The green synthesis of PdO/Pd anchored on hierarchical ZnO microflowers with a synthetic effect for the efficient catalytic reduction of 4-nitrophenol

Based on green chemistry, 3D hierarchical ZnO microflowers (MFs) constructed from layered 2D nanosheets have been designed as carriers to uniformly load PdO/Pd nanoparticles by the calcination of the precursor (ZnO/Pd(II) microflowers) in air. The ZnO/Pd(II) microflowers are prepared by dipping the 3D ZnO MFs in an ethanolic solution of PdCl2 without involving additional agents. The as-prepared 3D hierarchical ZnO microflowers are a stable support to enhance the dispersibility of PdO/Pd nanoparticles to achieve better catalytic performance for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). In addition, the synergistic effect between the PdO and Pd nanoparticles is another major driver that promotes the catalytic process. Over 98% of 4-NP is reduced within 7 min. Furthermore, structural analysis of the ZnO/PdO/Pd microflowers can provide useful information for understanding structure-performance relationships.