Abstract
Hydrogen generation from water using noble metal-free photocatalysts presents a promising platform for renewable and sustainable energy. Copper-based chalcogenides of earth-abundant elements, especially Cu2ZnSnS4 (CZTS), have recently arisen as a low-cost and environment-friendly material for photovoltaics and photocatalysis. Herein, we report a new heterostructure consisting of CZTS nanoparticles anchored onto a MoS2-reduced graphene oxide (rGO) hybrid. Using a facile two-step method, CZTS nanoparticles were in situ grown on the surface of MoS2-rGO hybrid, which generated high density of nanoscale interfacial contact between CZTS and MoS2-rGO hybrid. The photoexcited electrons of CZTS can be readily transported to MoS2 through rGO backbone, reducing the electron-hole pair recombination. In photocatalytic hydrogen generation under visible light irradiation, the presence of MoS2-rGO hybrids enhanced the hydrogen production rate of CZTS by 320%, which can be attributed to the synergetic effect of increased charge separation by rGO and more catalytically active sites from MoS2. Furthermore, this CZTS/MoS2-rGO heterostructure showed much higher photocatalytic activity than both Au and Pt nanoparticle-decorated CZTS (Au/CZTS and Pt/CZTS) photocatalysts, indicating the MoS2-rGO hybrid is a better co-catalyst for photocatalytic hydrogen generation than the precious metal. The CZTS/MoS2-rGO system also demonstrated stable photocatalytic activity for a continuous 20 h reaction.
Highlights
Hydrogen generation from water using noble metal-free photocatalysts presents a promising platform for renewable and sustainable energy
We found that the photocatalytic activity of CZTS/MoS2-reduced graphene oxide (rGO) heterostructure outperforms those of many other hydrogen photocatalysts based on earth abundant elements reported in the literature, and it showed excellent long-term stability[38,39,40]
The CZTS/MoS2-rGO heterostructure was prepared by a two-step reaction
Summary
The CZTS/MoS2-rGO heterostructure was prepared by a two-step reaction. In the first step, MoS2-rGO hybrid was synthesized by hydrothermal reaction where few-layered MoS2 nanosheets were constructed in the presence of graphene oxide. In a series of control experiments, the photocatalytic H2 evolution from GO, MoS2, MoS2-rGO hybrid, Au nanoparticle decorated CZTS (Au/CZTS) and Pt nanoparticle decorated CZTS (Pt/ CZTS) were tested for comparison (Figs S7 and S8) All of these systems showed much lower photocatalytic activities than CZTS/MoS2-rGO heterostructure. MoS2, which has larger size than CZTS, could provide efficient electron transfer path, as well as additional active sites for H2 generation With both MoS2 (9 wt%) and rGO (1 wt%) present in the heterostructure, the highest electrocatalytic current density and lowest onset potential were obtained. The high density of nanoscale interfacial contact between CZTS nanoparticles and MoS2-rGO hybrid was demonstrated to favor the photogenerated electron transfer from CZTS directly to MoS2 or through rGO, reducing the exciton recombination, increasing the activity sites, and enhancing the photocatalytic efficiency for H2 generation. The MoS2-rGO hybrid has shown a synergistic effect when combined with CZTS, which makes this heterostructure an excellent H2 evolution photocatalytic system with a long-term durability
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