Hierarchical mesoporous network of amorphous α − Ni(OH)2 for high performance supercapacitor electrode material synthesized from a novel solvent deficient approach

- A novel, simple, scalable and robust solvent deficient synthesis approach for the preparation of hierarchical mesoporous network of amorphous α − Ni(OH)2.
- Removal of different spectator ions during the synthesis and their size plays the significant role in forming the mesoporous network.
- Unimodal pore size distribution and high surface area is achieved for α − Ni(OH)2 obtained from nickel nitrate and ammonium bicarbonate.
- Maximum achieved specific capacitance is 2338 Fg−1 in 2 M KOH at 2 mV s−1.
- The solid state full cell asymmetric supercapacitor maintains excellent capacity retention i.e. 91.08% after 5000 cycles.

The hierarchically porous materials have led to a significant improvement in the applications of electrochemical energy conversion and storage, owing to their outstanding properties, such as high surface area, admirable ease of access to active sites, enhanced mass transport and diffusion. Hence, a significant attention has been diverted towards the synthesis of hierarchically porous nanostructured materials using various methods. Here, we report a novel, simple, scalable and robust solvent deficient approach for the synthesis of hierarchical mesoporous network of amorphous α − Ni(OH)2, using Ni(NO3)2.6H2O in the presence of ammonium bicarbonate as well as sodium bicarbonate, separately. The X−ray diffraction, Raman and FTIR studies confirms the formation of amorphous α − Ni(OH)2. The obtained mesoporous network shows the hierarchical pore size and pore volume distribution depending on the size of different spectator ions evolved during the process. The hierarchical mesoporous network is perceived from the TEM and BET analysis. The SAED pattern endorses for the amorphous nature of the samples. Furthermore, the electrochemical properties exhibit the maximum specific capacitance 2338 Fg−1 and 231 Fg−1 for α − Ni(OH)2 obtained from ammonium bicarbonate and sodium bicarbonate, respectively. Through various measurements, it has been corroborated that, the different bicarbonate used during the synthesis in solvent deficient environment strongly affects the pore size distribution and hence the electrochemical performance. In addition, the high performing electrode material has been utilized as an anode material in the asymmetric supercapacitor shows good capacitive behavior with a cycling stability of 91.08% after 5000 CV cycles.

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