Round-the-clock photocatalytic hydrogen production enabled by an S-scheme Sr ₂ MgSi ₂ O ₇ :(Eu,Dy)/CdS heterojunction

Round-the-clock photocatalytic hydrogen production is essential for overcoming the intermittency of solar energy and achieving continuous solar-to-hydrogen conversion. However, the development of efficient round-the-clock photocatalysts remains a considerable challenge due to limited light availability and inefficient charge utilization in the dark. In this work, a long-afterglow-based S-scheme heterojunction photocatalyst, Sr2MgSi2O7:(Eu,Dy)/CdS (referred to as SMSED/CdS), is constructed via a ball-milling strategy. The luminescence from Sr2MgSi2O7:(Eu,Dy) (referred to as SMSED) is efficiently captured by CdS, thus serving as a built-in light source to drive dark catalytic reactions. Meanwhile, the unique electron transfer pathway in SMSED provides sufficiently long-lived electrons for the SMSED/CdS system. The S-scheme heterojunction formed between SMSED and CdS directs the photogenerated charge transfer, while maintaining the strong redox capability of SMSED/CdS. Consequently, the SMSED/CdS exhibits hydrogen production of 45.20 mmol g-1 under ultraviolet-visible light within 1 h and a dark activity of 4.37 mmol g-1 sustained over 3 h. The corresponding mechanism was comprehensively studied via analysis of physicochemical properties, band structure, ex-situ and in-situ X-ray photoelectron spectroscopy, and density functional theory calculations. This study provides a significant breakthrough in developing round-the-clock photocatalysts.