Ultra-stable oxygen species in Ag nanoparticles anchored on g-C3N4 for enhanced electrochemical reduction of CO2

Oxide-derived silver catalysts containing stable oxygen species have been proved to be efficient for the electrochemical reduction reaction of CO2 (CO2RR) due to their enhanced binding energy to *COOH intermediate. Here we developed a hydrothermal decomposition method to synthesize silver nanoparticles (NPs) supported on carbon nitride (Ag/g-C3N4) from silver oxide (Ag2O) precursor. The obtained Ag/gC(3)N(4) electrocatalyst is capable of producing CO at a low onset overpotential (190 mV), and exhibits a high Faraday efficiency (FE) up to 94.0% at -0.7 V vs RHE along with a mass activity of 45.7 mA/mg. The improved electrochemical performance is attributed to the ultra-stable oxygen species derived from the incomplete decomposition of Ag2O and coexisted with Ag NPs in the final Ag/g-C3N4 composite. The presence and durability of oxygen species were verified from transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Ag MNN Auger spectra, and temperature-programmed reduction (TPR) measurements. The strong interaction between Ag NPs and g-C3N4 substrate via the Ag-N bonding alters the rate-determining step (RDS) of CO2 RR from the electron transfer (CO2 to*CO2 center dot-) to the proton transfer (*CO2 center dot- to *COOH) process. (C) 2021 Elsevier Ltd. All rights reserved.