Solvothermal Synthesis of a High Supercapacitive Humate–NiCo–LDH Composite Material Derived from the Humate–ZIF-67 Template
Shaoling Cong, Yufei Yang, Kanshe Li, Fan He, Jian Liu, Hua Yuan, Xiaoqin Wang, Runlan Zhang, Jia Chu, Ming Gong, Bohua Wu, Shanxin Xiong, Anning Zhou
Abstract
Metal organic frameworks (MOFs) have good porosity and adjustable morphology, which are always used as excellent sacrificial templates to derive high-performance layered double hydroxides (LDHs). Here, a humate-based ZIF-67 (HA–ZIF-67) template is first prepared by a natural precipitation method using humates as a substrate. And a humate-based NiCo–LDH (HA–NiCo–LDH) composite material is then successfully prepared via a solvothermal approach with ethanol as a protic solvent. Due to the special composite structure including NiCo–LDH nanocages assembled by interlaced nanosheets, suitable incorporation of layered humate substrate with graphitized microdomains and rich mesopores, the HA–NiCo–LDH exhibits a low resistance during the ionic diffusion, charge transfer, and electron conduction process, a large capacity of 1083 C g–1 (0.5 A g–1), and an excellent cycle stability with a capacity retention of 77% over 10000 GCD loops at 5 A g–1. The assembled asymmetric supercapacitor of the HA–NiCo–LDH//AC also has a decent capacity retention of 52% of initial value with the current density increasing from 0.5 to 10 A g–1, and a large energy density of 44.9 Wh kg–1 at a power density of 348 W kg–1. Its capacity retention is still high to 98% at 5 A g–1 over 5000 GCD loops. Hence, the moderate incorporation of humates is of great significance for practical applications of the NiCo–LDH in supercapacitors.