Synthesis of trigonal selenium nanorods by electrodeposition from an ionic liquid at high temperature

We report on the electrodeposition of trigonal selenium (t-Se) nanorods from 1-ethyl-3-methylimidazolium tetrafluoroborate/chloride ([C2mim][BF4]/[C2mim]Cl) at high temperature (T > 100 °C). It is shown that the Se4+ precursor salt significantly influences the electrochemical behaviour, as well as the phase, morphology and crystallinity of the Se deposits. Amorphous selenium (a-Se) films are deposited from [C2mim][BF4]/[C2mim]Cl-SeCl4 whereas high aspect ratio single-crystalline trigonal selenium nanorods are formed from [C2mim][BF4]/[C2mim]Cl-SeO2. The t-Se nanorods are characterized by XRD, SEM, TEM and Raman spectroscopy and the growth mechanism of the single-crystalline t-Se nanorods from a-Se particles during the electrodeposition process is elucidated. The crystallinity of the t-Se nanorods is improved by increasing the temperature from 100 to 160 °C. Photoelectrochemical measurements performed in the ionic liquid confirm the p-type conductivity of the t-Se nanorods.

► The electrochemistry of SeCl4 and SeO2 in EMI-BF4/Cl are presented and show significantly different behaviour. ► The electrodeposition of selenium from the two precursors at T > 100 °C leads to deposits with distinct phase, crystallinity and morphology. ► Synthesis of high aspect ratio single-crystalline trigonal Se (t-Se) nanorods from EMI-BF4/Cl-SeO2. ► The t-Se nanorods show improved crystallinity with increasing deposition temperature. ► The t-Se nanorods are photoactive, showing p-type conductivity, measured for the first time in an ionic liquid.