Cyano-bridged coordination polymer hydrogel-derived Sn–Fe binary oxide nanohybrids with structural diversity: from 3D, 2D, to 2D/1D and enhanced lithium-storage performance

Abstract

Metal oxide nanohybrids with uniform dimensions and controlled architectures possess unique compositional and structural superiorities, and thus harbor promising potential for a series of applications in energy, catalysis, and sensing systems. Herein, we propose a facile, general, and scalable cyano-bridged coordination polymer hydrogel-derived thermal-oxidation route for the construction of main-group metal and transition-metal heterometallic oxide nanohybrids with controlled constituents and architectures. The formation of Sn-Fe binary oxide nanohybrids has been demonstrated as an example by using cyano-bridged Sn(iv)-Fe(ii) bimetallic coordination polymer hydrogels (i.e., SnCl4-K4Fe(CN)6 cyanogels, Sn-Fe cyanogels) as precursors. The physicochemical properties of Sn-Fe cyanogels with different Sn/Fe ratios have been systematically examined, and it is found that perfect Sn-Fe cyanogels without unbridged Sn(iv) or Fe(ii) can be formed with Sn/Fe ratios from 2 : 1 to 1 : 2. More importantly, the simple adjustment of Sn/Fe ratios in the Sn-Fe cyanogel precursors can realize flexible dimensional control of the Sn-Fe binary oxide nanohybrids, and 2D/1D SnO2-Fe2O3 hierarchitectures, 2D SnO2-Fe2O3 nanosheets, and 3D SnO2-Fe2O3 networks have been synthesized using the Sn-Fe 1 : 2, Sn-Fe 1 : 1, and Sn-Fe 2 : 1 cyanogels as precursors, respectively. To demonstrate their compositional/structural superiorities and potential applications, the lithium-storage utilization of the Sn-Fe binary oxide nanohybrids has been selected as an objective application, and the nanohybrids exhibit Sn/Fe ratio-dependent lithium-storage performance. As a representative example, the 2D/1D SnO2-Fe2O3 hierarchitectures manifest markedly enhanced Li-storage performance in terms of reversible capacities and cycling stability in comparison with their constituent units, i.e., bare SnO2 nanosheets and Fe2O3 nanorods. The proposed cyanogel-derived thermal-oxidation strategy could open up new opportunities for constructing heterometallic oxide nanohybrids, and the rationally designed metal oxide nanohybrids may find broad applications in energy, catalysis, and sensing fields by virtue of their structural and compositional features.

3D Space-Confined Pyrolysis of Double-Network Aerogels Containing In-Fe Cyanogel and Polyaniline: A New Approach to Hierarchically Porous Carbon with Exclusive Fe-N x Active Sites for Oxygen Reduction Catalysis

“…After mixing, the nitrogen end of cyano ligand from K 3 Fe(CN) 6 replaces the chloride ligand from InCl 3 , forming the bridges between Fe(III) and In(III) centers (FeCNIn). This coordination–substitution reaction generates the extended cyano bridges, and the whole reaction system finally forms the stable In–Fe cyanogel . During pyrolysis, the vaporization of the in situ generated In is beneficial for the porous nature of the final Fe‐based product.…”

Silica template-assisted synthesis of SnO2@porous carbon composites as anode materials with excellent rate capability and cycling stability for lithium-ion batteries

“…For the SnO 2 @PC1 electrode, the charge specic capacity of SnO 2 @PC1 aer 100 cycles could reach 1130 m Ah g À1 , with a capacity retention of 90.0%, which is much higher than that of bare SnO 2 and SnO 2 @C. These results demonstrated that the novel porous carbon structures directed by the silica template can effectively enhance the structural stability and cycling performance, which can be evidenced in previous literature. 44 Herein, the complete carbon enclosure and the large void space between the core and shell can physically restrict the SnO 2 core and buffer its volume expansion, preventing it from pulverization and detaching from the current collector, which can favor a high specic capacity aer long-time cycling. It should be noted that the discharge specic capacity of the SnO 2 @PC1 electrode can deliver 1130 m Ah g À1 at 0.2 A g À1 aer 100 cycles, which is much higher than the theoretical capacity of SnO 2 ($790 m Ah g À1 ).…”

Hydrogels: Promising Energy Storage Materials

“…In recent times, hydrogels have emerged as promising groups of functional materials for energy conversion and storage systems . Their potential applications are mainly due to their larger specific surface area, porous microstructure, variable chemical/physical properties, short pathways for charge/mass transfer, and so forth . Efforts have also been made to apply the utility of nanotechnology and directed the research towards nanostructured hydrogels ,,.…”

“…Their potential applications are mainly due to their larger specific surface area, porous microstructure, variable chemical/physical properties, short pathways for charge/mass transfer, and so forth . Efforts have also been made to apply the utility of nanotechnology and directed the research towards nanostructured hydrogels ,,. These types of materials present fabulous properties at nanoscale.…”