Electrochemical reduction of nitrate on silver surface and an in situ Raman spectroscopy study

Abstract

Electroreduction of nitrates to other essential fertilizers is becoming an important method for the treatment of nitrate contamination. In this study, Ag nanocrystal catalyst on the quasi-cavity architecture of ZnO nanowalls has been rationally designed and synthesized. This hierarchical structure can efficiently catalyze nitrate reduction as well as a sensitive surface-enhanced Raman signals (SERS)-active substrate, which make it possible to figure out the mechanism for Ag-catalyzed electroreduction process at the atomic level. The catalyst exhibits an ammonia production of 516 mmol g_cat⁻¹ h⁻¹ and a Faradaic efficiency of about 66% at −0.6 V vs. reversible hydrogen electrode (RHE). The in situ Raman spectra clearly show SERS signals of NO, HNH and NH₃, which provide direct evidences to analyze the final production of ammonia and nitrite during the electroreduction process. This work can offer a fundamental understanding of the mechanism of the electroreduction process and further design strategies for other energy-related catalysts.