Modulating chemical composition and work function of suspended reduced graphene oxide membranes through electrochemical reduction

Electrochemical reduction in aqueous graphene oxide (GO) dispersion has emerged as an alternative route to producing a reduced GO (rGO) membrane on Au mesh. Under scanning electron microscopy, an interesting pattern formed by distinct differences was discovered from the deoxidization evolution. Scanning transmission X-ray microscopy shows the chemical composition coordination mixing of C–OH, C–O–C, HO–C[dbnd]O, and C[dbnd]O bonds at nanoscale resolution. The electrochemical reduction of C–OH, new bonding of C–O–C, and structure recovery of C[dbnd]C were obtained from GO transformation into the rGO membrane. In Kelvin probe force microscopy, the same pattern of rGO was also observed for the diversity of work functions ranging from 5.55 to 5.70 eV compared with the uniform distribution of GO of 5.78 eV. Density functional theory calculations predicted that the work function variation originated from the dependence of O atom number and functional group species. A high (low) diversity in work function values was ascribed to the C–O–C (HO–C[dbnd]O) bond even with increasing oxygen numbers, accounting for the peak variation. Controlling the work function holds great significance for photovoltaic behavior and band alignment in photoelectric devices. Thus, growing large-area rGO membranes offers a new route to obtaining membranes for applications requiring transparent materials.