Chlorophyll derivatives/MXene hybrids for photocatalytic hydrogen evolution: Dependence of performance on the central coordinating metals

Development of efficient photocatalytic hydrogen evolution reaction (HER) with illumination of visible light is challenging. In this work, five chlorophyll derivatives (M-Chls; M = H 2 /Cu/Ni/Co/Zn) with different central ions in its cyclic tetrapyrrole ring including free base, copper, nickel, cobalt, and zinc were synthesized and employed as the effective visible-light harvester for efficient HER. In addition, two-dimensional (2D) noble metal-free co-catalyst Ti 3 C 2 T x MXene was used as an excellent electron capturer due to its outstanding conductivity property. These M-Chls are modified on the surface of Ti 3 C 2 T x MXene with 2D accordion-like morphology by means of a simple deposition process to form noble metal-free Chl/Ti 3 C 2 T x -based photocatalysts for HER. It is found that the best HER performance as high as 49 μmol/h/g cat was achieved with the Co-Chl@Ti 3 C 2 T x hybrid, which was much higher than those of other M-Chl@Ti 3 C 2 T x composites. This research provides a specific way to synthesize low-cost and environmentally friendly natural Chls for developing highly efficient photocatalytic HER through molecular engineering. • Chl- a derivatives M-Chls with five different central ions, were used for HER. • Noble metal-free photocatalytic system of M-Chls@Ti 3 C 2 T x hybrid is developed. • This work provides a way to synthesize environmentally friendly Chls for HER.