S‑Scheme Interface\nBetween K–C₃N₄ and FePS₃ Fosters\nPhotocatalytic H₂ Evolution

Abstract

In photocatalysis, photogenerated charge separation is\npivotal\nand can be achieved through various mechanisms. Building heterojunctions\nis a promising method to enhance charge separation, where effective\ncontact and charge exchange between heterojunction components remains\nchallenging. Mostly used synthesis processes for making heterostructures\nrequire high temperatures, difficult processes, or expensive materials.\nHerein, a heterojunction of potassium intercalated graphitic carbon\nnitride (K-CN) and nanoflakes of iron phosphor trisulfide (FPS) is\ndesigned via a simple mechanical grinding process to boost the hydrogen\nevolution by a factor of more than 25 compared to pure K-CN. This\nsignificant improvement is rarely reached by other combinations of\ntwo semiconductors without cocatalysts, such as platinum. It can be\nattributed to the band alignment and band bending of an S-scheme that\nis validated via optical and X-ray photoelectron spectroscopy. As\na consequence, strong quenching of the photoluminescence and significant\nH₂ evolution occur for this unique heterojunction. Furthermore,\nthe excellent durability of the designed photocatalytic heterostructure\nis confirmed by monitoring the catalysts’ H₂-evolution\nrate and crystal structure after 72 h under light illumination. This\nstudy opens up promising and simple pathways for constructing efficient\nS-scheme heterojunctions for photocatalytic water-splitting.