Suppressing Reverse Processes in the Perylene Diimide/Strontium Titanate Z-Scheme Heterojunction for Efficient Photocatalytic Overall Water Splitting

Abstract Photocatalytic overall water splitting is promising for sustainable H2 supply but is hindered by severe charge recombination and the reverse reaction. Herein, we design a novel organic/inorganic heterojunction by coupling π-conjugated perylene diimide polymer (PDIP) with aluminum-doped strontium titanate (SrTiO3:Al) to suppress these reverse processes for boosting photocatalytic H2 evolution. In situ characterizations reveal a direct Z-scheme charge transfer pathway between PDIP and SrTiO3:Al, which promotes high‑energy charge carrier separation and suppresses the reverse reaction by spatially segregating the H2 and O2 evolution sites onto SrTiO3:Al and PDIP, respectively. Further, combined with selective co-catalyst engineering for preventing H2 and O2 from contacting on the catalyst surface, these reverse processes are fundamentally suppressed. Consequently, the PDIP/SrTiO3:Al heterojunction exhibits substantially enhanced photocatalytic activity for overall water splitting, achieving an H2 evolution rate 11.8 times higher than that of pristine SrTiO3:Al. This dual-suppression strategy provides a validated blueprint for highly efficient solar-to-hydrogen conversion.