Nanotextured cupric oxide nanofibers coated with atomic layer deposited ZnO-TiO2 as highly efficient photocathodes

We report the fabrication and performance of a CuO/ZnO/TiO2 nanofiber photocathode that achieved a photocurrent density (PCD) of -4.1 mA/cm(2), which is among the highest PCD values reported for a copper oxide based photocathode without a co-catalyst. To prepare this photocathode, we coated electrospun nanofibers with copper by electroplating, then dried them in air to produce cuprous oxide (Cu2O) nanofibers. Further annealing in air converted them to cupric oxide (CuO). The CuO nanofibers exhibit nanotextured surfaces, resembling the skin of the thorny-devil lizard of Australia, providing high accessible surface area for photocatalysis. These CuO nanofibers were uniformly coated with thin ZnO and TiO2 layers by atomic layer deposition (ALD) to promote electron migration from CuO to TiO2 and protect the CuO from corrosion. The nanofibrous photocathode films were characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, and transmission electron microscopy, as well as by incident photon-to-electron conversion efficiency measurements. (C) 2016 Elsevier B.V. All rights reserved.