The Application Of Composite Materials Based On Hydrogel And Cadmium Sulfide In Photocatalytic Hydrogen Production

Due to the non-renewability of fossil fuels and the increasing environmental pollution caused by the combustion of fossil fuels,hydrogen has been extensively studied as a clean energy source,because of its environmentally friendly,renewable and non-toxic reaction products,and its high efficiency and power density.Among numerous photocatalytic hydrogen-producing catalysts,CdS has a narrow bandgap（2.4 eV）that is more efficient absorption of visible light and a conduction band edge is more negative than the H⁺/H₂ redox potential,so it has been considered as an excellent visible-light-driven catalyst.In this paper,hydrogels are used as substrates for CdS to enhance its photocatalytic activity and stability.Cadmium sulfide/polyacrylamide hydrogels（CdS/PAM）was synthesized by in situ loading CdS nanoperticles and used for photocatalytic decomposition of water for the first time.The size distribution of the loaded CdS nanoparticles is 3-12 nm.We studied the enhanced photocatalytic activity and photo-corrosion inhibition of CdS/PAM the compared with pure CdS and probed the mechanism of the improvement.In particular,the CdS/PAM prepared in 0.003 M CdCl₂ solution exhibited the highest hydrogen production efficiency of 2.929 mmol g^-11 h^-1,about 79times that of pure CdS.The results demonstrate that the formation of new N-Cd bond and high transmittance of CdS/PAM dramatically enhance photocatalytic activity.The electron cloud of nitrogen atom can attract holes and repel photogenerated electrons,which lowers the carrier recombination probability.The results also reveal that the excellent hydrophilicity of hydrogel plays an important role in the inhibition of photocorrosion.The proportions of monomer DM,AA and AM were controlled,and the concentration of initiator and ambient temperature were adjusted to synthesize cationic hydrogel（DAM）and anionic hydrogel（AAM）,respectively.Swellability,scanning electron microscopy（SEM）and infrared spectroscopy（FTIR）were used to analyze the morphology and composition of hydrogels.X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）and thermogravimetric analysis（TGA）were used to characterize the composition of the composites.Photocatalytic experiments in a closed environment show that cationic hydrogels can improve the photocatalytic activity and stability of CdS.Among them,the H₂ production efficiency of sample DAM₂-CdS was the highest,reaching 10.35 mmol h^-11 g^-1,TOF=1.495 h^-1,and the H₂production efficiency only decreased by 12.7%after 5 cycles.Using different electron donors as sacrificial agents,it was found that the pH and the redox potential of sacrificial agents are also important factors affecting the H₂ production activity of the catalyst.