Au/Ti 3 C 2 /g-C 3 N 4 Ternary Composites Boost H 2 Evolution Efficiently with Remarkable Long-Term Stability by Synergistic Strategies.

The use of novel two-dimensional MXene materials and conventional g-C 3 N 4 photocatalysts to fabricate the composites for hydrogen evolution reaction (HER) has attracted much attention, for which there is plenty of room for the enhancement of hydrogen evolution rates particularly under visible light and photostability. Herein, g-C 3 N 4 was modified by copolymerization of malonamide and melamine and used to fabricate the ternary composites of Au particles and Ti 3 C 2 MXene, and based on the synergistic effect, the composites enhanced the hydrogen evolution rates by 2.1, 99.8, and ∞ times compared with the unmodified g-C 3 N 4 under UV, simulated sunlight, and visible light illumination, respectively. Moreover, the composite exhibited a sustained hydrogen evolution capacity in the cycle test for up to 120 h. Theoretical calculations and experimental results indicated that the hot electrons of Au are injected into the modified g-C 3 N 4 and transferred to Ti 3 C 2 simultaneously along with the photogenerated electrons of the modified g-C 3 N 4 and then further transferred to Au, forming a photogenerated electron transfer channel of Au and modified g-C 3 N 4 → Ti 3 C 2 → Au within the composite. Ti 3 C 2 acts as a bridge for fast separation of photogenerated electrons and holes on Au and modified g-C 3 N 4 , playing a key role in the enhanced photocatalytic performance. In addition, the visible light absorption ability of Au also positively contributed to the enhancement of visible light photocatalytic performance by providing hot electrons. Therefore, the selection of suitable cocatalysts for the design of composites is a crucial research direction to improve the photocatalytic performance and photostability of photocatalysts.