High-Throughput Exploration of Metal Vanadate Thin-Film Systems (M–V–O, M = Cu, Ag, W, Cr, Co, Fe) for Solar Water Splitting: Composition, Structure, Stability, and Photoelectrochemical Properties

Combinatorial synthesis and high-throughput characterization of thin-film materials libraries enable to efficiently identify both photoelectrochemically active and inactive, as well as stable and instable systems for solar water splitting. This is shown on six ternary metal vanadate (M–V–O, M = Cu, Ag, W, Cr, Co, Fe) thin-film materials libraries, fabricated using combinatorial reactive magnetron cosputtering with subsequent annealing in air. By means of high-throughput characterization of these libraries correlations between composition, crystal structure, photocurrent density, and stability of the M–V–O systems in different electrolytes such as acidic, neutral and alkaline media were identified. The systems Cu–V–O and Ag–V–O are stable in alkaline electrolyte and exhibited photocurrents of 170 and 554 μA/cm², respectively, whereas the systems W–V–O, Cr–V–O, and Co–V–O are not stable in alkaline electrolyte. However, the Cr–V–O and Co–V–O systems showed an enlarged photoactive region in acidic electrolyte, albeit with very low photocurrents (<10 μA/cm²). Complete data sets obtained from these different screening sets, including information on nonpromising systems, lays groundwork for their use to predict new systems for solar water splitting, for example, by machine learning.