Many crystalline nanomaterials have distinctive crystallographic facets that exhibit facet-dependent properties such as surface charges/charge densities, hydrophobicity and photo-electronic responses. This facet dependence results from different terminated atomic or molecular attributes and receives increasing interests in nanomaterial fabrication and applications such as in catalysis and sensing. Cuprous oxide (Cu2O) has been extensively studied owing to its excellent optical, magnetic, and environmentally benign properties. In this work, we synthesized cubic, octahedral, rhombic dodecahedra shaped Cu2O crystals and evaluate the facet-dependent activities for methyl orange (MO) detection. Cyclic voltammetry (CV) and chronoamperometry (CA) were performed to investigate the linear range, detection limit and sensitivity. Electrochemical impedance spectroscopy (EIS) was used to further reveal facet-dependent adsorption behavior of MO on Cu2O crystals. The (111) facet has better electrochemical sensing performance than that of the (100) facet of Cu2O nanocubes. Density-functional theory (DFT) calculations further indicated that adsorption of MO is responsible for the difference of electrochemical properties. Our combined experimental and computational chemistry approaches unravel new mechanism of surface electrochemical properties of Cu2O crystals at crystalline facet levels. Furthermore, this study aims to provide insight into the design of safe and functional nanomaterials for chemical sensing, selective electroanalysis or electrodes and antimicrobial applications.

Facet-dependent electrochemical behavior of Cu2O microcrystals for methyl orange: Theoretical prediction and experimental validation

ACS Fall 2021

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