Noble metal free MoS 2 /g-C 3 N 4 catalyst has attracted intense attentions for visible light photocatalytic hydrogen evolution as a result of its earth abundance, low cost and unique heterojunctions stacked with two dimensional sheets. However, the low charge separation efficiency resulted from the poor conductivity of g-C 3 N 4 and MoS 2 , and lack of abundant active sites from coordinative unsaturated atoms in MoS 2 , restricts the photocatalytic hydrogen evolution activity and stability enhancement of MoS 2 /C 3 N 4 composite catalysts. Herein, CoMoS 2 /rGO/g-C 3 N 4 catalysts with ternary heterojunctions are prepared by facile solvothermal method, which exhibit high visible light photocatalytic activity and stability for hydrogen evolution. The optimal hydrogen evolution rate of CoMoS 2 /rGO/g-C 3 N 4 catalysts is 684 μmol g −1 h −1 when the content of CoMoS 2 is 2% and the content of rGO is 0.5%. The stability of CoMoS 2 /rGO/C 3 N 4 catalysts just decrease about 3% after 4 cycling runs for 16 h. The good catalytic performances of catalysts are attributed to the synergistic effect among the g-C 3 N 4 nanosheets, rGO nanosheets and CoMoS 2 nanosheets. The high conductivity of rGO nanosheets enhances the electron-hole separation and charge transfer, and Co doping increases the active sites for hydrogen evolution due to the increase of unsaturated atoms in CoMoS 2 nanosheets.
Lu Qi,Peng Zheng,Zhen Zhao,Aijun Duan,Chunming Xu,Xilong Wang
The intrinsic kinetics of hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) over mesoporous CoMoS 2 /ZSM-5 (CoMoS 2 /MZSM-5) was investigated by comparing the commercial CoMoS 2 /γ-Al 2 O 3 . A pseudo-first-order kinetic model considering the direct desulfurization (DDS) and two detailed partial and full hydrogenation pathways was formulated with simple power law rate equations. The apparent rate constants of five lumped reactions on CoMoS 2 /MZSM-5 are 2–4 times larger than those of CoMoS 2 /γ-Al 2 O 3 . With both catalyst system, the pre-exponential factor plays a dominant role in the reaction rate of DDS pathway showing equally high activation energies. The apparent activation energies show a critical effect on the reaction rate of two hydrogenation and subsequent desulfurization reactions. Furthermore, the Delplot analysis was applied to identify the reaction sequence of product formation and verify the reaction network. The HDS performance and reaction rates of individual reaction steps can be rationally linked to the morphology and available content of CoMoS phase as identified by HRTEM and XPS characterization. Thus, multi-stacked MoS 2 nanocrystallites on CoMoS 2 /MZSM-5 provide more available sulfur vacancies to facilitate the DDS pathway, and catalyze efficiently the hydrogenation and subsequent desulfurization with the synergy of brim sites and sulfur vacancies.
Rational creation of efficient, stable, and economical bifunctional electrocatalysts is highly desired for water splitting.CoMoS2/NiSe2 heterostructure electrocatalyst supported on nickel foam (NF) was successfully synthesized using a hydrothermal method. The distinctive chrysanthemum-like hierarchical architecture of CoMoS2/NiSe2 not only offers numerous accessible active sites but also enhances electrolyte diffusion and charge transfer. In a 1.0 M KOH electrolyte, the overpotentials for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at 10 mA cm⁻² are 47 mV and 246 mV, respectively, demonstrating remarkable stability over 100 hours and excellent turnover frequency. X-ray photoelectron spectroscopy (XPS) analysis indicated that the formation of the CoMoS2/NiSe2 heterojunction facilitates interfacial electron transfer, thereby optimizing the electronic structure and augmenting the intrinsic catalytic activity. This study presents a viable method for the design of high-performance heterostructured electrocatalysts for efficient water electrolysis through interface engineering and electronic structure modulation.
Jia-Xin He,Yong-Shan Xiao,Chang Liu,Min-Li Zhu,Yong-Hong Song,Zhong-Wen Liu
MoS 2 is an attractive sulfur-resistant catalyst for directly converting sulfur-containing syngas to high value-added chemicals. However, the effect of the layered structure on the catalytic activity for CO hydrogenation reactions is far from clear. Herein, MoS 2 /carbon composite catalysts with 1–8 stacking layers in MoS 2 crystallites are synthesized, and the impact of the layer numbers on the catalytic performance is probed for the low-temperature methanation of sulfur-containing syngas. The results indicate that the turnover frequency of CO methanation increases from 2.4 × 10 -3 to 3.7 × 10 -3 s −1 with decreasing layer numbers of MoS 2 crystallites from 8.3 to 1.1. This result is thoroughly explained by the fact that the higher ratio of rim sites in MoS 2 crystallites with fewer layer numbers enhances the catalytic activity, which originates from the facilitated activation of CO and H 2 . These understandings are important for the rational design and development of more efficient MoS 2 -based catalysts for CO hydrogenation.
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