A Red Brick‐Derived Fe ₂ P‐Based Cocatalyst Sheet Enables Monolithic Photocatalysts for Efficient Solar Hydrogen Production

Beyond powder-suspension photocatalytic systems, monolithic photocatalysts featuring excellent recyclability and enhanced light utilization efficiency have been promising candidates for large-scale solar-driven photocatalytic water splitting, yet often suffer from complex fabrication processes and reliance on the use of expensive scaffolds and additional cocatalyst loading. Herein, we develop monolithic photocatalysts via utilizing a cocatalyst sheet (Fe₂P/RB) derived from red brick (RB) by vapor-phase phosphidation as a scaffold to anchor particulate semiconductors (e.g., CdS, Zn_0.5Cd_0.5S, TiO₂, and g-C₃N₄), for solar-driven photocatalytic H₂ production from the water splitting. The endogenous Fe oxides within RB sheet are in situ converted into embedded Fe₂P during phosphidation, serving as electron sinks to promote charge separation and H₂-evolving active sites to improve water splitting performance. Impressively, the monolithic CdS-Fe₂P/RB photocatalyst sheet achieves a visible-light (λ ≥ 420 nm) photocatalytic HER rate of 7.7 mmol g_CdS ^-1 h^-1 and an apparent quantum yield (AQY) as high as 30.5% at 420 nm, which are 12.4 and 3.2 times higher than that of the powder-suspension system, respectively. Furthermore, the excellent integrity enables CdS-Fe₂P/RB to stably produce H₂ for 120 h with negligible activity decay. This work offers an effective strategy for the rational designs of cost-efficient and high-performance monolithic photocatalysts for solar water splitting.