Hierarchical flowerlike metal/metal oxide nanostructures derived from layered double hydroxides for catalysis and gas sensing

The development of advanced functional materials for catalytic reduction and gas sensing is one of the most important issues for the detection and prevention of environmental pollution. Herein, hierarchical peony-like metal/metal oxide (Co/Al2O3 and Co3O4/Al2O3) composites assembled with uniform nanosheets were successfully synthesized using CoAl layered double hydroxides as self-sacrificial templates. Co/Al2O3 composites exhibited high surface dispersions and low metal-support interactions which can be confirmed by a series of structure and morphology characterizations. With the above advantages, Co/Al2O3 composites showed remarkable catalytic ability and stability towards 4-nitrophenol (4-NP) reduction with a nearly 100% conversion within 3 minutes and a conversion efficiency over 98% after 10 successive recycles. After that, Co/Al2O3 composites with different Co/Al ratios were fabricated to investigate the optimal Co content in the catalytic reduction of 4-NP. The results indicated that when the Co/Al ratio reaches 4 : 1, the fabricated composites have the best catalytic reduction abilities. Furthermore, the fabricated Co3O4/Al2O3 gas sensors exhibited a superior response time of 1 s towards 50 ppm ethanol with a sensing response of 8.9. These excellent catalytic reduction and gas sensing abilities could be attributed to the unique peony-like hierarchical structure which could provide large surface areas and abundant active sites. More importantly, this work provided a new synthesis strategy to design materials with enhanced catalytic reduction and gas sensing abilities, which will be beneficial to the development of highly effective catalysts and gas sensing materials.