Ionic-Liquid-Functionalized Copper Oxide Nanorods for Photocatalytic Splitting of Water

Thin films of imidazolium (Im) ionic liquids with bis(salicylato)-borate (BScB) and hexafluorophosphate (PF6-) anions were grafted onto copper oxide (CuO) nanorods. Chemical and structural features of ionic-liquid-functionalized CuO (CuO-IL) nanorods were examined by X-ray photoelectron spectroscopy, FTIR spectroscopy, XRD, and high-resolution TEM analyses. The CuO-IL nanorods were demonstrated to be efficient photocatalysts for the splitting of water under visible-light irradiation without using any sacrificial agent. The pristine CuO nanorods could not split water, whereas CuO-IL nanorods exhibited excellent photocatalytic activities and produced 1827 and 1082 mu mol of hydrogen in 2 h with 20 mg of CuO-ImBScB and CuO-ImPF(6) as photocatalysts, respectively. The photocatalytic activity of the CuO-IL nanorods was attributed to the synergistic effect of ionic-liquid thin films and CuO nanorods. The trapping of photoinduced charge carriers by ionic liquids inhibits the recombination process, and consequently, the CuO nanorods facilitate the water-splitting reaction. The CuO-IL photocatalysts were efficiently recycled without loss of catalytic activity, which revealed the stability of the ionic-liquid thin films grafted on the CuO nanorods.