Elucidating facet dependent electronic and electrochemical properties of Cu2O nanocrystals using AFM/SCEM and DFT. (August 2022)

• Record Type: Journal Article
• Authors: Ma, Qingquan; Young, Joshua; Basuray, Sagnik; Cheng, Guangming; Gao, Jianan; Yao, Nan; Zhang, Wen
• Is Part Of: Nano today. Volume 45(2022)
• Publication Date: 2022-08
• Subjects: Cu2O -- Facet engineering -- Electrochemical activity -- AFM-SECM -- KPFM -- DFT; Nanotechnology -- Periodicals; Nanosciences -- Périodiques; 620.505
• DOI: 10.1016/j.nantod.2022.101538
• Languages: English
• ISSNs: 1748-0132

Abstract

Abstract: Cuprous oxide (Cu2 O) has extensively been studied owing to its excellent optical, magnetic, and catalytic properties. Many of these properties are facet-dependent and have not been well elucidated. This work synthesized cubic, cuboctahedral, octahedral, and rhombic dodecahedral shaped Cu2 O nanocrystals of ∼300 nm in size to evaluate the facet-dependent electrochemical activities. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were firstly used to reveal the average electrochemical activities at the ensemble level. Atomic force microscopy-scanning electrochemical microscopy (AFM-SECM) was further used to assess the electrochemical activities of different Cu2 O nanocrystals at the facet level. Hexaammineruthenium (III) chloride ({Ru(NH3 )6 }Cl3 ) was employed as the probe molecules that reacted with four different Cu2 O nanocrystals under 400 mV and yielded ∼300 pA current between the probing tip and the nanocrystal surface. The tip-current mapping results indicate that rhombic dodecahedral Cu2 O exhibits higher electrocatalytic activity than other shaped Cu2 O, due to the presence of dominant exposed facet of {110} as indicated by the relatively high tip current. Density-functional theory (DFT) calculations confirmed the facet dependence of local surface energy and electronic structure of Cu2 O nanocrystals. Besides electrochemical activity, the surface work function and adsorptive properties were both observed to vary with the shape and dominant exposed facets of Cu2 O. This study presented a unique experimental and computational chemistry approach to analyze surface electrochemical properties of Cu2 O crystals at a crystalline facet level. Graphical Abstract: Experimental approaches using AFM/SECM revealed the facet depdence of electronic and electrochemical properties of Cu2 O nanocrystals. ga1 Highlights: AFM-SECM reveals facet dependent electrochemical properties of Cu2 O nanocrystals. KPFM demonstrates nanoscale facet dependent electronic properties of Cu2 O. Rhombic dodecahedral Cu2 O exhibits higher electrocatalytic activity than other shaped Cu2 O. Cu2 O {110} facet shows a metallic surface state that matches the DFT simulations. Local surface energy and electronic structures of Cu2 O nanocrystals are also facet dependent.