Tailored Nickel Oxide Interfacial Layers Unlock Enhanced Charge Dynamics in LaTiO _x N _y Thin Film Photoanodes

ABSTRACT LaTiO 2 N (LTON) is a very attractive visible light responsive semiconductor for the fabrication of photoanodes for H 2 production by solar`ting. To design a feasible process, the other half of the water splitting reaction, the oxygen evolution reaction (OER), must be realized, and it is crucial to pair the photoanodes with appropriate OER catalysts such as nonstoichiometric nickel oxide (NiO x ). The application of NiO x interfacial layers to LTON thin film photoanodes significantly enhances photocurrent performance by improving charge extraction and minimizing recombination. This work demonstrates that NiO x functions as both a charge‐selective layer and a recombination barrier, achieving record photocurrents for sub‐50 nm LTON films in alkaline and sulfite‐buffered electrolytes. Time‐resolved and electrochemical analyses reveal that these improvements stem from effective Fermi‐level de‐pinning, bulk‐to‐surface charge transport enhancement, and the presence of scavengeable long‐lived charges. These findings underscore the potential of NiO x as a highly effective interfacial layer for solar water splitting utilizing LTON, a superior oxynitride.