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The idea of exploiting the inexhaustible solar energy-driven photocatalytic hydrogen evolution reaction (HER) to generate hydrogen energy, a sustainable clean energy source, to solve problems such as fossil fuel-induced greenhouse gas emissions is believed to be a feasible strategy. However, photocatalytic HER is inefficient due to insufficient light trapping capability and low charge separation efficiency of the single semiconductor material employed. Therefore, it remains a great challenge to achieve fast and efficient photocatalytic HER. In this work, a novel ternary Chl@Cu2O/Ti3C2Tx photocatalyst with an organic–inorganic heterojunction structure has been designed by employing a stepwise deposition process for efficient solar energy conversion to hydrogen. The results showed that the photocatalytic activity of Chl@Cu2O/Ti3C2Tx organic–inorganic heterojunction photocatalysts for HER was significantly improved compared with that of single Chl@Ti3C2Tx and Cu2O/Ti3C2Tx. The improvement of the photocatalytic performance of Chl@Cu2O/Ti3C2Tx compared to Chl@Ti3C2Tx and Cu2O/Ti3C2Tx is attributed to the construction of the Chl–Cu2O organic–inorganic heterojunction structure in Chl@Cu2O/Ti3C2Tx, which extends the absorption range of the spectra and dramatically enhances the separation efficiency of the photogenerated carriers in Chl@Cu2O/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]