Preparation Of Hierarchical Porous CdS/Pd/TS-1 Based Catalysts And Their Photocatalytic Performance For Hydrogen Production From Water

The conversion of water into hydrogen through solar energy is considered to be an important method to solve or alleviate environmental pollution and energy crises in the future.The two main factors that limit the process of photocatalytic hydrogen production are the low utilization efficiency of solar energy and the competition between the recombination and transfer of photogenerated electrons and holes.Based on these,a multi-porous Titanium silicalite-1(TS-1)molecular sieve was prepared by different concentrations of alkaline solution,a series of CdS/Pd/TS-1 catalysts were synthesized,and its internal mechanism and photocatalytic performance were studied in this article.Subsequently,the best carrier 0.3NaOH-TS-1 was selected,and the non-precious metal promoter Ni was introduced to prepare a series of CdS/PdNi/0.3NaOH-TS-1 catalysts with different bimetallic ratios,which can promote the effective separation of photogenerated electrons and holes under visible light,and enhance the photocatalytic hydrogen evolution rate.At the same time,the catalytic mechanism of the bimetallic composite catalysts were also discussed in this article.The details are as follows.Using the TS-1 titanium silicate molecular sieve with a hierarchical pore structure after alkali treatment as the carriers,CdS/Pd/xNaOH-TS-1 catalysts(alkali treatment concentration x=0.1,0.2,0.3,0.4 mol/L)with a large specific surface area and a wide photoresponse range were prepared.Under visible light,the hydrogen evolution rate of CdS/Pd/0.3NaOH-TS-1 can reach 13144.1 μmol·g-1·h-1,which is about 3.5 times that of CdS/Pd/Untreated TS-1.Through alkali treatment,the hierarchical porous TS-1 carrier has a larger mesoporous specific surface area,which is conducive to the uniform dispersion and loading of active Pd sites and CdS quantum dots.And after alkalization,the content of active phase four-coordinated titanium in the framework of TS-1 molecular sieve increases,which is more conducive to the separation of photogenerated carriers in the system.In addition,the enhancement of light reflection and scattering in the multi-level holes strengthens the absorption of light by the catalysts,thereby promoting the photocatalytic hydrogen production reaction.Based on the good crystallinity and large specific surface area of 0.3NaOH-TS-1 molecular sieve,the idea of using CdS/Pd/0.3NaOH-TS-1 based catalyst was continued,and the single metal CdS/Pd/0.3NaOH-TS-1,CdS/Ni/0.3NaOH-TS-1 and a series of different bimetal ratios of CdS/PdNi/0.3NaOH-TS-1 catalysts were prepared by the one-step co-reduction method of sodium borohydride.The effects of PdNi bimetal with different metal molar ratios on the photocatalytic hydrogen production reaction were explored.Among them,the CdS/Pd1Ni1/0.3NaOH-TS-1 catalyst has the best photocatalytic hydrogen production rate,which is respectively 1.3 times and 2.0 times that of the the single metal CdS/Pd/0.3NaOH-TS-1 and CdS/Ni/0.3NaOH-TS-1 catalyst,and it has the better photocatalytic hydrogen production stability.This shows that the introduction of non-precious metal nickel can effectively improve the photocatalytic activity of the palladium-based catalyst,and the bimetallic PdNi can replace the precious metal Pd as a promoter to enhance the photocatalytic hydrogen production reaction.