Copper Vanadate Nanobelts as Anodes for Photoelectrochemical Water Splitting: Influence of CoO Overlayers on Functional Performances.

The design and development of environmentally friendly and robust anodes for photoelectrochemical (PEC) water splitting plays a critical role for the efficient conversion of radiant energy into hydrogen fuel. In this regard, quasi-1D copper vanadates (CuVO) were grown on conductive substrates by a hydrothermal procedure and processed for use as anodes in PEC cells, with particular attention on the role exerted by cobalt oxide (CoO) overlayers deposited by radio frequency (RF) sputtering. The target materials were characterized in detail by a multitechnique approach with the aim at elucidating the interplay between their structure, composition, morphology, and the resulting activity as photoanodes. Functional tests were performed by standard electrochemical techniques like linear sweep voltammetry, impedance spectroscopy, and by the less conventional intensity modulated photocurrent spectroscopy, yielding an important insight into the material PEC properties. The obtained results highlight that, despite the fact that the supposedly favorable band alignment between CuVO and CoO did not yield a net current density increase, cobalt oxide-functionalized anodes afforded a remarkable durability enhancement, an important prerequisite for their eventual real-world applications. The concurrent phenomena accounting for the observed behavior are presented and discussed in relation to material physico-chemical properties.