Solvothermal Synthesis of a High Supercapacitive Humate-NiCo-LDH Composite Material Derived from the Humate-ZIF-67 Template

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.