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

ABSTRACT 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 (Fe 2 P/RB) derived from red brick (RB) by vapor‐phase phosphidation as a scaffold to anchor particulate semiconductors (e.g., CdS, Zn 0.5 Cd 0.5 S, TiO 2 , and g‐C 3 N 4 ), for solar‐driven photocatalytic H 2 production from the water splitting. The endogenous Fe oxides within RB sheet are in situ converted into embedded Fe 2 P during phosphidation, serving as electron sinks to promote charge separation and H 2 ‐evolving active sites to improve water splitting performance. Impressively, the monolithic CdS‐Fe 2 P/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‐Fe 2 P/RB to stably produce H 2 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.