Defect tailoring in K-doped carbon nitride: Enabling efficient decoupling of light and dark reactions for timely and delayed on-demand solar hydrogen production

Abstract

Decoupling hydrogen production from diurnal cycles is challenging in solar energy conversion. Recently, defect-modified K-doped carbon nitride has demonstrated the potential to realize this unique property. However, the concomitant undesirable defects during eutectic treatment, such as triazine ring insertion, impose substantial limitations on the decoupling performance. In this study, a one-step eutectic method assisted by CCl₄ was developed, which removed the detrimental triazine-based defects while introducing beneficial nitrogen vacancies. The engineered structure efficiently enhances visible light absorption, and spatially separates the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). The localized LUMO on N-K sites serves as an electron reservoir, facilitating carrier separation and inhibiting the recombination. Consequently, one of the highest timely light-driven activities among polymeric photocatalysts was achieved, reaching 2557 times the H₂ production rate compared to the un-engineered counterpart. More significantly, the electron reservoir could store active electrons for several weeks, successfully enabling delayed on-demand solar H₂ production and decoupling H₂ evolution from diurnal cycles. This study effectively achieves both spatial and temporal separation of light absorption, solar storage, and release through defect tailoring, which is expected to advance the development of decoupled catalytic studies.