Interfacial Regulation by a NiO x Overlayer Enables Enhanced Near‐Infrared Photoelectrochemical Water Splitting

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Photoelectrochemical (PEC) water splitting provides a promising pathway for sustainable hydrogen production. However, the inefficient use of near‐infrared (NIR) light, which accounts for nearly half of the solar spectrum, remains a major limitation to overall energy conversion efficiency. Here, we present a NIR‐responsive dye‐sensitized photoanode enabled by a boron–dipyrromethene–carbazole‐based organic sensitizer ( 1 ), combined with a thin NiO x overlayer that acts as both an oxygen evolution reaction (OER) cocatalyst and an interface regulator. The NiO x layer, deposited via low‐temperature pulsed laser deposition, exhibits low crystallinity and mixed Ni 2+ /Ni 3+ valence states, as confirmed by transmission electron microscopy and X‐ray photoelectron spectroscopy. Adding the NiO x overlayer results in a 1.9‐fold increase in photocurrent density and significantly better photostability. Electrochemical testing indicates that NiO x alters interfacial charge–transfer kinetics and the local electrochemical environment, thereby improving carrier utilization and reaction efficiency. The multilayer photoanode retains a measurable photocurrent response at 850 nm, demonstrating its capability to extend PEC activity into the NIR region. This work elucidates the synergistic functions of NiO x in interfacial charge regulation and catalytic kinetics, offering a viable strategy for NIR‐driven solar fuel conversion. Additionally, it establishes the longest‐wavelength photoelectrocatalytic performance reported to date for non‐noble‐metal dye‐sensitized systems.

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