ZnO nano-tetrapod photoanodes for enhanced solar-driven water splitting

ZnO nanotetrapod (ZnO-TP) photoanodes have been fabricated by a simple thermal evaporation method followed by characterization of their morphological, structural, optical and photoelectrochemical properties. The reaction time was found to be a critical factor in the synthesis of well-defined tetrapod nanostructures. The crystallinity of the grown tetrapods was investigated using X-ray diffraction as well as Raman spectroscopy. The photoluminescence (PL) spectra of the fabricated ZnO nanostructures showed two peaks; a near-band-edge (NBE) emission in the UV region and a broad deep-level emission (DLE) in the green emission region. Used as photoanodes to photoelectrochemically split water, the 90 min-treated ZnO-TP electrodes showed a photocurrent density of 0.4 mA/cm2 under AM 1.5G illumination (100 mW/cm2, 0.5 M Na2SO4), a significantly greater photocurrent than the bulk ZnO counterpart electrodes. The transient photocurrent measurements revealed exceptional stability of the as-fabricated ZnO-TPs.