The conversion of p-nitrophenol (4-NP) to p-aminophenol (4-AP) is of great significance for pharmaceutical and material manufacturing. In this work, Au-M@SiO2 (M = Rh, Pd, Ir, Pt) nanoparticles (NPs) with core–shell structures, which are expected to be excellent catalysts for the transformation of 4-NP to 4-AP, were synthesized by a facile one-pot one-step method. The structure and composition of the NPs were characterized through transmission electron microscopy, X-ray powder diffraction and X-ray photoelectron spectroscopy. Au-M@SiO2 (M = Rh, Pd, Ir, Pt) core–shell NPs showed excellent catalytic activity in the reduction of 4-NP, which is superior to most catalysts reported in the previous literature. The enhanced catalytic activity of Au-M@SiO2 core–shell NPs is presumably related to the bimetallic synergistic effect. This study provides a simple strategy to synthesize core–shell bimetallic NPs for catalytic applications.

In this article, one unusual coordination polymer [Co(bib) 1.5 (NO 3 ) 2 (CHCl 3 )] ∞ , named as CP-3-ZX, is assembled from ligand 1,4-bis(imidazol-1-yl)benzene (bib) and cobalt nitrate. In CP-3-ZX, the Co II ion is connected by bib into one-dimensional (1D) double-track ladders, which are mutually packed to form tetragonal channels with a porosity of 23.9%. Subsequently, CP-3-ZX is employed as a precursor, and a sequence of Co 3 O 4 @C composites with various carbon contents is obtained through changing the annealing temperature. A moderate amount of carbon can enlarge the Brunauer−Emmett−Teller specific surface area, enhance the conductivity, and finally augment the capacitance of the carbonaceous material. An extensive comparison reveals that Co 3 O 4 @C-400, designated by setting the calcined temperature at 400 °C, has the highest specific capacitance of 317 F g −1 because of the optimized carbon content among these Co 3 O 4 @C composites. Moreover, an asymmetric supercapacitor Co 3 O 4 @C-400//AC is fabricated using the positive electrode of Co 3 O 4 @C-400 and the negative electrode of activated carbon (AC). Co 3 O 4 @C-400//AC exhibits an energy density of 13.8 Wh kg −1 , and a retention of 82% after 5000 cycles indicates good cycling durability. Significantly, the 4 × 2 battery unit of Co 3 O 4 @C-400//AC can be utilized to run a time counter for 11 s and light a toy Christmas tree for more than 20 min. The outstanding propulsion competence proves that Co 3 O 4 @C-400 has tremendous applications in supercapacitors.