Annie Greenaway1,John Mangum1,Sijia Ke2,3,Andriy Zakutayev1,Jeffrey Neaton2,3
National Renewable Energy Laboratory1,University of California, Berkeley2,Lawrence Berkeley National Laboratory3
Annie Greenaway1,John Mangum1,Sijia Ke2,3,Andriy Zakutayev1,Jeffrey Neaton2,3
National Renewable Energy Laboratory1,University of California, Berkeley2,Lawrence Berkeley National Laboratory3
Development of photoelectrochemical (PEC) systems requires, among other advances, photoelectrode materials that are both photocatalytically active and stable in harsh electrochemical environments. We have intentionally searched for a candidate photoabsorber based on co-design principles, wherein design for photoactivity is based on the ability to integrate the new material with established semiconductors and design for stability is based on the propensity for the photoabsorber to self-passivate during operation. This has led to the first synthesis and substantial development of wurtzite ZnTiN<sub>2</sub> as a photoabsorber. Initially, high-throughput combinatorial synthesis was used to identify the radio-frequency co-sputtering parameter space for ZnTiN<sub>2</sub>.<sup>1</sup> Cation disorder in these films reduced the bandgap to ~2.0 eV, appropriate for solar fuel generation, and the ZnTiN<sub>2</sub> surface was found to transform to stable oxides under CO<sub>2</sub>R-relevant electrochemical conditions. Together, these characteristics indicate that ZnTiN<sub>2</sub> could be used as a photoelectrode, but the optoelectronic and crystalline properties of the material would require substantial improvement before operation in PEC applications. Next, experimental integration of ZnTiN<sub>2</sub> with established semiconductor systems allowed us to rapidly improve the crystalline and optoelectronic properties of the sputtered ZnTiN<sub>2</sub> films, paving the way for high photocatalytic activity for PEC to be demonstrated using this semiconductor. We will report on materials quality advances in ZnTiN<sub>2</sub> thin films as well as progress toward demonstration of this material as a photoelectrode. Future work will focus on developing PEC device structures based on the improved ZnTiN<sub>2</sub> photoelectrode films by optimizing semiconductor properties (e.g. doping) and interfaces with surrounding device layers.<br/><br/>(1) Greenaway, A. L.; Ke, S.; Culman, T.; Talley, K. R.; Mangum, J. S.; Heinselman, K. N.; Kingsbury, R. S.; Smaha, R. W.; Gish, M. K.; Miller, E. M.; Persson, K. A.; Gregoire, J. M.; Bauers, S. R.; Neaton, J. B.; Tamboli, A. C.; Zakutayev, A. Zinc Titanium Nitride Semiconductor toward Durable Photoelectrochemical Applications. <i>J. Am. Chem. Soc.</i> <b>2022</b>, <i>144</i> (30), 13673–13687. https://doi.org/10.1021/jacs.2c04241.