Copper vanadate nanobelts as anodes for photoelectrochemical water splitting: influence of CoOx overlayers on functional performances

The design and development of environmentally friendly and robust anodesfor photoelectrochemical (PEC) water splitting plays a critical role for the efficientconversion of radiant energy into hydrogen fuel. In this regard, quasi-1D copper vanadates(CuV2O6) were grown on conductive substrates by a hydrothermal procedure andprocessed for use as anodes in PEC cells, with particular attention on the role exerted bycobalt oxide (CoOx) overlayers deposited by radio frequency (RF) sputtering. The targetmaterials were characterized in detail by a multitechnique approach with the aim atelucidating the interplay between their structure, composition, morphology, and theresulting activity as photoanodes. Functional tests were performed by standardelectrochemical techniques like linear sweep voltammetry, impedance spectroscopy, andby the less conventional intensity modulated photocurrent spectroscopy, yielding animportant insight into the material PEC properties. The obtained results highlight that,despite the fact that the supposedly favorable band alignment between CuV2O6 and Co3O4did not yield a net current density increase, cobalt oxide-functionalized anodes afforded aremarkable durability enhancement, an important prerequisite for their eventual real-world applications. The concurrent phenomenaaccounting for the observed behavior are presented and discussed in relation to material physico-chemical properties.