Design And Catalytic Performance Of Co-based Photocatalyst For Hydrogen Production

The large consumption of fossil energy and the environmental problems caused by the increasing use of fossil fuels restrict the development of human society.The conversion of inexhaustible solar energy into clean and storable hydrogen through a photocatalytic water split process is considered an ideal way to solve these problems.Among many semiconductor catalysts,CdS has attracted much attention due to its suitable valence band structure and good visible light response capability.Compositional regulation and modification of CdS are effective strategies to enhance its photocatalytic activity and stability.Herein,a series of MoS₂ modified Co_0.2Cd_0.8S nanorods?CCS?was synthesized by a hydrothermal method and used for photocatalytic hydrogen evolution reaction?HER?under visible light irradiation.The results indicated that the HER activity and stability of CdS could be substantially improved by the introduction of Co²⁺into CdS lattice,which can accelerate the separation of photoinduced charge carriers and avoid the formation of high oxidation power holes?h⁺?due to the upward shift of the valence band edge.The HER performance of CCS could be further enhanced by the decoration of MoS₂ nanosheets.CCS loaded with 5%MoS₂?wt%?showed the highest activity(2835.6?mol·g^-1·h^-1),which is about 8.9 and 1.6 times higher than that of CdS and CCS.The type II heterojunction formed between CCS and the intimately contacted MoS₂ accounts for the improvement,that is,MoS₂ can serve as trapping centers for photoinduced electrons?e^-?and active sites for HER.This work demonstrated that the activity and the stability of CdS for photocatalytic HER could be boosted by a consolidation of CoS with the host CdS to form a solid solution and a further decoration with low-cost MoS₂ cocatalyst.In addition,trial-and-error methods,a relationship mapping synthesis-structure-property,are widely used to find efficient molecular catalysts.However,the reduplicate and time/energy consuming processes cause it unsatisfactory.By getting insight into the structure-properties relationship,density functional theory?DFT?provides us a convenient method in approaching excellent cobalt photocatalysts.Herein,DFT was used to pre-design effective non-precious metal catalyst for H₂O split hydrogen production based on Co^III?dmgH?₂pyCl.The feasibility and rationality of DFT design was verified by the consistency of photocatalytic experiments and theoretical results.In a hydrogen production system composed of organic dye Eosin Y?EY?as a photosensitizer,cobalt complex as a catalyst,and triethanolamine?TEOA?as an electron sacrificial agent,the hydrogen production ability was exhibited in the pure water without further organic solvent addition.As the best performing photocatalyst,Co^III?dmgH?₂?pyrazine?Cl was selected for in-depth exploration.After optimizing the hydrogen evolution conditions,the hydrogen production of 25 mg Co^III?dmgH?₂?pyrazine?Cl reached 1356?mol after 3 hour of visible light irradiation in water.Furthermore,the cause of system deactivation and mechanism of hydrogen evolution were explored.This work provides a new time/energy saving approach for the design of high effective photocatalysts for hydrogen production.