Multinary metal oxide photoelectrodes

Metal oxides are an intriguing class of materials that can potentially enable large-scale solar fuel production via photoelectrochemical (PEC) water splitting. Binary metal oxides, consisting of a single type of metal combined with oxygen, have been studied as photoelectrode materials for decades. Unfortunately, these materials have not yet enabled efficient and stable PEC water splitting due to their inherent limitations in light absorption, stability, and carrier transport. Recently, more complex, multinary metal oxides, composed of at least two metals and oxygen, have shown promise as photoelectrode materials. In many cases, the multinary metal oxides have shown fewer material limitations and higher photoelectrochemical efficiencies than their binary counterparts. The number of available material combinations is much greater for multinary metal oxides, and many combinations have not yet been explored. In this chapter, we discuss the crystal structure and electronic, optical, and photoelectrochemical properties of several n- and p-type complex metal oxides that can potentially be used as photoelectrode materials. We summarize the current research status of these materials and discuss their future outlook. In addition, we explain how these multinary metal oxides might be employed in a tandem photoelectrochemical device to relax the stringent material requirements for PEC water splitting and allow for higher efficiencies. Lastly, we discuss some to the challenges of using multinary metal oxides as photoelectrode materials along with future work that still needs to be completed for this class of materials. © Springer International Publishing Switzerland 2016.