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[Display omitted] Ti 3 C 2 T x MXene, a new family of 2D materials, has been successfully used as an ideal co-catalyst for enhancing photocatalytic activity due to its excellent physicochemical properties. Bacteriochlorophyll (BChl), one of the most abundant photosynthetically active pigments, has been studied in the field of artificial photosynthesis due to its constant and efficient absorption of solar energy and conversion of the excitation energy into chemical energy. In this work, five BChl- a derivatives with a range of different side chain groups in the C17 substituent were prepared and deposited on the Ti 3 C 2 T x MXene surface by a solvent evaporation process to form BChl-n@Ti 3 C 2 T x (n = 1∼5) composite photocatalysts, which were used for the visible light-driven photocatalytic hydrogen evolution reaction (HER) in an aqueous solution. Among the five BChls investigated, BChl-5 possessing a quaternary ammonium terminal showed the best performance and BChl-5@Ti 3 C 2 T x composite exhibited an excellent hydrogen production activity of as high as 51 μmol/h/g cat. This is primarily attributed to the excellent photophysical and photochemical properties provided by the self-aggregation of BChl-5 in the BChl-5@Ti 3 C 2 T x composite and the outstanding charge transport capability of the 2D Ti 3 C 2 T x MXene. At the same time, the fast carrier separation and transfer capability between BChl-5 and Ti 3 C 2 T x provides reliable charge transport for photocatalytic HER. [ABSTRACT FROM AUTHOR]

Hydrogen energy is an abundant, clean, sustainable and environmentally friendly renewable energy source. Therefore, the production of hydrogen by photocatalytically splitting water on semiconductors has been considered in recent years as a promising and sustainable strategy for converting solar energy into chemical energy to replace conventional energy sources and to solve the growing problem of environmental pollution and the global energy crisis. However, highly efficient solar‐driven photocatalytic hydrogen production remains a huge challenge due to the poor visible light response of available photocatalytic materials and the low efficiency of separation and transfer of photogenerated electron‐hole pairs. In the present work, organic heterojunction structures based on bacteriochlorophyll (BChl) and chlorophyll (Chl) molecules were introduced and used for solar‐driven photocatalytic hydrogen production from water under visible light. Also, noble metal‐free photocatalyst was successfully constructed on Ti3C2Tx nanosheets by simple successive deposition of Chl and BChl, which was used for the photocatalytic splitting water to hydrogen evolution reaction (HER). The results show that the optimal BChl@Chl@Ti3C2Tx composite has a high HER performance with 114 μmol/h/gcat, which is much higher than the BChl@Ti3C2Tx and Chl@Ti3C2Tx composites. [ABSTRACT FROM AUTHOR]

[Display omitted] • Organic heterojunction of Chl–g-C 3 N 4 was constructed for visible-light driven H 2 evolution. • Highly efficient electron-hole separation occurred through the organic heterojunction structure. • Chl@g-C 3 N 4 /MXene-based photocatalytic system were developed for noble metal-free HER. • This work provides directions for preparation of organic heterojunction structures suitable for HER. Sustainable conversion of solar energy to hydrogen energy by photocatalytic splitting of water through the use of semiconductor photocatalytic materials is considered to be a promising and sustainable alternative proposal to replace conventional fossil fuels. However, efficient solar-driven photocatalytic hydrogen production has remained a great challenge due to the prevailing problems of existing semiconductor photocatalytic materials. It is shown that constructing heterostructures is a very powerful way to improve the photocatalytic hydrogen production capacity of composites under visible light. Therefore, in this work, an organic heterojunction structure based on chlorophyll (Chl) molecules and graphitic carbon nitride (g-C 3 N 4) is reported and exploited for efficient solar energy-driven photocatalytic hydrogen evolution reaction (HER). Meanwhile, noble metal-free photocatalysts were successfully constructed with Ti 3 C 2 T x MXene nanosheets through a simple stepwise complexation process of Chl, g-C 3 N 4 , and Ti 3 C 2 T x for the achievement of HER for the photocatalytic decomposition of water. The results show that the optimal Chl@g-C 3 N 4 /Ti 3 C 2 T x organic heterojunction composite has a remarkably advanced HER performance of 131 μmol/h/g cat , as compared with the traditional Chl@Ti 3 C 2 T x and g-C 3 N 4 /Ti 3 C 2 T x composites. The results provide new ideas for exploring MXene based catalysts for highly efficient conversion of solar energy. [ABSTRACT FROM AUTHOR]