Conformal surface intensive doping of low-valence Bi on Cu2O for highly efficient electrochemical nitrate reduction to ammonia production

Abstract

Electrochemical nitrate reduction reaction (NO₃RR) has been regarded as a promising alternative to the Haber-Bosch process for sustainable and clean NH₃ production. To develop highly active and stable electrocatalysts for NO₃^– to NH₃ production, Cu-based materials have been considered as potential candidates owing to the excellent NO₃^– adsorption to easily overcome the rate determining step of nitrate to nitrite conversion in NO₃RR, although the poor NH₃ yield rate is still challenging. In this study, we report a hybrid electrocatalyst with Bi dopant substitutionally incorporated on cuboctahedra Cu₂O platform (Bi/Cu₂O) via in-situ hydrothermal method. The Bi/Cu₂O shows the NH₃ yield rate of 2562.56 μg h⁻¹ mg_cat^-1 and Faradaic efficiency of 99.2 % at −0.8 V versus reversible hydrogen electrode in a neutral electrolyte, which is the highest performance among previously reported Cu-based electrocatalyst for NO₃RR to NH₃. The interfacial synergetic effect of sufficient protonation from Bi-doped overlayer and efficient NO₃^– adsorption from the Cu₂O platform results in excellent NO₃RR performance. The experimental variable investigations with in-situ attenuated total reflectance-Fourier transform infrared measurement elucidate that not only nitrate to nitrite conversion but also the protonation of *NO₂ is the rate limiting step for NH₃ production.