate reduction reaction (NRR). The faradaic efficiency for N2O formation by Cu-CTF reached 18% at −200 mV versus RHE, whereas that for Cu metal was negligible. On the basis of density functional calculations for Cu-CTF, both solvated and surface-bound nitric oxide (NO) were generated by the NRR due to the moderate adsorption strength of Cu atoms for NO, a property that facilitated the effective dimerization of NO through an Eley–Rideal-type mechanism.