Synergistic Effect of ZnO-ZnFe2O4 Heterostructure for Enhanced Surface Catalytic Activity in Cr (VI) Reduction, Green H2 Generation and CO Sensing: Experimental Study supported by DFT

Higher energy demand is a hallmark of progress which necessitates careful management of environmental pollution for our healthy life and ensures better planet for future generations. Heterostructure material-based catalysts have emerged as a comprehensive solution to combat the diverse challenges related to energy and environment. Here, a n-n type ZnO-ZnFe2O4 heterostructure synthesized through simple reflux followed by a co-precipitation technique is explored for the same. Detailed photocatalytic and gas sensing studies reveal that the 50% ZnO - 50% ZnFe2O4 based sample (ZZF-11) showed the highest Cr (VI) degradation with a rate constant of ~159×10-4 s-1, which is ~23 times higher than pristine ZnO and 6.4 times higher than pristine ZnFe2O4. Additionally, the ZZF-11 sample produces ~550 μmol/g of H2 within a 300-minute interval through a photocatalytic water-splitting reaction. The ZZF-11 sensor also shows a significantly high response to 1 ppm CO gas (S= 29.4%) compared to all other pure and composite samples. The formation of the heterostructure and transfer of charges through interface played important role here. Most possible mechanism for the enhanced surface catalytic performance of ZZF-11 has been discussed critically by corroborating experimental results with DFT studies. The study demonstrates a unified pathway to enhance the various surface catalytic processes by tuning different parameters of heterostructure material to jointly combat environmental and energy related issues.