Synthesis of Cu2O NPs using bioanalytes present in Sechium edule: Mechanistic insights and application in electrocatalytic CO2 reduction to formate

Abstract

Efficient electrocatalytic reduction of CO2 to value-added chemicals is a promising and challenging task as well. In fact, synthesis of low-cost electrocatalysts in an environmentally benign process is the need of the hour. Bioactive compounds including polyphenols, reducing sugars, and ascorbic acid (AA) present in different plant organs are proven competent in reducing metal ions to their lower or zero oxidation states. The present study focuses on the synthesis of Cu2O NPs using the bioactive compounds present in Sechium edule fruit. The mechanistic pathways for the understanding of the formation of the face-centred cubic Cu2O NPs (37.5−42 nm) and metal-organic (intermediates) ligand leading to the development of its stabilizing cap are investigated in details. Cu2O NPs were decorated on the Toray carbon paper electrode. The modified electrodes could decrease the charge transfer resistance by 50 folds and catalyze the electrocatalytic CO2 reduction to HCOO‾, a sole liquid product in 0.5 M KHCO3 electrolyte with a faradaic efficiency of 65.3–66.6 % within 60 min as the existence of predominant Cu2O (111) NPs could be responsible for selective formation of formate. Nevertheless, Cu2O underwent oxidation to CuO after 100 voltammetric cycles which was resulted in declining CO2 reduction reaction rate. The stability of Cu2O NPs and its delamination from the electrode surface was also studied in this work.