Chitosan hydrogel anchored phthalocyanine supported metal nanoparticles: Bifunctional catalysts for pollutants reduction and hydrogen production

Metal nanoparticles possess high catalytic activity in various organic transformation reactions. A catalyst must be recovered and re-used effectively and economically to lower the overall reaction cost. The recovery of a catalyst remains a challenge due to their extreme small size. In this research work, catalytic metal nanoparticles were synthesized on Zn-phthalocyanine (ZnPc) and chitosan hydrogel (CH) composite which acts as catalyst support. The ZnPc-CH support facilitate the easy recovery of the loaded metal nanoparticles. Metal nanoparticles (M-0) based on Cu-0, Ag-0, Ni-0, Co-0 and Fe-0 were decorated inside and on ZnPc-CH hydrogel surface. The developed M-0@ZnPc-CH were utilized for the enhanced selective reduction of toxins and hydrogen production by meth-anolysis and hydrolysis of NaBH4. Effective catalytic reduction and hydrogen generation was successfully ach-ieved with Co-0@ZnPc-CH and ZnPc-CH. Under optimized conditions, Co-0@ZnPc-CH showed complete reduction of 4-nitrophenol (4-NP) in 8.0 min with the fast 4-NP reduction kinetics (K = 0.611 min(-1)). Among the developed catalysts, ZnPc-CH showed fast H2 generation with high H-2 generation rate (HGR = 4100 mLg(-1)min(-1)) under optimized conditions. Metal leaching from Co0@ZnPc-CH was negligible during recycling of the catalyst, suggesting that it could be implemented to 4-NP treatment from real water samples. Similarly, ZnPc-CH could produce same quantity of H-2 throughout 4 continuous cycles of durability testing without any deac-tivation and leaching and ZnPc-CH showed high stability, indicating the effectiveness of the catalyst to be applied for H-2 production on large scale.

Automated summary

Metal nanoparticles were synthesized on a composite of Zn-phthalocyanine and chitosan hydrogel, acting as a catalyst support, to enhance the recovery and re-use of the catalyst. Various metal nanoparticles were deposited on the surface and inside the hydrogel. Co-0@ZnPc-CH and ZnPc-CH showed effective catalytic reduction and hydrogen generation.