Chlorosome‐Like Molecular Aggregation of Chlorophyll Derivative on Ti₃C₂T_x MXene Nanosheets for Efficient Noble Metal‐Free Photocatalytic Hydrogen Evolution

Abstract

such as global warming and climate changes. [1][2][3][4] Solar energy is clean and abundant, for example, nearly four million exajoules (4 × 10 18 J) of solar energy reaches the earth annually. [1,5] Conversion of solar energy into chemical energy through photocatalytic decomposition of water to produce hydrogen is one of the suitable approaches to utilize solar energy. [6][7][8][9][10] The different types of fundamental photocatalytic reactions include i) semiconductor-based photocatalysis, ii) dye-sensitized semiconductor-based photo catalysis, iii) quantum dot-based photocatalysis, iv) 2D layered materials-based photocatalysts, and v) plasmonic photocatalysts. [11] Photocatalytic hydrogen evolution reaction (HER) are mainly based on inorganic semiconductor and poly merbased organic semiconductors, for exampl, in a conventional dye-sensitized semiconductor photocatalytic hydrogen production system, the dye molecules are excited to inject electrons into the conduction band of a semiconductor or polymer (inorganic semiconductor TiO 2 or g-C 3 N 4 is usually chosen), then the electrons are quickly captured by the co-catalyst (such as precious metals Efficient photocatalytic hydrogen evolution reaction (HER) in the visibleto-near infrared region at a low cost remains a challenging issue. This work demonstrates the fabrication of organic-inorganic composites by deposition of supramolecular aggregates of a chlorophyll derivative, namely, zinc methyl 3-devinyl-3-hydroxymethyl-pyropheophorbide a (Chl) on the surface of Ti 3 C 2 T x MXene with 2D accordion-like morphology. This composite material isemployed as noble metal-free catalyst in photocatalytic HER under the white light illumination, where Chl serves as a small molecule organic semiconductor component instead of ordinary inorganic and polymer organic semiconductors such as TiO 2 and g-C 3 N 4 , and Ti 3 C 2 T x serves as a co-catalyst. Different composition ratios of Chl/Ti 3 C 2 T x are compared for their light-harvesting ability, morphology, charge transfer efficiency, and photocatalytic performance. The best HER performance is found to be as high as 52 ± 5 µmol h −1 g cat −1 after optimization. Such a large HER activity is attributed to the efficient light harvesting followed by exciton transfer in Chl aggregates and the resultant charge separation at the interface of Chl/Ti 3 C 2 T x .

Semisynthetic Chlorophyll Derivatives Toward Solar Energy Applications

“…In contrast, incorporation of chlorophyll aggregates in the photocatalytic H 2 evolution systems is of great potential. We recently demonstrated the fabrication of organic–inorganic composites by deposition of supramolecular aggregates of ZnChl‐9 on the surface of Ti 3 C 2 T x MXene with 2D accordion‐like morphology (Figure e) . MXenes are a new family of 2D nanostructured materials, which have attracted more and more attention since 2011 due to their unique optoelectronic properties with tunable surface termination .…”

Chlorophyll‐Based Organic Heterojunction on Ti3C2Tx MXene Nanosheets for Efficient Hydrogen Production

“…It was shown that they could form aggregates to efficiently capture sunlight and transport charge compared with their monomers. Such properties of Chl derivatives have been applied in solar cells, [11–13] energy storage, [14] and photocatalytic hydrogen evolution [15] . Compared with other photocatalysts that use synthetic photoactive materials, Chls are cost‐effective, environmentally friendly, easy to be disposed of, abundant, and nonpoisonous natural pigments.…”

“…In our previous investigation, we combined zinc methyl 3‐devinyl‐3‐hydroxymethyl‐pyropheophorbide a (Chl‐1; Figure 1) with Ti 3 C 2 T x MXene for the HER, and we proved that hydrogen was generated through exciton transfer in Chl‐1 aggregates followed by charge transfer to Ti 3 C 2 T x [15] . However, the performance of this system was still insufficient and required further improvement.…”

Strategies to improve electrocatalytic and photocatalytic performance of two-dimensional materials for hydrogen evolution reaction

“…Compared to MoS2 and graphene, MXene research is still in the early stages. Unlike MoS2 and graphene, MXenes do not have stacked structure that can be peeled directly, and most MXene syntheses are based on the structure removal of MAX phases [86][87][88][89].…”