Se–S bonded non-metal elementary substance heterojunction activating photoelectrochemical water splitting

Non-metal elements are often merely regarded as electronic modulators, yet their intrinsic characteristics are frequently overlooked. Indeed, non-metal elements possess notable advantages in high-abundance, excellent hydrogen adsorption and the ability of active sites to be inversely activated, rendering them potential photoelectrochemical (PEC) materials. However, weak non-metal interbinding, susceptibility to photocorrosion, and high photogenerated carrier recombination rates hinder their practical applications. Herein, for the first time, we report a novel non-metal elementary substance heterojunction Se/S based on interfacial bonding engineering strategy. Atomic-level tight coupling of sulfonyl-rich sulfur quantum dots (SQDs) with selenium microtube arrays (Se-MTAs) enhances the structural stability of Se/S and introduces crucial Se–S heterointerfacial bonds, which not only endow Se/S with robust internal electronic interactions, but also provide high-speed channels for charge separation via unique bridging. Consequently, Se/S achieves optimal photocurrent density of 3.91 mA cm⁻² at 0 V_RHE, accompanied by long-term stability over 24 h. It is the highest value reported to date for Se-based photocathodes without co-catalyst and outperforms most metal-selenide-based photoelectrodes. Furthermore, the direct Z-scheme charge transport mechanism is exposed by in-depth spectroscopic analyses. Our work fills the gap in application of non-metal elementary substance heterojunction for PEC, poised for potential expansion into other new-energy devices.