Synthesis of flower-liked twin crystal ternary Ni/NiS/Zn0.2Cd0.8S catalyst for highly efficient hydrogen production.

• A flower-liked twin crystal Zn 0.2 Cd 0.8 S is synthesized via a simple hydrothermal method. • Theoretical calculations (DFT) reveal the reaction mechanism of photocatalytic hydrogen production. • Positron annihilation demonstrates the surface defect variation in the catalysts. • Synergistic effects of the heterojunction and Ni greatly improve the separation of the photo-generated carriers. • The catalyst exhibits 83-times hydrogen production rate increments comparing to Zn 0.2 Cd 0.8 S. The applications of sulfide in photocatalytic hydrogen production are limited due to the rapid recombination of the electron-hole pairs. In this paper, a kind of novel flower-like ternary Ni/NiS/Zn 0.2 Cd 0.8 S composite catalyst with twin crystals and heterojunction structure is synthesized by a multi-step method. Compared with pure Zn 0.2 Cd 0.8 S, the ternary Ni/NiS/Zn 0.2 Cd 0.8 S catalyst shows significantly a highly visible light absorption, photoelectric performance and hydrogen production, i.e., both transient photocurrent and hydrogen production rate are increased by 18 times and 83 times, respectively. Combining the theoretical calculations and experimental results, a possible photocatalytic reaction mechanism is proposed. In this catalyst, it is known that the twin crystal Zn 0.2 Cd 0.8 S belongs to the homojunction structure, Zn 0.2 Cd 0.8 S combines with NiS to form a heterojunction and simultaneously supports the excellent conductivity of Ni, Which therefore, the synergy of the nano-scaled NiS and Ni co-catalysts show a great improvement in separation efficiency of the photo-generated electron-hole pairs, and allows the Ni/NiS/Zn 0.2 Cd 0.8 S catalyst to have excellent hydrogen production performance in photocatalytic decomposition of water. [ABSTRACT FROM AUTHOR]