Advancing Hematite Photoanodes for Photoelectrochemical Water Splitting: The Impact of g‐C₃N₄ Supported Ni‐CoP on Photogenerated Hole Dynamics

The increasing demand for clean hydrogen necessitates the rapid development of efficient photoanodes to catalyze the water oxidation half‐reaction effectively. Here a strategy is introduced to fabricate photoanodes that synergistically combine and leverage the properties of porous Ti‐doped hematite (Ti‐Fe 2 O 3 ) and graphitic carbon nitride (g‐C 3 N 4 ) nanosheets anchored with in situ grown Ni‐doped CoP co‐catalyst (Ni‐CoP). The resulting hybrid photoanodes exhibit >7 times higher photocurrent density at +1.23 V RHE compared with Ti‐Fe 2 O 3 photoanodes. Comprehensive characterization techniques, including ambient photoemission spectroscopy, intensity‐modulated photocurrent spectroscopy, and transient absorption spectroscopy complementarily reveal the key impact of g‐C 3 N 4 in these composites with enhanced solar oxygen evolution reaction: The incorporation of g‐C 3 N 4 leads to enhanced charge separation through a type‐II heterojunction, thereby increasing the hole flux at the surface, and extending the charge carrier lifetime to the ms‐s range needed for water oxidation. Additionally, g‐C 3 N 4 facilitates efficient transfer of photogenerated holes to the fine Ni‐CoP nanoparticles confined in the graphitic matrix for a boosted oxygen evolution reaction. These findings highlight the advantages of complex heterostructure photoanodes and demonstrate a new application of g‐C 3 N 4 as a multifunctional support of co‐catalysts for future photoanodes with enhanced performance.