۱- Introduction

۲- Experimental section

۳- Result and discussion

۴- Conclusions

References

Abstract 

High-efficient noble-metal-free photocatalyst is vital to realize high H2 evolution. In consideration of this, we design a CdS@NiS reinforced concrete structure derived from nickel foam (NF) via a simple one-pot oil bath strategy. The whole preparation process is started with the growth of NiS rods on NF. Subsequently, NiS rods are encased in CdS gradually under oil both conditions. After the combination of NiS rods and CdS, the photoelectrical properties of primeval CdS are greatly optimized, e.g., photoelectric responsiveness, impedance and light absorption capacity. Moreover, the H2 evolution rate of CdS@NiS is increased significantly from 2706 to 40601 μmol g−۱ h−۱ under visible-light irradiation (λ > 420 nm), which is about 15 times higher than that of pure CdS, thereby confirming the excellent synergistic effect between NiS rods and CdS. Additionally, the photocatalytic performance of CdS@NiS was stronger than that of CdS/NiS-NPs (6726 μmol g−۱ h−۱ ) and CdSNPs/NiS (1639 μmol g−۱ h−۱ ), highlighting the advantages of CdS (prepared using oil bath treatment) and NiS rods (originated from NF growth). Lastly, according to experiment data and DFT calculation results, a viable mechanism for CdS@NiS is tentatively proposed.

Introduction

During past few decades, photocatalytic hydrogen generation has been considered as a promising strategy to overcome energy crisis [1–۸]. Since Fujishima reported the photocatalytic H2 generation phenomenon in 1972 [9], photocatalytic materials for water splitting, especially metal sulfides, has gradually been a research focus. Up to now, CdS attracted extensive attention because of the unique optical response [10], high light-harvesting efficiency [11] and narrow band gap [12]. However, pure CdS generally exhibits poor photocatalytic H2 production due to the low charge carriers separation [2,13,14]. One of the promising solutions is combining cocatalysts with CdS to refine its photocatalytic properties [15–۲۰]. Among the various cocatalysts, nickel sulfide (NiS) has been regarded as an effective cocatalyst because of its high electrical conductivity and excellent power conversion efficiency. For instance, Xu et al. firstly reported the excellent synthetic effect between NiS and CdS for H2 production (ca. 7266 μmol h−۱ g−۱ , λ > 420 nm) [21]. After that, some studies about NiS/CdS hybrid photocatalysts have been carried out to develop novel fabrication strategies or further improve its H2 production [22–۲۸]. Despite the remarkable advances, there are still great challenges and improvement space for NiS/CdS catalysts: (1) Compared with pristine CdS, the H2 production of NiS/CdS is only improved to a limited degree (ca. 25000 μmol h−۱ g−۱ , λ > 420 nm). Its water splitting efficiency may be further enhanced to ca. 40000 μmol h−۱ g−۱ via specially designed strategies; (2) Generally, CdS was first synthesized and then decorated with NiS. Thus, the as-prepared CdS needed to suffer additional reactions treatment, which may destroy the active site and weaken its light absorption capacity due to the poor physicochemical stability of CdS.