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

Abstract

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‐Fe2O3) and graphitic carbon nitride (g‐C3N4) 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 VRHE compared with Ti‐Fe2O3 photoanodes. Comprehensive characterization techniques, including ambient photoemission spectroscopy, intensity‐modulated photocurrent spectroscopy, and transient absorption spectroscopy complementarily reveal the key impact of g‐C3N4 in these composites with enhanced solar oxygen evolution reaction: The incorporation of g‐C3N4 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‐C3N4 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‐C3N4 as a multifunctional support of co‐catalysts for future photoanodes with enhanced performance.